JP2007515785A - Two-stage wafer coating underfill - Google Patents

Abstract

A method and material for applying underfill to a microelectronic chip assembly, particularly an integrated circuit.
A 100% non-volatile, one-part liquid underfill encapsulant applied to the active surface of a large wafer or integrated circuit chip is disclosed. Upon application, the encapsulant is converted to a liquefiable, non-sticky solid by exposure to radiation, particularly UV, visible and infrared. Underfill coated wafers show significant shelf life without progress of curing. Large wafers are singulated into small wafer sections and stored for several months, after which the wafer connection assembly is fixed during solder reflow, the underfill liquefies, drains into fillet, and heat cures during heat activated crosslinking Convert.
[Selection] Figure 1

Description

  The present invention relates to microelectronic chip assemblies and more particularly to methods and materials for applying underfill to integrated circuit wafers.

  Surface mounting of electronic components is well developed in automated package assembly equipment. Integrated circuits are made up of devices such as transistors and diodes and elements such as resistors and capacitors that are coupled together by conductive connections to form one or more functional circuits. These devices are formed on a silicon wafer or sheet, and the surface of the device goes through a series of manufacturing steps to create a score line or saw street on the surface of the wafer that acts as a boundary between dies, chips or dies. By repeating the rectangular pattern, patterns of the same integrated circuit separated from each other are formed. The dice singulated from the wafer in the final stage of the manufacturing process are bonded to the substrate to form an IC package.

  Conventional flip-chip technology generally refers to an assembly in which the active surface of an integrated circuit is attached to a package substrate or printed circuit board (collectively referred to as a PCB). The flip chip assembly can be designed with or without underfill mounting. For flip chip use, the chip comprises small bumps or balls of solder that are placed at locations on the active surface that are designed to correspond to recesses in the surface of the circuit board. The chip is mounted to align the bump with the substrate so that the solder bump is sandwiched between the pad on the substrate and the corresponding pad on the chip. Heat is applied to the point where the solder of the assembly reflows after the flux is applied. Upon cooling, the solder hardens, thereby attaching the flip chip to the surface of the substrate. Conventional underfill is used in a few different ways, applied to the attached chip and applied to chemical attacks, moisture, airborne contaminants, etc., and mechanical shocks encountered in transportation and use Protect the chip against vibration and temperature cycling. Conventional capillary flip chip underfill methods require chip and circuit board alignment, flux distribution, solder reflow, flux cleaning, underfill application, underfill flow and cure.

  Underfill used in chip packages interconnects the chip and package or substrate to protect solder seams from environmental elements such as moisture and contaminants, and redistribute mechanical stress to extend device life Fulfills the function. Protects the chip against corrosion of metal interconnects by contaminants such as moisture. However, inadequate selection of adhesives results in flip chip package breakage in several modes such as shrinkage, delamination, hydrolysis instability, corrosion and underfill contamination.

  The chip underfill is designed to avoid stressing the adherend as a result of the difference in coefficient of thermal expansion between the chip, interconnect, underfill and substrate. The failure mode due to stress becomes more widespread as the substrate is organic and the device size increases. Chip underfills are ceramic or organic PCBs (eg, FR4 epoxy) coated or uncoated with a solder mask; metal alloys or organic interconnects; and integrated circuit dies (chips) (typically from silicon or other inorganic materials). It must provide the ability to adhere to the substrate (such as, with or without the passivating thin layer).

  One of the two main methods for packaged electronic components is soldered to the same side (side) of the board when attached. These devices are referred to as “surface mount”. Two conventional underfills are actually used in surface mount devices: capillary flow and “no flow” types. Detailed descriptions of these techniques can be found in the literature. For example, John H. et al. Lau's book Low Cost Chip Chip Technologies for DCA, WLCSP and PBGA Assemblies, McGraw-Hill, 2000. Both of these techniques typically use heat to cure the liquid thermoset formulation or laminate the solid film to the assembly. A vacuum is used to remove voids from the system. Underfill is typically applied over a surface mount (SMT) assembly for chip-in-package or chip-on-board. The use of traditional flow and no-flow underfill requires several steps on the STM line, and this method is generally an obstacle to these microelectronic assembly lines.

  A typical conventional no-flow underfill is disclosed in US Pat. No. 6,180,696. The underfill material is first dispensed onto the substrate or semiconductor chip, followed by solder bump reflow and underfill encapsulant curing simultaneously. Underfills taught in US Pat. No. 6,180,696 include epoxy resins and / or mixtures of epoxy resins, organic carboxylic anhydride curing agents, curing accelerators, autosolvents, viscosity modifiers, couplings. And a surfactant. The underfill formulation exhibits a cure peak temperature in the range of 180-240 ° C. These underfills must be stored at subzero temperatures (° C.) to prevent the cure from proceeding.

  Underfill is different from the photoresist material that can be imagined as a patented composition applied on a PC substrate, but there is a slight similarity in the use of an epoxy resin. Photoresist coatings may use a photoinitiator to cure in areas exposed through a mask of actinic radiation and a secondary heat-activated free radical curing component that causes polymerization in unirradiated or shadowed areas. Are known. One commonly used secondary cure mechanism depends on the addition of heat-activated peroxide to the formulation; however, temperatures above 100 ° C. are required to initiate peroxide-induced polymerization, and therefore For example, the use of heat sensitive electronic components is excluded.

  U.S. Pat. No. 5,077,376 discloses an epoxy adhesive containing a latent heat curing component. US Pat. No. 5,077,376 results in widespread use of epoxy resin compositions containing latent curing agents such as dishan amine, dibasic acid dihydrozide, boron trifluoride-amine adduct, guanamine, melamine, and the like. Teaches the known storage stability of liquid epoxies, and guanamine is deficient in requiring high temperatures above 150 ° C. to cure.

  U.S. Pat. No. 5,523,443 discloses a dual cure adaptive coating that includes an ultraviolet curable polymerizable system and a moisture cure mechanism. The polymerizable coating system is a one-component system and comprises at least one alkoxy-urethane-acrylate or methacrylate, an acrylate or methacrylate or vinyl ether diluent, a cationic or free radical initiator type polymerization initiator, and a metal catalyst.

  US Pat. No. 5,249,101 (IBM, 1993) states that the brittleness of protective epoxy coatings for circuit elements on the circuitized surface of a chip carrier having an elastic modulus of about 69 MPa or more results in cracking and delamination. Disclosure. This patent proposed to provide a coating consisting of an acrylate urethane oligomer, an acrylate monomer and a photoinitiator, having a modulus of elasticity of about 10,000 psi or less and a chloride ion concentration of 10 ppm or less. An acrylate urethane wafer coated with underfill lacks sufficient heat resistance and cannot withstand solder reflow.

U.S. Pat. No. 5,494,981 discloses a curable composition of cycloaliphatic epoxy resin, shannate ester resin, optionally polyol, and Bronsted acid as initiator. Upon curing, the composition provides a penetrating polymer network (IPN). The IPN is useful as a binder for high temperature stable vibration damping materials, adhesives and protective coatings.
U.S. Pat. No. 5,672,393 initially provides a relatively thick skin when exposed to radiation containing wavelengths in the ultraviolet and visible range, and eventually has a relatively low stress with good physical and surface properties. An acrylate encapsulating composition is disclosed that reacts at a high rate to cure the adhesion layer. The method requires the composition on the object to be exposed to radiation to initiate photopolymerization and thermal polymerization, and the apparatus includes an actinic radiation and a thermal energy source in close proximity.

  U.S. Pat. No. 5,706,579 discloses an integration fabricated from a die, printed wiring board and metal lid using a β-stageable resin pre-applied to a metal lid and containing a thermally conductive filler material. A method for assembling a circuit package is disclosed. With the lid in place on the die and substrate, the package is heated to flow the resin into contact with the die. Further heating causes the resin to cure and a permanent thermal bridge between the die and lid.

  U.S. Patent No. 6,194,788 discloses an integrated thermoplastic, self-fluxing two-component underfill for flip chips. The underfill consists of an epoxy resin and an acetate diluent together with a melt type acidic epoxy curing agent.

  US Pat. No. 6,323,062 discloses a method of applying a solvent-based underfill to a flip chip. The method involves bonding a bumped wafer to an expandable carrier substrate, first cutting the wafer to form individual chips, and stretching the carrier substrate in two directions to form channels between each chip, Applying underfill material around the surface of the chip and the edge of the chip. Although the underfill material is not disclosed, the underfill is taught to dry after application and subsequently cut the underfill material in the channels between the chips to remove individual underfill coated chips from the carrier. Yes.

U.S. Pat. No. 6,383,659 discloses an underfill b-stage membrane based on a low Tg epoxy containing a thermoplastic polymer having a MW of 5,000 to 200,000. U.S. Pat. No. 6,383,659 is a block polymerization type epoxy resin composition, typically containing an imidazole or phenolic curing type, with limited storage stability, moisture resistance and high temperature of the cured composition. It shows performance and teaches that it is difficult to control the progress of the B-stage reaction.
US Pat. No. 5,077,376 US Pat. No. 5,523,443 US Pat. No. 5,249,101 US Pat. No. 5,494,981 US Pat. No. 5,672,393 US Pat. No. 5,672,393 US Pat. No. 5,706,579 US Pat. No. 6,194,788 US Pat. No. 6,323,062 US Pat. No. 6,383,659

  The above prior art illustrates a double cure method of forming a coating, but does not relate to storage of a b-stage coating that includes a second curing chemistry for a brittle substrate such as a silicon wafer. Wafer distortion, breakage, and long-term ambient storage at temperatures easily reaching about 50 ° C. can occur in transport or storage except in a controlled environment.

  A problem that occurs with underfill applied to a wafer when it is cured with a delay of several months until underfill is applied and a double-step cure underfill solder reflow process is required: First of liquid paint Wetting and adhesion of the coating; solidification of the coating without delamination from the wafer at ambient temperature; long-term ambient temperature storage of the coated wafer without loss of reflow capability from curing or gel progression; from singularization or dicing from the wafer Avoidance of delamination; ability to be screen printed into the cutter street of the wafer; slow start of thickening during the first heating from solder reflow; The ability to form fillet; the absence of voids in the underfill after the solder reflow process; and the presence of the device Is a long-term reliability (defect-free) in the device in Do shelf life.

All of these technical problems identified with underfill applied to the wafer for long-term storage prior to assembly are not addressed by prior art materials. Accordingly, the objective is to provide materials and methods for adding underfill and decoupling flip chip assemblies so that liquid underfill can be produced on large wafers, eg, 100-500 mm ² by conventional coating techniques. It is applied directly to the active surface of a wafer having a surface area, followed by solidification of the applied wafer or die slice and long term storage, for example several months.

The present invention relates to a wafer-underfill assembly and a method of applying a one-part, solventless, non-self-dissolving underfill to a wafer active surface, typically to a coating thickness of about 0.076-1.77 mm. The underfill is initially a liquid paint that partially or completely covers the solder bumps of the wafer. The underfill is a filled, 100% solid (non-volatile) liquid paint. The underfill is solidified into a solid, heat-liquefiable state by exposure to about 50-2400 mJ / cm ² of actinic radiation on the wafer. Underfill is applied to the grid pattern outside the cutter street of the wafer, or a continuous coating is formed that is subjected to wafer dicing into a single piece or die. Coated wafers or coated singulated sections can be stored in the environment for an uncertain delay period on the order of months before the assembly and solder interconnect. In an assembled chip that uses a coating of ambient encapsulant applied around the wafer-coated underfill, the thermal cure initiation of the solid, thermally liquefiable underfill can be 150 ° C. or higher. In the underfill embodiment, where the fillet is formed by heat liquefaction and flow to the edge of the wafer, and some amount of upward flow, the underfill thermoset activation temperature must be 170 ° C. or higher. The heat applied to reflow the solder is sufficient to activate underfill melt flow before activating the thermoset system, which results in gelling of the underfill to a solid thermoset state .

  One-part liquid underfill is composed of one or more ethylenically unsaturated monomers, one or more epoxy curable materials, one or more photoinitiators, a latent heat curing agent, thermal conductivity, And a mixture of electrically insulating fillers and is characterized by a photocurable component of 5% to 30% of the total weight of underfill and an epoxy resin component of 10% to 45% of the total weight of underfill. The preferred photocurable component consists of 100% monofunctional ethylenically unsaturated acrylate or methacrylate monomer. Suitable photopolymerizable components are monofunctional cyclic ethers and / or cyclic acetals of acrylic acid.

  In terms of method, the underfill according to the present invention is adapted to conventional coating techniques such as casting, stencil printing, printing, etc. on the active surface of the wafer. The rheology of the liquid underfill material can be easily adapted to the chosen coating method. The liquid underfill is applied to the active surface or bumps of a large wafer supported on the substrate, undergoes light-induced radical polymerization, and forms a solid, free-standing layer that remains rapidly attached to the wafer. Photocuring solidification provides a tack free solid underfill without wafer deformation. The ambient temperature solid state underfill coating withstands months of exposure at 50 ° C. for extended environmental storage periods and remains heat liquefiable without stressing the wafer.

  The delay period in which photocured, heat liquefiable solid underfill-coated wafers or specific parts are stored prior to solder interconnection is uncertain, on the order of weeks, months or years. Storage conditions during the delay include underfill exposure to ambient temperature without refrigeration. Underfilled wafers are different from conventional thermoplastic or thermoset materials cast from solvents and melts processed using heat and / or vacuum. On the other hand, the underfill according to the present invention undergoes light-induced solidification via addition polymerization on the wafer active surface and does not progress at ambient temperature over a significant delay time until a second thermally initiated cure occurs. 100% solid material that remains in a plastic state, its thermoplastic underfill has no delamination, no void formation, sufficient reflow under solder reflow conditions, and no device breakage or breakage in a thermoset state It has several critical properties including long term adhesion under repetitive thermal cycling conditions. The thermoset underfill has a flexural modulus of 1000-5000 MP at 25 ° C. and a heat below the glass transition temperature in the range of 15-60 ppm / ° C., more typically about 25 (+/− 10) ppm / ° C. Indicates the expansion coefficient.

  Wafer level underfill consists of a 100% solids mixture. There are no volatile components such as solvents that contribute to weight loss during long-term ambient storage. The absence of volatile components avoids the solvent removal step and improves the shrinkage control and delamination of the light induced solidified coating from the surface on the active side of the wafer. The elimination of volatile organic components prevents harmful shrinkage and stress, exhaust gases during the solder reflow process, and prevents voids formed between the wafer or section and the PCB. Underfill is non-self-soluble. In other words, the components used do not provide a melting function and are non-acidic.

In general method aspects, the present invention applies liquid underfill adhesive to an integrated circuit wafer, administration of a controlled dose of light energy (ultraviolet, visible, infrared, etc.), heat-liquefaction of underfill or Includes solidification to a melt flowable state, optionally wafer singularization by dicing or sawing, and storage of coated wafers or dies during a lag period. After the delay period, electrical connection is made, the photocured solid underfill is heated to liquid and flowed to the edge of the device during solder reflow, and is cured and converted from the heated liquid to the thermoset solid state. During the intervening lag time of storage, the coating of the present invention remains in a liquefiable solid state and does not progress into the gel. Thus, in one aspect, on a weight basis, a photocurable acrylic component,
Polyfunctional epoxy resin,
At least one photoinitiator,
Consisting of a non-conductive filler and a non-melting heat-activated epoxy resin,
The thermoset underfill composition has a flexural modulus of 1000 to 5000 MPa at 25 ° C. and a photocuring, one-part composition showing a thermal expansion coefficient of 15 to 50 ppm / ° C. below the glass transition temperature of the underfill composition. An ambient temperature stable integrated circuit wafer is provided having an active surface bonded to an underfill composition of matter.

  In another aspect, the present invention relates to a two-stage method for curing an underfill composition applied to a wafer. The method comprises applying an underfill composition in liquid form to an active surface of a semiconductor wafer. Coating methods include liquid spin casting, printing or screen printing, and non-volatile (100% solids) coating directly on the active surface of the chip. The coated wafer is solidified via UV irradiation at a dose selected to form a solid film. A wafer coated with a solid can be arbitrarily diced into sections. The wafer or slice can be stored at ambient temperature, followed by a second stage in which the solder bumps are electrically connected to the PCB in a solder reflow process, followed by thermal curing of the solid underfill to a thermal effect state.

  The 100% solids underfill composition comprises a photocurable acrylate comprising a monofunctional ethylenically unsaturated monomer and / or oligomer, a multifunctional epoxy resin, a photoinitiator, a latent epoxy thermal initiator, and an inorganic CTE- Contains a reducing agent. The underfill is not alkali-soluble in the solid state and does not contain acid radicals such as free carboxylic acid, phosphate, or sulfonate groups in the liquid photocurable unsaturated monomer, oligomer and / or polymer. The weight percent of the components utilized in the wafer composition is a total of 100 weight percent mixed and is as follows:

Component weight%
Photocurable acrylate component 5-30%
Liquid multifunctional epoxy resin 10-45%
Photoinitiator 0.3-3%
Low CTE filler 40-70%
Latent cure accelerator 1-3%

  Underfill compositions in a solid, heat-liquefiable state are self-supporting, storage-stable prior to conversion to a thermoset state, and adhere to the active surface of a wafer or slice over a long delay period at ambient temperature The underfill coating and the solder reflow chip installation process can be decoupled. The present invention allows storage of wafers at ambient temperature for later mounting on a PCB.

  The photocurable component of the underfill composition consists of an ethylenically unsaturated monomer or mixture of monomers having at least 6 carbon atoms in the structure. Incorporation of monomers of 6 carbon atoms or less poses a problem in unacceptable volatility to solid state photocuring and causes shrinkage in conversion to photocured heat liquefiable solid state, which is adhered to it There is a tendency to apply stress to the chip. Underfill containing 10% by weight or more of the liquid polyfunctional ethylenically unsaturated comonomer results in poor melt-flow of thermoliquefiable underfill during the solder reflow process during chip attachment. Therefore, it is desirable that the polyunsaturated monomer is not present in the underfill or is limited to 10% by weight or less of the underfill photocurable component.

  The term “photocurable component” collectively refers to ethylenically unsaturated monomers and / or oligomers. More desirably, the ethylenically unsaturated material comprises vinyl esters, vinyl ethers, and / or α, β-unsaturated acrylate esters. Suitable photocurable components are ethylenically unsaturated acrylates, unsaturated oligomers, or pendant unsaturated oligomers as monomers, and combinations thereof. The term oligomer means an unsaturated compound that can be dissolved in a liquid state at 25 ° C. or in a photocurable liquid carrier. If the diluent softening temperature does not significantly inhibit the melt flow of the heat-liquefiable underfill at the solder reflow temperature, a non-functional or unsaturated thermoplastic polymer diluent such as polyacrylate, polyvinyl ether, polyvinyl ester, Polyesters, polyamides, polyolefins, and functionalized derivatives can be used. Such diluents can be used to enhance various characteristics such as fine control, or melt flow properties and / or cohesive strength.

  When underfill containing a photocurable acrylate polymerizes under the influence of UV radiation, the underfill is converted from a liquid to a solid state at ambient temperature. The solid remains as a thermoplastic, meaning that it remains in a heat-liquefiable state until it is thermoset. The specific amount of photocurable component is 5-30% by weight of the total underfill weight. The amount of multifunctional epoxy material is important with respect to the weight of the photocurable component in order to provide proper solidification during photocuring and to maintain melt flow during the solder reflow process. Polyfunctional epoxy materials in the range of 10 to 45% by weight or more also tend to increase underfill which damages the wafer after photocuring. The cross-sectional thickness of the underfill film on the active surface is optimally such that a part of the solder bump is exposed.

The implication of this exposure is that the metal is exposed to air or that there is a thin underfill of about 0.01 μm or less on the outermost protrusion of the solder bump. In the preferred embodiment, the thickness of the underfill film after photocuring is 50 to 90% of the cross-sectional shape of the solder bump. The cross section is the depth of the solder bump portion extending beyond the surface on the wafer active side.

  The photocurable oligomer optionally used here is liquid at ambient temperature or can be dissolved in a liquid ethylenically unsaturated acrylate monomer. The oligomer contains pendant groups or terminal ethylenically unsaturated groups. A typical oligomer contains two terminal unsaturated groups. The average number of unsaturated groups in the oligomer photocurable acrylate component having a MW of 500-3000 can be 1-2. The photocurable acrylate component excludes only di-, tri-, or tetra- and higher ethylenically unsaturated monomers, dimers or trimers.

  The underfill embodiment of the present invention exhibits a melt flow under solder reflow conditions sufficient to flow outward in the chip edge direction and fully fill the gap between the chip underside and the PCB. In some cases, the flow-out can include flowing up along the die edge to form a fillet. The photocured solid underfill adheres well to the wafer and has sufficient cohesive strength necessary for long storage delay periods and / or dicing that does not distort or distort the wafer. After its storage delay period, the heat liquefiable solder flows sufficiently under the heat encountered in the solder reflow process when the weight ratio of photocurable acrylate component: epoxy functional component is in the range of 1:10 to 1: 2. And the photocuring component contains a certain proportion of monofunctional and polyfunctional monomers and / or oligomers. Under a photocurable component: epoxy functional component ratio of 1:10 or less, underfill typically lacks sufficient cohesive strength and exhibits unacceptable surface adhesion. At a ratio of 1: 2 or higher, the wafers are distorted, exhibit fracture, and / or the underfill tends to delaminate or undergo insufficient flow to form fillet.

Here Examples of useful monoethylenically unsaturated monomers are those having at least 6 carbon atoms, alkyl C ₃ -C ₁₂ alkyl esters of acrylic or C ₁ -C ₄ alkyl-substituted acrylic acid, collectively (Alkyl) acrylate is included. Specific examples of suitable monofunctional monomers include butyl acrylate, ethyl methacrylate, butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, cyclic ether acrylate, and monocyclic acetal acrylate.

Monocyclic acetal acrylates are known and disclosed in US Pat. No. 4,076,727. Acetal acrylate reacts with aldehydes from polyols such as trimethylolpropane, trimethylolethane, glycerin, 1,2,4-butanetriol, 1,2,5-pentaerythritol, and 1,2,6-hexanetriol. And transesterification with [alpha], [beta] -unsaturated carboxylates such as acrylic acid or esters. An example of a photocurable component is a combination of a cyclic ether-containing acrylate such as tetrahydrofurfuryl acrylate (THFA) and a cyclic acrylol formal acrylate. Suitable monofunctional acrylates are tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, pentaerythritol monomethacrylate, pentaerythritol monoacrylate, trimethylolpropane monomethacrylate, trimethylolpropane monoacrylate, and cyclic alkylol formal acrylate, and ketal acrylate It is. Acetals and ketal acrylates include mixtures of isomers. Cyclic alkylol formals and ketal acrylates are readily prepared by esterification of acrylates or methacrylates with monohydroxyacetals derived from triols, such as trimethylolpropane and triethylolpropane. Suitable triol starting material structures that can be reacted with aldehydes or ketones and acylated using methacrylate acrylates include:

  The prepared cyclic acrylol formal acrylate has the following structure (AC):

式中のＲ_１はＣ_１−Ｃ_４アルキレン基、例えば、−ＣＨ_２−，−ＣＨ_２ＣＨ_２−、等、及びＲ_２，Ｒ_３，及びＲ_４アルキル基、例えば、−ＣＨ_３，−ＣＨ_２ＣＨ_３等である。最適の環状アルキロールホルマルアクリレートはトリメチロールプロパンホルマルアクリレート（構造Ｂ’）である。

R ₁ in the formula is a C ₁ -C ₄ alkylene group, such as —CH ₂ —, —CH ₂ CH ₂ —, and the like, and R ₂ , R ₃ , and R ₄ alkyl groups, such as —CH ₃ , — CH ₂ CH _{3 and the} like. The optimum cyclic alkylol formal acrylate is trimethylol propane formal acrylate (structure B ′).

  Other photocurable monomers used alone or in combination with any of the above monomers are acetoacetoxyethyl methacrylate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxypropyl methacrylate, 2-acetoacetoxypropyl acrylate 2-cyanoacetoxyethyl methacrylate, 2-cyanoacetoxyethyl acrylate, N- (2-cyanoacetoxyethyl) acrylamide, 2-propionylacetoxyethyl acrylate, N- (2-propionylacetoxyethyl) methacrylamide, N-4- ( Acetoacetoxybenzyl) phenylacrylamide, ethyl acrylol acetate, acrylol methyl acetate, N-ethacryloylmethyl acetoacetamide, ethyl methacryloyl acetoacetate N-allylshanoaacetamide, methylacryloyl acetoacetate, N- (2-methacryloyloxymethyl) cyanoacetamide, ethyl-α-acetoacetoxymethacrylate, N-butyl-N-acryloyloxyethylacetoacetamide, monoacrylate polyol, And reactive organisms of hydroxyl group-containing acrylates such as monomethacryloyloxyethyl phthalate with anhydrides. (Alk) A copolymerizable monomer copolymerizable with an acrylate monomer, but not too slow as compared with a polymerization rate galacrylate monomer.

  Rapid photocuring of acrylic monomers is a desirable feature. The photocurable ethylenically unsaturated monomer other than acrylate and alkacrylate is limited to about 6 or more. Examples thereof include, but are not limited to, butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether p- (2-acetoacetyl). ) Ethyl styrene, and 4-acetoacetyl-1-methacryloylpiperazine. Epoxy-reactive groups such as ethylenically unsaturated monomers containing active hydrogen-containing groups are not used for the photocurable component.

  Typical known polyfunctional ethylenically unsaturated compounds are ethylene di-unsaturated monomers such as ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, hexanediol diacrylate, and triethylene glycol diacrylate. is there. Exemplary tri-unsaturated monomers include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, glycerol triacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate. Typical acrylic unsaturated photocurable materials are Sartomer SR205, SR306, CD401, SR508, SR603, SR9036.

  Other suitable photopolymerizable oligomeric materials include, for example, bis-phenol based polyether acrylates, vinyl ether capped oligomers, hydroxy functional acrylate and methacrylate reactive organisms, and epoxides included in the photocurable component. Acrylic or polyether, ethylenically unsaturated polyalkyl ether, the cyclic ether acrylate and the cyclic ether acetate acrylate.

  The photopolymerizable component is a mixture of a monounsaturated acrylate monomer and an ethylenically unsaturated oligomer having a number average molecular weight of 500 to 5,000, preferably 1,000 to 4,000. The photocurable liquid oligomer consists of a urethane acrylate oligomer that does not have an active isocyanate group. Urethane acrylate oligomers can be mixed with ethylenically unsaturated acrylate monomers. Acrylate urethanes can be aliphatic or aromatic. Commercially available acrylate urethanes are Henkel's trade designation PHOTOMER (eg, PHOTOMER 6010); UCBR Radcure EBECRYL 220 (hexafunctional aromatic urethane acrylate having a molecular weight of 1000), EBECRYL 284 (1,6-hexanediol diacrylate diluted) Aliphatic urethane diacrylate having a molecular weight of 1200), EBECRYL4827 (aromatic urethane diacrylate having a molecular weight of 1600), EBECRYL4827 (aliphatic urethane diacrylate having a molecular weight of 1200 diluted with tetraethylene glycol diacrylate), EBECRYL6602 (trimethylolpropane) Trifunctional aromatic urethane acrylate having a molecular weight of 1,300 diluted with ethoxytriacrylate) and EB CRYL840 (aliphatic urethane diacrylate having a molecular weight of 1000); SARTOMER from SARTMER (for example, SARTOMER 9635, 9645, 9655, 963-B80, 966-A80, etc.): and UVITHANE from Morton International (for example, UVITHANE 782) Including

  Although the photocurable acrylate component can include an acrylate modified epoxy material having one or more photocurable unsaturated acrylate groups, such as a diacrylate ester of bisphenol A, such a mixture is undesirable. Typical acrylate modified epoxies are obtained by reaction of oxirane groups with hydroxy groups on the acrylate. No unreacted epoxy curable function remains. Commercially available noacrylate epoxies include those of the trade mark CMD of Radicure Specialties. Other suitable acrylic unsaturated epoxy or urethane acrylate oligomers are CN929, CN136, CN970, CN104, CN120C60, etc. from Sartomer. The proprietary acrylate modified epoxy liquid is blended with additional monofunctional or polyfunctional acrylates. The amount of additional monofunctional or multifunctional acrylate is included in the entire composition range in the photocuring component.

  Exemplary diacrylate functional photocurable materials include SR205, SR306, CD401, SR508, SR9036. Exemplary trifunctional materials include SR350, SR444, CD501, SR9021. Tetrafunctional acrylates include SR295, SR355, SR399, SR9041.

  Underfill's thermosetting multifunctional epoxy resin has at least two epoxy groups, a viscosity of about 1000 poise or less at 25 ° C., an average weight per epoxide (WPE) in the range of about 100-1000, and about 500- Containing at least one liquid resin having an average molecular weight in the range of 3,500. Easily usable epoxies are known and include the diglycidal ether of bisphenol A, 2,2-bis-4- (2,3-epoxypropoxy) -phenylpropane. Suitable commercially available epoxide compounds are Shell Chemical's trade names EPON 828, EPON 1004 and EPON 1001F, and Dow Chemical's DER-331, DER-332 and DER-334. Other suitable epoxy resins include cycloaliphatic epoxides, glycidyl ethers of phenol formaldehyde novolac (eg, DEN-431 and DNE-428 from Dow Chemical). Blends of free radical curable resins and epoxy resins are further described in US Pat. No. 4,751,138 (Tumey et al.) And US Pat. No. 5,256,170 (Harmer et al.). In a preferred embodiment, a combination of three epoxy resins is employed, which is a biphenyl epoxy resin having a WPE of about 192 g / equivalent, a diglycidyl ether of bisphenol F having a WPE of about 172 g / equivalent, and about 101 g / A mixture of triglycidyl ethers of p-aminophenyl with an equivalent WPE. These three epoxy resins are available under the trade names RSS, EPICLON and ARALDITE.

  The liquid wafer paint contains about 1-3% by weight of at least one photoinitiator effective to solidify the liquid underfill to a tack-free surface upon exposure to normal levels of actinic radiation. The type of photoinitiator selected will depend on the required cure depth, the type of contrast agent used, and the wavelength of the actinic radiation used. Commercially available free radical generating photoinitiators suitable for use herein include, but are not limited to, benzophenone, benzoin ether and acylphosphine oxide-types such as those sold under the trade names IRGACURE and DAROCUR from Ciba Specialty Chemicals. Is a photoinitiator

  A suitable photoinitiator is a mixture of 25-50% ketone functional photoinitiator and 50-75% monoacylphosphine, bisacylphosphine oxide, or phosphinate containing photoinitiator. Examples of ketone photoinitiators are 1-hydroxycyclohexyl phenyl ketone, hydroxymethylphenylpropanone, dimethyloxyphenylacetophenone, 2-methyl-ru- [4- (methylthio) -phenyl] -2-morpholinopropanone -1,1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecyl-phenyl) -2-hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl-2 (2-hydroxy-propyl) -ketone, diethoxyphenylacetophenone, 2,4,6 trimethylbenzoyldiphenylphosphone, 2-hydroxy-2-methyl-1-phenylpropan-1-one , 1- [4- (2-hydroxyethoxy) phenyl] -2-hydro Shi-2-methylpropan-1-one, and 2-hydroxy-thioxanthone-9-one. Exemplary acyl phosphine oxide photoinitiators include ethyl 2,4,6-triethylbenzoyl diphenylphosphine oxide and 2,4,6-triphenylbenzoyl diphenylphosphine oxide. A specific example photoinitiator component for deep cure of liquid underfill applied to a wafer is 0.2-0.5 wt% 1-hydroxycyclohexyl phenyl ketone, and phenyl based on the total weight of underfill It is a mixture containing bis (2,4,6-trimethylbenzoyl) phosphine oxide.

Sources of actinic radiation that do not raise the coating temperature above 120 ° C. can be used to perform photocuring to underfill solid liquefiable gels. Ultraviolet light, as well as other forms, such as RS solar lamps, carbon arc lamps, xenon arc lamps, mercury vapor lamps, tungsten halide lamps, etc. are most easily used. Radiation energy is emitted from a point source or in the form of parallel lines. However, divergent beams can also be manipulated as actinic radiation. A UV dose in the range of 100-2400 mJ / cm ₂ provides depth for underfill cure of about 1.2-1.8 mm and is effective to complete radical polymerization at underfill temperatures of 100 ° C. and below. is there. The underfill composition is photocured on the tack-free surface. The curing time is adjusted to make an appropriate choice of UV source, underfill photocuring component concentration, and contrast agent.

  In product package assembly, automated visual inspection, the use of pigments is necessary to provide contrast between board, underfill and chip. Contrast agents such as carbon black and pigments such as those available under the trade name Sandorin of the company Clariant AG are suitable. In one embodiment, a 15% by weight carbon black dispersion system is used for the epoxy resin and 0.1-0.2% by weight carbon black is blended with underfill to provide effective contrast for automated visual inspection.

Thermosetting system The epoxy resin system utilized in the present invention is from a latent heat accelerator having a curing onset temperature of 150 ° C or higher, preferably 160 ° C ± 5 ° C or higher, optimally 170 ° C ± 5 ° C or higher and higher. It is a non-melting type. Solidification, aging underfill is adapted to initiate curing using a latent heat curing agent on the epoxy resin at the temperature encountered immediately after the solder reflow occurs to enter the curing stage. Although dicyandiamide cannot be used alone as a thermosetting agent, it can be used in small amounts with a latent heat accelerator (but preferably not). Suitable latent heat curing agents include amines and amine-adducts; these are imidazole and urea derivatives such as 2,4,6-trimethyl-1,3-bis (3,3-dimethylureido) benzene and 1 , 5-bis (3,3-dimethylureido) naphthalene. The thermosetting agent must be non-halogenated. Examples of curing agents are mixed epoxy compounds or isocyanate compounds and amine compounds, or mixed epoxy compounds or isocyanate compounds, amine compounds and active hydrogen compounds, as taught in US Pat. No. 5,543,486. Is obtained by a known method. Various blocked amines are suitable. Preferred thermosetting agents are tertiary amines and amines blocked with urea moieties. Examples of imidazoles suitable for thermosetting components are: 2-methylimidazole; 2-ethylimidazole; 2-ethyl-4-methylimidazole; 2-phenylimidazole; 2-phenyl-4-methylimidazole; 2-undecenylimidazole 1-vinyl-2-methylimidazole; 2-n-heptadecylimidazole; 2-ethyl-4-methylimidazole; 1-benzyl-2-methylimidazole; 1-propyl-2-methylimidazole; 1-cyanoethyl-2 1-cyanoethyl-2-ethyl-4-methylimidazole; 1-cyanoethyl-2-undecylimidazole; 1-cyanoethyl-2-phenylimidazole; 1-guanaminoethyl-2-methylimidazole; 2- (p- Dimethuraminophenyl)- 2- (2-hydroxyphenyl) -4,5-diphenylimidazole; 2-phenyl-4-hydroxymethylimidazole; 2-phenyl-4,5-di (hydroxymethyl) -imidazole; , 5-diphenyl-2-imidazole) -benzene-1,4,2-naphthyl-4,5-diphenylimidazole; addition product of imidazole and trimellitic acid; addition formation of imidazole and 2-n-heptadecyl-4-methylimidazole Product; phenylimidazole; benzylimidazole; 1- (dodecylbenzyl) -2-methylimidazole; 2- (2-hydroxy-4-t-butylphenyl) -4,5-diphenylimidazole; 2- (2-methoxyphenyl) -4,5-diphenylimidazole; Til-4,5-diphenylimidazole; 2,3,5-triphenylimidazole; 2-stilimidazole; 2- (3-hydroxyphenyl) -4,5-diphenylimidazole; 1-benzyl-2-methylimidazole; Contains 2-p-methoxystilimidazole. A suitable thermosetting agent is available from Air Products and Chemicals under the trade name Curezol 2-PHZ-S.

  Another thermal curing agent comprises a blocked Lewis acid, for example, latent metal acetoacetate-functional curing agents such as aluminum chelates include ethyl acetoacetate metal diisopropylate, metal tris (ethyl acetoacetate), alkyl acetoacetate. Acetate metal diisopropylate, including aluminum monocesylacetonate bis (ethyl acetoacetonate), aluminum tris (acetylacetonate); and examples of cyclic aluminum oligomers include cyclic aluminum oxide isopropylate.

  In order to provide adequate reflow of the photocured liquefiable solid, no thermal cure system progression occurs in the photocured solid coating on the wafer or die during the storage delay period. The minimum temperature for initiating thermosetting is predetermined by the choice of the thermosetting agent used and occurs after the start of solder reflow at a temperature of 150 ° C. or higher. Preferably, the lowest underfill onset of heat cure is in the range of 150 ° C to 225 ° C. The thermosetting onset temperature and peak curing rate are easily determined by differential scanning calorimetry. The thermal cure initiation temperature depends on the choice of accelerator and peak cure rate and should not be above about 280 ° C. The onset of thermosetting should not be too close to the peak temperature, typically at or near 250 ° C. for eutectic solder and 300 ° C. for lead-free solder. Typical solder reflow times are 3-4 minutes, and underfill is typically exposed to its peak temperature for 30 seconds or less. Thermal curing initiated at temperatures below 150 ° C. results in inadequate underfill liquefaction and flow.

  Non-conductive fillers are used to limit the underfill CTE. These fillers are known and various types are suitable. Microelectronic grade fused silica, crystalline silica, boron, aluminum and silicon nitride, magnesium, magnesium silicate and silica coated aluminum are available. The viscosity formed in the liquid underfill is a criterion for selection. Due to the absence of solvent or inactive diluent, the underfill embodiment according to the present invention is readily applicable to methods utilizing relatively low viscosity paints such as known spin coatings. Embodiments of the spin-castable underfill according to the present invention exhibit a normal viscosity that is relatively lower than the viscosity used for underfill applied by screen printing or printing.

  In a preferred embodiment, underfill is applied by screen printing to a pattern that covers at least 70% of each wafer area between saw streets. The CTE of underfill in the thermoset state is in the range of 15-50 ppm / ° C., and the non-conductive filler level used in the range of 40-70% by weight, preferably 45-60% by weight, Preferably spherical fused silica particles are required. More desirably, an inorganic low CTE filler is used in an amount of 45-55% by weight. Suitable low CTE inorganic fillers have an average particle size of at least 10 μm and an average particle size of about 75 μm or less. The upper limit of the filler diameter used should be less than or equal to the thickness of the underfill coating.

  Optionally, the underfill can contain an adhesion improver. Adhesion improvers are known and include organosilanes, organopolysiloxanes, organohydrogenpolysiloxanes, prehydrogenated organosilanes, siloxanes and silsesquioxanes. Examples of organosiloxanes are mono (epoxy hydrocarbyl) such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. It contains an epoxy functional group such as trialkoxysilane; or an ethylenically unsaturated group is desirable. Ethylenically unsaturated organosilicon compounds are mono- or multi-alkenyl functional organosilanes such as 3- (meth) acryloxypropyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane and multi-alkenyl functional siloxanes such as 1,1,3,3-tetramethyldisiloxane and 1,2,4-trivinylcyclohexane and / or 1,3,5-trivinylcyclohexane.

  One method of applying underfill to a wafer requires known screen printing techniques. Advantageously, the wafer underfill according to the present invention can be printed on the wafer in a registered pattern to cover together portions of the wafer surface outside of the saw street. The underfill applied by the printing method desirably contains an optional rheology modifier. Suitable known types are, for example, amorphous fumed silica or silylated amorphous fumed silica available from Cabot.

  Any known flow control agent can be used. Thermoplastic flow control agents increase the tendency to escape during hot liquid liquefiable underfill solder reflow. A typical flow improver is an I.D., such as that available under the trade name Elvacite. V. Contains about 0.2 to 0.6 polymethacrylate copolymer. An example is considered to be a 64% butyl methacrylate / 36% methyl methacrylate copolymer with the trade name Elvacite-2013 from ICI Acrylics and having an IV of 0.2. Other known flow control agents include the trade name Lanco Flow P10 from Lubrizol, USA, and MODAFLOW Powder available from Solutia. The flow improver can be based on SAN or alpha-olefin polymers, and the like. A preferred flow improver is a thermoplastic PMMA copolymer having a molecular weight of 60,000, such as the trade name Elvacite from INEOS Acrylics. The optional thermoplastic flow improver suggested as weight percent of the photocurable component is 1.0 to 10.0 weight percent. As an improvement in underfill flowability in the photocured, heat liquefiable state, the use of small amounts of up to 10% by weight of plasticizers such as carboxy esters or lubricants such as ethylenebis-stearamide is contemplated.

Test method
1. Glass transition temperature (Tg)
Using a sample of b-stage or thermoset material, the glass transition temperature is 5 ° C./min heating rate thermomechanical analyzer, 5 ° C./min heating rate dynamic mechanical analyzer, or 5 ° C./min Was measured with a differential scanning calorimeter at a heating rate of.
2. Thermal expansion coefficient In the measurement of the thermal expansion coefficient equal to or higher than Tg, the thermal expansion coefficient was measured using a normal thermomechanical analyzer.
3. Viscosity Brookfield VDIII cones and plates are suitable, but Haake RheoStress I (trade name) was used.
4). Die retention was tested according to ASTM D1002.
5). Thermal and oxidative stability is measured by thermogravimetric analysis. Underfill is 5% by weight or less at 300 ° C. in air.

Photopolymerization conditions The following conditions using the AETEK UV processing equipment properly solidify the liquid underfill to the entire depth of the coating.
Lamp 1 (W) Lamp 2 (W) Belt speed Curing energy
(Fpm) (mJ / cm ² )
400 400 34 1170
200 200 30 761
200 200 45 515
200 200 60 384
200 200 65 349
200 200 70 327
125 125 30 712
125 125 70 297
200 0 45 274
200 0 60 205
200 0 70 176
125 0 70 149
125 0 90 116

Processing Embodiments Underfill Examples 1-4 were prepared by adding the ingredients to a Hauschild (trade name) cup and mixing at 3000 rpm for 30 seconds. The formulation was spin coated onto a 10.1 cm diameter x 400 ± thick semiconductor wafer (trade name Umicore). The coated wafer was photocured in an Aetec UV furnace at 30 fpm, N ₂ atmosphere, 200 W / 200 W setting and one pass. Storage of the photocured underfill for 8 months did not provide further curing activity as confirmed by DSC. The thermosetting start temperature was 150 ° C. ± 2 ° C. (peak heating value at 166 ° C.).

Component Weight part
1. Bisphenol A-epichlorohydrin 19.03
Epoxy resin (residual epichlorohydrin <1ppm)
RSL-1462 from Shell Resins)
2. Poly (acrylic) unsaturated urethane acrylate oligomer (CN120C60 from Sartomer)
3. Epoxy acrylate oligomer 18.5
(CN136 from Sartomer)
4). Epoxy curing agent 1 1.14
(Ancamine 2441 from Air Products & Chem)
5). Epoxy curing agent 2 1.33
(Dyhard 100s from SKWCem)
6). Trifunctional acrylate 7.00
(SR351 from Sartomer)
7). Photoinitiator Irgacure 184 2.00
Irgacure 819 1.00
8). Fused silica 50.00
(F5BLDX from Dennka)
Total 100.00

Component Weight part

1. Bisphenol A-epichlorohydrin 36.28
Epoxy resin (residual epichlorohydrin <1ppm)
RSL-1462 from Shell Resins)
2. Epoxy curing agent 1 2.18
(Ancamine 2441 from Air Products & Chem)
3. Epoxy curing agent 2 2.54
(Dyhard 100s from SKWCem)
4). Trifunctional acrylate 6.00
(SR351 from Sartomer)
5). Photoinitiator Irgacure 184 1.50
Irgacure 819 1.50
6). Fused silica 50.00
(F5BLDX from Dennka)
Total 100.00

Component Weight part

1. Bisphenol A-epichlorohydrin 36.29
Epoxy resin (residual epichlorohydrin <1ppm)
RSL-1462 from Shell Resins)
2. Latent amine accelerator 2.18
(Ancamine 2441 from Air Products & Chem)
3. Dicyandiamide 2.54
(Dyhard 100s from SKWCem)
4). Trifunctional acrylate 6.00
(SR351 from Sartomer)
5). Photoinitiator Irgacure 184 2.00
Irgacure 819 1.00
6). Fused silica 50.00
(F5BLDX from Dennka)
Total 100.00

1. Bisphenol A-epichlorohydrin 18.15
Epoxy resin (residual epichlorohydrin <1ppm)
RSL-1462 from Shell Resins)
2. Acrylate-modified epoxy oligomer 19.50
(CN136 from Sartomer)
3. Latent amine accelerator 2.18
(Ancamine 2441 from Air Products & Chem)
4). Dicyandiamide 2.54
(Dyhard 100s from SKWCem)
5). Trifunctional acrylate 6.00
(SR351 from Sartomer)
6). Photoinitiator Irgacure 184 1.50
Irgacure 819 1.50
7). Fused silica 50.00
(F5BLDX from Dennka)
Total 101.37

Examples 5-7 were prepared and spin coated onto a 10.1 cm diameter x 400 ± thick semiconductor wafer (trade name Umicore). The coated wafer was photocured in an Aetec UV furnace at 30 fpm, N ₂ atmosphere, 200 W / 200 W setting and one pass. The photocured film of Example 5-7 in a solid heat-liquefiable state was non-tacky.

  In the preparation of Example 5, ingredients 1-4 were mixed together in a 40 gram Hauschild (trade name) cup and heated to 60 ° C. until the photoinitiator was completely dissolved. The sample was then mixed in a Hauschild mixer at 300 rpm x 30 seconds. The remaining ingredients were each added with mixing during each addition.

Component Description Weight part
1. CN136 amine modified, acrylate epoxy 6.70
2. SR203 THFMA 12.40
3. Irgacure 184 photoinitiator 0.30
4). Irgacure 819 photoinitiator 0.50
5). RSL-1462 Diglycidyl ether of bis A epoxy 14.35
6). RSS-1407 Bisphenol epoxy resin 14.35
7). Curezol 2PHHZ-S 1.43
Imidazole latent curing agent8. Filler Fused silica 49.99
Total 100.0 2

The thermosetting start temperature of Example 5 was 167 ° C.
Example 5
Tg-UV-B stage 23.56 ° C
Tg-thermosetting 106.25 ° C
CTE-Tg or less 40.37ppm / ° C
CTE-Tg or more 107.7ppm / ° C
Storage modulus (@ 25 ° C) 2,761Mp
Storage modulus (@ 175 ° C) 0.025 Gpa

  Example 6 was prepared by adding the ingredients to a 40 gram Hauschild (trade name) cup except 50% fused silica and mixing at 300 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photoinitiator. The solution mixture was again mixed for 30 seconds at 300 rpm.

Raw material explanation Weight part
SR203 THFMA 19.10
Irgacure 184 photoinitiator 0.30
Irgacure 819 photoinitiator 0.50
RSS-1407 Bisphenol epoxy resin 14.35
Curezol 2PHHZ-S 1.43
Imidazole latent curing agent filler Fused silica 50.01
Total 100.00

  Referring to FIG. 1, FIG. 1 shows the DSC scanning curve of Example 6. The differential scanning calorimetry conditions were: DSC DSC7 model from Perkin-Elmer, and the heating lamp conditions were in the range of 20 ° C-300 ° C with a heating rate of 5 ° C / min. All samples were tested in the photocured state. The scan shows the melting point of the solid epoxy resin at 95.23 ° C., the onset temperature of 191.65 ° C., and the peak reaction temperature of heat cure at 193.71 ° C.

  Example 7 was prepared by adding 40 grams of Hauschild (trade name) cup except 50% fused silica and mixing at 300 rpm for 30 seconds. The remaining portion of the fused silica was then added with mixing at 300 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photoinitiator. The solution mixture was again mixed for 30 seconds at 300 rpm.

Raw material explanation Weight part
SR285 THFM 19.05
Irgacure 184 photoinitiator 0.30
Irgacure 819 photoinitiator 0.50
RSS-1407 Bisphenol epoxy resin 28.71
Curezol 2PHHZ-S 1.44
Imidazole latent curing agent filler Fused silica 50.01
Total 100.00

  FIG. 2 shows the DSC scan curve of Example 7. The differential scanning calorimetry conditions were: DSC, DSC7 from Perkin-Elmer. The heating lamp conditions were in the range of 20 ° C-300 ° C with a heating rate of 5 ° C / min. All samples were tested in the photocured state. The scan shows the melting point of the solid epoxy resin at 99.5 ° C., the onset temperature of 189.62 ° C., and the peak reaction temperature of heat curing at 192.6 ° C.

  Example 8 was prepared by adding the ingredients to a 40 gram Hauschild (trade name) cup except 50% fused silica and mixing at 300 rpm for 30 seconds. The remaining portion of the fused silica was then added with mixing at 300 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photoinitiator. The solution mixture was again mixed at 300 rpm for 30 seconds.

Component Description Weight part
CN136 amine modified, acrylate epoxy 6.70
SR203 THFMA 12.40
Irgacure 184 photoinitiator 0.30
Irgacure 819 photoinitiator 0.50
RSL-1462 Diglycidyl ether of bis A epoxy 14.35
RSS-1407 Bisphenol epoxy resin 20.09
Curezol imidazole 1.43
Filler FB5LDX (fused silica) 49.99
Total 100.02

Example 8
Tg-light B stage WAU 41.47 ° C
Tg-thermosetting 116.44 ° C
CTE-Tg or less 40.56ppm / ° C
CTE-Tg or more 120.5ppm / ° C
Storage modulus (25 ° C) 3,313 Mpa
Storage modulus (175 ° C) 0.0268 Gpa

Comparative Example A (77-5)
Component Weight part
1. Mixture of tri (acrylic) functional monomer and acrylate modified epoxy oligomer 43.00
(Sartomer CN120C60)
2. Tri (acrylic) functional monomer 4.00
(Sartomer SR351)
3. Dicyandiamide 1.33
(SKWCem Dyhard 100s)
4). Photoinitiator Irgacure 184 2.00
Irgacure 819 1.00
5). Fused silica 50.00
(F5BLDX from Dennka)
Total 100.00
Comparative Example A peeled off the wafer after 24 hours of ambient storage after photocuring and this was believed to be due to excessive shrinkage induced by photocuring.

Comparative Example B
Component Weight part
1. Bisphenol A-epichlorohydrin 18.15
Epoxy resin (residual epichlorohydrin <1ppm)
Shell Resins RSL-1462)
2. Acrylate modified epoxy oligomer 20.5
(CN136 from Sartomer)
3. Latent amine accelerator 1.09
(Air Products & Chem
Ancamine 2441)
4). Dicyandiamide 1.27
(SKWCem Dyhard 100s)
5). Photoinitiator Irgacure 184 1.50
Irgacure 819 1.00
7). Fused silica 50.00
(F5BLDX from Dennka)
Total 100.00
Comparative Example B was also peeled after 24 hours ambient storage.

  The present invention has special industrial applicability as underfills applied to wafers and methods for their preparation. Compositions of the present invention can be used for glove tops, chip direct attachment and other thermosetting compositions. It is also used for microelectronic applications beyond underfill such as applications. While several preferred embodiments have been described above, many modifications and variations are possible in view of the above teachings. Therefore, it will be appreciated that the invention may be practiced otherwise than as specifically described without departing from the scope of the claims.

It is a DSC curve of Example 6, Comprising: Melting | fusing point, the thermosetting start, and the peak temperature of reaction are shown. It is a DSC curve of Example 7, Comprising: Melting | fusing point, the thermosetting start, and the peak temperature of reaction are shown.

Claims (6)

An ambient temperature stable integrated circuit wafer having an active surface bonded to an underfill composition, wherein the underfill composition comprises the following one-part mixture: Wafer:
Liquid photo-curable acrylic component,
Polyfunctional epoxy resin,
At least one photoinitiator,
A non-conductive filler, and a non-melting heat-activated epoxy curing agent,
The underfill composition in a solid state exhibits a flexural modulus of 1000 to 5000 MPa at 25 ° C. and a thermal expansion coefficient of 15 to 50 ppm / ° C. below the glass transition temperature of the underfill composition. 5% to 30% monofunctional unsaturated photocurable component,
10% to 45% polyfunctional epoxy resin,
0.3% to 3% of at least one photoinitiator, and 40% to 70% non-conductive filler,
A liquid, 100% solid, non-self, wherein the cured underfill exhibits a flexural modulus of 1000 to 5000 MPa at 25 ° C. and a thermal expansion coefficient of 15 to 50 ppm / ° C. below the glass transition temperature. A one-pack type underfill composition. The photocurable component, C ₃ -C ₁₂ according to claim 2, characterized in that it comprises at least one compound from the group consisting of alkyl-substituted C ₃ -C ₁₂ esters of alkyl esters and acrylic acid Acrylic acid Underfill composition.   The photocurable component is selected from at least one of the group consisting of tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, pentaerythritol monomethacrylate, trimethylolpropane monoacrylate, acrylic alkylol formal acrylate, and ketal acrylate. The underfill composition according to claim 2.   The photocurable component is a group consisting of bis-phenol polyether acrylate, vinyl ether crown oligomer, acrylated epoxy resin, ethylenically unsaturated polyalkyl ether, poly (cyclic) ether acrylate, and polycyclic (ether) acetate acrylate. The underfill composition according to claim 2, which is an unsaturated oligomer selected from the group consisting of:   The underfill composition according to claim 4, further comprising a monounsaturated acrylate monomer, wherein the oligomer has a number average molecular weight of 500 to 5,000.

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