JPH036892A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE: To obtain a specified inplane coefficient of thermal expansion, by constituting a multilayered printed wiring board of laminates sandwiching a bonding sheet between them, and forming at least one layer out of them by using liquid crystal polymer selected out of specific compositions and a group composed of their mixture. CONSTITUTION: A multilayered printed wiring board(MLPWB) and laminates contains at least one layer formed of liquid crystal polymer selected out of poly (paraphenylene benzo bisthiazole), poly (paraphenylene benzo bisoxazole), poly (2.5-benzo thiazole), poly (2.5-benzo oxazole), and a group composed of mixture of them. The liquid crystal polymer can be supplied as forms of yam, short fiber, pulp, etc. By the negative coefficient of thermal expansion and the high Young's modulus of desirable liquid crystal polymer, a coefficient of thermal expansion which is accurately controlled in the wide range of, e.g. about 0-15ppm/ deg.C can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The United States Government awarded United States Air Force (υ5AP) Contract No. F33615.
-84-C-5023 has rights to this invention.

The present invention relates to multilayer printed wiring boards (MLPWBs), and more particularly to the manufacture of printed wiring boards (PWBs) whose in-plane coefficient of thermal expansion (CTE) is adjusted and controlled.

In recent years, there has been an accelerating trend to simultaneously reduce circuit size and expand functionality in high-performance electronic systems. P.W.
B technology plays a vital role in this development. Surface mount technology (SMT) allows PWB designs such as the use of fine lines and closely spaced substrates, small diameter metallized through-holes and vias, and chip carriers with many fillet solder joints. New requirements were introduced.

The development of PWB stacks (often composed of many thin laminates) has been driven by the increasing complexity of devices and the need to package these devices into small volumes. I came.

Maximum circuit density under harsh conditions is also a design criterion. Selecting materials that exhibit desirable properties is one way to improve PWB performance.

For example, for PWBs to continue to evolve with chip development, both the resin system or matrix and the reinforcing materials, as well as their combination, need to be tailored to be a good match. For example, resin systems have low volume CTE
It is generally known that a compromise is required between properties such as low dielectric constant (E), high thermal stability, high glass transition temperature (T), & and ease of processing. The point is rapidly approaching where the mechanical, physical and electrical properties of currently commercially available PWB materials will be inadequate to meet increasing packaging demands.

Presumably, the above requirements are such that conventional (and future) ceramic chip carrier materials are
It will be even better to realize that it becomes necessary to have an in-plane CTE of less than m/° C. (where ppm means 10 −6 ). Furthermore, an in-plane CTE in this range also facilitates the implementation of direct die bond attachment in the future. CTE values for silicon, GaAs, and many other ceramic materials fall within this range. It is also important that the combined expansion in the Z-axis direction is close to that of copper (17 ppm/° C.) to reduce stress within the PTH.

Lower dielectric constants (eg, less than 3°0 at IKHz) are becoming increasingly desirable as this minimizes propagation delays when the device's clock rate is high. MLP by heat-resistant resin T (e.g. 185℃ or higher)
It is ensured that the expansion of the WB remains relatively low during the thermal stroke and linear as a function of temperature. The low synthesized hygroscopicity (eg, less than 0.5% at saturation) ensures stability of the electrical properties and keeps the swelling of the matrix low when the environmental humidity changes.

The development of new and improved materials for PWB fabrication can advantageously use existing manufacturing techniques (e.g., treating, B-staging, lamination, etc.) while utilizing non-traditional techniques, e.g., papermaking and coextrusion. You have to be in harmony with what you can do.

Another issue to be aware of is thermal fatigue of solder joints and full barrel cracking of LCCCs (Leadless Ceramic Chip Carriers).

Thus, laminate and PWB designers and manufacturers will be faced with a difficult task.

SUMMARY OF THE INVENTION The present invention, in its broadest aspects, relates to improved composite materials, such as MLPWBs and laminates, for use in the manufacture of PWBs. This improved MLPWB and laminate
Poly(para-phenylenebenzobisthiazole), poly(para-phenylenebenzobisoxazole), poly(para-phenylenebenzobisoxazole),
2,5-benzothiazole), poly(2,5-benzoxazole), and mixtures thereof. A preferred liquid crystal polymer is poly(p-
phenylenebenzobisthiazole). The liquid crystal polymer can be provided in the form of yarns, staple fibers, pulp, paper films, platelets, molecular composites, woven fabrics (including knitted fabrics), nonwoven mats, or continuous films. The negative coefficient of thermal expansion and high Young's modulus of the preferred liquid crystal polymers allow for the laminates and MLPWs produced therefrom.
B can have a precisely controlled coefficient of thermal expansion, for example in a wide range of about 0 to 15 ppm/'C, advantageously in the range of 3 to 7 ppm/'C.

A method of controlling the in-plane coefficient of thermal expansion of an MLPWB also forms another aspect of the invention. The use of polymeric core layers utilizing the preferred liquid crystal polymers of the present invention is also possible. When such liquid crystal polymers are combined with other conventional reinforcing materials, M
A degree of freedom in design that was previously impossible with LPWB and laminated products can be obtained.

An advantage of the present invention is that without adversely affecting the Z-direction expansion of the MLPWB or sacrificing other properties,
It may be possible to control the in-plane thermal expansion coefficient of the MLPWB. Another advantage is that traditional metal core layers can be replaced with layers formed from the liquid crystal polymer materials disclosed herein. Yet another advantage is that the unique liquid crystal polymers disclosed herein can be used to
It is possible to use processing technology. These and other advantages will be readily apparent to those skilled in the art from the disclosure contained herein.

Hereinafter, the present invention will be described in detail with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION Controlling the in-plane CTE of single-layer or multilayer PWBs over a temperature range of, for example, -65 to 125 degrees Celsius for stacked substrates is a method that achieves negative CTE and
This is made possible by the use of reinforcing materials that exhibit extremely high axial modulus, greater than 1,000 psi. The equation established by Halpin and Pagano (AI"ML TR6g-395) describes the relationship between resin matrix and reinforcing fibers in controlling the CTE of composites. For example, a relatively simple equation for the CTE of a composite material unidirectional in the fiber direction shows the effect of the components as follows.

E　rar　Vr　+Efflamvffla11″″ EfVr+EllVffl However, a E--modulus V - volume fraction f, m - fiber, matrix 11 - Direction parallel to the fibers.

That is, the CTE of the composite is directly affected by the modulus and CTH of the reinforcing fibers.

A highly oriented polymer with such properties is PW
To obtain accurate in-plane CTE of B, it can be used in various physical forms in combination with other materials. Preferred anisotropic or liquid crystal polymers for use in the present invention having the requirements listed above include poly(p-)unilenebenzobisthiazole) (
(includes both cis and trans forms), poly(p-phenylenebenzobisoxazole) of structure H below (includes both cis and trans forms), poly(2,5
-benzothiazole), and poly(2,
5-benzoxazole). The structural repeating units of these liquid crystal polymers and the abbreviations used herein are shown below.

(I) PBZT (or PBT, indicating lance type)
(n) PBO (indicates lance form) (III) ABPBZT (mV) ABPBO In the literature, the designation PBT is used for Structure I (and Structure I
Note that for II). Their compounds are identical. The synthesis of the above liquid crystal polymers and the conversion of their fiber morphology can be found in the following literature: U.S. Patent Box 4.225.700, No. 4,6
No. 06,875, No. 4゜487.735, No. 4.53
No. 3,724, No. 4.545,119, No. 4,533
, 692 and 4,533,693, Macromolecules (
Macroa+olecules), 1981, Vol. 14, pp. 909 et seq., and Polylier Preprints % No. 28
Volume, No. 1, Page 50 (April 1987). The disclosures of these are incorporated herein by reference.

PBZT is often referred to herein as it is best characterized as the preferred liquid crystal polymer. Such description is for illustrative purposes only and is not meant to be limiting in any way. Fibers and films made from PBZT have unique properties, including
Some are comparable to, and some are superior to, fibers and films made from the materials used to strengthen WB. The table below shows the properties of fibers and films made from PBZT and some conventional materials.

Comparison of PBZT film properties
．． duPont deNemours and Co.
Keylar brand poly-p-phenylene terephthalamide manufactured by mpany.

Zero - E.I. DuPont dispute de Bonnemours (E, 1.
duPont de Ne5ours and Co.
, ) manufactured by Iapton brand, poly (maleimide).

Kimoto - E.I. DuPont de Nemours (E, 1
．． duPont de Newors and C
Mylar brand, poly(ethylene terephthalate) manufactured by O.

Concerning fiber properties, desirable axial CTE values of PBZT are observed to be negative and Kevlar (Kevl
ar) So is the value of branded fibers.

However, the modulus of PBZT fiber is different from the other two listed above.
Much improved compared to seed material.

This combination of improved high modulus and negative CTE makes PBZT fibers valuable as reinforcing materials in the manufacture of PWBs. Regarding film properties', it can be seen that among the materials listed in the table above, PBZT is the only material with a tunable CTE that can be varied to very low and even negative values. Its high service temperature, tensile strength and tensile modulus also contribute to its usefulness as a reinforcing material in PWBs.

As is clear from the table above, two useful forms of PBZT to supply for use in the manufacture of PWBs are (P
It is in the form of a yarn (composed of BZT fibers) and in the form of a continuous film.

In the case of fibers, such fibers usually have a size of about 20
~1.000 denier. The fibers can also be stretch cut as is commonly used in the textile industry. The PBZT fibers may also be fabrics formed therefrom, such as plain weave, twill weave, sash weave, and locust weave. When providing PBZT as a fabric, its thin gauge means that a balance must be struck between the crimp factor (out-of-plane fiber generation) and the fiber loading of the fabric. Such a balance can be achieved using conventional textile techniques.

The fabric can be woven from monofilaments or cut filaments of PBZT material alone, or it can be woven from conventional reinforcing fibers, such as E-glass,
S glass, quartz fiber, Nextel brand inorganic fiber, organic fiber [e.g. Kevlar
lar) branded fiber or Nomex (Nomex)
) brand fibers], metal fibers, aluminum oxide and other ceramic fibers, and graphite fibers (however, in the case of metal fibers and graphite fibers, conductivity must be considered).

For more information on common fibers, see Lytton (1978).
Educational Publishing Company (Lltton)
Educational Publishing,
Inc., published by Van Nostrand Reinholt Co.
Handbook of Fillers and Reinforcements in Plastics, edited by Katz and MI Ievskl
('FilIers and Re1nf'orce
It can be seen in Ilents ror Plastics) J. The CTE of multi-component composite fiber is PBZT
Typical fiber types and volume percentages (%) used with fibers
It can be adjusted appropriately by selecting .

A second form for providing PBZT reinforcement is in the form of a continuous film, such as cast from polyphosphoric acid as taught in the references cited above. The film can have unidirectional properties on the surface and
Alternatively, it can be made biaxially oriented by stretch rolling techniques, also as described in the above-cited documents. Although the tensile strength of this continuous film tends to be lower than the PBZT fiber form, the advantageous effect of improved fill volume is that it covers as much reinforcing material (in the resin) per layer as is manufacturable. A continuous film of 70-80% by volume can be produced. It is recognized that in the case of textiles, a textile content of about 40% by volume is a practical maximum. It is also possible to cast the PBZT film with other materials, such as PBO or one of the other liquid crystal polymers preferably used in accordance with the teachings of the present invention, although such co-casting has not yet been performed. Additionally, PBZT films may be made with other materials dispersed within their own matrix. This "resin soaked film" is useful for promoting adhesion between the film and the matrix. The use of PBZT films also allows the production of single or multi-conductor layer flexible circuits with unique CTE properties. Not only can the resulting flexible circuits have in-plane CTE values that match a variety of chip carrier substrates, but such circuits can also be used, for example, in space base radar antennas where zero CTE is desired. It can also be used as a structure.

A third form for delivering PBZT materials is a nonwoven sheet or mat formed from PBZT fibers that may optionally contain a heat-meltable binder. As is known to those skilled in the art, papermaking techniques are applied in the production of polymeric fiber reinforced mats. Such techniques can also be applied to form mats using PBZT fibers. Heat-fusible (e.g., thermoplastic or thermoset) binders can be used in combination with the mat in a conventional manner, as needed, desired, or convenient. PBZ
Mats formed from T and other fibers can also be made from fibers such as those listed above. Moreover, the use of such composite nonwoven mats allows designers and manufacturers to tailor the properties of the resulting composite sheet, particularly with respect to its CTE. actual,
Discontinuous particulate reinforcement can be added to nonwoven sheets or PBZT fabrics to provide further flexibility in adjusting their CTE. Such discontinuous particulate reinforcements include, for example, PBZT itself, glass spheres, mica, quartz, β-nycryptite, and the like. Other discontinuous particulate reinforcements are available, for example in the plastic fillers and reinforcements handbook (Ilandb) cited above.
ook of Fitlers and Re1nfo
rcea+ents f'or Plastics)
It is listed in J.

Due to the negative CTE properties of the PBZT material, the in-plane CTE of the layer containing the PBZT material can be reduced to a desired value, e.g.
A value of 15 ppm/°C can be adjusted. Various techniques may be used to modulate such CTE. Since MLPWB utilizes materials to bond the various laminates together, the PBZT layer, regardless of its form, is combined with a matrix or adhesive such as is commonly used in conventional MLPWB manufacturing. .

Typical matrices and adhesives have CTE values that are significantly higher than desired, so a simple way to control the CTE of the resulting composite layer is to determine the type of matrix or adhesive used and the amount contained in such layer. There is P
The volume fraction (%) of BZT reinforcement is selected. This PB
Due to the CTE efficiency of ZT material, less PBZT material is used to obtain the desired CTE value of 0-15 ppm/°C.

Another technique that can be implemented to tune the CTE of the PBZT layer is to use other alternative materials in combination with PBZT. This has already been described to some extent regarding the combination of PBZT and other materials, for example to form fabrics and mats. Additionally, PBZT layers and layers made from conventional reinforcing materials may be used alternating to control the CTE of the resulting composite laminate. Such alternating layers may use conventional reinforcements or a combination of conventional reinforcements with PBZT or the preferred materials disclosed in the Isui specification.

Referring to FIG. 1, an eight-layer MLPWB can be constructed from the various laminated veneers and bonding sheets shown. Each of the laminates 10.12.14.16 is provided with conductive circuits on both sides, and has a PWB of 8 conductive layers.
It becomes. Between these laminated plates, two joining sheets 18 to 28 are sandwiched between each laminated plate. As will be readily apparent, the number of bonding sheets can be as small as one, or as many as four or more. As mentioned above, the bonded sheet, the laminate, or one or more of the bonded sheets or laminates can be constructed from PBZT. FIG. 2 is an enlarged perspective view of one of the laminate layers that may be suitably used in a substrate configuration such as that shown in FIG. Laminated layers are fine. Also, by a suitable well≠M,
A conductive layer indicated at 30 is provided on the top surface of the laminate 32, and a circuit 34 is provided on the bottom surface. As will be readily appreciated, this conductive layer may be any suitable conductive material, most commonly copper, but other metals and conductive non-metals may also be used.

The metal foil or conductive layer is preferably copper in any form including, for example, rolled, annealed or electrodeposited metal. This is also a normal thing, as will be discussed in detail later on. The laminate 32 of the present invention has an upper nonwoven PBZT mat 36 that supports conductive circuitry 30. A PBT/resin layer 38 is sandwiched between the mat 36 and the circuit 34. It can be seen that the shape of the laminate 32 allows it to be used as the outer layer of this substrate. In that case, the mat 36 controls the fine finish of the surface and the textile layer 38 is inside the surface layer. By designing and selecting the materials and material concentrations, the in-plane CTE of the laminate 32 can be accurately controlled. As mentioned above, the materials of construction of layers 36 and 38 need not be the same.

That is, either layer 36 or 38 is made of PBZT.
They may be manufactured in combination with one or more conventional reinforcement materials and/or one of these layers may be manufactured entirely from conventional materials.

FIG. 3 shows another embodiment of a laminate structure in accordance with the teachings of the present invention. Laminate 40 is shown in its pre-etched form and has an upper conductive layer 42 and a lower conductive layer 44. The laminated areas are etched away in the usual manner. Supporting conductive layers 42 and 44 are biaromatic films 46 and 48 of PBZT, respectively. The intervening layers 50 may suitably be manufactured from conventional materials such as E-glass, quartz, or similar fibers in a conventional resin matrix. Of course, layer 50 may include only PBZT or PBZT
and one or more of the conventional reinforcing fillers. Again, the laminate 40
The unique configuration of allows precise control of the in-plane CTE of this laminate and adjustment of other laminate properties.

FIG. 4 shows a conventional 8-layer MLPWB in cross-sectional elevation. There is a top conductive layer 52 followed by conductive layers 56-64 and finally a bottom conductive layer 66. Although the reinforced dielectric matrix carrying these conductive layers is shown simply as 68, it will be understood that the generally homogeneous composition is not a limitation of the laminate shown in FIG. 4 or of the present invention.

Holes 70 are etched through the laminate to interconnect the various circuit layers. A conductive layer 72, such as copper, is then plated over the walls of the hole 70 in the conventional manner. The PBZT reinforcement is designed to minimize microcracks that occur between each conductive layer in the immediate vicinity of the conductive barrel 72 and at such crossing points. The aspect ratio from the PTH, i.e., the aspect ratio through 70, often ranges from about 1:1 to 1:10 (diameter:height) according to modern MLPWB technology.

Each iMLPWB is made of copper clad amber metal (nickel iron alloy with high nickel content), alloy (A11oy)
42, or a similar low expansion metal. A unique aspect of the present invention is the use of a polymeric core layer as a replacement for the conventional metal core layer. P
The superior properties of the BZT layer allow such substitutions to be achieved while maintaining advantageous properties that were previously only achievable using metal core layers. PBZT
The use of the core layer allows for the design of various electrical and physical properties of the substrate to be achieved. Of course, it is not necessary to replace all metal core layers.

That is, the polymer core concept of the present invention, in its broadest aspect, includes replacing at least a portion of a conventional metal core, although complete replacement is achievable. For example, during the production of the PBW of the present invention,
A metal backplate may be used to ensure heat dissipation. Several specific examples of polymer core layer embodiments of the present invention can be readily envisioned. M shown in Figure 1
Regarding LPWB, in one specific example, the laminates 10-
16 is manufactured from a normal fiber-reinforced laminate, and the bonded sheet 18
~28 are manufactured with PBZT reinforced matrix material. In another example, the laminates 10-16 include PBZT reinforcement and the bonding sheets are made of conventional materials. In yet another example, laminates 10-16 are composite structures, such as laminate 32 of FIG. At that time, the bonding sheets 18 to 28 may be either normal ones or PBZT-containing ones. In fact, it is not necessary that all of the bonding sheets 1g to 28 have the same composition. According to the core layer embodiment of the present invention, CT of MLPWB
It can be seen that the degree of freedom when adjusting E is extremely large.

The resin or matrix material used may be conventional or non-conventional. As a normal resin material,
For example, ABS-containing resin material (ABS/PC%ABS
/ polysulfone, ABS/PVC), acetal, acrylic, alkyd, allyl ether, cellulose ester, chlorinated polyalkylene ether, cyanate/cyanamide, epoxy and modified epoxy, furan, melamine-formaldehyde, urea-formaldehyde, phenolic resin, poly( (bis-maleimide), polyalkylene ether, polyamide (nylon), polyarylene ether, polybutadiene, polycarbonate, polyester, polyfluorocarbon, polyimide, polyphenylene, polyphenylene sulfide, polypropylene, polystyrene, polysulfone, polyurethane, polyvinyl acetal, polyvinyl chloride, polyvinyl These include chloride/vinylidene chloride, polyetherimide, acetylene terminated BPA resin, polyetheretherimide, IPN polymer, triazine resin, etc., and mixtures thereof. High performance resins specifically designed for PWBs are available and are being developed in industry.

Substrate processing using the PBZT, PBO and similar materials of the present invention can be performed in a conventional manner.

For example, a B-stage resin may be suitably used with PBZT reinforcement, or a C-stage may be used during final substrate layup. Forming PTH or vias in place is also a conventional practice. actual,
Blind or buried biases can also be used with PBZT reinforced PWBs. Not glPBZ
Note that a unique process has been developed for using T-mat. It has been found that such mats are brittle and sometimes difficult to handle. Laminate plate 32 in FIG.
It has been found convenient to use a non-woven mat of PBZT fibers as layer 36 when manufacturing. layer 38
was PBZT, a conventional B-stage resin. circuit 30
The conductive layer etched to form the PBZT mat had a resin layer applied thereon, and the resin layer was placed in parallel with the PBZT mat. During the temperature/pressure treatment necessary to form laminate 32, this resin layer (and possibly the resin from layer 38) flowed through the mat to form layer 36. The resulting laminate layer 36 was a continuous resin matrix with PBZT fibers. Any conventional or specialized method for providing metal or conductive layers over internal and external printed wiring board layers is encompassed by the present invention. Currently commonly used methods include, for example, those classified into additive processes, subtractive processes, and semi-additive processes. Also encompassed is the use of a combination of processes within these categories to create single-sided or multilayer PWBs such as that shown in FIG.

The following examples illustrate how the invention may be practiced, but are not meant to be limiting in any way. All references cited herein are incorporated by reference.

EXAMPLES Example 1 Test vehicle for 155 coupons, each with 3.25
It was constructed from three substrates measuring 3.5 inches by 3.5 inches and having a thickness of about 0.6 to 0.72 inches. Each 8-layer board was made with the configuration shown in FIG. 1, except that only one bonding sheet was sandwiched between each laminate. Each laminate has 1,000
It was made from a PBZT fabric woven from 0 denier PBZT monofilament fibers. The matrix for this PBZT fabric was a 70/30 weight ratio bismaleimide-triazine/epoxy resin [Dow Chemical Co., Ltd.
Epon 1123 (manufactured by OV Chemical Company) blend. Each laminate contained approximately 60% resin by volume, which appeared to be too low in resin. The technology used is MIL-STD-
It was a 2750 pattern (revised version).

In-plane CTH measurements were carried out over the relevant temperature range from -65°C to +125°C. The in-plane CTE of the substrate is 1.55 ppm in the X direction/0.24 ppm in the C1y direction.
It was found that ℃.

After repeated thermal cycling (200 cycles) from −65° C. to +125° C., electrical oven PTH and other failure modes are observed.

These defects are due to the lack of resin exhibited by the PBZT laminate. This lack of resin in the laminate is believed to be due to the rather large size of the fibers used in weaving the PBZT fabric. With lower denier fibers, low resin conditions are not expected to be an issue and will not exhibit failure modes on the 155 coupon test boards. Nevertheless, this example shows that very low CTH PWBs can be fabricated according to the teachings of the present invention.

Example 2 Another 8-layer PBZT substrate was fabricated from 1.000 denier plait fabric (0.008 inch thick). Each laminate was coated on both sides with 1 oz. class 3 copper foil (0,0015 inches thick) mediated by a PBZT C-stage bismaleimide-triazine/epoxy matrix (see Example 1).

A single bonding layer was sandwiched between each of the four laminates.

Each bonding layer is made of 1,000 denier woven PBZTl
A and a bismaleimide-triazine/epoxy matrix (0.059 inch thick). The resulting substrate had a nominal thickness of 0.685 inches in the unclad portion and 0.072 inch in the clad portion. In-plane measurements (strain meter) and out-of-plane measurements (processing thermal analysis) were performed. In a study using a strain meter, the calibration value for aluminum was approximately 21.3. The sample probe reading was 26°2 before the test.
, after the test it was 25.5. These readings confirmed the stability of the probe readings during testing. Process Thermal Analysis (TMA) used a "macro-expansion" probe weighing 1 g, and the sample heating rate was 10° C./min. 2
Both tests are shown below. This is because it behaved well in the first test and was indicative of the substrate expansion behavior during the initial thermal transient. We obtained the following data.

Table 1 vaCTE value (+) I at C2-200℃ (1g or more)
)m/'C) The data in the above table is for PBZT-reinforced MLPWB.
It is possible to design a board that increases the CTE value to the desired level of 3 to 7 ppm/”c. Ton (Eva
nston)'s Interconnecting φ and Fist Packaging Electronic Circuits Laboratory (T
he In5 position for Intercon
nectlng and Packaging Ele
Improved IPC-
It was A-48 artwork.

Example 3 Another 8-layer board was manufactured in the same manner as Example 2 except that two bonding sheets were used for each layer.

Each laminate has a structure similar to that shown in Figure 2, with 1 oz class 3 copper foil (0,0
Immediately below the outermost foil layer was a 0.3 oz. PBZT mat (0°001 inch), followed by a C-stage layer of PBZT as described in Example 2. The laminate is made by applying B-stage resin to the underside of the copper foil and
It was manufactured using a technique using a non-resin dry mat of BZ fibers. Again, modified IPC-A-48 artwork was used. Measurements were carried out as described in Example 2.

Table 2 Once again, the above data shows the excellent low CTE values achieved with PBZT reinforcement. Therefore, adjustment of high CTE values is possible.

Example 4 Several substrates were made in accordance with the "polymer coat layer" embodiment of the present invention using only a portion of the IPC-A-48 artwork pattern repeated across the substrate. All four laminates were manufactured in Chandler, Alisina, USA.
Rogers Corporation (Roge
RO2800 fluoropolymer composite laminate manufactured by RS Corporation. The data sheet for this laminate is: E -2,9 (measured at IOG 'Hz), loss factor 0.0012, CTE in x-y plane 16.2 in plane 24 (ppm 7°C), tensile modulus was 0.12 Mpsi.

Each laminate was 2.5 mils thick and had 1 ounce copper foil on both sides. 11 companies (E, 1.DuPont
Kevlar 108 brand reinforcement (CT
E--5ppm/'C1 tensile modulus-18,5M
PSI) was used. The matrix material is manufactured by Dow Chemical Company.
)'s Quatrcx brand epoxy resin, its physical properties/ln2℃, copper peeling -91b
It could be cured at 177° C. for 90 minutes at s/In. Each bonded sheet was 2 mils thick. The second set of substrates used the 8 mil thick PBZT fabric layer of Example 2. The number of bonding sheets per layer was varied for each set of substrates produced. The data shown below (showing readings of samples measured separately) was obtained.

Table 3 Samples 10 to 12 for comparison have the target 3 to 7 ppm/
' indicates a CTE value greater than c. Sample 13 of the invention
~15 indicates a smaller CTE value than desired, but
It should be possible to increase this CTE value quickly. Samples 13-15 demonstrate the utility of the polymer core layer embodiment of the present invention. Advantages of this approach include the use of conventional process steps and deposition techniques. This means that such an approach can be readily implemented in current commercial manufacturing equipment.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of the MLPWB. FIG. 2 is an enlarged perspective view of a laminate suitable for use in an MLPWB such as that shown in FIG. FIG. 3 is an enlarged perspective view of an unetched laminate suitable for use in an MLPWB such as that shown in FIG. FIG. 4 shows an MLPWB mesh through hole (P) that can be formed as shown in FIG.
TH) is a partially transparent cross-sectional view.

Claims (27)

[Claims] (1) A multilayer printed wiring board made of laminates with a bonding sheet sandwiched between them, at least one of which contains poly(p-phenylenebenzobisthiazole), poly(p-phenylenebenzobisoxazole). ),
A multilayer printed wiring board characterized in that it is formed from a liquid crystal polymer selected from the group consisting of poly(2,5-benzothiazole), poly(2,5-benzoxazole), and mixtures thereof. (2) The multilayer printed wiring board according to claim 1, wherein both the laminate and the bonding sheet are made of layers formed of the liquid crystal polymer. (3) The multilayer printed wiring board according to claim 1, wherein only the laminate is formed from the liquid crystal polymer. (4) The multilayer printed wiring board according to claim 1, wherein only the bonding sheet is formed from the liquid crystal polymer. 5. The multilayer printed wiring board according to claim 1, wherein the laminate is formed from a combination of the liquid crystal polymer and a different reinforcing material. (6) The multilayer printed wiring board according to claim 1, wherein the bonding sheet is formed from a combination of the liquid crystal polymer and a different reinforcing material. 7. The multilayer printed wiring board of claim 1, wherein the liquid crystal polymer is in the form of woven fabrics, nonwoven mats, continuous films, yarns, pulps, and discrete particles. (8) The multilayer printed wiring board according to claim 1, wherein a combination of the layer configurations is used. (9) The multilayer printed wiring board of claim 1, having an in-plane coefficient of thermal expansion in the range of about 0 to about 15 ppm/°C. (10) The multilayer printed wiring board according to claim 1, wherein the liquid crystal polymer is made of poly(p-phenylenebenzobisthiazole). (11) Two outer conductive layers, poly(p-phenylenebenzobisthiazole) and poly(p-phenylenebenzobisthiazole) sandwiched between them.
phenylenebenzobisoxazole), poly(2,5-
1. A laminate for use in the manufacture of printed wiring boards (PWB), comprising a resin bonding layer having a liquid crystalline polymer reinforcement selected from the group consisting of poly(2,5-benzoxazole) and poly(2,5-benzoxazole). (12) The laminate according to claim 11, wherein the liquid crystal polymer reinforcing material comprises poly(p-phenylenebenzobisthiazole). 13. The laminate of claim 11, wherein the liquid crystal polymer reinforcement is in the form of a woven fabric, a nonwoven mat, or a continuous film. (14) The laminate according to claim 13, wherein a combination of the forms is used in forming the laminate. (15) The laminate according to claim 11, comprising a combination of the liquid crystal polymer reinforcing material and a different reinforcing material. (16) The laminate of claim 11, wherein the conductive layer is made of copper. (17) When constructing a multilayer printed wiring board, at least one layer of the multilayer printed wiring board is made of poly(p-
phenylenebenzobisthiazole), poly(p-phenylenebenzobisoxazole), poly(2,5-benzothiazole), poly(2,5-benzoxazole),
and a method for controlling the in-plane linear expansion coefficient of the multilayer printed wiring board, the method comprising forming the multilayer printed wiring board with a liquid crystal polymer selected from the group consisting of a mixture thereof. (18) The in-plane linear expansion coefficient is about 0 to about 15 ppm/
18. The method according to claim 17, wherein the method is controlled to be within a range of °C. (19) The method according to claim 17, wherein the layer is formed from a heat-meltable resin and the liquid crystal polymer. (20) The method according to claim 17, wherein the liquid crystal polymer comprises poly(p-phenylenebenzobisthiazole). 21. The method of claim 17, wherein the multilayer printed wiring board laminate comprises two outer conductive layers and the liquid crystal polymer layer sandwiched therebetween. 22. The method of claim 21, wherein the laminate also includes another different reinforcement. (23) The method according to claim 17, wherein at least one bonding layer sandwiched between the laminates of the multilayer printed wiring board is formed from the liquid crystal polymer. 24. The method of claim 23, wherein at least one bonding sheet of the multilayer printed wiring board is formed from another different reinforcing material. 25. The method of claim 17, wherein the liquid crystal polymer is provided in the form of a woven fabric, a nonwoven mat, or a continuous film. (26) The method of claim 25, wherein a combination of forms is used. 27. The method of claim 17, wherein the liquid crystal polymer is in the form of yarns, particles, or pulp.