CA2220901A1 - Plastic platelet fuel cells employing integrated fluid management - Google Patents

Abstract

Improved fuel cell stacks (1) constructed from a plurality of cells, each comprising a series of interrelated mono and bipolar collector plates (BSPs), which in turn are built up by lamination of a core of related non-conductive plastic or ceramic platelets (12) sandwiched between conductive microscreen platelets of metal or conductive ceramic or plastic with an electrode membrane (EMA) (5 A, B, C, D) between adjacent BSPs. The platelets, both metal and plastic of the composite BSPs, are produced from sheet material with through and depth features (18, 17) formed by etching, pressing, stamping, casting, embossing and the like. Adjacent plates each with correspondingly relieved features form serpentine channels within the resultant monolithic platelet/cell stack for integrated fluid and thermal management. The plastic platelets are particularly useful for PEM fuel cells employing H2 and Air/O2 as fuel. The platelets are easily made by printing (embossing) processes, and dies made by photolithographic etching for rapid redesign. Each BSP can be individually tailored to each type of membrane, fuel, and intra-cell location within the stack (1). As materials are cheap and easy to manufacture and assemble, lightweight fuel cells of very high power density are realizable. Industrial applicability includes both stationary and vehicular power supplies, in both micro and macro sizes.

Description

W 096/37005 PCTrUS96/06877 Sr~ClrlCATlON Dt~ r 1 1l~1J

CROSS-httt~tr~lCE TO RELATED APPLICATION: This ~ ;on is a continuation-in-part of US
~FP ~ .SN 08f322.823filedOctoberl2. l994byspearetal.~entitledFuelcellsEmployingllll~ldl~d FluidMa,layt:,llentplateletT~llnùloy!f~thebenefitofthefilingdateofthecollllllonsubiectmatterofwhich is claimed under 35 U.S.C. 120 and the subject matter of which is hereby i--co.~o.dl~d by lef~ ce herein.

TECHNICAL FIELD:
This invention relates to plastic platelet fuel cells. and more particularly to fuel cells constructed of stacked platelets having i..leyldled fluid ~--~,ag~l-ent (IFM) features, and to methods of manufacture and op~dliùn of the IFM cells. A particular ~--bodi,--ent employing the ~ci-i..L,i~,les of this invention is a hydrogen-airiO2fuelcellemployingmultiplecc....pGaitesepd,dlu-afOrmedOfbondedplateletsofplast fomling a fluid ...~,dy~--enl core. with metallic or other el~hi~.al conduction type surPdce pl t ~
f~)~;~io~ ~9 as current ~~ 'c a. The platelets have individually configured ~ ,.uul.a....el reactant gas.
coolant and hu-- ' - ~ zones therein. Typical IFM plastic platelet cells of this invention operate in the range of about 50 to 150 C, with an output on the order of .25-1.0 kW per Kg t.5-1.0 kW/L) for use in both sldliùlh~y and mobile power ye~dtiùl~ ~F-F' ~a in open or closed loop configurations. The IFM
platelet and s~ dtOI design can be ~r~jllct~ throughout the fuel cell stack to acco~ dte var~fin9 thermal l--a..ag~.-w.l and hu-l ~l ~ re~l~ ~--e lta within each cell as a function of its position in the StdCk.

BACKGROUND OF THE ART:
Fuel cells for direct conversion of hydrogen or Cdl bonaceous fuels to LIQ,I- i~.ity have shown great Il ~e~ li"al promise. but have not become widely used in co-, -. . .~;e t~ec~ ~ce of ~h- ~ ~- ubl~ - -s and econo...ic reasons. In the field of hydrogen-air/02 fuel cells. power density, that iâ h'~w~ila of power gen~ dlion per ! ' _ dl l l, has been I l ldl ~ Idl, and the lifetime has been u~ - ,Iy short. Prior art cells have ~eli~lced drop-off in power with age due in part to po;soi ~9 of catahysts or r;l~l-ulyte 111~11 It~l dl ~es. and the poor distribution of fuel gases i- ,le- . 'Iy has led to thermal hot spots leading to cell failure and the like.
A particularly illlpulldlll class of fuel cells with promise for ~laliùnaly and mobile ele~ .ily gw ~t:- cLiol) is the low temperature H2/~2 fuel cell employing solid polymwric proton excha.-ge membrane having a noble metal catalyst coated on at both sides thereof, which mem~rane is located between the fuel cell elec,l.udes. These fuel cells employ H2 as fuel, whether directly sl~FFI ~i as such or gen~dled in a~<o~ .n with the cell by Cl)w"il,al reaction, such as electrolysis, from metal hydrides or from reformed Si.q~TUTE SHEEr ~RULE 2~3 W O 96/37005 PCT~US96/06877 hydloLdlL~ùns. The oxidant is ~2 or air where suitable. Water is required both for cooling and for hul~ r~ n of the m~ dlle, to keep it from drying out and becoming il,t Iri-,;~"L or stnucturally v.,~ ~ ,~ through sl,c~ h ,9 and cracking. Typieally, the anode side dries out first for a variety of reasons, including: electro-osmotic pumping from anode to cathode; supply of gases in excess of the el~L.uclle,.l.cal reaction rate; and the air or oxygen flow on the cathode side purges both the product water and the water vapor passing through the membrane from the hydrogen anode side. Acc-ul .J;~ ~y~, the fuel gases need to be humidified In the fuel cell stack to reduce the dehydration effect. The cooling water removes excess heat generated in the slow combustion of the catalyst-mediated ele ll ocl ,el l ,ical reaction in the cells. and is conducted extemal of the stack for heat ~:~cl.dnye. In some designs the cooling water is used to humidify the reactant gases.
- There are several suitable ele~ude me.,-~.dne dSSt~ (EMAs) available for such low le.,.p~dlure fuel cells. One is from l l Pc N~D' Corp of P~" :;cJ~, New Jersey which employs a Pt catalyst coated on a polymer film, such as DuPont NAFION~ brand perflourosulru.,dlad hyd.ucd,L,o,, as the , - l~l l Ibl ane. Altematively, Dow Chemical provides a perflourosulfonated poiymer which has been, ~pGI led in US Patent 5,316.869 as perrnitting current dt n~itias on the order of 4000 ampsls.f. with cell voltages in excess of .5V/cell, for a cell stack power density in excess of 2 kW/s.f.
A typical design of a currently available fuel cell stack is the Ballard Fuel Cell Stack of 35 active el~l, ocl ,~,lical cells, 19 thermal md,)cy~ l-~ ll cells. and 14 reactant hull ~id~ I ;on cells el I l, ' ,1;. l9 a Pt on NAFION-117 EMA in stacks of 1/4~ thick graphite plates. The staek is r~po,lad to have an overall volume of 0.5 cu. ft. with a weight of 94 Ibs and a 3 kW output from H2 and ~2-However, the graphite plates must be relatively thick to provide structural integrity and to preventreactant crossover. That is, since the graphite is porous to H2 and ~2. it must be at least .060~ thick to reduce the permeation crossover to an r~ ' ' level. Further, graphite plates are brittle. Thus, they are prone to crack as the cell sbcks must be placed under co,llp,~sion to effect intra and inter-eell sealing to prevent reactantgas leakage. Graphite plates have low thermal and elecl- ical conductivitywhich gives rise to hot spots and dead spots. They are also difficult to manufacture. es~.e ~ "y the gas distribution cl~anr,~ . The stack output is relatively low, on the order of .03 kW/lb. In the example cited above, the number of inactive cooling and hurr.~ ;ol) cells almost equals the number of active el~LIucl,~,ical cells. This effectively doubles the number of g~cl~lecl seals required in a stack thereby d~l~asil Ig stack reliability and pel ~ul-llance.
The aforementioned US Patent ri,316,869 does not offer a solution to graphite plate cell stack design as it is con~;ell,ad with ",hilu,ulucessor control of a closed loop system extemal to the stack.
Accol ~lil ,gly, there is a need for an improved fuel cell design, and I II~U lods of producing the fuel cells and ope, c,~ion thereof which overcome limiting pl u~ '~ lls of the prior art.

Dl~ OslJRE OF INVENTION:
sllr~1ARy: The invention is directed to improved fuel cell stacks constnucted from a plurality of cells, each co.,.,u,isi..9 a series of i.lLt~ laled, plastic, ceramic and metal platelets having illl~yldL~I fluid I l la. ,agel I lent (IFM) features. The invention also includes methods for design, construction, platelet feature SUBSTITU~E SHEET (RUEE 2~) W 096/3700S PCTrUS96/06877 forming~assemblyandbondin9oftheplateletsintomodularpolarselJdldlola(~llhst~kcellassemblies)~
and ..,~II,ocis of op~dLion of fuel cell stacks employing the Illl~ldldd Fluid Ma"ag~",ent TechnGlo (IMFT) metal and plastic platelets of this invention.
While particularly ~iic~oS~ as ~PF'-- '~ to proton excl,~ge membrane (PEM) fuel cells employing H2 and Air/02 as fuel (whichever is most app,up,idld), the l~ch-l, ~os of this invention are equally applicable to alkaline, molten l.;dl i~ordle and solid oxide type fuel cells, and to reformers used in conjunction with fuel cells. A wide variety of other fueVoxidizer comb ndlions may be employed, such as NH3/02; H2/C12 H2/Br2 CH30H/02. and the like, it being IJ"de alood that .~e,~ce to ~2 includes Air.
In referring to ~fuel cells~ herein. it should be u, .d~. alOOd that temm includes one or more unit cells, each of which cu,..p.iaes a bipolar sep~dlù, plate (BSP) in contact with an app-upridld cle_t.ude mernbrane (EMA) as an assembly and includes stacks of unit cells lt~---;, aled by current ce" ' plates.
The fuel cells of this invention are constructed of one or more cells, each cell of which in tum c-olllpliaes a pair of bi-polar sdpdldlul plates (BSP) sandwiching an elecl.ude membrane assembly (EMA) 11 ~~l~b~we~. The sep~dlu- a may be either unipolar (for the terminal end plates) or bipolar, with one side being the anode (H2) side and the other the cathode (~2) side. In tum, each unipolar or bipolar sepa. alul assembly of this invention comprises a fluid ,..d..ag~---enl core assembly (FMCA) sandwiched between a pair of mic. uacl ~n plates (MSP). Each of the core asst~ ~-bly and the ~--;~- USLI ~dn plate may be made of a plurality of pl-lF~ in contact with each other, and pr_.t~,.dbly bonded as a unitary whole. The ~.,ic.usc,~en plate (MSP) functions as a current cc"~ to pass eleu~-uns to edge conductors (bridges, tabs, spring clips, edge jumpers, pleated conductive current bridges, edge bus bars, and the like) and/or to intemal bus bars, and is constructed of current conductive material, such as metal or conductive plastic.
The ~--ic-osc.~" plate may be of window frame design, with a ,ecessed or inset central section surrounded by a posilior .9 frame. In bus barembodiments, the window frame may be of non-conductive material, such as plastic or ceramic. while the screen is conductive. e.g., conductive plastic, metal, graphite, metal i...prt yndled graphitepaper. orthelike. Bytheterm l,.ic.uac.~n, wemeananysheet-like construction which permits distributed flow ll ,e~ ~tl " uugh of a gas, such as a pe, ~u, dled, drilled, woven or non-woven sheet material having very small holes or p~CC~g,oc 1 hdl~lhl uugh.
The fluid ",a-.dge..-ent core assembly (FMCA) colllplia~:, a plurality of thin plates, p-~i~ ~dLly of non-conductiveplastic,ceramicorothersuitablematerialintowhichnumerousintriCatelnicluyluuvefluid distribution cl ,a. Incla have been fommed, preferably by compression molding but also by injection molding, laser ablation or cutting, embossing, solvent etching. pressing, sld. ,.F ,g or other pressure p, oceases that create through-and-partial-depth features. Adjacent plates, each having coo- ,Ji- ~ale partial depth features (e.g., half-cl .a. .nel~i), upon bonding provide gas, coolant and vapor distribution channels, typically round or oval in cross section which, by virtue of their continuous, sinusoidal and b- dnLI 1' Iy configurations are ~ ollldl~ .c illlpc~- ' ' to constnuct. Platelet fluid ",anage",ent circuits are constructed from depth and through features. Combi"alions of these features are used to create flow fields, close-outs. man ' ~ '~
vias, via bases, clldllllcl~, filter elements. metering orifices, mixers, splitters. diverters, lands, islands, NACA ports and Coanda-effect fluid control circuits. The p, _~ d material of the FMCA is plastic, hence the ~ nce herein to plastic platelet fuel cells. These plastic FMCA and MSP window frame pl~t~letc or SllBs~ HFFT l~ R~

W 096137005 PCTrUS96/06877 assemblies also may be constructed by laser photolithography, in which a laser beam impinges on a monomer or prepolymerto photopoiymerize the monomer to a hard stnucture. Iayer-by-layet i"~ " ,entally.
This teL;I " ~ ,~e can be used for individual p'~t~l~ts or to build the entire FMCA so that individual platelet bonding is not required, but the mi-.,uyluu~es and cl,annel~ are constructeci internal to the FMCA in the process.
When two uni-polar sepa dlu,a are assembled with an EMA II,~bel~Neen it co",p,iaes an 01~l.ucl.emical cell. An array of aligned cells. when secured together by bonding or clamping, and oplion 'ly including sealing gaskets between cells. cc"-,p~isea a fuel cell stack, a finished fuel cell.
In typical examples, the number of platelets to fomm an individual Cell Polar sep~ dLùr s~ ss~ bly of the overall fuel cell stack may range from 3-10 plates, and pl~dbl;~ 4 7. EMAs are ~ uos~ b~
aLijdcent polar sepa dlu~:" and p-~f~.dl ly are inserted in anode and cathode ,ecesses therein. rhe presently prdre,, ~d EMA comprises a 2-17 mil thick perflournsl 'fondled membrane coated on both sides with a mixture of microfine Pt-black and carbon black in a solvent, and overlain on each side with a 10 mil thick 65% open graphite paper having a Teflon hyd- ophobic binder therein.
The IFMT fuel cell p,;" ~ 13~ of this invention will be des-,,iLed herein, by way of ~,~d-"ple only, in r~rdl~ce to a bipolar hydrogen/air or oxygen fuel cell employing a Pt-black/NAFlON EMA, ope, dLil ,9 in the l~"pe,dt-Jre range of from 70-115C.
An important feature of the plastic platelet design of this invention is that 5iyl ,if,c~ IL improvements are made in thermal "-a..ay~"~l and in hul~l- ~- ~ " ~ of the gases and electrolyte ",~--,b,dnes to very siyl .ifi~;d"lly improve the power output of the platelet fommed fuel cell of this invention as co" ".~ ~ to the prior art. In a p, ~,f~., ~ ~, Ibod~. "enl, the surface conduction tcurrent .. - " ~ ' ) platelets are constructed of metal, typically aluminum, copper, ! ' ' I' 9 steel. niobium or titanium, and the fluid " ,~ ,ayt:",ent core platelets are constructed of plastic, typically filled or unfilled plastic such as: polyc~ Londle, polyamide, polystyrene, polyplefin, PVC, nylon, or copolymers, terpolymers, or the like, thereof. The metal r' ~-provide surface conductivity leading to edge conducting current bridges or through-conducting bus bars.
The metal surface platelets surround or sandwich the plastic core fluid m dl ,as~" ,ent ~' ~ " The metal current ~c~'~ 'c - platelets can be evated or treated, e.g., by nitriding, for co"uaiun ,eaisld"ue, after, but pl~:~d,~y before assembly into the BSPs.
After the platelets are formed, they are then IdlllilldLiùn bonded tc,rJr,ll,e~ by any suitable combinationofadl,es;Jc,heatand/orpressuretofomlapolarsepd dLors~ cc~,-bly. TheEMAsarethen insetintooptionalspecialmembrane~ c~windowframed~p~essiu"s~inthese~3d~dlu~ plates,forming individual ele~.~, uel ,~, . ,icc,l cells, and a plurality of the cells are stacked to form fuel cell stacks. The entire stack assembly is then bound under compression to promote sealing. e.g., by through tie rods, nuts and cor,sLd--L culllplt:àsion devices, to form a unitary monolithic fuel cell sl.ack, with gaskets as required.
A wide variety of solid but porous polymeric proton excbd, lcJe membranes may be employed, typically s~ lf~ naLed fluorocarbon membranes from Dow Chemical, Asahi Chemical, Gore or DuPont, with duPont's NAFION being presently p-t~ --e~. The membrane is coated on both sides with a noble metal catalyst such as Pd, Pt, Rh, Ru, noble metal oxides or mixtures thereof. A ,u- .,~Ç~. I ~ membrane of this type is available from H Power Corp of '' ~ ;. t" New Jersey. Other types of EMAs that can be used include SUBSTITUTE SHEET (RULE 26) W 096/37005 PCTrUS96/06877 porous thin sheets of carbon or graphite, or catalyst-coated polyimidazole membranes.
While a specific membrane type and manufacturer may provide some improvement in p~ ru, 1, Idl ,ce, the invention is not dependent on any one type of membrane or EMA. The i, lleyl dled fluid management leclmoloyy (IFMT), plastic platelet approach of this invention is ~rt~hle to a wide variety of fuel cell types, and improved pe, ~UI l l ldl ,ce will result therefrom .
The plastic platelet technique pemmits fomming a wide variety of ",i~-ucl,a..nel designs for any exterior configuration of the fuel cell. yet with ~,~ " IL themmal eAC hdl ~ye and humidity control for more efficient distribution of the gases with no fuel or oxygen starvation and better steady-state r;lecl, ical output.
An important advantage in the IFM plastic platelet lech,)ology of this invention is that the manufacture of the fuel cells can be aulull-dl~d. and emptoys high rate ph_'L' loy,duh;c, etchlng, p,~si"g, elllbossi~g or sld,, ,9 lecl-nuloyy to ~dLIlicale platelets from thin metal and plastic sheets, typically4to40milsthick. C.,,bossi,.g,comp-t~siùnmolding.injectionmolding,ornumericallycùnl..'' milling is plt r~ IdLJly used to rdLIicdle the plastic (FMCA) core p~t~9t~
A siynir,c~" industrial apF'- " ty and lech" - ' advantage arises from the fact that the IFM
platelet lechncjloyy pemmits rapid changes to be made in the sepdldLor ~ s~ bly design using phol 'i ,og,d~b lecl", ~PS bothwithrespecttoPlasticandmetalp~-te'~ Asinglefactorycansupport a wide range of fuel cell designs without the need for high output c", ~dlily recJuired for production econo",y. That is, fewer fuel cells of widely different design can be produced and still be econG" - '~
feasible. In addition, the capital invesl",~nl is sub~la, ' lly and s;y" ~lly reduced as the production eql i",e"l is close to off-the-shelf ph3~c' ,oy,dphic, masking, and etching or sldl"p;.,g ec~uipment.
By way of exam ple of the ph ~c ' ' hoy, d~hlc u printingU process, the multiple sheets of a se~.d, ~
can be accurately yl dp~ 'y desiy"ed in large fommat, pholoyl d,ul~ ~ 'Iy reduced, and the plates ~ "ped, embossed or co",p,t:ssion molded out of continuous rolls of metal, plastic or conductive plastic sheet material. Altematively, and in the present best mode, the current c ~ "r. metal sheets are ph-- "'hoy,d~ 'lymasked with resist. etched to fomm the fluid Illa lag~l,entmicro-grooves~ the photo-resist mask layer cl ~", i~ - ~'y or physically removed, and the platelets cleaned. Plastic core (FMC) p~:~t~let~
are formed from sheets of plastic stock by compression molding. Alternatively plastic core pl~3t~4t~ can beformedusingrollerembossing,injectionmoldingor~ldlllr ,9. Preferablythetoolingfortheembossing or comp,~asiun molding can be ph ~ loyldpl 'Iy etched in metal as described above with negative instead of positive masks, or vice versa.
The finished platelets are then assembled to fomm the sepdldlul-~i, placed in a lamination bonding oven having a pressure ram and ld~ dled together under a specific schedule of heat and pressure to form a monolithic composite sepdldlul plate s~h~sPmbly having conductive surface features and intricate intemal plastic FMC mic, ucl)annela~ including channel~ at different levels o, ll ,ogonal to each other, through which the various gases and water or other coolant flow. Lamination bond aids such as adhesives, solvents or glues may be applied to the surfaces of the plastic and metal platelets to facilitate bonding and sealing. The specific choice of metal and core plastic dictates the particular choice of bond aids used, if any.
The metallic surface.platelets may be treated with specific chemicals to fomm a passivating or SUBSTITUTE SHEET (RULE 26~

W 096/37005 PCTrUS96106877 anLiccl I usiveand conductive layer. In the preferred embodiment, titanium micl osw ~, platelets are placed in a nitrogen atmosphereat elevated temperature which resuits in the reaction of nitrogen with the titanium to fomm a passivating or an anti-corrosive and conductive titanium nitride layer on all ~Yposed surfaces, including the interior gas and water cl~annels.
Platelet polar sepd,dlo, design and production can be done on a continuous production line, ~, 'c ,- ,c to a PC-boara manufacturing iine. The EMAs are then inserted between individual BSPs, the cells then stacked, and exterior end plates added to form the completed fuel cell stack which is held together under pressure by tie rods, and nuts, or other co, Isldl IL compression devices, to effect reactant-tight sealing. Electrical leads, reactant gases and coolant water are hooked-up, gas and/or fluid fuels introduced, and the cells brought on line.
In a typical 4-platelet IFMT bipolar sep~alo- c~ Ib~ hly of this invention, there are 4 different plates, with plates 1 and 4 being joined by a current bridge, and each of plates 2-3 being different. The platelets in sequence are:
1. Anode metal . . .ic. us~,- ~n platelet (to provide current conduction from the EMA);

2. Anode plastic flow field platelet (to provide anode flow field distribution, anocle reactant humi~liri~ inn and cathode water circulation);

3 . Cathode plastic flow field platelet (to provide sepa ~lo. /cell thermal ~ - ~anage. . ,e, .l, cathode flow field distribution, cathode reactant hu,..;d r~ n,- and anode watercirculation; and 4. Cathode metal ...ic.osc.~en platelet (to provide current conduction to the EMA);
Intheedgeconductionembo~;,..entthetwo,--ic,uac-~en -"~ plateletsarejoinedbyatleastoneedge current bridge to effect electron flow from anode to cathode.
The current carrying capacity of the current bridge may be augmented by one or more current tabs that are folded over and ela ;l- lly bonded to effect elect, ical conduction thorough the sep~ alor.
In the bus bar embodiment, the two ...icrc,s...~en ~ ,t~ platelets are joined by at least one bus bar, preferabiy two, passing transversely t~rough the FMC separator to effect electron flow from anode to cathode. There is at least one, p- ~le, dLly two, bus bars that are elecl, 'ly bonded to the anode and cathode ll~iCIu5CIwn platelets and occupy positions with in the plastic core platelets to effect ele~l.icdl conduction thorough the separator.
The details of platelet fommation, described herein by way of example, are shown to evidence that there is no Illil..lUI~:IIdllllt:l collapse or in-fill during the cell Id..-inalion bonding process.
In the two bipolar St:~dldlul examples above, plates 1 and 4 are each about 12 mils thick and plates 2 and 3 are each about 35 and 45 mils thick respectively. Upon lamination bonding the plates compress somewhat, and the total ll lichl ,ess of the resulting monolithic: bipolar sepd, dtur laminate is about 1 00 mils.
For embodiments incorporating a wrndow frame de~ sion to receive the EMA, the anode and cathode recess depths are on the order 11 mils deeP to accommodate 11 mil thick EMA graphite paper el~l,udes. The total EMA tl k..ess is on the order of 26 - 30 mils thick depending upon the choice of graphite paper elecL-udes, catalyst ink and membrane II.;~.h.less and is somewhat compliant. The SUBSTITUTE SHEET (RULB 26) W 096/37005 PCTrUS96/06877 p~ d DuPont NAFION mem~rane coated on ~oth sides with the microdispersed Pt-black catalyst in carbon bic-Ck~ is on the order of 4-5 mils thick and each of the outer graphite/teflon paper layers is about 11 mils thick. The graphite paper is on the order of 65% open to provide good and uniform reactant gas distribution. On the anode side the graphite paper conducts el~-l~ un5 away from the catalytic reaction sites on the electrolyte membrane to the lands of the separator plate for draw-off as fuel cell el~il,ical output. Electrons return from the extemal circuit via the cathode. On the cathode side graphite paper conducts elecl,uns from the lands of the sepdldlor plate to the catalytic reaction sites on the el~l,ulyte mem~rane.
The fuel cell multiple bipolar sepdl dtOr stack must be temminated at each end with an anode and a cathode unipolar sepd-dlo~ terrninal end plate which also serves as the terminal current cc"e ~ " ~. For the unipolar anode sepdldlol we use: an anode ,.,iL;,usc,~n (platelet 1); an anode flow field plate~et (platelet 2); and a one-sided cathode platelet. i.e. the cooling circuits of the cathode flow field platelet (platelet 3) with the cathode flow field circuits closed out. For the unipolar cathode s~pa,dlu- we use: a one sided platelet i.e.. the anode flow field platelet (platelet 2) with the anode flow field closed out; a cathode flow field platelet (platelet 3); and a cathode ..,i~;.us.i.~ an platelet (platelet 4). In both the edge conduction and bus ~ar through-conduction embodi,--anl~ the temminal end plates conduct ele_l.i,;al power to the extemal load. Both embodi(,-arls may use terminal end plates of similar design and construction.
As an altemative example where no reactant gas hurr~;di~c~ n is required a 4-platelet bipolar sepd,dlu, assembly may be employed and the sequence of platelets is as follows:
Anode metal mic-,u:,c,~n platelet (to provide current conduction from the EMA);
2 Anode plastic flow field platelet (to provide anode flow field distribution and cathode water circulation);
3 Cathodeplasticflowfieldplatelet(toProvideSePd,dlu,/cellthemmal,,,d,,ag~,,,anL
cathode flow field distribution and anode water circulation; and 4 Cathode metal mic,osc,~" platelet (to provide current conduction to the EMA);
As with the two previous 4-platelet ,. ,s current conduction is accomplished using the edge conduction or bus bar conduction me~;hanh",s previously desc, il.ed.
The assembled sep~ alOI (multi-platelet sub-assembly) is on the order of 100 mils l h hl ,ess and weighs around 3-6 oz (85-170 grams) depending on the number and thickness of plates and materials.
Ap,~lu~illla~!y 10 sepdldlul~kw are used in a cell stack. Completed bipolar sefidldlul plates are assem bled with alle" Idlil ,9 EMAs on tie rods to effect alignment and com pression. After assembly on the tie rods, comp,~ssiun endyldleS on the order of 1.5 inches thick are applied and the entire fuel cell stack assembly is placed under compression of 50-200 psi by threaded tie rods to fomm the monolithic fuel cell stack. The cell operating pressure of 1-65 psi is easily achievable with output at around 70-150 amps at a voltage detemmined by the number of cells. To seal adjdce"l sepa dur sub-assemblies an inl~l lockil lg sealing ridge (which is generally triangular in cross section) on the order of 1-2 mils in height is etched pressed or molded onto the sealing surface (outside surface) surrounding IlldnifGl.ls and flow so that the ridge will fully interlock with the mating seal ridge of the adjac~,L se~d~dlu, sub-assembly or with the SUBSTITUTE SHEET (RULE 26) W 096/37005 PCTrUS96/06877 app.uprid1e temminal endplate. as the case may ,~e.
The fuel cells of the IFMT platelet design of this invention can include a refomler section to provide H2 e.g., via the steam-shift process employing an unde, w~idi~ d bumer plus steam to produce H2. ~2 and C02. Any other hypocarbon refommer may be employed in combination with the IF,MT platelet cells of this invention.
A key feature of the platelets of this invention is the use in CUII t ~ ~dliUn of gas and water distribution cl~dl)l.el~ fommed in co"~ o"di"g aligned half chdlll.cl~ in each of a pair of coo,di Id1e opposec~ mating plate faces (i.e. mating faces of acljace, 11 plates that face each other and contact each other in the stack) and similarly formed delivery 1"~ - Optional but ,sl~r~ d are formed sealing rir ges on the periphery of the plates to assist in sealing adjacent ceil ass-"
Critical to efficient high-output operation of PEM cells is proper thermal balance arld hydration, and controlthereofbyunifommgasflow. CurrentPEMfuelcellsexhibitp,l ,sofpoorthemmal",~.age,..e.~l and water balance low graphite conductivity and ductility limited - : y and excessive reactant Proper themmal ",~,ag~",e,l1 in PEM cells is critical. The p-~-~l membranes have a maximum op~ dling lt:" ".~ dlure in the range of 9~98 C. since temperatures above that permanently ruin the membrane by dd ll _ ,9 the ionophoric pore stnucture. Since the IFMT plastic platelet fuel cells of this invention have heat ~ ,~,;h~ ,ge,- sections i, ll~ yl dl~ d in each bipolar sepd, ~llor as co,~ Ipdl ~I to one bet~veen every 4-5 se~pd~ dlOI a in graphite PEM cells our stacks can be scaled easily to larger sizes since both the heat g~ ,e,dliun and control (heat t:AC hcu)ge) scalewith area. Since we can easily tailor heat control to each type of m~:- "~, dl ,e and fuel, and the intra-cell location within the stack we can ernploy higher p~ ~u, " ,ance EMAs resulting in higher power de"siti~s.
In regard to water balance the il lley- dl~d hul l ~ ;on in eacll sep~ dLu, maintains better water balance as each is individually varied to acco" " "o~l~le the different req- i ~" ,e"Ls of the anode and cathode sides of the fuel cell. Water is removed from the anode side by electro-osmotic pumping through the membrane and reactant gas flow drying. Water builds up on the cathode side from the throughput of the electro-osmotic pumping and production o~ reaction water which are both removed by airt ~2 gas flow drying.
In contrast to graphite PEM cells the composite metaVplastic IFMT sepdldlùl~ of this invention are some 3~ times more conductive thus reducing the 12R losses in the stack under high current de"sities.
These losses reduce voltage and power o~: ,dL,le from the stack. The lower intemal ~is1d"ce of the composite sepdJ dlUI a provides a more even distribution of current thus reducing the build-up of hot spots and dead spots in the cells. Graphite sepdld1ula are placed under compression to effect sealing, but pressure affects the . ~:~i;,1ance of graphite in a non-linear fashion. This cl ,~ d~ l islic makes it very difficult to produce graphite cells with unifomn output. In contrast composite separators have excelle. ,L themlal and clc~1, ical conductivity which reduces hot and dead spots.
Graphite is porous to H2. ~2 and a~ which reduces the ch~.llicdl efficiency of graphite stacks because some H2 is consumed in non-productive. sometimes destructive direct oxidation. To overcome the porosity of yl dpl, ~ . nonconl uctive plastic binders are used which further dec, ~ases the conductivity of the sep~1ù, plates. t~nother commonly used a,up~uach to reducing graphite plate permeation is to W~;nTUI~ SHEr ~E 2~) W 096137005 PCTrUS96/06877 make the plates thicker but this adversely affects electrical and the. .,îal conductivity.
Graphite se~dldlula also crack when the cell is subjected to comp,~asion to effect the sealing necessary to prevent gases leakage. as the cells operate at 1-60 psig. The tende",.-y to crack severely limits the number and size of the cells in the stack. Where one or more sepd,dlo.s on the interior of the ~ stack develops leaks the t:le~ al output is co,.,~,u",ised or siu,l;"ca"lly reduced. Composite metaVplastic p'~t~le~c being ductile do not present these problems.
Further it is an important advantage of the invention that the IFM technoloyy of the invention permits variation of intra-stack platelet design to effect better themmal management. That is the cells in the middle of an uncooled stack do not have the same themmal env;- u~ ~n ~dnl, and aCc~- di~ Iyly not the same hurn;cl;r~ n rec;uirements of cells at or nearer the ends of the stack. The platelet design, in temms of relativeanode~cathode~coolantandhlJlllid;ricA~ lllicluLllanneldesigncanbeeasilych~lgedandintra-stack position defined to accG----.-odate the various yl_ ~la within the stack. i ~k ..;~c stacks can be desiyned to suit a wide variety of extemal conditiùns an arctic design differing from a troplcal and a subsea differing from a space design.
This advantage of flexibility of design--the c~p ' y to tailor the configuration and path lengths and channel widths of mic-, u. l Idl 11 ICI:~ in each zone of the Sepdl dlUr (anode cathode heat e.~cl ,al ,ge and hu..,i~l;fin~lio,,)andfromsep~dlù~ tosepdldlol (celltocell)p,uyressivelyand individuallywithinthestack to acco,-,..,odate the intra stack env;-u-"--elll and y,dd;cnla--results in ease of scaling to higher power outputs e.g., on the order of greater than 50-1 OOkw.
The series/parallel serpentine channel design provides more unifomm distribution of the reactant gases. Thisisparticularlyi".po.ld,.linprovidings;y.,;'i--dnllybettercathodepe,ru,---~,-cewhenoperating with Air due to ~e~ ~f ~2 as the air travels through the clldllll_ls. In current channel design, air enters ~2 rich and leaves ~2 cl~ . since the ~2 is consumed in the cl~cl-uche--,ical reaction. The same f~Apletion effect is true of H2 resulting in i"..,t:asi"g conce"l,dlions of impurities relative to H2. In our invention the shorter series of cl Idl InC13 11 ,an;rc Ided in parallel and the ability to design and r~des;y"
Ch~)~ ,el ~ of varying configurations or graduated width improves cathode kinetics a currently dc,l l ,i. ,~ ll limitation of current fuel cells. In our invention the flow is divided into a series of parallel circuits in which the precise pressure drops can be obla;. ,ed. By i". ~t:as;"g the number of parallel circuits the pressure drop can be lowered as the flow rate is reduced and the channel side wall r, i~lional effects are reduced due to shorter path length.
While the currently p,t:rt~ d best mode of the invention employs window frame pl~teletc with EMAs of carbon paper over the catalyst/carbon-black coated membrane to provide a highly porous sheet having random gas distribution cl-ann l, there throughl an important altemative embodiment of the invention employs a carbon-paper-less membrane wherein microfine holes are etched through the ~window pane area of the window frame to effect the same gas distribution function. In producing the window frame plateletl the window pane area is defined in the apprup, iale medial areas of the plate that is located interiorly of the outer plate edges. (Lines defining the pane area may be through-fomled except for a few thin bridges holding the window pane section in place during platelet rdL,ricalion. The bridges are later cut and the pane removed or let fall out to complete the window frame platelet.) The open areas W 096/37005 PCTI~ ,'OCY77 receive the carbon fiber paper upon compression of the full sheet membrane between adjacent rll~tF~l~tC.
In the altemate embodiment, instead of removing the window pane area material, a "window screen" area is created in the window pane area by micro-fine through fomming, the holes being on the order of 5000-1 0,000/sq. inch. Then carbon paperless membrane is co" ,p, essed between the adjacent sepd, alOt plates.
Objects and A~l.d,.la~a. It is among the objects and advantages of this invention to provide an improved fuel cell design and methods of constnuction and operation, particularly plastic platelet fuel cells of the hydrogen an~ oxygen or air tyPe designed with IFM features which show 3X or better improvement in cost and pe, ru",.a"ce over currently available graphite cells.
The improved fuel cell stacks of the invention have the advantage of employing plastic platelet s~paldlula, which platelets have specially configured gas and water distribution mic.u(.hdnncls created by COlllpl ~aaion molding, injection molding, t:lllbossil ,g, etching, laser ablation or cutting, or aldl llp 19.
It is another object to provide improved cc""posiLe bipolar and unipolar sepdla~ul plates and methods of constnuction having the advantage of construction from plastic fluid l.,dn~r",ent platelets which are e,)closed by conductive rlli-,luScl~ll current sol'-~ tL - platelets of metal or conductive plastic.
Another advantage of the IFM plastic platelets of this invention is that bipolar and unipolar sepd dLo, plates constructed therefrom exhibit improved current c~ by use of one or more edge-conductive current bridges and/or through-conductive metal bus bars.
It is another object to provide an i, lleyl aLed process for manufacture of fuel cells via a plurality of stackedse~c,a,dLu, plateassemblies,co",p-iai-,y. ph:' ' ,oy,a~.hyofaseriesofindividualmetalliccurrent , p'-te~ets followed by feature fomming thereof by etching ~cl-e",ical milling), pounding or s~ r ,9. and oplior 'Iy coating the metal current ~-"'L platelets with an ~ILiUAid~lL, fcllc~ by co,-,,u,~ :s ion molding, etching, stamping, or injection molding of core plastic fluid ",andy~".ent r~ -~PIetC
and Ll ,e, edtLer assembly of the metal and plastic platelets into sepa, dLor stacks; and then low temperature la",i"aLio,) bonding of the co",posiLt:unipolar or bipolar sepa,dlol platelet stacks under heat and pressure schedules with the advantages of low cost, ease of manufacture, and rapid design change to suit power demand needs.
It is another advantage of the invention to apply i"Ley,al~d fluid management (IFM) to fuel cell stack design, particularly to the design of plastic, conductive plastic, plastic and metal and cu",posite platelets assembled into unipolar or bipolar sepdldlul~ (individual cells), and plural cells into stacks, to improve fuel and oxidant gas hu" ,i. l~r,~ " and distribution for contact with the membranes, and for heat and humidity control to prevent hot spots and membrane deg,adalion due to dehydration.
It is another object and advantage to provide !~hC ' ,oy, ~pl~;c~lly and Lh~:l 1 l ' 'Iy milled tooling for comp, ~sion or iniection molding of plastic platelets employing IFM pri"c;~.les. It is another advantage that the IFM designs of plastic platelets of the invention can be rapidly produced by any suitable sheet plastic p,ucessi"9 technique, including injection molding, stamping, solvent or plasma etching, and laser pl- _: ' ,ography in a suitable monomer or prepo~ymer bath. It is another object to provide com p, essiu, -or injection molded plastic platelets for fuel cell separator assemblies having special sealing ridges which have the advantage of pe- " lillil ,9 good sealing of EMAs between polar sep~ alul ~ to fomm cells which are then secured under co",p.~:,SiO,l to fomm fuel cell stacks.

W 096~3700S PCT~US96/06877 It is another advantage of the invention that IFM clesign principles permit rapid design redesign or ,-,oA-~c~l;on of platelet polar sepdldlula which include i"ley,dled reactant humid;ri~ n thermal ,and~e",ent, and reactant flow and distribution control within a polar sepa,dlu, formed of a plurality of plastic composite or conductive plastic platelets bonded into a monolithic unitary stnucture. It is another object of the invention to provide variable IFM platelet polar se~d, dlor design within a fuel cell stack with the advantage that use of a plurality of different platelet and polar 5~dlul designs within a stack can acco",l~mûdate the differing thermal envi,o""~enl and humi~lir~ n recluirements that are intra-stack position dependent. Still other objects and advantages will be evident from the desc, i~tion drawings and claims of the invention.

BRIEF DESC~lr I l~t~ OF DRAWINGS:
The invention will be des-;,iL,ed in more detail by r~fe.~"ce to the drawings grouped by suL,~ ~ ,gs i.l~:nliried below.
General Fuel Cell, Sepd-alu-;- and Plat~let~.
Fig. 1 is a sche~"alic section view through a fuel cell stack employing plastic/conductive IFM
plateletbipolarsepa,dlu,aembodyingtheprinciplesofthisinventionparticularlyadaptedforoperationwith H2 and Air/02;
Figs. 2A and 2B are schematic section views through a cooled, non-humidified (Fig. 2A) and a humidified (Fig. 2B) and cooled fuel cell IFMT platelet sepdldh)l of this invention showing the wide variation pss- '~ in number of platelets used;
Fig. 3 is a sch~",dlic cross section detailing elecl.ude membrane dss~",bl;~ constnuction with a part r~;r 'c de 5 away;
Fig. 4A is a schematic of the fluid circuits for an illl~yldl~d humidity and thermal ",d"age",ent bipolar St:~dldlOI of this invention;
Flg. 4B is a schematic of the fluid circuits for an i"t~, dled thermai " ,~u ,age, ~ ,ent bipolar se~ dlO
of this invention;
Fig. 5 is a s.~ " ,alic drawing of the ele~ll uLl~emBll y of a PEM i~ lleyl dled humidity and thermal ."d"agt:",ent fuel cell of this invention;
Figs. 6A and 6B are diagrams cullLld~til,g single level depth and through features formed by chemical etching of metal (Fig. 6A) with multilevel depth and through features fommed by CGIllplt:55h~n or injection molding of plastic (Fig. 6B);
Fig. 7 shows a plan view of a metal conductive plastic or m ~ - ~ plastic current ~ having first (upper) cathode section joined by an edge conductive current bridge (lower section) in which the screen apertures are slots;
- Figs. 8A-D depict typical but not exhaustive hole patterns for metal current . ~ ~ 1 l liC-I uSCi ~n Fig. 8A being hexagons Fig. 8B et~i, sqids Fig. 8C dlltllldlillg inverted Ts and Fig. 8D
~ alt~., Idlil ,g inverted interleaved chevrons;
Edge Conductlon Blpolar Sepd~alor Plate:
Fig. 9 is an ~Yp'oded iso",el, ic view of 2-cell sub-assembly for a fuel cell stack made from edge SUIlSrl~UlE S~ ~LE26) W 096/37005 PCTrUS96/06877 conduction bipolar se~a, dLul ~, with window frame and with i~ gl dlecl humidity, therrnal and reactant flow field ll,a.lage---ent of the invention in Figs. 10 and Figs. 11A-G;
Fig. 10 is an ~ lo~l~d isu,~ . view of one t:---bodL..ent of a 4-platelet CGIllpOSile edge conduction bipolar sep~ dlor with window frame and il It~gl dl~d humidity, thermal and reactant flow field management for an IFMT fuel cell sep~dl~" of this invention;
Figs. 11 A-G are a series of detailed plan views of the em bodiment of a 4-platelet edge conduction sepdldLur of Fig. 10 in which: Figs. 11A-C depict a double ~"i-,,usc,~" platelet with the front side of the anode mi~;-ua-,reen at bottom and back side of the cathode ll,i.;loscl~en platelet at top (,~ t~ ,ta 1 and 4), cu, ,n~led by a single bridge.
Fig. 11 A is a front view of a single current bridge double mic- usc- ~n platelet with window frame an inset detail depicts one e-..bodi,..~-~ of a typical ,-.ic-u~c;-~- hole pattern;
Fig. 11B shows the double mic.u~c-~n platelet of Fig. 1lA and coll~spondi.l~J section views;
Fig. 11 C shows a double mic. usc- ~:, . platelet without window frame and corresponding section views;
Figs. 11 D and 11 E are front and back sides, respectively, of the plastic anode flow field platelet (platelet 2);
Figs. 11 F and 11 G are front and back sides, respectively, of the plastic cathode flow field platelet (platelet 3);
Fig. 12 is an t., 1~ iaOI I leLI ic view of 2-cell sub-assembly for a fuel cell stack made from edge conduction bipolar sepdldlola, with window frame and with illl~ldl~ themmal and reactant flow field ,ana~,l,ent of the invention in Figs. 14A-G;
Fig. 13 is an exploded isometric view of one embodiment of a 4-platelet composite edge conduction bipolar sep~dlc~l with window frame and illleyldl~d thermal management and reactant flow field l"anage",ent for an IFMT fuel cell sepdldlol of this invention;
Figs. 1 4A-G are a series of detailed plan views of the embodiment of a 4-platelet edge conduction sepdldlul of Fig. 13 in which:
Figs. 14A-C depict a double miclusc;l~en platelet with the front side of the anode Illicr~.acr~en at bottom and back side of the cathode mic. ua-,-~n platelets at bottom (platelets 1 and 4) COI Inecl~ by a single current bridge; an inset detail depicts one embodiment of a typical mi-;lusc-lt en hole pattern;
Fig. 1 4A is a front view of a single current bridge double ~ - -i~,- us.il ~, . platelet with window frame;
Fig. 14B shows the double ~ ;lua~;l~l I platelet of Fig. 14A and corresponding section views:
Fig. 1 4C shows a double ,. Ii~;r~scl e~n platelet without window frame and co" t:sponclil 19 section views;
Figs. 14D and 14E are front and back sides, respectively, of the plastic anode flow field platelet (platelet 2):
Figs. 1 4F and 1 4G are front and back sides, respectively. of the plastic cathode flow field platelet (platelet 3);
Fig. 15 is a detailed plan view of a micloscl~en platelet having multiple current bridges and/or tabs;

W 096137005 PCT~US96/06877 Fig. 16 is an ~Y~ de~ i~o"~ ic view of one em~odiment of a 4-platelet composite edge conduction bipolar sepd,dlu, with window frame having four edge conduction current bridges and featuring h lleg- dled humidity themmal " lal ~age~ ~ent and reactant flow field management for an IFMT fuel cell septD alur of this invention;
Bus Bar Through-Conduction Bipolar Sepd, dlo- Plate:
F~g. 17 is an PYrlocled isometric view of a 2-cell sub-assembly for a fuel cell stack made from bus bar through-conduction bipolar sepd, dlol ~ with window frame and with i"ley, aled thermal and reactant flow field ",d"agt:",ent of the invention in Figs. 19A-G;
Fig. 18 is an ~Yr'~ded isometric view of one embodiment of a 4-platelet composite bus bar through-conduction bipolar sepd,du, with illleyldled humidity thermal and reactant flow field .na. !ag~..,e, ll for an IFMT fuel cell of this invention;
Figs. 1 9A-G are a series of detailed plan views of the embodiment of a 4-platelet bus bar through-conduction sepdldlu, of Fig. 18 in which:
Fig. 1 9A depicts the anode (left side) and cathode (right) current ~ c mk ~ o~c, ~en platelets (plat~ lel i 1 and 4) in the lower right;
Fig. 19B is a plan view of the anode flow field platelet (platelet 2) and fragmentary portion of the anode current ~ n ~-,ic-u:.c.~n (platelet 1) oriented thereon;
Figs. 19C and 19D are front and back sides of the plastic anode flow field platelet (platelet 2);
Figs. 19E and 19F are front and back sides of the plastic cathode flow field platelet (platelet 3);
Fig. 19G is a plan view of the cathode flow field platelet (platelet 3) and a fragmentary portion of the cathode current ~ ~--ic.osc~een (platelet 4);
Fig. 20 is a e-~,'oded isometric view of a 2-cell sub-assembly for a fuel cell stack made from bus bar through-conduction bipolar sepd, dlUI ::., with i, ll~yl dLt d thermal and reactant flow field, nd, lagel 1 ,ent of the invention in Figs. 22A-22G;
Fig. 21 is an ~Yp~ ed isometric view of one embodiment of a 4-platelet composite bus bar through-conduction bipolar sepdld~cl with i, lleyl dlacl thermal and reactant flow field ",dndye",ent for an IFMT fuel cell of this invention;
Figs.22A-Garedetailed planviewsoftheembodimentofa4-plateletbusbarthrough-conduction sepa dlU~ of Fig. 21. in which:
Flg. 22A depicts both the identical anode and cathode current 2C"~ mic,us~-~n F
e~ 1 and 4);
Fig. 22B is a plan view of the anode flow field platelet (platelet 2) and a fragmentary portion of the anocie current 2-'1~ 1 ,,,ic.usc.~n (platelet 1);
Figs. ~c and 22D are front (22C) and back (22D) sides of the plastic anode flow field platelet - (platelet 2);
Figs. 22E and 22F are front and bacic sides of the plastic cathode flow field platelet (platelet 3);
~ Fig. 22G is a plan view of the cathode flow field platelet (platelet 3) and a fragmentary portion of the cathode current ''C'~L ' ~ mic,us~,~n (platelet 4);

SUBSTI~UIE S~EJ ~RULE ~6) W 096/37005 PCTrUS96/06877 Edge and Through-Conductlon Section Views:
Figs. 23A-23D show various altemative constructions of the metal mic,usc,~ ~"e ~ ~ plates al 1 dl ,ged for edge conduction with respect to the core plastic platelets in the sepa, aLol plates of the type of Fig. 16 taken along line 23-23 therein;
Figs. 24A and 248 show t~,vo altemative constnuctions of the through-conduction bus bars for the sep~aIu, p~ate assembly of the type of Fig. 18 taken along the line 24-24 therein;
Platelet, BSP and Cell Fab,icaIlon P~ ~cess~s Fi~. 25 is a flow sheet of a continuous metal platelet manufacturing process in which features are formed by depth and through etching;
Fig. 26 is a flow sheet of a continuous plastic piatelet manufacturing process in which features are formed by co---p-~ss;un molding and cc,-..pc site bipolar sepm~lor plates are ~aiJIicaLed by lamination bu- '' )g F~g. 27 is a flow sheet of the process for adaptively rapid ~n~,aIion of the pi ' '--' al l~hork:, for individual platelet designs in accord with the IFMT principles of this invention.

BEST MODE OF CA~P.~ OUT THE INYENTION:
The ~ ,;..g detailed descli~ tion illustrates the invention by way of example not by way of I lilalion of the ,u- i, ~ ~ of the invention. This desc, iplic.n will clearly enable one skilled in the art to make and use the invention, and describes several embodi., lenl~;, a, ~r~ ol l~ a, ialions. altematives and uses of the invention including what we presently believe is the best mode of carrying out the invention.
Fig. 1 shows in simplified (scl~e,--alic) cross section a fuel cell stack 1 of this invention ~-,~' ,ri--g a plurality of multi-platelet bipolar s~pa,alo,:j 2A B C and a pair of cathode and anode unipolar end sepaldlul:,3 4respectively. Protonec~l~angeElectrodeMe"~b,a"eAsSemblieS(EMAs)5A B C andD
are ~ poc~ between the sepa,aIo,a as shown. Air and/or o2 is inlet via ~a~-irold system 6; H2 and/or other fuel is inlet via r~lal ,iroW 7; and cooling/hum~ fi~tion water is inlet at 8 and outlet at 9.
Figs. 2A and 2B show in schematic section view the construction of one embodiment of composite bipolar sep~ aIol :, 2 formed from bonded metal and plastic or ceramic platelets 12 for the non-humidified version of Fig. 2A and platelets 13 for the humidified version 15 of Flg. 2B. This figure also illustrates the wide variation in the number and types of plates that may be employed to constnuct a sepalalur by various COlllt' ~alions of depth etching (or feature forming) and through-etching (through feature fomming) of metal pl~tPlPt~ Plastic platelet features are fo~med by compression or injection molding. For example Fig. 2A shows a 4-platelet configuration as follows: 12-1 is the anode mi.., ~s~
current ~ ~ " - ~ 12-2 is an anode flow field platelet; 12-3 is the cathode flow field platelet; and 12-4 it the cathode",i~;,us"~current~ . Themetalanode",i-,usc,~enplatelet12-1 iseleul,i.allycol")e~;l~l to the conductive current bridge 14 which is ele( l,: 11y co~"1ecled to the cathode mic~u~c~wn current cc'l~ ' -12-4. The anode flow field platelet is constructed from plastic or ceramic and contains the features that implement the se"~enIi"e cl~a"nel~ of the anode active area flow field. The cathode flow field platelet is constnucted from plastic or ceramic and contains the features that illlpl~llelll the se,~e"li"e ~;l ,a, Inels of the cooling water heat ~ g~, and the cathode active area flow field.
--~ 4--W 096/37005 PCT~rS96/06877 Similarly Fig. 2B shows a 4-platelet configuration as follows: 13-1 is the anode mic,usc,~,l current cc '~ . 13-2 is an anode flow field platelet; 13-3 is the cathode flow field platelet; and 13-4 the cathode miL, O5L- ~en current s ~ . ~( . The metal anode mic~ usc, ~n platelet l 3-1 is elr~l, ically co,)nected to the conductive current bridge 14 which is cle_ll 'Iy co~,ecltd to the cathode ~"ic,usc,~n current - - - 13-4. The anode flow field platelet is constnucted from plastic or ceramic and co" ,s the features that implement the serpentine channels of the hydrogen hUl~ r~ on flow field. cathode ~ hurr~ ;ri.-~llion water flow field and anode active area flow field. The cathode fiow field platelet is constnucted from plastic or ceramic and contains the features that implement the serpentine chdl l, ~ Is of the cooling water heat e,-~.l ,ar,ge" anode water flow field. air hurr~id;f~ inn flow field. and the cathode active area flow field.
Fig. 3 is a partially a., - ~ - ~ view of the constnuction of an cl~l- ude membrane assembly ~EMA) H1 of the type used with this invention. EMA H1 coi,~,onds to the EMA 5 (5A-D) of Fig. 1. An EMA is constructed from a laminate of a graphite anode eleol,ode H3, anode catalyst layer H4 el~l,l,lytic membrane H2 cathode catalyst layer H6 and a graphite cathode electrode H~. In typical EMA
constnuction the elecil,udes, catalyst layers and electrolytic membrane are lamination bonded to fomm an ionically conductive composite structure.
EleCtrOdeSare~d~ljCaledfrOm 9raPhjtePaPer,TOraYTGP-HQ9OtYPjCallYbejn9USed. CGIIIPOS;~
platinum catalysts are dApO i~~~ on the cl~l,ude prior to Idlllilldlion bonding with the ele~llulytic membrane. Typical catalysts are mixtures of platinum black, carbon black and h~.lluphobh agents.
Car~on black Vulcan XC-72R is typically used to suspend the platinum black. Teflon is used to give the Gle_tl ude hy~, ophobic p, up~ lies. DuPont Teflon PTFE suspension TFE027 is a typical h~dl upho~h; agent used to treat el~l,udes. DuPont Nafion~ is the sldnddld electrolytic membrane used in PEM fuel cells.
Lamination bonding of the anode and cathode el~l, ode assemblies H8 and H7 (I ~n~oded away from H2) pe ;li~ely is '. ~ ~ by treating the Lle~l.udes with a 5% solution of Nafion~ polymer. Lamination bonding follows a p,~ele""ined schedule of temperature and pressure to effect a polymeric bond between the electrode assemblies H8 and H7 and the membrane H2.
Bipolar Sepd,alur Scllt:llldliw,.
Fig. 4A is a single cell fluid flow circuit schematic for il lleyl dled humidity and themmal l lla~ ~agt:",e"l IFM sepdldlola. The sL~ ",dlic is drawn down the center line D32 of the el~l,ucl,t:,.,ical cell. The ce, llel ,e passes down the center of the electrolytic membrane D2. The anode side of a sepd, dlul is on the left side la~eled Anode, and depicts the features found on the anode flow field platelet. The cathode side of a sepd-dlù, is l~ ~ on the right side. Iabeled Cathode, and depicts the features found on the cathodeflowfieldplatelet. Thescll~:lllali~clearlyshowstheillLeyldlionofsevenfluidmanagementdevices into a single bonded composite s~:pdldlur. The seven functions are the cathode hU"~ r~ on water serpentinechannelDlûflowfield~hydrogenhumkJi~ ollserpentinechannelDl8flowfield~anodeactive area serpentine channel D21 flow field, anode humidir;~ ;on water serpentine channel D14, cooling water s~",enli,le channel D6 heat ~,~cha,)ge" cathode humid~r~ o-1 serpentine channel D26 flow field and cathode active area se"Je, llil ,e channel D29 flow field. These functions are co, Inecled using a series of intemal manifolds. This mecl-d, ~I fluid and thermal i,,l~y,dliùn is a key element of this invention.

W O 96/37005 PCTrUS96/06877 Counter-flow humidific~tinn flow D1 through the electrolytic memorane D2 which is a key element of this invention is clearly derirtecl by the di~ ~iliundl arrows, t:pn:à~"li"g molecular water flow. Counter-flow humiri;r~ n is implemented using water on the anode side (referred to as cathode water) to humidify cathode air (oxygen). By analogy, water on the cathode side (re~erred to as anode water) is used to humidify anode hydrogen. In IFM fuel cells the electrolytic membrane performs a dual rolls as a hulllifl;f..~ n membrane and a solid electrolyte.
Theelectrolytic membrane D2 is ionically conductiveto hydrated protons. During nommal operation protons D3 fommed on the anode are electro-osmotically pumped across the membrane to the cathode.
Protons being pumped across the membrane carry one or more ~coci~t~ water m~-'e ' - causing anode dry-out during high power operation. Hul~ r~ ~linn of anode hydrogen ",;ligall:s this problem.
Hu".iJ:r~ n of cathode air is also required becauseair is only 20% oxygen and is 78% nitrogen.
Toco,,,~,~nsc.lefortheloweroxygencu,.,posilionofair,cathodeclldlll~ havelargercrosssectionsthan co, . espond;. ,9 pure oxygen designs. Larger cross sections are required to support higher flow rates while ", , , ~9 . ~afJ. ' ' pressure drops. High air flow rates tend to dry out the cathode which is I l l iliycll by cathode air h~ r~
Control of the amount of hum ' " - - n is achieved by varying the area ratio of anode active area to hydrogen humi~l;r;~ n area, and by COIIIl " 19 the ratio of cathode active area to air (oxygen) hull ''1L ~ area. Typical anode and cathode area ratios are 15% to 24% hur~ r~ n to active area.
Dry hydrogen gas enters the hydrogen inlet D16. flows through intemal Illdl ,ifold~ and feed circuits to the ano~de hull~;~lir~ lion s~ "li"e channel inlet D17, flows through the anode hUllli~J;rili~lio~l serpentine channel D18 picking up water vapor (beco",i"g hydrated). flows out the anode h~ ;cJir~ n se~ ~.enli"e channel exit D19, through intemal _ - " , and distribution " ,~ifol~s to the anode active area s~".e,-li"e channel inlets D20, passes through the anode active area serpentine cl ,am~el3 D21 where the hydrogen is oxidized to produce protons and r,l~;l,o,)s, leaves the active area through the anode active area serpentine channel exits D22, flowing through intemal ~ - 'le ' ~n manifold finally exiting as d ?F '~
hydrogen through the hydrogen exit D23.
Dry air (oxygen) gas enters the air (oxygen) inlet D24, flows through internal Illdllirulels and feed circuits to the cathode hulllirJ;f~ n s~ er,li"e channel inlet D25, flows through the cathode hurrli~lifi~liu,)serpentinechannelD26pickingupwatervapor(becominghydrated)~flowsoutthecathode humid;f..-..l;u ~ serpentine channel exit D27. through internal cc"e ' ~ and distribution manifolds to the cathode active area serpentine channel inlets D28, passes through the cathode active area serpentine ~hdl " ~ a D29 where the air (oxygen) is reduced by elecll ~ns and protons to produce product water, leaves the active area through the cathode active area serpentine channel exits D30, flowing through intemal cc"e ~ manifold and finally exiting as deple~ air (oxygen) and product water through the air (oxygen) exit D31.
Coolin~}andhurni~l;r~ onwaterentersthecoolingwaterinletD4.flowsthroughintemal,,,~)ifulds to the cooling water serpentine channel inlet D5, flows through the cooRng water serpentine channel picking up heat produced as by product of the elacl,ut;ll~lllical lua~iliùns, flows out the cooling water serpentine channel exit D7, into intemal ",a, lirùlcls, to the hur~ ;r~ n water inlet manifold junction D8, SUBS~I~TE S~tRULE~) W 096/3700S PCTrUS96/06877 feeding the two hurrliclir~ on water circuits. Hot water from the humidification water inlet manifold junction D8 flows through intemal manifolds to the cathode hurr~ ;ri, ~l ion water 5el ~,e, ~Li- ,e channel inlet Dg flows into the cathode hurr~id ~ n water Se"~enline channel D10 with a small potion osmotically pumped across the electrolytic membrane D2 to humidify cathode air (oxygen) flows out the cathode hurriiclir;c~l;.Jn water serpentine channel exit D11 through internal ",al.ifoW,~ finally exiting through the cooling water outlet D12.
By analogy hot water from the humifl;r~ n water inlet Illdnifold junction D8 flows through internal manifolds to the anode hum;~l;ri. ~i;on water se,~,e"li"e channel inlet D13 flows into the anode hL",~ - ~ water serpentine channel D14 with a small portion osmotically pumped across the electrolyticmembraneD2tohumidifyanodehydrogen~flowsouttheanodehum~ e~lionwaters~ lille channel exit D15 through intemal ",an finally exiting through the cooling water outlet D12.
Fi~3. 4B is a fluid circuit s~ ",dlic for inley,dlec themmal (only) ",anay~l"ent IFM sepdldlul~. The s..l lel l lalic is drawn down the center line E18 of the u le~ l, uu h ~" ,ical cell. The cenle, ~e passes down the center of the electrolytic membrane E1. The anode side of a sepdidlol is on the left side labeled An,ode and depicts the features found on the anode flow field platelet. The cathode side of a sep~,dlu- is depictr~ on the right side labeled Cathode and depicts the features found on the cathode flow field platelet. The s~ llldlic clearly shows the illleyldliol) of three fluid ",d"ag~,nent devices into a single bonded composite sepd,dlur. The three functions are: an anode active area serpentine channel E10 flow field; cooling water se,~e"li"e channel E5 heat e~clldnyel, and a cathode and cathode active area se",e"li"e channel E15 flow field. These functions are conne~led using a series of internal distribution and ~~ ~ Illdl,ifoliis. This mec~l,d" ~ I fluid and therrr,al i"ley,dlion is a key element of this invention.
The electrolytic me" ~L" di ,e E1 is ionically conductive to hydrated protons. During normal ope. dlion protons E2 fomned on the anode are electro-o:"".: ~Iy pumped across the membrane to the cathode.
Protons being pumped across the membrane carry one or more ~c50r;~ watem~ causing anode dry-out during high power operation. At low powers this is ",iliydled by back diffusion of water moleculesfromcathodetoanode. Athighpowersthisismitigatedbyextemalhu",iclir~Calionofhydrogen.
Cathode dry-out occurs when operating on air at high power. This is also mitigated by extemal hulllirJ;HI~ c n of cathode air.
Hydrogen gas enters the hydrogen inlet E8 Hows through intemal distribution manifolds and feed circuits to the anode active area se,~,~"li"e channel inlets E9 passes through the anode active area serpentine clldl)l)el~ E10 where the hydrogen is oxidized to produce protons and el~llulls leaves the active area through the anode active area se, ~ , llil ,e channel exits E11, flowing through intema H ~ t ~ -, C ~L' finally exiting as ~Pp'et~d hydrogen through the hydrogen exit E12.
Air (oxygen) gas enters the air (oxygen) inlet E13, flows through intemal distribution manifolds and feed circuits to the cathode active area s~ l ILiue channel inlets El 4, passes through the cathode active area se,l-e"li"e Cl~dlll-~.lS Ela where the air ~oxygen) is reduced by ele~ t,uns and protons to produce product water leaves the active area through the cathode active area serpentine channel exits E16 flowing throughintemal A~ ' )1l ,a"U,ld finallyexitingas~ler~c'--1air(oxygen)andproductwaterthroughthe air (oxygen) exit El 7.

SUBSTlTUTE Sl IEEr ~Rl~E 26) W 096/37005 PCTrUS96/06877 Cooiingandhum~ rlc~lllnnwaterentersthecoolin9waterinletE3~flowsthroughintemalmanifolas to the cooling water serpentine channel inlet E4. flows through the cooling water serpentine channel picking up heat produced as by product of the ele. I-ucht:",ical ,~aclions flows out the cooling watff se",a. .li. .e channel exit E5 into internal manifolds to the humil l;t~ " water inlet manifold junction E6 flowing into internal manifolds finally exiting through the cooling water outlet E7.
Flg. 5 depicts the overall el~l- ucl ~em ical fuel cell operation for an i- Il~yl dLed humidity and the rrnal Ill~D~dyelll~t fuel cell. The center section of Flg. 5 depicts the overall fuel cell e;~ ,ucl)el,,istry and is cross-,ef~ ced to Fig. 3, H 1 H 2 on the anode side is catalytically oxidized to yield two el~l,uns (indi.-. Ied by 2e- at the end of a di~ ~lional arrow) and two hydrated protons (i".li- . led by H+/H20 in the membrane). The el~l.u,-s are conducted away from the anodic catalytic site by the graphite G~ lu~leS
WtliCh are in contact with the metal mic,os~;,~n platelet. The hydrated protons are electro-osmotically pumped through the wet electrolytic membrane (illdicdl~cl by H+/H20 in the ",e",b, D~e) to the cathocfe catalytic site where they combine with ~2 and two r;le_l,u.)s (i---licated by 2e-) to form product water (H2O). The upper and lower sections of Fig. 5 depict the counter-flow hu. . .i~l ric~ n mecl ..D ,;~", which is a central element of this invention. The electrolytic membrane serves a dual roll as a solid electrolyte and hum i~l;r~ n membrane. The upper section Shows oxygen gas on the cathocfe side being humidified by water on the anode sfde. Conversely hydrogen on the anode side is humidified by water on the cathode side.
Platelet Drawing Desc..i~ n.
Flg. 6 A is a diagram conl-dali- ~9 single level depth 17 and through-features 18 formed by etching metal platelets 16, e.g. by cl 'e, . IiCdl, plasma. or erosion by ele~l- ical arc w high pressure fluid, or the like techniques. Fig. 6 B shows multilevel depths 20 21 and through-features 22 formed by embossing, compr~asion or injection molding plastic platelets 19. Chemical (solvent) etching, or the aforeme, ~lioned erosion or plasma techniques may also be used on plastic. Platelets are typically designed with depth features that are 6û% of the II.;ch.,ess of the platelet stock. Through features 18 are formed by simultaneously etching depth features 17 from both sides. Etching yields round bottom features with the result that etched through features have a residual cusp 23. This cusp aiyl ~ii-.c~ ILly changes the fluid flow cl .a, dclt:l ialiCS of through features and must be taken into account when desiy- ~ ~9 etched platelet devices.
Fig. 6 B sho w s features fommed cc,- ~ ~p- e:aaiun molding yields more rectangular features with slight mold draft. These features may be of varying and ~ P~ d depths 20 21. The multiplicity of depths available in cû~p~a:,ion molded plastic platelets siy"iri- ~Inlly reduces manufacturing costs and design CGIllr . ~y by reducing the number of platelets required to achieve a given depth proflle. Analytical fluid models are simpler due to the lack of residual cusps.
Fig. 7 is a plan view of a llliCI US~ el l current c ~ having a slotted flow field patterns Z1 and Z2 as shown. The slots are posilioned to be COOI di- ldl~ with grooves and ~ h~ -nels in the plastic fluid "~ ,age, . ~ent core pl -t~lPtC For many stack designs slotted flow field patterns Z1 and Z2 are the preferred embodiment.
Figs. 8 A-D depicttypicalbut not exhaustive hole patterns for m etalcurrent col'e ~ mic,u~c,t~en pl~tel~, 8A being heAagons 8B being ~ ;ds. 8C being Tees and 8D being dll~lllal~: inverte~

sussm~ u~ F~E) W 096137005 PCTrUS96/06877 interleaved chevrais. These patterns are fahricated by cnemical miliing, punching, or piercing thin metal plates. Microscreens are typically 65% open with uniform spacing of holes. The hole features are typicaliy 8 - 20 mils with the web being 4 - 10 mils. Oriented he~a~ons Fig. 8A with major and minor axis aligned to the underlying serpentine ~ihdllllels are the p-~r~-,ed embodiment for mi.,lus.;le~lls. 1 I~,~agc".s yield the best design control over hole to web dimensions. In another embodiment, x-met (sheet that is slit in pattems, opened and nallt ,-ed) is also useful.
Detailed Platelet Sepd,dL~r Drawing Des-,.l~.li.~...
There are two major embodiments of composite metaUplastic se~udlu, ~;, edge conduction with one or more current bridges and through-conduction with one or more bus bars. These embodiments will be ~is~ ~s~e~ sequentially starting with the edge conduction realizations.
Edge Conduction 1~ llèy~ dldd Humldlty and Them-al ' ' ~age~
Fiç1. 9 is an ~ isometric view of a single cell F1 internal of the stack co. ~ ~p~isi- ~g sepd- alul :, F2A and F2B Sdn~ ~9 on two EMAs F3A and adjact:, ~l EMA F3B of the next cell in the series. In this view, only the H2 (anode) side of the bipolar sepd dlu.~ are visible, but as shown below, there are COGI dind~e air (oxygen) zones on the hidden (call ,ode) side. The large rectangular areas on the bipolar sep~du, plates are conductive screens that cover the ele~l-ocl-t:l..ical active area on the EMA, F4A
- ~li- ~9 the anode side and F4C (hidden) the cathode side. The small rectangular areas above and belowtheactiveareaarethecathodewaterhumi~l r~c~tionareaF6andanodehydrogenhu--~ 'ri~lionflow field F5 respectively, and will be desc, iL,ed in more detail below.
The EMAs F3A and F3B include catalyst coated areas F7A and F7C that are COGI dil ~ate with the C-OI I t:apOUdil 19 active areas F4A, F4C. Reactant and cooling water I l ldl _ ' are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet Il ldl l-' 'd F9, flows through the hydrogen hu-- ~;~ I r~ l ;on flow field F~, through the anode active area F4A and leaves via the hydrogen outlet ~ - Idl ~ f~ 'd F8. Air (oxygen) enters via the air (oxygen) inlet manifold, flows field through the air (oxygen) hu- "irl~;c~ ;on flow field F14, through the cathode active area F4C and leaves through the air (oxygen) outlet l--dl-ifold F12. Water for hu-, ~ ;ri~ on and thermal management enters through water inlet - - ,~ -i~uld F1 1. flows through an intemal heatLAcl,d..ge"dividesandflowsthroughthecathodewaterh-l,--id;r;~ ;onareaF6andtheanodewater humi~lir~ n area F6. Water leaves through the water outlet Ill~llifold F10. M~l;f.'d~ pass through bipolar sepdldlu~:i F2 and EMAs F3. Culllp,~sion tie rod holes F16 are evident on the margins of the bipolar sepdldlùl:j and EMAs.
Fig. 10 is an ~Yp'oded isometric view of a composite 4-platelet humidified bipolar IFMT sépa- dlUr F2 of this invention comprising plates of three different types, plates F17-1 and F17-4 being identical configuration conductive current - r,'l~ n ,..i.i- usc, ~, p' ' '~ - While the configuration is p.t i~dLly identical, although it could be different, the conductive material may be metal, conductive plastic, - conductive ceramic, or ceramic or plastic having its surface metalized by plating or vacuum dPpo~ition).
Current is conducted around the two plastic core platelets F17-2 and F17-3 by one or more edge current ~ bridges F18, shown partly broken away. Sealing is effected around the margin of the miw us~;. ~n platelet by the anode mic. u:,cr~n sealing surface F23, which may include sealing ridges (not shown) around the reactant and water ~a~liful~s F93. Optional sealing ridges (not shown) may be used to effect sealing W 096/37005 PCTrUS96/06877 around the active and hurr~ c~'ion areas F19 as well.
Platelet F17-1 is the anode current ~c 1. - ~ miclusc,~n consialillg of a repeating pattem of through etched, punched or otherwise forrned holes, ,lldl)ll~ or slots. Platelet F17-2 is the plastic or ceramic anode flow field platelet co"sialil ,9 of molded depth and through features. Platelet F17-2 contains the features that define the hydrogen humirl;r;o~ on flow field F5, anode active area flow field F21, and the cathode water hurr~;~li'ic~'ion area F6. The obverse side of platelet F17-2 forms the close out for the themnal ",ai,agt:",ent circuit F20 of platelet F17-3. Platelet F17-3 is the plastic or ceramic cathode flow field platelet consialillg of molded depth and through features. Platelet F17-3 contains the features that define the thermal ".anage",~l-l heat L,cch~-ger F20, air (oxygen) humid;ri ~'ion flow field F14, cathode activeareaflowfieldF22andtheanodewatffhull~ ;c~ nareaF15. Theair(oxygen)hu".;.i;ri.~ .)flow field F14, cathode active area flow field F22 and the anode watff hull~ ;c~ l area F15 are on the obverse side of platelet F17-3.
In all plates Ft7-2 to F17-3, the through transverse border p~s~es or Illdr, f~ l~ F93 and comp.~asion tie rod holes F16 are coo-~.-ale with those of EMA F3 in Fig. 9.
Fi~s. 11A-G are a series showing in plan view from the facing side of each platelet and the details of one ~ bod;~ of the through and depth features of the 4 platelet bipolar se~ dldot plate of Fig. 10 in accord with the IFM pri" , le~ of the invention. The plOyl~:,aiOII of plates is as shown in Flg. 10, with the figure desig"dlion ~Front~ being the front of the plate as seen from the anode (foreground) side of Flg.
10, while the Back side is the non-visible side of the respective platelets of Fig. 10 when tumed over.
That is, the views are all ~artwork or plate facing (face-up) views. Platelets 1 and 4 are e55~n' lly the same with the ~ pl n of when sealing ridges are employed. Figs. 11 A-11 C are plan views showing the front of platelet 1 and the back of platelet 4 joined by the current bridge Ft 8. The anode platelet current ~c ~ ~u~ ~"i ;,usc,~n F17-1 is ~1, on the bottom with the cathode platelet current -C"t;
~ic-~us~ten F17-4 on the top joined by the current bridge F18 in the middle. The anode and cathode current .,- ~ t~ ~"i~,us ;,~n platelets are constnucted with through features that define the ,,,ic,uscrt:an (shown cr~,sal)al.;l ,~). These features may be of diverse shapes and sizes as de~ ed in Figs. 7 and 8.
As seen in Fig. 11A the anode current rc - mic,usc,~, platelet F17-1 features define the cathode water hun~id;riG<.IiPn area F6, anode active area F4A, and hydrogen hurr~; ';t~ on flow field F5.
A sealing surface F23 with optional sealing ridges surrounds the active and humi~l r;~ on areas F19.
Manifold close-outs for distribution and ~- ~ ~ ) Ill~liFulls of the anode flow field platelet F17-2 are formed by the anode mil.,usc,t:e" Illdl~ifUId close-outs F25. The cathode current col ~l ",i.,.~,sc,~, platelet F17-4 features define the air (oxygen) humi~J;';c~liul) flow field F14, cathode active area F4C, and theanodewaterhumi~lirir~lionareaF15. AsealingsurfaceF24withoptionalsealingridgessurroundsthe active and hullli~lit~ lion areas F19. Manifold close outs for distribution and co"~ li~ n Ill~lirulds of the anode flow field platelet F17-3 are formed by the cathode ~ usu~n manifold close outs F26.
Flg. 11B is a plan and section views of typical metal mi,,os,,~n current col;_cLu, platelets with window screen dt:,c,e:ssions. The anode current co le ,~ " i1 US .,~en dep,~ssion F31, cathode current us~ de~ ssionF9O,transverseborderp~s~ orlllarliful~JaF93~anodemic~ùscl~:l) sealingsurfaceF23,cathode~ic~uac~l)sealingâurfaceF24~anodemicluscl~lllllani~oldclose-outF25 W 096/37005 PCT~US96/06877 and cathode microscreen manifold close-out F16 are derict~d in plan and section view. The depth of the windows screen dep, ~ssions F3 1 and F90 are desiy"ed match the depth of the dep, ~::,sions on the anode and cathode flow field platelets F17-2 and F17-3.
Fi~. 11C is a plan and section views of metal mic,osc-,~n current co" ' platelets without w;.ldo.vs screen de~ ssions. The transverse border p~ es or manifolds F93 anode mic,u:,c.~, sealingsurfaceF23.cathodemic,us~ ensealingsurfaceF24,anodemiclus~;l~nmanifoldclose-outF25 and cathode mic,uscl~n manifold close-out F16 are ~r~ d in plan and section view.
Fig. 11 D depicts the front side of the plastic anode flow field platelet F17-2 -Front. This platelet has both through and depth features. The major through features are the comp~t:ssion tie rod holes F16, transverse Illall'' ' ' hydrogen outlet ",anirold F8 hydrogen inlet Illanifold F9 water inlet ",an;~W F10 water outlet ",an,f~,ld F11, air (oxygen) outlet Illdn '~ 'd F12 and air (oxygen) inlet Illdn ' ~' F13. Other through features are the hydrogen inlet via F32 hydrogen outlet via F35 cathode hu",i- ~-r;u.~ n water inlet via F44 and cathode humicl:~ic ~ n water outlet via F41. The major depth features on the front of the anode flow field platelet are the hydrogen hu".;~ ;on serpentine cl-~-,-eL F36 anode active area S~ ~ llil ,e chdl " lelj F39 and the cathode hul- I jr l;r;~ n water se, ~ l llil ,e channel F43. These features are designed to opli",i~e the flow rates and pressure drops of the device.
Hydrogen fuel for the anode enters the hu"~ ;f~ n area through the hydrogen inlet via F32 enters the hydrogen distribution " Idl lifuld F27 through the hydrogen distribution " Idl '' ' inlet F33 and is distributed to the two hydrogen serpentine chdl 0~r l ~ F36 through the hydrogen se, u~ ,li"e channel inlets F34. HydrogengasishumidifiedthroughthewaterpemmeableeleCtrOIyticmelllb,d,,ewhichisincontact withthehydrogenhn",i.i;fi. ~ nse"J~,Ii"echannelF36. Humidifiedhydrogenleavesthehu"-;-~;rc~l;o., area through the hydrogen serpentine channel exits F37, enters the hydrogen ~ ~ "~ ",anirGI.I F28 and passes into the anode active area distribution " ,a"irùld F29. flows into the anode active area serpentine c~a, Inel3 F39 though the anode active area st:"~ il ,e channel inlets F38. Within the active area hydrogen is catalytically oxidized on the anode side of an EMA to produce el~ll o"s and protons. Protons pass from the anode catalytic site through the electrolytic membrane to the cathode. Electrons are drawn off from the anode catalytic site through the graphite electrode. Electrons from the graphite electrode are c ~
by the anode current c - '~ ' - mi~, usc, ~" F17-1 and conducted through the composite bipolar Sepdl dlOI
by edge conductors F18.
l~ep~et~d hydrogen leaves the active area via the anode active area serpentine ul ,annels exits F40 and flows into the hydrogen c - 'It " ~ manifold F31 finally exiting through the hydrogen exit via F35.
Hotwaterforcathode(air,oxygen)hu,,,i~lir;c-~ionentersthroughthecathodehtJ,,,i~ ic~lionwater inlet via F44. passes into the cathode hulll~ fi~-~liot- water st:"ue,)li"e channel F43 through the cathode hull.i~l~fi~ n water serpentine channel inlet F4~ exits through the cathode hurrlid;ri-~al;on water ~ se, ye"li"e channel exit F42, and leaves through cathode hull-;cl r~ - water outlet via F41. Part of the hot water flowing through the serpentine channel is osmoticaliy pumped across the electrolytic membrane - to humidify cathode air ~oxygen).
me anode current -"- ' mic,u~c,~n platelet F17~1 is bonded to the anode flow field platelet F17-2 and forms Illdll;f~ld close-outs for the hydrogen distribution Illdl '~ ~d F27 hydrogen c-~ : n W 096/37005 PCTrUS96/06877 The optional anocle microscreen d~p-t:ssion F31 receives the corresponding anode current collector mi~ ,osc,~en platelet F17-1 with anode mic-,us,_,~an dep,~ssion F31ci-~pict~ci in Fi~. 11B. The depth of the anode current c ~ " ~ mi~;, usc, ~n dep, ~ssion F31 is set to place the surface of the anode current cel'- -~ - mil,,usc.een platelet F17-1 flush with the surface of the anode flow field platelet F17-2, or it may be set to forrri a recess which receives graphite paper elecl,.,des of the el~l,ucie membrane assemblies.
Fig. 11E depicts the back side of the plastic anode flow field platelet F17-2 -Back. This platelet has both through and depth features. The major through features are the compression tie rod holes F16, transverse manifolds; hydrogen outlet ~ if old F8, hydrogen inlet manifold F9, water inlet manifold F10, water outlet manifold F11. air (oxygen) outlet " ,ar, ' 'd F12, and air (oxygen) inlet " ,a"iruld F13. Other through features are the hydrogen inlet via F32. hydrogen outlet via F35, cathode humid;fi~ oll water inlet via F44, and cathode hurr~ ri~ inn water outlet via F41. The major depth features are the hydrogen ~nlet channel F47, hydrogen outlet channel F~0. air (oxygen) outlet channel F63, and the air (oxygen) outlet via base FJ5. Most of the surface of the anode flow field platelet F17-2 is used as a close out for the cooling water ~,I Idl 11)_~5 on the cathode flow field platelet F17-3.
Hydrogen flows from the hydrogen inlet manifold F9, through the hydrogen inlet channel inlet F48, into the hydrogen inlet channel F47, through the hydrogen inlet channel exit F46, and finally into the hydrogen inlet via F32. Hydrogen passes from back to front of the anode flow field platelet Fig. 1tD, through the hydrogen inlet via F32. Dep'~t~ hydrogen from the active areas flows back through anoc-le flow field platelet through the hydrogen outlet via F35, into the hydrogen outlet channel inlet F49, through the hydrogen outlet channel F~0 and the hydrogen outlet channel exit F51, finally exiting into the hydrogen outlet ",aniflJI d F8.
Derleteci air (oxygen) is removed from the cathode humi~l;r..~ n and active areas through the air (oxygen) outlet via F55, air (oxygen) outlet channel inlet F64. air (oxygen) outlet channel F53, air (oxygen) outlet channel exit Fs2, finally flowing into the air (oxygen) outlet manifold.
Fig.11 F depicts the front side of fhe plastic cathode flow field platelet F17-3 -Front. This platelet has both through and depth features. The major through features are the compression tie rod holes F16, transverse manifolds; hydrogen outlet manifold F8, hydrogen inlet manifold F9, water inlet manifold F10, water outlet manifold F11, air (oxygen) outlet manifold F12, and air (oxygen) inlet Illdl C~d F13. Other through features are the air (oxygen) inlet via F60, air (oxygen) outlet via F61, anode hurr~ ~if ~ ' ~n water inlet via Fs8, and anode hur~ on water outlet via F57. The major depth features are the cooling water serpentine cl ~ l3 F62~ humi~ n water inlet manifold F64 and the humidiri~ n water outlet ~.,ani[old F63.
Cooling water enters through the water iniet manifold F10, cooling water channel inlet F66, cooling water channel F66 finally entering the cooling water serpentine channel F62 through the cooling water serpentine channel inlet F67. Flowing throu9n the cooling water serpenl ine channel the cooling water picks up heat which is a by product of the elecl, ucht:- l licdl r~acLions~ Hot water leaves through the cooling water s~iJ~"li"e channel exit F68 and flows into the hUll~idiri~ ion water inlet manifold junction F69, into the W 096/37005 = ~ PCT~US96/06877 humi. I;r;~ n water inlet manifold F64, and finally exits through the humi ';'i~ n water cathode exitFr~
and cathode water hurl~idir~ n inlet via F56 or the hurlliciir~ water anode exit F71 and anode water humi~Jiri~ ion inlet via F58. Hot water is used for humi~l;rc-.lion because of it high diffusion activity.
Air (oxygen) enters the cathode from the air (oxygen) inlet manifold F13, flows into the air (oxygen) inlet channel inlet F72. passes through the air (oxygen) inlet channel i-73, into the air (oxygen) inlet channel exit F74, and flows to the cathode humidi i~lil n and active area clldnnelj through the air (oxygen) inlet via F60. Air (oxygen) is humidified as it passes through the air (oxygen) humidirlc~'io,l ch~llll~ls and is consumed in the cathode active area d~ t~ in Fig.11 G. ~'er le~c air (oxygen) and product water leave via the air (oxygen) outlet via F61 which conll~la to the air (oxygen) outlet manifold F12 through the air (oxygen) outlet channel on the anode flow field platelet F17-2.
Fig.11 G depicts the back side of the pl~tic cathode flow field plate'et F17-3 -Back. This plate~et has both through and depth features. The major through features are the co, ~ ssi ,n tie rod holes F16, transverse ., Idl ~' ~ . hydrogen outlet ., Idn-' ~(- F8, hydrogen inlet ~ ~ Idl lifol J F9, water inlet ~ ~ ~~": c F10, water outlet Illdl l'' ' ' F11, air (oxygen) outlet md~iruld F12, and air (oxygen) inlet l.lanifuld F13. Other through features are the air (oxygen) inlet via F60. air (oxygen) outlet via F61, anode humid;r~AIil n water inlet via F58, and cathode humi~'~r~ n water outlet via F59. The major depth features on the cathode flow field platelet are the air (oxygen) hurr~ lio~l s~,lJe"li"e chdrlnels F80, cathode active area serpentine cl ,~n~ls FB6, and the anode hull,L; r c~ n water serpentine channel F77.
Air (oxygen) for the cathode enters the hul, ~ area through the air (oxygen) inlet via F60, enters the air (oxygen) distribution ",a"irol i F79 through the air (oxygen) distribution Ill~,iful i inlet F78 and is distributed to the two air (oxygen) s~,~,li"e ch~",.~ F81 through the air (oxygen) se,,uel)lille channei inlets F80. Air (oxygen) gas is humidified through the water permeable electrolytic membrane which is in contact with the air (oxygen) hu"-idir~ lil n serpentine channel F81. Humidifieci air (oxygen) leaves the hum i~ l ri~ ion area through the air (oxygen) serPentine channel exits F82. enters the air (oxygen) hum i l;ri. ~l il n cc ~ " ,anircJI i F83, and passes into the cathode actiYe area distribution l "~ L' F84, flows into the cathode active area serpentine chan,.~ F86 though the cathode active area se",enline channel inlets F85. Within the active area oxygen is catalytically reduced receiving protons and el~l,ùns from the anode to produce water. Electrons flow from anode to cathode via current bridge F18, into the cathode current - - en or mi~. usc, ~" 17-4, through the cathode graphite el~l, ude on the EMA and finally docking with a cathode catalytic site where the el~ll u,-s react with anode ~ene~ dl~d protons and oxygen to produce surplus heat and product water. ~ air (oxygen) and product water leaves the active area via the cathode active area se".e"li,)e channels exits F87 and flows into the air (oxygen) ~r"~ 'i I
".ar.iruld F88, through the air (oxygen) ., - ~c ~n l~ Idl 1' _ ~(' exit F89 finally exiting through the air (oxygen) exit via F61.
~ Hotwaterforanode(hydrogen)humi~;f~ nentersthroughtheanodehumid~riC~l~ionwaterinlet via F58, passes into the anode hurni~'ir~ n water s~, ,u~, ,li, ,e channel F77 through the anode humi~l;ril,,lil~nwaterserpentinechannelinletF76~exitsthroughtheanodehun~ r~ lionwaterserpentine channel exit F75, and leaves through anode hu",i~' ril~lion water outlet via F59. Part of the hot water flowing through the se".;--Li,.e channel is os.,-uli~.llly pumped across the electrolytic membrane to SUB~ ESHE~t~26) W 096/37005 PCTrUS96/06877 humidify anode hydrogen~
Platelet F17-3 is bonded to platelet F17-4 which may have an ol~tional cathocde current ~ c ,l ua-,l e~- clep, ~aSiOn Fso and forms manifold close outs for the air (oxygen) hul, ~ un distribution manifold F79, air(oxygen) humid;t~ n ~ )n '''an ~ 'c F83~ cathodeactiyeareadistribution nlanil~Jh F84 and cathode active area ~ n manifold F88.
The depth of the cathode current ~ mi,;, osc, ~- de~l ~asion F90 is set to place the surface ofthecathodecurrentcr' mi.;,~sc,~nplateletF17-4flushwiththesurfaceofthecathodeflowfield platelet F17-3 or it may be set to form a recess which receives graphite paper elecl, odes of the electrode membrane assemblies F~ in Fig. 9.
EdRe Conduction l~ cy.dl~d Thermal ~- .ag~-..e..l.
Fig.12isan~ lc~o~iaG",e~ ;viewofasinglecellG1 internalofthestackco".~,iai"gsep~dlo~
G2A and G2B sandwiching EMA G3A and conlacli"g the next EMA G3B of the next adjac~ IL cell in the stack. In this view, only the H2 (anode) side of the bipolar se~,d, dlul :- are visible but as shown below, there are COGI~ ' Idlt3 ~2 zones on the hidden (cdlhodd) side. The lar~e rectangular areas G4A are the active areas of the cell G4A I ~ ael llil 19 the anode side and G4C the cathode side.
The EMAs G3A and G3B include catalyst coated areas G7A ancl G7C that are COGI di, Idl~3 with the corresponding active areas G4A. G4C. Reactant and cooling water Illdl ~ituW~ are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet mdl);fokl G7 flows through the anode active area G4A and leaves via the hydrogen outlet manifold G6. Air (oxygen) enters via the air (oxygen) inlet Illdnif~ld G10 flows through the cathode active area F4C and leaves through the air (oxygen) outlet manifold G11.
Cooling water for thermal " lanas~en ,~ ,l enters through water inlet manifold G9 flows through an internal heat e,~cl Idl ,gef and leaves through the water outlet Illdl ,itolcl G8. Transverse reactant and cooling water inlet and outlet n ,a, lifulJs G6, G7 G9. G11 G10 and G12 pass through bipolar sepa, dlU~ G2 and EMAs G3. Compression tie rod holes G12 are evident on the margins of the bipolar sepa, dl.n a and EMAs.
Fig. 13 is an ~Yp'oded isometric view of a 4-platelet bipolar IFMT sep~dlur G2 of this invention comprising plates of three different types plates G13-1 and G13-4 being identical current CC"~L 3--~I~ic~usc~ee~l platelets con"ecled by current bridge G14 shown partly in dashed lines. Platelet G13-1 is the anode current ~ mic, OaCI ~" consisling of a, t:pedlin9 pattern of through etched or punched holes. Platelet G13-2 is the plastic or ceramic anode flow field platelet conaialillg of molded depth and through features. Platelet G13-2 contains the features that define anode active area flow field G16. The obversesideofplateletG13-2formsthecloseoutforthethermal"-anage"-entcircuitG170fplateletG13-3. Platelet G13-3 is the plastic or ceramic cathode flow field platelet collsialil,g of molded depth and through features. Platelet G13-3 contains the features that define the therrnal management heat ~,~ch~ ,gel G17 and cathode active area flow field G18. The cathode active area flow field G18 is on the obverse side of platelet G13-3. Sealing is effected around the margin of the mi~ ,s.;,~n platelet G13-1 and G13-2.
Optional sealing ridges (not shown) may be used to effect sealing around the active areas G4A and G4C.
In all plates G13-2 to G13-3 the through transverse border p~ g~s or manifolds G15 and cu"",,t::,sion tie rod holes G12 are coo,di. ,ale with those of EMA G3 in Fig. 12.
Figs. 14A-G and G are a series showing in plan view from the facing side of each platelet and the S~ST~

W O 96/37005 PCT~US96/06877 details of one em~odiment of the ttlroush and depth features of the 4 platelet bipolar separator plate of Fig.13 in accord with the IFM p, in '~~ of the invention. The p. oy, t:asion of platelets and fronVback sides are the same as the Figs. 11 A-G series.
Fig. 14A is a plan view of the anode and cathode current ~2 'e '- - microscreen pl~t,~letC G13-1 and G13-4 anode screen on the bottom cathode screen on top. The through features of the ~iC~uSC~ S may be of diverse shapes and sizes as dep - ~ ?d in Fig. 8. The anode current ~-mi~i,uac,~,l platelet has features that define the anode active area G4A. A sealing surface G19 wlth optional sealing ridges G60 (shown in phdlllolll) surrounds the active G4A. Manifold close outs for distribution and c~ lifolds of the anode flow field platelet G13-2 are formed by the anode ",i~;,usc,~n Illal,iru,W close outs G21.
The cathode current cc - - mic-,usL,een platelet G13-4 features define the cathode active area G4C. A sealing surface G22 with optional sealing ridges surrounds the cathode active area G4C. Manifold close outs for distribution and c~ Illdn ~d of the anode flow field platelet G13-3 are formed by the cathode .,.ic,usc-w,, manifold close outs G22.
Fig. 14B is a plan view of metal ",ic,usc,~n current ~ platelets with window screen dep, t:ssions shown in sections to the right. The two platelets G13-1 and G13-4 are joined by the current bridge G14. The anode current ~c ~ ~ ~ ".i.,os-r~n dep,~ssion G25 cathode current c-l -.us~n de~,~asion G59 trarlsverse border p~c~g~c or Ill~irolda G15 anode ",ic,us.;,~:" sealingsurface G19 cathode mi~.,usc,~n sealing surface G20, anode ",i~,usc,~n ",a-, close-out G21 and cathode IlliClu5~ "an close-out G22 are d?,' ' in plan and section view. The depth of the window screen dep, ~SaiunS G25 and G59 are desiy"ed match the depth of the de~ asionâ on the anode and cathode flow field platelets G13-2 and G13-3.
Fig. 14C is a plan view of metal Illi..lusc,~" current ~. 'e platelets without window screen depl~as.ons with coll~aponlJ;.,g plan as section views shown to the right. The two platelets G13-1 and G13-4 are joined by the current bridge G14. The transverse border p~Csa9~c omlldllirulds G15 anode ",i~;,usL.~-,sealingsurfaceGl9 cathodemic,usc,~nsealingsurfaceG20.anodemic,usc,~n,,,~,i close-out G21 and cathode microscreen ",anirul-J close-out G22 are d~ tt.~ in plan and section view.
Fig. 14D depicts the front side of the plastic anode flow field platelet G13-2 -Front. This platelet has both through and depth features. The majorthrough features are the co",p,~ssiùn tie rod holes G12, transverse ",~ ,irol~s hydrogen outlet manifold G6 hydrogen inlet manifold G7 water inlet manifold G8 water outlet Ill~irGld G9 air (oxygen) outlet manifold G11, and air (oxygen) inlet ",an 'c't G1û. Other through features are the hydrogen inlet via G2~ and the hydrogen outlet via G28. The major depth features on the front of the anode flow field platelet are anode active area seu~enli"e cl)~ll ln IS G31 anode active area distribution I,,an 't G23 and the anode active area cc ~n manifold G24. These features are ~ desiyned to optimize the flow rates and pressure drops of the device.
Hydrogen fuel for the anode area enters through the hydrogen inlet via G26 passes through the - anode active area distribution manifold inlet G27 into the anode active area distribution manifold G23 flows into the anode active area serpentine channels G31 though the anode active area s~".,~"line channel inlets G30. Within the active area hydrogen is catalytically oxidized on the anode side of the EMA to SU~I~rES~tE~T (R~F2~

W 096/37005 PCTrUS96/06877 produce e~ectrons and protons. Protons pass from the anode catalytic site through the electrolytic membrane to the cathode. Electrons are drawn off from the anode cal:alytic site through the graphite electrode. Electrons from thegraphiteelecl.udeare~ ' bytheanodecurrent c-"~ liclusL.
G13-1 and conducted by tab or bridge G14 to the cathode mic,os~,~en G13-4.
Depleted hydrogen leaves the active area via the anode active area serpentine Lh~ Incl3 exits G32 and flows into the anocie active area cc" ' ~ manifold G24, through the active area ~ -''e ' ~ manifotd exit G29 and finally exits through the hydrogen exit via G28.
Platelet G13-1 is bonded into an anode current _-"~ ' - miLi.us~ e,- deu.ussiù.) G25 and forms manifold close outs for the anode active area distribution manifold G23 and anode active area ~c" '' manifold G24.
Thedepthoftheanodecurrentcc"~tc mic-us~,~,areaG25maybeselectedflushtoplacethe surface of the anode mic,usc,~, platelet G13-1 flush with the surface of the anode flow field platelet G13-2, or it may be dep, ~sed to fomm a recess which receives graphite paper el~_l- ucles of the elc ~.t~ u~le ..~..,tj.dne assell -'' Fi~. 14E depicts the back side of the plastic anode flow field platelet G13-2 -aack. This platelet has both through and depth features. The maior through features are the compression tie rod holes G12, transverse ,..~ '~ hydrogen outlet ",dnirold G6, hydrogen inlet ~- ~a. ~irul~i G7, water inlet Il lalli~old G9, water outlet ",an '~ ' ~' G8. air (oxygen) outlet Illdl l''.i~d G11, and air (oxygen) inlet I lldn''~ G10. Other through features are the hydrogen inlet via G28 and the hydrogen outlet via G26. The major ciepth features are the hydrogen inlet channel G34, and the hydrogen outlet channel G37. Most of the surface of the anode flow field platelet G13-2 is useci as a close out for the cooling water cl Idl In'c31~; on the cathode flow field platelet G13-3.
Hydrogen flows from the hydrogen inlet ~ - Id n,fold G7, through the hydrogen inlet channel inlet G35, into the hydrogen inlet channel G34, through the hydrogen inlet channel exit G33, and finally into the hydrogen inlet via G26. Hydrogen passes from back to front of the anode flow field platelet Fig. 14D, through the hydrogen inlet via G26. n p~e~i hydrogen from the active areas flows back through anode flow field platelet through the hydrogen outlet via G2a, into the hydrogen outlet channel inlet G36. through the hydrogen outlet channel G37 and the hydrogen outlet channel exit G38. finally exiting into the hydrogen outlet ",ar ~c' -' G6.
Fig.14F depicts the front side of the plastic cathode flow field platelet G13-3 -Front. This platelet has both through and depth features. The major through features are the comp~b~sio~ l tie rod holes G12.
transverse ",ani~l~s, hydrogen outlet Illal);fullJ G6. hydrogen inlet manifold G7, water inlet manifold G9, water outlet ,,,a-,iruW G8, air (oxygen) outlet Illall '~'d G11, and air (oxygen) inlet Illalliruld G10. Other through features are the air (oxygen) inlet via G44 and the air (oxygen) outlet via G45. The major depth features are the cooling water s~- ~e"Li- ,e ch~ "~els G46, air ~oxygen) inlet and outlet cl ,a"n~ G50 and G40.
Cold cooling waterenters through the cooling water inlet ,,,anirulcl G9. flows into the cooling water serpentine channel inlet G47, and passes into the cooling water s~:u,e, ILi"e channel G46. Flowing through the cooling water serpentine channel G46 the cooling water picks up heat which is a by product of the W 096/37005 PCT~US96/06877 electrochemicai reactions. Hot water exits through the cooling water serpentine channel exit G48. finally leaving through the cooling water outlet manifold Ga.
Air (oxygen) flows from the air (oxygen) inlet manifold G10, through the air (oxygen) inlet channel inlet G49, into the air (oxygen) inlet channel G50, through the air (oxygen) inlet channel exit G51, and finally into the air (oxygen) inlet via base G42 which communicates with the air (oxygen) inlet via G44 on the cathode flow field platelet G13-3 in Fig. 14D. The air (oxygen) inlet via G44 brings air (oxygen) to the cathode active area flow field.
rler' - air (oxygen) is removed from the cathode active area through the air (oxygen) outlet via G45 (Fig. 14G) into the air (oxygen) outlet via base G28, into air (oxygen) outlet channel inlet G36, through the air (oxygen) outlet channel G37. past the air (oxygen) outlet channel exit G38, finely exiting through the air (oxygen) outlet ..,ar ' 'd G6.
Fig. 14G depicts the back side of the plastic cathode flow field platelet G13-3 Back. This platelet has both through and depth features. The major through features are the co, . . pfession tie rod holes G12, transverse ..-;~irul~s, hydrogen outlet ..,an ' ' ' G6, hydrogen inlet ,--ar ' ~I G7, water inlet ~lanirold G9, water outlet ."~,irol~ G8. air (oxygen) outlet manifold G11, and air (oxygen) inlet ...~.ifol~ G10. Other through features are the air (oxygen) inlet via G44 and the air (oxygen) outlet via G45. The major depth features on the cathode flow field platelet are the cathode active area distribution ~- -ar if uld G53, cathode active area c-"- ~ ~ Illdnifùl~ G57, and the cathode active area s~ ~,e"li"e chdnnels G55.
Air (oxygen) for the cathode enters the hulll ' ~ ~ area through the air (oxygen) inlet via G44, passes the cathode distribution manifold inlet G52, flows into the cathode distribution manifold G53 and is distributed to the cathode active area s~ t:,-li--e .,hdn-)~,ls G55 though the cathode active area serpentine channel inlets G54. Within the active area oxygen is catalytically reduced - ~ce;~;ng protons and el~l. uns from the anode to produce water. El~ll uns flow from anode to cathode via current bridge G14, into the cathode current ~ mi-" u:,~.,~,, 13-4, through the cathode graphite r le_l, ude on the EMA
and finally docking with a cathode catalytic site where the el~llu"s react with anode gene,.lled protons and oxygen to produce surplus heat and product water. rey~' ' ' air (oxygen) and product water leaves the active area via the cathode active area s~ ~,e, llil ,e channcla exits G56 and flows into the cathode active area c~ G57, through the air (oxygen) c:" ' , manifold exit G58 finally exiting through the air (oxygen) exit via G45 which communicates with the air (oxygen) outlet channel G40 and the air (oxygen) outlet ",anifol~ G11 on the cathode flow field platelet 13-3 -Front Fig. 14F.
Fig. 15 is a plan view of an anode (bottûm) and cathode (top) current c~" micros~,een p~ ~t~ F17-1 and F17-4, respectively, with a current bridge F18 and multiple current tabs. The anode current cc"~~ ~"ic.osc.~e,l platelet features define the cathode water humi~l;r~ orl area F6, anode active area F4A, and hydrogen humirJir~ lion flow field F5. Three current conducting tabs F94 protrude from the edges of platelet F17-1. These current tabs mate with the three corresponding current tabs on platelet F17-4 and are joined by spot welding, micro brazing, SGIdt:lill9 or gluing with conductive adhesives. The number of current bridges is p~ clec as a function of the required current-carrying requirements of a given sealing ridges F95 are optional.
The cathode current c "~ mic,us.;,~en platelet F17-4 features define the air (oxygen) S~Bs~~sHEET~

CA 0222090l l997-ll-l2 W 096/3700S PCTrUS96/06877 hu, . ~ r~ Al flow field F1 4l cathode active area F4c~ and the anode water hLll l ~ n area F15 Three current condJcting tabs F94 protnude from the edges of platelet F17-4. These current tabs mate with the three corresponding current tabs on platelet F17-1 and are joined by spot welding, micro brazing, sol:le. i. .g or gluing with conductive adhesives.
Through reactant and cooling water Illdllirolds F93 and tie rod holes F16 are located in the same peripheral positions as for the single current bridge 1 ' n d~rictecl in Fi~. 14A.
Fig. 16 is an ~ ~ isG..-el,ic view of a 4-platelet humidified bipolar IFMT sepdldlur F2 of this invention comprising plates of three different types, plates F17-1 and F17-4 being identical current cc " ~ - -iL. usc. c en platelets as above. Current is conducted around the two plastic core platelets F17-2 and F17-3 by an edge current bridge F18 and three joined current tab-~ F94.
Platelet Ft7-1 is the anode current ~ lua~.l~ll cOll~ialill9 of a l~pedlillg pattem of through-etched or punched holes. Platelet F17-2 is the plastic or cerdmic anode flow field platelet consiali"g of molded depth and through features. Platelet F17-3 is the plastic or ceramic cathode flow field platelet cons;sli--g of molded depth and through features. Platelet F17-4 is the cathode current e~le ~ mic-ua-,.~" cùnsisli"9 of a rt:pedlillg pattem of through-etche!d or punched holes.
Bus Bar Conduction Integrated Humidity and Therrnal IU .agc~....~lo Fig. 17 is an , ' ' o ~ iaul~~el ic view of asinglecell A1 internal of the stack co...~ i- ~g sepd..~t~a A2A and A2B s~ .~w;~;l ~ .9 an EMAs A3A in contact with EMA A3B of the next adjdc~l cell. The plate sequence and views are as above. The ~ "ic-. uaL- ~-) A4A, ~ ael lla the anode side and A4C the cathode side which are conne~l~d by intemal bus bars desc, iL,ed in detail below. Anode hydrogen hul, ~ ;l riri,~ Jn flow field A5 and cathode water hul..i l;f~ o n area A6 are present in the sepdldlùla, and described in more detail below.
The EMAs A3A and A3B include catalyst coated areas A7A and A7C that are coo, di~ with the c~ spord;, .g active areas A4A, A4C. Reactant and cooling water ,~Idl '( ' ' are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet manifold A9, flows through the hydrogen hurr~irl;~ic~ ,) flow field A5, through the anode active area A4A~nd leaves via the hydrogen outlet manifold A8. Air ~oxygen) enters via the air (oxygen) inlet Illdl .;fuhl, flows field through the air (oxygen) hull~ r;c,.lion flow field A14, through the cathode active area A4C and leaves through the air ~oxygen) outlet manifold A12. Water for hurn irl r,c~ and thermal management enters through water inlet manifold A11, flows through an intemal heat e,~l ,d, ,g~, divides and flows through the cathode water h~ u~liol l area A6 and the anode water hurnirl;~ area A~. Water leaves through the water outlet manifold AlQ. Mall ~ulds pass through bipolar sepd,dlola A2 and EMAs A3. Compression tie rod holes A16 are evident on the margins of the bipolar sepd dlu,a and EMAs.
Fig. 18 is an ~-, ' ied isometric view of a 4-platelet humidified bipolar IFMT sepdldll~l A2 of this invention comprising plates of three different types. plates A17-1 and A17-4 being identical current c~ n mic.o:,c.een p.~ c Current is conducted through the two plastic core platelets A17-2 and A17-3 by one or more intemal bus bars A18. While two rectangular cross section bus bars are depiAt~ri any number, geometrical cross-se.,tion and o, ie"ldlion may be employed, both within the screen field or extemal of it. Sealing is effected around the margin of the .- ,ic. osc. ~n platelet by the plastic core pl~t~l.-t~::

S~ ESHEEl lRU~

W 096/37005 PCTrUS96/06877 A17-2 and A17-3. which may inciude sealma riclges (not shown) around the reactant and water manifolds, and around tne active areas A21, A22, and the hurr irlifiuc~ion areas A5, A6, A14, A15 and A19.
The two metallic current ~ n mic,u~;-~n platelets At7-1 (anod* and A17-4 (cathode) are identical. Platelet A17-2 is the plastic or ceramic anode flow field platelet consisli"g of molded depth and through features. Platelet A17-2 contains the features that define the hydrogen humi~l r;~ n flow field A5, anode active area flow field A21, and the cathode water humid;ric~ion area A6. The obverse side of platelet A17-2 fomms the close out for the thermal management circuit A20 of platelet A17-3. Platelet A17-3 is the plastic or ceramic cathode flow field platelet cu-,sisli--g of molded depth and through features.
Platelet A17-3 contains the features that define the thermal ~, Idl ,aye, ~ ,enl heat e~chan9ef A20. air toxY9en) hu..,i~ n flow field A14, cathode active area flow field A22 and the anode water hurr~ ;on area A15. Theair (oxygen) hurr~;rl~fi-~ "~ flow field A14, cathode active areaflow field A22 and the anodewater hul~ area A15 are on the obverse side of platelet A17-3.
In all plates A17-2 to A17-3 the through transverse border p~ ec or Illd -;fuld~ A93 and comp. ~sion tie rod holes A16 are coo. ii. Idl~ with those of EMA A3 in Fig. 1~.Figs. 1 9A-G are a series showing in plan view from the facing side of each platelet and the details of one embodiment of the through and depth features of the 4 platelet bipolar sep~dlor plate of Fig. 18 in accord with the IFM p, i, , ' s of the invention. It should be noted that the ri, uyl ~:asion of plates is as shown in Flg. 18 with the same conventions as used above in the edge conduction embodiments.
PI~Ll-,b 1 and 4 are ess~ 'Iy the same with the ~ - ~ epl;on of when sealing ridges are employed, Fig. 19A shows as A17-1 the front of platelet 1 on the left and as A17-4 the back of platelet 4 on the right.
The anode current c - " ~ ~ - ,ic-. usc. ~n platelet features define the Cathode water hum i~ ~:r~ n area A6~
anode active area A4A, and hydrogen hu---i-J;r~ on flow field A5. A sealing surface A23 with optional sealing ridges surrounds the active and hul ~ ~;d;fi~ ;~1 ion areas A19. Manifold close outs for distribution and ...d..iruldsoftheanodeflowfieldplateletA17-2arefOrmedbytheanode~ic~us~ dnir~ld close outs A25.
The cathode current c-"~ - ..,i..rosc.~e" platelet A17-4 features define the air (oxygen) humir~ i(Jn flow field A14, cathode active area A4C, and the anode water hu..licl;ri~ n area A15. A
sealing surface A24 with optional sealing ridges surrounds the active and hul-.;~l;r~ l;on areas A19.
Manifold close-outs for distribution and ~ lion ",a"itulds of the anode flow field platelet A17-3 are formed by the cathode mi~,.us~.~n l~dnifùld close-outs A26.
Fig. 19E~ is a plan view of the plastic anode flow field platelet A17-2 -Front with a fragmentary portionoftheanodecurrentc-"- ",i..,osc-,tenplateletA17-1 overlainonthelowerrightcomertoslow the posilio, ,9 and Oli~ldliOn. Platelet A17-1 is bonded into an anode current c~ ",ic-,u:,c,~
de,u.~asion A31 and forms "~d~.ir.~ld close outs for the hydrogen distribution manifold A27, hydrogen --"~'-- ~ Illdlli~OICl A28, anode active area distribution manifold A29 and anode active area cc"e Illdl '' ' ' A30. Two bus bars A18 are el~l" "y bonded to the anode current cO"?C~ mic,us~ en platelet.
The anode current c c "~ ~ mic, USL, ~en area A3 1 may be COpldl Idl with the rest of the platelet to place the surface of the anode current --"~ ~c microscreen platelet A17-1 flush with the surface of the S~IT~E S~Et~RlJLE2~) anode flow field platelet A17-2 or it may be inset to form a recess which receives graphite paper r le_l, udes of the EMAs.
Fig. 19C depicts the front side of the plastic anode flow field platelet A17-2 -Front. This platelet has both through and depth features. The major through features are the comp, ~sion tie rod holes A16 transverse manifolds; hydrogen outlet manifold A8, hydrogen inlet manifold A9 water inlet manifold A10, water outlet ,,,a,,ifulu A11 air (oxygen) outlet manifold A12 and air (oxygen) inlet manifold A13. Other through features are the hydrogen inlet via A32 hydrogen outlet via A35 cathode hul, ~ ; r;C ~ n water inlet via A44 and cathode humicl;r;~ ;on water outlet via A41. The major depth features on the front of the anode flow field platelet are the hydrogen hull~ rc~liol) s~l-er,li"e c~neL, A36 anode active area se".t:"li"e cl~annr ls A39 and the cathode humi~ lir~ - l water serpentine channel A43. These features are desi~"ed to optimize the flow rates and pressure drops of the device.
Hydrogen fuel for the anode enters the h~"--;d;r~ n area through the hydrogen inlet via A32 enters the hydrogen distribution ,--ar ~ A27 through the hydrogen distribution ...anif~ld inlet A33 and is distributed to the two hydrogen st:, ~.e"li"e .J ~dnnr lj A36 through the hydrogen se~ ~e,)li, ,e channel inlets A34. Hydrogen gas is humidified through the water p~""-~ ~ electroiytic membrane which is in contact with the hydrogen hu",i~/ ~;. .liorl se, I,~"li"e channel A36. Humidified hydrogen leaves the hurni~iiri, ~ n area through the hydrogen se".~ ~li- .e channel exits A37 enters the hydrogen 'e ~ ,- Idl A28, and passes into the anode active area distribution manifold A29, flows into the anode active area st:. ~er,li- Ie il ,annel~ A39 though the anode active area ~ ,e, llil ,e channel inlets A38. With in the active area hydrogen is cataiytically nY~ Pd on the anodesideof an EMAto produceel~l-u, s and protons. Protons pass from the anode catalytic site through the electrolytic m~" ~b~ dl ,e to the cathocie. El~l, u, la are drawn off from the anode catalytic site through the graphite el~il, ude. Electrons from the graphite elect, ude are c bytheanodecurrents- 'e ~c Illiclu:,- l~nA17-1 andconductedthroughthecompositebipolarsepcudto, by bus bars A18.
n~p'etcd hydrogen leaves the active area via the anode active area se".~"li"e il Idl .nr l ~ exits A40 and flows into the hydrogen Ic~ man~old A31 finely exiting through the hydrogen exit via A35.
Hot water for cathode (air, oxygen) hu.,,~ r~ n enters throu9h the cathode hum;~ ion water inlet via A44, passes into the cathode hu~ l riu~lio~ l water se",~:"li"e channel A43 through the cathode hu,,~;cl;r~ lion water se"~,li"e channel inlet A45 exits through the cathoc~e humi.lir;~ n water sel ~J~I lline channel exit A42 and leaves through cathode hu-, id;ri~ .1 ;on water outlet via A41. Part of the hot water flowing through the serpentine channel is osmotically pumped across the electrolytic membrane to humidify cathode air ~oxygen).
Fig. 19D depicts the back side of the plastic anode flow field platelet A17-2 -Back. This platelet has both through and depth features. The major through features are the comp,~sion tie rod holes A16 transverse m~ ,ifol~l:" hydrogen outlet manifold A8 hydrogen inlet manifold A9 water inlet manifold A10 water outlet Illdl.;fol~ A11 air (oxygen) outle~manifold A12 and air (oxygen) inlet IlldnifOld A13. Other through features are the hydrogen inlet via A32 hydrogen outlet via A35 cathode hurT~ ;ri.i tl i.~n water inlet via A44 and cathode hull .~ r;~ ~lion water outlet via A41. The maior depth features are the hydrogen inlet channel A47, hydrogen outlet channel A50, air (oxygen) outlet channel A.~3, and the air (oxygen) outlet via SY~SrrFUlE SHEET ~RIJLE 2~

W 096/37005 PCTrUS96/06877 base A55. Most of the surface of the anode flow field platelet A17-2 is used as a ciose out for the cooling water channels on the cathode flow field platelet A17-3.
Hydrogen flows from the hydrogen inlet " lal lifuld A9, through the hydrogen inlet channel inlet A48, into the hydrogen inlet channel A47, through the hydrogen inlet channel exit A46, and finally into the hydrogen inlet via A32. Hydrogen passes from back to front of the anode flow field platelet (Flg. 19C), through the hydrogen inlet via A32. Depleted hydrogen from the active areas flows back through anode flow field platelet through the hydrogen outlet via A35, into the hydrogen outlet channel inlet A49, through the hydrogen outlet channel A50 and the hydrogen outlet channel exit A51, finely exitlng into the hydrogen outlet ,,,~irul~ A8.
DPr' ~.~ ' air (oxygen) is removed from the cathode hUll~ ;u~liorl and active areas (Fig. 19F), through the air (oxygen) outlet via base A55, air (oxygen) outlet channel inlet A54, air (oxygen) outlet channel As3, air (oxygen) outlet channel exit A52, finally flowing into the air (oxygen) outlet " ,~ 'c ' ' Current is conducted through the anode flow field platelet via the two bus bars A18.
Fig.1 gE depicts the front side of the plastic cathode flow field platelet A17-3 -Front. This platelet has both through and depth features. The major through features are the C GI I Ipl ~:~iùn tie rod holes A16, transverse I l lal~ 'c ~c~ hydrogen outlet " ,~ ' 'c' A8, hydrogen inlet I l IdnitGId A9, water inlet manifold A10, water outlet Illdl 'L ~C' A11, air (oxygen) outlet ",~ ' ' A12, and air (oxygen) inlet ,,,cu, ' 'c' A13. Other through features are the air (oxygen) inlet via A60, air (oxygen) outlet via A61. anode hu", ' q~ ~n water Inlet via As8~ and anode hull ~ ~ ~ water outlet via A57. The major depth features are the cooling waterse,i,enli"ecl,~"~ A62,h~""iJ';~ nwaterinlet",ar,'':''A64andthehL""i~lric~lionwateroutlet IIIcD '' ' ' A63.
Cooling water enters through the water inlet I l lcl lifulcl A10, cooling water channel inlet A65, cooling water channel A66 finally entering the cooling water sc u,e"li"e channel A62 through the cooling water sc_, ~ li"e channel inlet A67. Flowing through the cooling water serpentine channel the cooling water picks up heat which is a by product of the 01~ ~ill ucl)e,, ,ical, ~aclions. Hot water leaves through the cooling waterserpentinechannelexitA68andflowsmtotheh~ ;r~ nwaterinletlllallifuld junctionA69,into the humi~l r~ on water inlet manifold A64, and finely exits through the hlJ" ~ riC~ ,n water cathode exit A70 and cathode water humicl~ n inlet via A56 or the hum~ ic~ n water anode exit A71 and anode waterh~""i~l r.. ,~lioninletviaA58. Hotwaterisusedforhu"~ c~lionbeCauseofithighdiffusionactivity.
Air (oxygen) enters the cathode from the air (oxygen) inlet " ,ar 'd A13, flows into the air (oxygen) inlet channel inlet A72, passes through the air (oxygen) inlet channel A73, into the air (oxygen) inlet channel exit A74, and flows to the cathode humi~ n and active area .,I ,annels through the air (oxygen) inlet via A60. Air (oxygen) is humidified as it passes through the air (oxygen) hu"~ lion channels and is consumed in the cathode active area d ~ r ;c ~ in Fig.19F. Depleteci air (oxygen) and product water leave via the air (oxygen) outlet via A61 which conne~b to the air (oxygen) outlet Illaniruld A12 through the air (oxygen) outlet channel on the anode flow fierd platelet A17-2.
Current is conducted through the cathode flow field platelet via the two bus bars A18.
Fig.19F depicts the back side of the plastic cathode flow field platelet A17-3 -Back. This platelet has both through and depth features. The major through features are the co" ,p, ~aSiOn tie rod holes A16, SUllSrnU~E SHEE~ (RULE 2B~

transverse manifolds; hydrogen outlet manifold A8 hydrogen inlet manifold A9 water inlet manifold A10 water outlet manifold A11 air (oxygen) outlet Illal)ifuldi A12 and air (oxygen) inlet ~ irul~ A13. Other through features are the air (oxygen) inlet via A60 air (oxygen) outlet via A61, anode humi- l;r(j .lion water inlet via A58. and cathode hum i- l;r c~l ;on water outlet via A59. The major depth features on the cathode flow field platelet are the air (oxygen) humi-l;r~ on serpentine l.;hdllll_i A80, cathode active area se. ye, .Lil ,e cl Idl ll'.CIS A86 and the anode hurr~;Uir.~ " water serpentine channel A77.
Air (oxygen) for the cathode enters the hulllid~r~ area through the air (oxygen) inlet via A60 enters the air (oxygen) distribution manifold A79 through the air (oxygen) distribution manifold inlet A78 and is distributed to the two air (oxygen) st:.~.~,li"e ch~ " ,cls A81 through the air (oxygen) serpentine channel inlets A80. Air (oxygen) gas is humidified through the water permeable electrolytic membrane which is in contact with the air (oxygen) hu-. ' ' ~ ' ) se~- ~.~ ~li- ~e channel A81. Humidified air (oxygen) leaves the hu- - "~ ~ ~ area through the air (oxygen) se. ~ t:r li- -e channel exits A82, enters the air (oxygen) hu~ c-~e.t ~.. Idllirl.~ i A83 andpassesintothecathodeactiveareadistribution,- IdnirUIli A84 flows into the cathode active area serpentine cl ,dnnels A86 though the cathode active area se".er,li"e channel inlets A85. With in the active area oxygen is catalytically reduced receiving protons and el~l- un~
from the anode to produce water. Electrons flow from anode to cathode via bus bars A18, into the cathode current c ~ "e ' - " ,ic, osc, ~n 17-4 through the cathode graphite el~ll uoe on the EMA and finely docking with a cathode catalytic site where the electrons react with anode ge"t:,dl~d protons and oxygen to produce surplus heat and product water. r~, ~ air (oxygen) and product water leaves the active area via the cathode active area se- ~ t:"lil ,e ~ l ldl ll l. ls exits A87 and flows into the air (oxygen) c ~
~"~ ' 'd A88 through the air (oxygen) c c " ~ manifold exit A89 finely exiting through the air (oxygen) exit via A61.
Hot water for anode (hydrogen) hu. "id~ ;on enters through the anode h~ d;~ n water inlet via A58 passes into the anode hu, ~ ca~ n water serpentine channel A77 through the anocle hU."iri:~;c~l;. nwaterserpentinechannel inletA76, exitsthroughtheanodehum~ waterst:" enli"e channel exit A75 and leaves through anode humi~ ;on water outlet via A59. Part of the hot water flowing through the se-~,enline channel is os".oi --'ly pumped across the electrolytic membrane to humidify anode hydrogen.
The bus bars A18 (top and bottom) project through the plate to contact the ~ - ,ic-, ~,sc, ~n - ~ "~ 'o~-plate A17-4 as seen in Fig.19a which shows a plan view of the plastic cathode flow field platelet A17-3 -Back with a fragment of the cathode current c ~ mi~.l USLI ~n platelet A17-4 in the lower right comer.
Platelet A17-4 is bonded into a cathode current c "~ t~ micl u~ en deprt:~siùn A90 and forms manifold close outs for the air (oxygen) hull,i~ n distribution manifold A79, air (oxygen) hull~ ion ~ ~ "~ " l manifold A83 cathode active area distribution manifold A84 and cathode active area " - r ~
I-l~l'~'-A88. TwobusbarsA18arebondedtothecathodecurrent~ c-llli~,uS-,tenplateletA17-4 to provide a good el~l. icdl connection.
The cathode current c-"- ~ - microscreen area A90 is selected to either place the surface of the cathode current - 'l~ h ll licl us~ en platelet A17-4 flush with the surface of the cathode flow field platelet A17-3 or it may be inset to form a recess which receives graphite paper elec~,ùdes of the elecl,ude W 096137005 PCT~US96/06877 membrane assemblies A3 in Fi~. 17.

Bus Bar Conduction l~.lag,aled Therrnal l~i .age~-~Q~
Thefollowingdetaileddesc~ tionillustratesbusbarthrough-conductionlH~ noftheinvention by way of example, not by way of limitation of the p- i- , 'e~ of the invention. This desLi- i,uLion will cleariy enable one skilled in the art to make and use the invention, and describes several emboLli...e~
adapldliUns, \~dl idlions, altematives and uses of the invention, including what I presently believe is the best mode of cartying out the invention.
Fig. 20 is an ~ isometric view of a single cell B 1 intemal of the stack CCJI 11 pl isil 19 sepd. dlul :, B2A and B2B sar,~vricl . ~9 EMA B3A and cu, lld~lil ,9 EMA B3B of the next adja.;~ ~t cell. In this view, only the H2 (anode) side of the bipolar sepdldlul:, are visible, but as shown below, there are cool~L~iirldle ~2 zones on the hidden ~cdtl .ode) side. The large rectangular areas B4A are the active areas of the cell, B4A
r~pl~s~,li"g the anode side and B4C the cathode side.
The EMAs B3A and B3B include cataiyst coated areas B7A and A7C that are coo- Liil ldle with the CGI I ~ponciil~9 active areas B4A, B4C. Reactant and cooling water ~ - .~u ~irOIds are evident on the margins.
Hydrogen fuel enters via the hydrogen inlet ...ar f~ B7 flows through the anode active area B4A and leavesviathehydrogenoutlet...ar.'~'dB6. Air(oxygen)entersviatheair(oxygen)inlet---a ~'c'B10flows through the cathode active area A4C and leaves through the air (oxygen) outlet Illdlli~oWi B11. Cooling water for thermal ...anag~ ent enters through water inlet ~--d -iful~ B9, flows through an intemal heat L~ I ~ge and leaves through the water outlet .. Id n;fold B8. Transverse reactant and cooling water inlet and outlet Illal~iful~s B6, B7, B9, B11, B10 and B12 pass through bipolar sepdldlol:~ B2 and EMAs B3.
Compression tie rod holes A16 are evident on the margins of the bipolar sepdldlul:~ and EMAs.
Fig. 21 is an e ,'~i~ isometric view of a 4-platelet humidified bipolar IFMT sepd dlur B2 of this invention comprising plates of three different types, plates B13-1 and B13-4 being identical current ~ "~ ;' ' ~ I. .ic. uaL. t en pl ~ Current is conducted through the two plastic core platelets B13-2 and B13-3 by one or more intemal bus bars B14. While two rectangularcross section bus bars are depicted, any number, geometrical cross section, and o- il :r,ldlion may be employed, both within the screen field or extemaltoit. Sealingiseffectedaroundthemarginofthe---i-.,us~ enplateletbytheplasticcorer'=t~ole~c B13-2 and B13-3, which may include sealing ridges (not shown) around the reactant and water " ,dn ~ 'cl~, and around the active areas B4A and B4C.
The two metallic current c ~ .-,iu-c,~.;-~,- platelets B13-1 and B13-4 are identical. Platelet B13-1 is the anode current - - "~ ~ ~ ~- -ic- usc~ con~ialing of a rt:pedlil lg pattem of through etched or punched holes. Platelet B13-2 is the plastic or ceramic anode flow field platelet consiili"g of molded depth and through features. Platelet B13-2 contains the features that define anode active area flow field B16. TheobversesideofplateletB13-2fommstheCloseoutforthethemmalllldllag-:l,,~,tcircuitB17Of platelet B13-3. Platelet B13-3 is the plastic or ceramic cathode flow field platelet cu~ lil ,9 of molded depthandthroughfeatures. PlateletB13-3containsthefeaturesthatdefinethethemmalllldnage,,,entheat cAchanger B17 and cathode active area flow field B18. The cathode active area flow field B18 is on the obverse side of platelet B13-3.

W 096/37005 PCT~US96/06877 In all plates B13-2 to B13-3 the through transverse border p~s~ges or manifolds B15 ana Cull Ipl ~ ion tie rod hoies B12 are coo- dil IdLt~ with those o~ EMA B3 in F~g. 20.
Figs. 22A-G are a series showing in plan view from the facing side of each platelet the details of one embodiment of the through and depth features of the 4 platelet bipolar st:pdl~lol plate of Fig. 21 in accord with the IFM pri"c;~.lrs of the invention. The p,ug,~:ssiùn of plates is as above. with Fig. 22A
showing front (anode B13-1 ) of platelet 1 on the left and the back ~cathode B13-4) of platelet 4 on the right.
The anode current c ~ m ic, u5L;I t en platelet B13-1 has features that define the anode active area B4A.
A sealing surface B19 with optional sealing ridges surrounds the active B4~. Manifold close outs for distribution and ~ manifolds of the anode flow field platelet B13-2 are forrned by the anode ...ic,usc.~,,...dn'c,c''closeoutsB21. Thecathodecurrent~~" ' ~--ic.us~,.~nplateletB13-4features define the cathode active area B4C. A sealing surface B22 wUh optional sealing ridges surrounds the active area B4C. Manifold close outs for distribution and ~~" '' )n ~ irulda of the anode flow field platelet B13-3 are fomled by the cathode ~ u~) ~--arifoW close outs B22.
Fig. "~B is a plan view of the plastic anode flow field B13-2 -Front with a section of the anode current ~ "~c' mic.u:,L.een platelet B13-1 in the lower right comer. Platelet B13-1 is bonded into an anode current -~ ~ mic.usc-~-, c~e,c,~;un B25 and forms IlldllirUId close outs for the anode active area d~stribution ~ ifol~l B23 and anode active area ~ d~iruld B24. Two bus bars B14 are bonded to the anode current ~c'~- ~c mic.os.,.~n platelet to foml a good el~l-i..al cc--ne~;lion.
The anode current ~ ;-os..-~n de~-~as;on B25 is selected to place the surface of the anode ~ Iu~Ll~ll platelet B13-1 flush with the surface of the anode flow field platelet B13-2, or it may be inset to forrn a recess which receives graphite paper u'~_L- udes of the el~l- ude me- ~ .b. dl ~e asse. ~ ~I' Fig. ~'7C depicts the front side of the plastic anode flow field platelet B13-2 -Front. This platelet has both through and depth features. The major through features are the com~ sion tie rod holes B12, transverse Illdl lirUI~.Js, hydrogen outlet manifold B6, hydrogen inlet Illdl lirc~ld B7, water inlet manifold B8.
water outlet Illdll'' '' B9, air (oxygen) outlet manifold B11, and air (oxygen) inlet manifold B10. Other through features are the hydrogen inlet via B26 and the hydrogen outlet via B28. The major depth features on the front of the anode flow field platelet are anode active area serpentine Clldlll)el~ B31, anode active area distribution ~--d--ifold B23 and the anode active area "~~' n manifold B24. These features are de~;y"ed to opli",i~: the flow rates and pressure drops of the device.
Hydrogen fuel for the anode area enters through the hydrogen inlet via B26, passes through the anode active area distribution Illar,iruld inlet B27, into the anode active area distribution manifold B23, flows into the anode active area serpentine cl~annels B31 though the anode active area St~ , llil ,e channel inlets B30. Within the active area hydrogen is catalytically oxidized on the anode side of an EMA to produce ele~L,uns and protons. Protons pass from the anode catalytic site through the elc~ll.,lytic ll,t:---b-~,e to the cathode. Electrons are drawn off from the anode catalytic site through the graphite electrode. Elecl. uns from the graphite electrocie are cc " ' i by the anode current ., ~ "~ ' m iCI usc, ~"
B13-1 and conducted through the composite bipolar se~dldLùl by bus bars B14.
Depleted hydrogen leaves the active area via the anode active area serpentine ch~ -- .e:s exits B32 and flows into the anode active area ~ manifold B24, through the active area ~ ..a, ~irold SUBST TU~ES~U~2B,) exit B29 and finally exits through the hvdroaen exit via B28.
Fig.22D depicts the back side of the plastic Anode Flow Field Platelet B 13-2 -Back. This platetet has both through and depth features. The major through features are the CGIllpl~:ss;on tie rod holes B12, transverse Illallir~Jlda, hydrogen outlet manifold B6, hydrogen inlet ",a"if~,lcl B7, water inlet manifold E~9, water outlet ")ar,iruld B8, air (oxygen) outlet ll)dllifuld B11, and air (oxygen) inlet ..,dnifulcl B10. Other through features are the hydrogen inlet via B28 and the hydrogen outlet via B26. The major depth features are the hydrogen inlet channel B34, hydrogen outlet channel B37, air (oxygen) outlet channel B40, air (oxygen) outlet via base B43, air (oxygen) inlet channel BCi0, and the air (oxygen) inlet via base B42. Most of the surface of the anode flow field platelet B13-21s used as a close-out for the cooling water ~;l Idnl ~el on the cathode flow field platelet B13-3.
Hydrogen flows from the hydrogen inlet Illdn-' ~d B7, through the hydrogen inlet channel inlet B35, into the hydrogen inlet channel B34, through the hydrogen inlet channel exit B33. and finely into the hydrogen inlet via B26. Hydrogen passes from back to front of the anode flow field platelet Flg. ggD, through the hydrogen inlet via B26. re r ~ hydrogen from the active areas flows back through anode flow field platelet through the hydrogen outlet via B28, into the hydrogen outlet channel inlet B36, through the hydrogen outlet channel B37 and the hydrogen outlet channel exit B38, finaliy exiting into the hydrogen outlet Illdllirold B6.
Air (oxygen) flows from the air (oxygen) inlet ",~ ~irold B10, through the air (oxygen) inlet channel inlet B49, into the air (oxygen) inlet channel BJ0, through the air (oxygen) inlet channel exit BCil, and finsly into the air (oxygen) inlet via base B42 which communicates with the air (oxygen) inlet via B44 on the cathode flow field platelet B13-3 in Fig. ggE. The air (oxygen) inlet via B44 brings air (oxygen) to the cathode active area flow field.
air (oxygen) is removed from the cathode active area through the air (oxygen) outlet via B4s (Fig. 22E) into the air (oxygen) outlet via base B43, into air (oxygen) outlet channel inlet B41, through the air (oxygen) outlet channel B4û, past the air (oxygen) outlet channel exit B39, finally exiting through the air ~oxygen) outlet Illdl lirGld B11.
Current is conducted through the anode flow field platelet via the two bus bars B14.
Fig. 22F depicts the front side of the plastic cathode flow field platelet B13-3 -Front. This platelet has both through and depth features. The majorthrough features are the com",~ssion tie rod holes B12, transverse Ill~D ,ir. ' ~ hydrogen outlet Illdnifold B6, hydrogen inlet ~"anirold B7, water inlet Illdl lirUId B9, water outlet manifold B8, air (oxygen) outlet Illdl ''_' ' B11, and air (oxygen) inlet manifold B10. Other through features are the air (oxygen) inlet via B44 and the air (oxygen) outlet via B45. The major depth feature is the cooling water sel~ e ,li"e cl Idl ll i. ls B46.
Cold cooling water enters through the cooling water inlet " ,anifold B9, flows into the cooling water s~, ,ut:nline channel inlet B47, and passes into the cooling water serpentine channel B46. Flowing through the cooling water serpentine channel B46 the cooling water picks up heat which is a by product of the cl~l.u.,lle,,,ical l~:aclions. Hot water exits through the cooling water serpentine channel exit B48, finally leaving through the cooling water outlet IllalliruW B8.
Air (oxygen) passes through to the cathode flow field platelet B13-3 -Back through the air (oxygen) -3j-W 096/37005 PCTrUS96/06877 inlet via B44 which communicates with the air (oxygen) inlet via base B42 and the air (oxygen) inlet manifold B, O on the anode flow field platelet B13-2 -Back in Fig. ""D. Depleted air (oxygen) and product water leaves the cathode flow field active area through the air (oxygen) outlet via B45 which communicates with the air (oxygen) outlet via base B43 and the air (oxygen) outlet manifold B11 on the anode flow field platelet B13-2 -Back in Fig. 22D.
Current is conducted through the cathode flow field platelet via the two bus bars B14.
Fig. G depicts the back side of the plastic cathode flow field p~atelet B13-3 Back with a portion of the cathode current r ~ .l uaCl ~n platelet B13-4 shown in position (fragmentary portion shown in the lower right comer). This platelet has both through and depth features. The major through features are the compr~:asion tie rod holes B12, transverse ",~ '( 'd~ hydrogen outlet manifold B6, hydrogen inlet Illar ' 'd B7, water inlet I lld~ old B9, water outlet Illal ' 'd B8, air (oxygen) outlet ~"ar iruld B11, and air (oxygen) inlet manifold B10. Other through features are the air (oxygen) inlet via B44 and the air (oxygen) outlet via B45. The major depth features on the cathode flow field platelet are the cathode active area distribution ,,,ar,irul~ B53, cathode active area --"- ~ ",~,' ' ' B57, and the cathode active area s~ ~-e, llil ,e cl ,d- Inels B55.
Air (oxygen) for the cathode enters the hull~ f~ or. area through the air (oxygen) inlet via B44, passes the cathode distribution Illdr ' ' ' inlet B52, flows into the cathode distribution manifold B53 and is distributed to the cathode active area s~ ,e cl-~,ncla B55 though the cathode active area serpentine channel inlets B54. Within the active area oxygen is catalytically reduced receiving protons and ele_LI uns from the anode to produce water. Electrons flow from anode to cathode via bus bars B14. into the cathode current & - " - ...;~,. OSL;I ~,- 17-4, through the cathode graphite el~l-ude on the EMA and finely docking with a cathode catalytic site where the ele_L. u-)s react with anode 9~ ~~- cled protons and oxygen to produce surplus heat and product water. Depleted air (oxygen) and product water leaves the active area via the cathode active area s~" e- lli"e channels exits B56 and flows into the cathode active area c-"~ ifoW B57, through the air (oxygen) c~ manifold exit B58 finely exiting through the air (oxygen) exit via B4~ which COIlllllull;~ dL~s with the air (oxygen) outlet via base B43 and the air (oxygen) outlet Ill~)iful~ B11 on the anode flow field platelet 13-2 -Back Fig. 22D.
Platelet B13-4 is bonded into a cathode current ~ ",ic, us~,, ~n dep- ~asiun B59 and forms , ..a. .i~uld close outs for the air (oxygen) active area distribution manifold B53, and the air (oxygen) active area ~ irul~ B57. Two bus bars B14 are bonded to the anode current ~ ~ " - ~ . ,i~i, ua~,-l ~,-platelet in a manner to provide good el~ .al conduction. The cathode current c - " miL. usc, ~n area B59 is selected either to place the surface of the anode mi.;, usc, ee,- platelet B13-4 flush with the surface of the cathode flow field platelet B13-3~ or it may be inset to fomm a recess which receives graphite paper electrodes of the electrode me".br~e assemblies B3 in Fig. 20.
Edge and Through-Conduction Section Views:
Fiç1s. 23A-D show several altemative constructions for edge conduction, taken along the section line 23-23 of Fig. 16. Fig. 23A shows the embodiment of Fig.16 in which the anode mic, us,i,~" F17-1 and cathode mic.usc-.~ en F~7-4 are connecL~d by current bridge F18, and folded togell.e. and bonded to the platelets F17-2 and F17-3 therebetween to form the BSP. Various depth, through and close-out S~SnMESff~r~$~~

CA 0222090l l997-ll-l2 features are descri~ed a~ove with respect to Fig- 16 (and related platelet drawings) so they will not be repeated here or in Fiç~s. 23B-D.
Flg. 23B shows the tabs F94 on both the anode mic,usc,~n F17-1 and cathode mi..-,usc,et,l platelet F17-4 bent together and bonded at the bottom, by methods such as brazing, SGldt:,ill9, spot welding, conductive cement. roll crimping, and the like. Fig. 23C shows an overlap of tabs F94 and bonded at F96. This type of contact could also be a press fit of tab F94 of platelet F1701 into the gap between the tab F94 of platelet F17-4 and the bottom of the two core pl~t~4t~ Fig. 23D shows an example of two edge bus bars or strips F97 top and bottom spot welded or bonded at F98.
Figs. 24A and B show section views of various emb- ll~ ll~ of the bus-bar conduction taken along line 24-24 of Fig. 18. FTg. 24A shows an e" lbodi. "enl wherein the " ,ic, us ;1 ~ ,s A17-1 and A17-4 are inset in a ,~cesses A94 in the respective core platelets A17-2 and A17-3. The bus bars A18 are inserted through the bus bar .~t~nliol) slots A95. The various depth, through and close-out features are des.,-. iL,ed above in cGl)l)eclion with Fi~. 18 and related platelet d~ yS. Fi~. 24B shows I I ,ic, usc, ~ ,:, with pe, i~,l)e, al edges COGI Ui. Idl~ with the edges of the core pl~t~letc Co.,.~.o~ B~polar Sep.-.dl~r FaL,icd~ P ~"ess~
Fig. 25 is a flow sheet depi ,lil lg the pl il l ,i~Jal steps in the platelet manufacturing process involving feature ru,ll,dlion by cl)~.,ical milling (etching). While this applies plill ~ Iy to a metal ",ic,us",~., platelet as desc, iL,ed in the example below, the metal dies for the plastic core ~ ~ ~ ~ are produced by thisprocess. Further~thisprocessisusedtoproducetheplasticplateletslll~lllselvesby~;llelllicalmilling~
typically by solvents. The steps are as follows:
A. PLATELETSTOCKlNSr~~ ; I,,cu,,,i.,gmetalplateletorsld,, ,gdiestockC1 is s~,s t~ ~ to il lip~liun C2 to verifymaterial type, rolled hdl-ll le~s, rolled l h 'c n:Ss, surface unifommity, and relevant supplier il lru~ dLiol).
B. PLATELET STOCK CLEANING AND DRYING: Platelet stock is cleaned and dried C3 forpholo,~sis~F~'ic ~ ~byscrubbing,deyltd~illg.andCll~llliCalCleaningUSinganaUtomatiCmaChine.
This process removes residual sheet stock roiling grease and oils in the case of metals and dirt and static cling COIIIdlllilldlll:, in the case of plastics. After dey,~dsi.lg the platelet is sll~, t~ ~ to a mild chemical cleaning at room temperature by a dilute etching solution to remove oxides and surface impurities. For titanium the cleaning solution is 3%-9~/O HF and 10%~18% HNO3. For other metals such as, I e s steel or aluminum, ferric chloride of 30-45 degree Baume at room temperature is used as the cleaning solution.
For plastics, the apprup, idle plastic solvent may be employed. Platelets are dried in a forced convection dryer as the final step prior to ~r~r~ n of pholo, ~si;il.
Depe~- Ig on whether the resist is wet or dry, the resist ~pp ~ ;on pl uceeds by either Steps C-1 and C-2, or by C-3, below.
~C-1. WET PROCESS PHOTORESIST APPLICATION: Wet process pholùl ~;sl allows the finest ~I s - - Ition of details due to the thinness of the pholol esisl layer. Wet pholul e:,isl is typically applied, -C4, using a dip tank. Small platelets may be spin coated using spin coating machines developed for the se,l l ,ico" luctor industry.
C-2. RESIST OVEN: Wet resist is baked (cured) in oven C5 to from a hard resilient layer.

RU~

W 096/37005 PCTrUS96/06877 C-3. DRY PROCESS PHOTO-RESIST APPLICATION: Dry film photo-resist is used where tolerances can be relaxed. For fuel cell sep~ ~llul i dry film resist is typically used. Dry film resist is peeled off a backing sheet and bonded, C6, using a heated roller press. The roller press is similar to those used in the printed circuit industry. The rolling process automatically peels off the backing material from the phOIolt:ai,l. Typical dry film photo-resist material is 2 mil "Riston 462~" manufactured by the duPont Company.
D. PHOTO-RESIST MASK UV EXPOSURE: Platelets are ~o~posed C7 using a UV contact exposure machine. Careful dLL~)Iion is paid to precise alignment of both sides of the artwork. Rey;~LI dLion targets on the mask are used to aid this process.
E IMAGE DEVELOPING: Tho ~ - ~ .oced platelet is passed, C8, through adeveloping solution and oven. Wet process resist is developed in a hylJI u~.-dl bon dcvelo,u~l . which removes uncured resist.
Typical dcv_lupe( is ~S~odd~J-s Solution", part number GW 325, manufactured by Great Western Ch~ and Butyl Acetate, part number CAS 104-46-4, available from \lan Waters and Rogers. Wet process dcvelopl"ent uses these solutions full strength at room temperature. After exposure to the dûv~ i.lg agents the ,~"~..., ~,9 wet resist is rebaked to form a resilient layer. Dry process dcv~ ,g uses duPont "Liquid Dcvelupel Conc~,LIdL~, part number D-4000, in a 1.5% solution at 80'F.
F. SPRAY ETCH TANK Cl -'1!C.'~I MACHINING: Developed platelets are etched C9 in a spray etch tank. Spray tanks are pl _~. l t d to dip tank etchers due to the higher etch rates which result in highe m "acl, ,e throughput rates. In some cases finer r- ~ 'ution can be _ t. ,~l with dip tank etchers than can be obtained from spray etchers. The etching process is ver~ sensitive to the strength of the etchant solution, speed of the conveyer belt, spray pressure and process l~:l l l ,ut:l dlure. Process f~ ~ k C11 on these parameters is " , ~ Ied during a production run by continuous in-process inspection C10.
Line speed is typically varied to obtain the desired etch results. Either ferric chloride or HF/nitric acid solution is used as the etchant. Ferric chloride is used for copper. aluminum, and r~ steel. HF/nitric acid is used for titanium. For titanium typical etchant conct:"l,dLions nun from 3%-10% HF and 1 û%-18%
HNO3. The range of etching temperatures for titanium are 80-130 F. For other metals typical ferric chloride concer,L,dLiuns are 30-45' Baume' with the etching temperature " ~ ,ed in the range of 80-130'F. The specific concel ILI dLiun and lel l ,pe, dlure condiLions can be cul lll~ for each different metal employed. Line speed is a function of the number of active etching tanks. Typical etchers are built up from individual etching tanks joined by a co"""on conveyer. Typical etchers are available from Schmid Systems, Inc. of Maumee, OH and Atotech Chemcut of State College, PA. Platelets are washed in a cascade washer after the last etch tank. The cascade washer removes excess etchant prior to il Ispe~liun.
G. IN-PROCESS INSI~ lOiN; Platelets are inspected at C10 to feed back etch rate and line speed il ,lu" "dliun to the etching process. In-process inspection is typicaliy performed visually.
H. STRIP RESIST: Wet process photo resist is stripped C'12 using a hydrocarbon stripper at 200'F. A suitable one being "Chem Strip", part number PC 1822, rnanufactured by Alpha Metals of Carson, C~ llia. Dry process photo resist is stripped using a ccmmercial strip solution such as ~Ardrox~, part number PC 40~i5, manufactured by Ardrox of La Mirada, (: ' , lia. Ardrox is diluted to 1 -3% and used at 130 F. After Ll i~pi. .g the platelets are cleaned using a cascade washer.

~Er RULE2~

CA 0222090l l997-ll-l2 W O 96/37005 PC~rrUS96/06877 1. FINAL INS~ ON: Visuai final inspection is performed C13 by measuring and cc""pd,i.,gwiththecriticaldimensions.plateletinspectioninformationC30selectedduringtheCADdesign process. This i"~, llldlion is fed back to control the etching and design process. After finai inspection the completed metal platelets are p,ucessed by either process J-1 or J-2.
J~ vl.Jr~ FD. .NACF- Completed titanium platelets are subjected to nitriding C14 in a vacuum fumace. Sepa,dlu,a are loaded into a vacuum fumace which is evacuated to 10-6 torr. Dry nitrogen is introduced into the fumace to a pressure of 1 psig. This cycle is ,~r~ Once the final pressure of 1 psig is attained the fumace is heated to between 1200 F and 1625 F for a period of from about 20 to about 90 minutes. The specific times and temperatures depend upon the thickness of the titanium nitride coating desired. The furnace is cooled, repressured and the finished product nitrided (passivated) platelet is ready for ass~"bl~ with plastic core fluid l,l~,ag~,lenl platelets to make a cu",posi~e sepdl J_2 NITRIDING FU..IJA~F BYPASS: Metals other than titanium are not nitrided.
K. METAL MIO~OS~I ~LLN MOTHER SHEETWORK IN l'I ~0; t~S BUFFER INVENTORY:
Completedmetallll;~lùscl~nmothersheetsarequeuedinabufferinventorybeingkeptlùy~:lll~ bytype or in groups. Note the roll stock is typically titanium of ll ~ 'c. ,ess 4-25 mils (dep~ ~ ,9 on platelet design req~ r ~, It:nla) 36 ' wide and the platelet blanks are 6-x8~, so that in the continuous feed process des., iL,ed above the pl-tF~letc are ~u I dl l~ed 6-up that is, 6 across the width of the sheet.
It is i",po,l~,l to note that this process can be used for forming the plastic core platelet CGIllpf255iOl I or embossing dies.
Flg. 26 is a process flow sheet depicli"g the presently p, ~ d method of r~bl icali~ ~9 plastic fluid anagel"ent platelets and Idlllilldlillg with metal Illiclus~l~n platelets to form Illon- h;~ composite bipolar sepdldlula.
A. COhll~t~SlON MOLDlNG PROCESS: Inco" ,i"g plastic platelet stock Cl 7 is s~ Ibjected to illspeclion to verify material type rolled hdl-~lless. rolled ll ;(hless. surface unifommity and relevant supplier i"lu" "alion. After i, lape~lion plastic sheet stock is Col llp- t:ssion molded C18 to fomm depth and through features. Co,,,~ asion molding is capable of fomming depth features with infinitelY variable depths as well as widths.
B. PLASTIC PLATELET SINGULATOR: Plastic platelet mother sheets are singulated by the plastic platelet singulator C19. Shears saws knives and punches are typical methods of singulating plastic pl~tPIetC
C. ADHESIVE 80ND AID APPLICATION PROCF~:S- Adhesive bond aid C20 is applied to the plastic core platelets to facilitate leak free bonding. The specific nature of the bond aid depends on the type of plastic being bonded. Bond aid varies from solvents epoxy glues and contact adhesives.
Bond aid is applied using spray or screen printing processes depending upon the plastic platelet being ~dbl iCdl~.
Bond aid is applied to the mating lands of platelets and must be prevented from flowing into depth features which can cause partial or total b'ock~ge of fluid p~Cs~es This requires precise control of bond aid viscosity and ~ppl;c~tion th P~.,ess. The viscosity and Ihiclh)ess parameters vary for each plastic /

SU~1u It SH~ ~lUlE ;~6~

W 096/37005 PCTrUS96/06877 bond aid combination and are well known in the art.
D. METAL PLATELET SINGULATOR: Metal mit,,usc,~,) platelets mother sheets C16 aresingulated by the metal platelet singulator C21. Shears, or saws are typical methods of singulating metal r' E. STACKING PROCESS: Metal and plastic platelets are oriented hu,i ul ly ordered(placed in proper sequence~. and verticaliy stacked in sequence C22 on hot platens. The platelet alignment holes (compression tie rod holes of the various figures) are placed over pins to precisely align the platel~
so that mating platelet features coll~ldle to foml thevias, lands, Illdllilulds and cl1dlll)els. in this manner up to 100 composite bipolar Sepdl dlUI ::i may be stacked for lamination at a time in a single bonding stack between a top and a bottom platen.
F. LAMINATION BONDING: The asselllbled platelet stacks are loaded into a heated Id"-i--dliun press for bonding C23. Different metals, plastic and bond aid comb;.,aliu.ls require different bonding schedules. Bonding cor - 1S are d~,---i--ed by a specific schedule of applied pressure and t~"p~dl,Jre. Typicat bond t~..pe,d-lresrange 15û deg. C to 30û deg. C. Bond pressureand temperature must be precisely co- .I-, ~ t to prevent excessive de~o",~dlion of internal p~csageC while achieving leak proof bonds.
G. PROOF AND/OR LEAK CHECK Bonded platelet sepdldlo.a are ledk checked, C24, using a test fixture to apply interrlal pressure to the ~;l Idl In~,lS, Illdl ~ifulds and vias to verify bond integri~y, i.e., that there are no edge ieaks or internal channel short circuits.
H. FINALTRIM: P, uces:,iny aids. such as handling frames and platelet se~uencing numbers (formed on the edges of the pl ~t~ ) are removed (cut offl in the final lrim op~dlion C25 to produce the composite bonded platelet sepdldlùt having the intricate, intemal Illil.;lUCIldllll~al fields des.;-iL,ed above.
Fig. 27 depicts the process of p. ~ldl il l9 the platelet design artwork for the ph - ~s ,og. dpl Iy wet or dry process etching of platelets des-" ibed above in Figs. 25 and 26. The steps are as follows:
A. PLATELET DRAWINGS: Platelet assembly drawings are developed on computer auLo,..dled drawing CAD systems C27. The II~Juiny~ are dimensioned in net dimensions. Both sides of each platelet are finalized as plan views riepi~li"g the front and back. These ~J, c.~;. ~yS are ele ,l, u- ily transmitted to the platelet mask artwork generation CAD system C29. From the CAD drawings a platelet i"spe~;lion ~ ce C30 is gene, dled. This inspection ~ e consists of critical dimensions that need to be verified during the artwork creation and manufacturing plucl~55es Both artwork and pl~t~'etC are inspecte~ during the manufacturing process.
B. MASK ARTWORK GENERATION: Platelet CAD dICL~ I9S are converted in the mask artwork CAD system C29 to photo tooling masks for each platelet. Etch factors are applied to each feature in each drawing. Etch factors adiust the width of the phot~ u )g mask to the width of the features to compensate for undercutting that occurs during the Ll,~:",ical etching p,ucesses used to mill individual ~ ~t~lefc This entails reducing channel d~mensions in the photo tooling mask to compensate for undercutting. EtchfactorsdependuponthetypeOfmetal.typeof ;h~lllicdlmi~ingequipment,etchspeed~
type and strength of the etchant used. FabriCdliOn aids are added during the mask 9 ~ 1dlion process.
Fab,icalion aids include .~;~,dlion targets, platelet numbers and handling frames to aid in the stacking SUBSm~ES~

and bonding process.
C. bRTWORK PHOTOPLOTTING: Platelet art work is plotted at a 1 times magnification on a film using an automatic photopl~tt~r C31.
D. POSITIVE INSI~tL~ I ION: Video inspection of the finished artwork is performed, C32.
using the i.,~pe~;lion ~ ce C30 ~el-elnL~d during the Platelet CAD drawing process. After i--speclion the top (front) and bottom (back) platelet artworks are joined in precise l ~.~1l dlion to fom platelet artwork C33.
Platelet artwork is used in the chemical milling p-ucesses that make metal ~ usCI~ r 't' It is also used to develop co...p.~:,sion molding tooling.
It should be Ul .~ ;.luod that various mo~ 'ic~ , ~s within the scope of this invention can be made by one of ordinary skill in the art without depd- li. ~9 from the spirit thereof. We ll ~~ ~u. ~ wish our invention to be defined by the scope of the appended claims as broadly as the prior art will pem~it, and in view of the sre~ :r~ n if neeci be.

Claims (46)

1. A method for producing fuel cell separator assemblies comprising the steps of:
a) forming in thin sheet stock a plurality of different individual platelets with coordinate features selected from microchannels, vias and manifolds, said features together forming at least one active area field for oxidant or fuel consumption in contact with a membrane electrode assembly;
b) stacking said platelets with said individual platelet features in precise alignment with corresponding features of a matingly adjacent platelet to provide continuous circulation paths for said oxidant or fuel;
c) bonding said aligned platelets to form a monolithic separator having internal microchannels and access manifolds thereto.

2. A method as in claim 1 wherein:
a) said sheet stock is metal; and b) said forming step includes the step of etch forming said features.

3. A method as in claim 2 wherein:
a) said etch forming includes a combination of depth etching and through etching.

4. A method as in claim 3 wherein:
a) said through etching comprises depth etching selected areas from both sides of said sheet stock to depths greater than 50% the sheet thickness.

5. A method as in claim 4 wherein:
a) said metal is selected from Ti, Al, Cu, W, Niobium, stainless steel, and alloys, laminates, platings and composites thereof.

6. A method as in claim 2 wherein:
a) photolithographically resist coating said sheet metal stack to define features thereon.

7. A method as in claim 2 which includes the step of:
a) passivating said separator after bonding.

8. A method as in claim 7 wherein:
a) said bonding is diffusion bonding under heat and pressure.

9. A method as in claim 8 wherein:
a) said metal is Ti; and b) said passivating includes exposure to Nitrogen at an elevated temperature.

10. A polar fuel cell separator assembly comprising in operative combination:
a) at least one core platelet of thin sheet material selected from ceramic or plastic having a first side and a second side;
b) at least one side of each platelet having fluid distribution features formed therein, said features being selected from at least one of fields. close-outs, splitters. via bases, lands, metering orifices, channels, vias, mixers. filters, Coanda-effect circuits. diverters, and manifolds;
c) said features are coordinate from platelet to platelet to provide at least one microchannel reactant flow field area;
d) said core platelet is bonded to selected ones of a current collector platelet to form a unipolar terminal current collector, to another core platelet, or to at least one other core platelet and at least one current collector to form a monolithic bipolar separator, for association with an electrolyte membrane assembly to form a fuel cell stack.

11. A polar fuel cell separator assembly as in claim 10 wherein said current collector platelet is selected from metal, conductive plastic, conductive ceramic, metallized plastic, metallized ceramic or composites thereof.

12. A polar fuel cell separator assembly as in claim 11 wherein at least some of said features form at least one coolant field for thermal management.

13. A polar fuel cell separator assembly as in claim 10 wherein at least one of said features form at least one humidification field for a fuel or an oxidant.

14. A polar fuel cell separator assembly as in claim 12 wherein at least one of said features form at least one humidification field for a fuel or an oxidant.

15. A polar fuel cell separator as in claim 14 wherein said coolant field communicates with at least one of said humidification fields to provide heated humidification fluid to said humidification field.

16. A polar fuel cell separator as in claim 10 wherein said features are formed by a combination of depth forming and through forming.

17. A polar fuel cell separator as in claim 11 wherein said core platelet is disposed between a pair of spaced apart microscreen collector platelets, or between a microscreen collector platelet and an endplate, and said pair of microscreen platelets and said microscreen and endplate combination are in electrical communication with each other by means selected from one or more current bridges, current tabs, spring clips. edge jumpers, pleated conductive current bridges, edge bus bars, internal bus bars, or combinations thereof.

18. A polar fuel cell separator assembly as in claim 17 wherein said core platelets are plastic and said features therein are formed by compression techniques selected from stamping, embossing, punching, compression molding of sheet stock and injection molding.

19. A polar fuel cell separator assembly as in claim 18 wherein at least some said features are formed on each side of said core platelet.

20. A polar fuel cell separator assembly as in claim 19 wherein said core comprises at least a pair of platelets bonded to each other, a first of which is an anode flow fluid platelet and a second of which comprises a cathode flow field platelet.

21. A polar fuel cell separator assembly as in claim 20 which includes bonded to said platelet core a pair of microscreen platelets, including a first anode microscreen platelet and a second cathode-microscreen platelet.

22. A polar fuel cell separator assembly as in claim 21 wherein said microscreen platelet includes areas having apertures therein, said apertures being selected from round holes, hexagons, slots, Tees, chevrons, squares, diamonds, triangles, ellipsoids and NACAs parts.

23. A platelet for a polar fuel cell separator assembly comprising:
a) a thin sheet material selected from ceramic, plastic, metal, conductive plastic, conductive ceramic, metallized plastic, metallized ceramic or composites thereof, each said sheet having a first side and a second side;
b) at least one side of said platelet having microchannel fluid distribution features formed therein, said features being selected from at least one of fields, metering orifices, channels, vias, via bases, lands, mixers, filters, diverters, splitters, Coanda-effect circuits, and manifolds;
c) said features. in cooperation with other platelets or an electrolyte membrane assembly in said fuel cell separator provide at least one microchannel reactant flow field area.

24. A platelet as in claim 23 wherein said sheet is selected from metal, conductive plastic, conductive ceramic, metallized plastic, metallized ceramic or composites thereof, and said features in said flow field area include through features forming a microscreen current collector platelet.

25. A platelet as in claim 24 wherein said sheet is selected from electrically non-conductive plastic or electrically non-conductive ceramic. and include features therein forming a core platelet selected from an anode flow field platelet and a cathode flow field platelet.

26. A platelet as in claim 25 wherein said features include features forming at least one microchannel coolant field.

27. A platelet as in claim 26 wherein said features include features forming at least one microchannel humidification field.

28. A platelet as in claim 27 wherein said coolant field and said humidification field microchannels are in communication to provide counterflow humidification of reactant gases.

29. A platelet as in claim 28 wherein said reactant flow field area is in an external surface of a plurality of platelets forming a core, and said coolant field is interior thereof and disposed with a substantial area coordinate with said reactant flow field area.

30. A platelet as in claim 29 wherein a platelet includes on said first surface at least one reactant flow field area and on said second surface said coolant field.

31. A platelet as in claim 30 wherein said first surface includes at least one humidification microchannel area.

32. A platelet as in claim 23 wherein said microchannels are tailored in length, cross-sectional dimensions and serpentine configuration to the reactant fluid composition and viscosity.

33. A fuel cell stack comprising in operative combination:
a) a plurality of cells comprising:
i) bipolar separator and membrane electrode assemblies in a stacked array;
ii) an anode separator end plate at one end of said stack in contact with one of said membrane electrode assemblies;
iii) a cathode separator end plate at a second end of said stack in contact with a membrane electrode assembly;
b) said bipolar separator, and said anode and cathode separators include core platelets as in claim 18; and c) said cells are assembled in sequence under compression to form an operating cell.

34. A fuel cell stack as in claim 33 wherein said features include at least one microchannel coolant field area.

35. A fuel cell stack as in claim 34 wherein said features include at least one microchannel humidification field for a fuel or an oxidant in communication with said coolant field to provide heated fluid to said humidification field.

36. A fuel cell stack as in claim 35 wherein said fields are tailored in length,microchannel cross-section dimension and serpentine configuration for H2 as fuel and air/O2 as an oxidant.

37. A fuel cell stack as in claim 36 wherein said separator include electricallynon-conductive core platelets of plastic or ceramic laminated between current collector microscreen platelets separators formed of diffusion bonded metal selected from Ti, Al, Cu, W, Niobium, stainless steel, alloys, laminates, platings and composites thereof.

38. A fuel cell stack as in claim 37 wherein:
a) said membrane electrode assembly is selected from a carbon paper coated PEM and a carbon paperless PEM, and b) said separators include a window frame platelet in contact with said carbonpaper coated PEM or a window screen platelet in contact with said carbon paperless PEM.

39. A process for producing platelets for fuel cell separator comprising in any operative sequence the steps of:
a) providing a thin sheet material having a first and a second side;
b) forming partial and through fluid distribution features on at least one side thereof, selected from at least one of microchannel fields, metering orifices, channels, vias, splitters, close-outs, via bases, lands, mixers, filters, Coanda-effect circuits, diverters and manifolds; and c) said microchannel features are oriented to coordinate with current collectors, adjacent core platelets, end plates and electrode membrane assemblies to provide at least one microchannel reactant flow held area for said fuel cell.

40. A process as in claim 39 wherein said forming includes feature forming on both sides of said sheet.

41. A process as in claim 40 wherein said forming step includes forming said microchannel reactant flow field on a first side and a microchannel cooling field on said second side at least a portion of said cooling field area overlapping said reactant flow field area.

42. A process as in claim 41 wherein said forming step includes forming at least one microchannel humidification field on said first side.

43. A process in claim 39 wherein said step of forming includes tailoring said microchannels in length, cross-section dimensions, and path configurations to the reactant fluid composition and viscosity.

44. A process as in claim 43 which includes the added steps of:

a) photolithographically designing at least one die pattern having microchannel patterns;
b) applying a resist to a metal sheet in said die pattern;
c) etching said sheet to form a die for said microchannel patterns: and d) using said die to form said features in said platelet.

45. A process as in claim 39 wherein said sheet is selected from plastic and ceramic for core platelets, and a conductive material selected from metal, a conductive plastic, a conductive ceramic, a surface metallized plastic, a surface metallized ceramic and composites thereof for microscreen collector platelets.

46. A process as in claim 45 which includes the added steps of a) photolithographically designing at least one die pattern having microchannel patterns;
b) applying a resist to a metal sheet in said die pattern;
c) etching said sheet to form a die for said microchannel patterns; and d) using said die to form said features in said platelet.

The comments in the ISR on claims 37 and 38 is noted and these claims are amended herewith.
The Amendment inserts the inadvertent omission of the antecedent reference to the separators, namely in claim 37, line 1, after "wherein" reference -said separators- has been inserted. For grammatical correctness, the word "said" has been deleted after "include." Thus, claim 37 would read: "A fuel cell stack as in claim 36 wherein said separators include electrically ...."
No amendments are necessary to claim 38. There is no impact on the description or drawings.
A replacement page 46 is enclosed with claim 37 retyped to correct the obvious grammatical error. No other changes have been made for the claims.