Low dielectric constant prepreg based on blends of polynorbornene and polyolefins derived form C.sub.2 -C.sub.4 monomers

This invention provides improved prepregs for producing laminates and improved laminates using such prepregs. Processes for producing the prepregs and the laminates are also provided. Processes for producing the prepreg include the steps of providing a dipping solution or suspension comprising a polynorbornene polymer, a polyolefin polymer derived from C.sub.2 -C.sub.4 monomers, and a solvent followed by impregnating a non-cellulosic cloth with the solution. The solvent is removed from the cloth to form the prepreg. Printed circuit boards are also provided by a process which includes the steps of providing such a prepreg and pretreating the surface of a conductive film with a solution of a silane compound, effective to increase the bond strength between the copper foil and the prepreg, followed by laminating the prepreg to the conductive film.

BACKGROUND OF THE INVENTION 
The present invention relates to improved prepregs and methods of producing 
them. In particular, the invention relates to improved printed circuit 
wiring boards having a low dielectric constant prepared from such 
prepregs, and to methods for producing such printed circuit wiring boards. 
Conventional printed circuit wiring boards are prepared from "prepregs" 
which, in turn, are typically prepared by pretreating a cloth substrate, 
e.g., a fiberglass cloth substrate, with a polymer resin, as by dipping in 
a solution of resin. The resin is selected so as to provide good strength 
and low dielectric constant. The solution is then dried to remove the 
solvent and provide a resin-impregnated prepreg or substrate. 
Advantageously, the glass substrate is treated with a silane compound to 
promote adhesion between the substrate and the resin. Such laminates are 
compared in the market place for such factors as dielectric constant, 
dissipation factor, chemical resistance, peel strength, solder bath 
resistance (resistance to delamination when immersed in molten solder), 
warping and punchability. It is particularly desirable that the dielectric 
constant of such laminates be low. Accordingly, skilled workers 
increasingly seek to lower the dielectric constant of such laminates and 
increase the bond strength between laminations. 
CA 106:51353g discloses laminated printed circuit boards having good heat 
resistance and low dielectric constant comprising non-woven glass fabric 
impregnated with polybutadiene and diallyl phthalate. 
Fibrous materials, e.g., cellulosic and fiberglass woven materials, have 
long been used to reinforce polymer substrates. It is also known that 
silane coupling agents can be applied directly to glass filaments to 
improve the flexural strength of laminates prepared from glass cloth 
impregnated with polymeric resins. Typical strength increases can be as 
much as 300% for compression molded test samples. Silane coupling agents 
have also been employed with the minerals which are used as reinforcing 
fillers in composites to increase strength, hardness, modulus, heat 
distortion and impact strength. Fiberglass cloth is typically treated with 
an aqueous coupling agent. 
In the preparation of printed circuit wiring boards using prepregs, two or 
more prepregs, prepared as discussed above, are pressed together to form 
an insulating layer for a printed circuit wiring board. To provide the 
conductive layer, one or more layers of a conductive film, e.g., a copper 
film, are placed on the outside of the prepregs and laminated to the 
prepregs at the same time the prepregs are laminated to each other. 
Alternatively, the conductive film can be applied by vapor deposition, 
electroplating, sputtering, ion plating, spraying and layering. Typical 
metals employed include copper, nickel, tin, silver, solder, gold, 
aluminum, platinum, titanium, zinc and chrome, with copper being used most 
often in printed wiring boards. 
A problem associated with such constructions is the difficulty in applying 
conductive films so that they bond well to the surface of the prepreg. In 
fact, prior workers have not been able to form a complete bond having 
excellent bond strength between the metallic layer and the substrate, and 
subsequently good solder resistance. 
Silane compounds have found wide acceptability for improving adhesion 
between different substrates. Silane coupling agents modify the interface 
between metal or mineral surfaces and organic resins to improve adhesion 
between the surface and the resin. The physical properties and water 
resistance of the reinforced resins are thereby improved. It is believed 
that silane coupling agents form bonds with metal surfaces through the 
silane functional group. The hydrolyzed silanes will condense to 
oligomeric siloxanols and eventually to rigid cross-linked structures. 
Contact with a polymer matrix should take place while the siloxanols still 
have some solubility. Bonding to a polymer matrix may take different forms 
or a combination of forms. Bonding may be covalent where the oligomeric 
siloxanol is compatible with the liquid matrix resin. The solutions might 
also form an interpenetrating polymer network as the siloxanols and the 
resin separately cure with only limited copolymerization. 
Prepregs composed of copolymers have been employed in the past. For 
example, CA 106:51353g discloses printed circuit laminates comprising 
1,2-polybutadiene and diallyl phthalate or polymers thereof. 
CA 106: 51354h discloses adhesive compositions employing isobutylene-maleic 
anhydride-styrene terpolymers. 
It is well known that not all silanes or mixtures of silanes will bond all 
metals to all substrates. McGee, 4,315,970, states that "it is generally 
accepted that specific silanes can be used for adhesion of specific 
materials to specific substrates. That is, the silane must be matched to 
the application and it cannot be assumed that all silanes will work in all 
applications." Therefore, the suitability of a silane bonding agent in 
improving adhesion of a metal to a substrate is unpredictable and it must 
be determined by experimentation. 
While suitable coupling agents are commercially available for bonding of 
many common plastics with a variety of metals, the application of silane 
coupling agents for bonding of polynorbornenes to metals is not previously 
known. Norbornene type monomers are polymerized by either a ring-opening 
mechanism or by an addition reaction wherein the cyclic ring structure 
remains intact. Ring-opening polymerizations are discussed with greater 
particularity in U.S. 4,136,247 and 4,178,424, assigned to the same 
assignee as the present invention and incorporated herein by reference for 
their discussion of such polymerizations. Ring-opening polymerization 
generally yields unsaturated linear polymers while addition polymerization 
yields polycycloaliphatics. It is desirable to produce polymers having 
high molecular weight monomers incorporated therein to provide good 
temperature resistance, i.e., high heat distortion temperatures and high 
glass transition temperatures. 
SUMMARY OF THE INVENTION 
The invention provides printed circuit wiring boards, prepregs for making 
such boards, and processes for producing such prepregs and boards 
(laminates). 
The prepregs of this invention comprise a core formed of a mixture of 
polynorbornene and polyolefin derived from C.sub.2 -C.sub.4 monomers, with 
reinforcing material, e.g., glass fiber cloth. In one aspect of this 
invention, they are prepared by providing a dipping solution comprising a 
polynorbornene dissolved in a solvent and polyolefin dissolved or 
suspended in a solvent. A non-cellulosic cloth is then impregnated with 
the dipping solution and the solvent is removed to form a prepreg. The 
prepreg can be employed to produce a printed circuit wiring board. In 
another aspect of the invention, the surface of a conductive film is 
pretreated with a solution of a silane compound effective to increase the 
bond strength between the conductive foil and the prepreg. The prepreg is 
then laminated to the conductive film across the surface of the pretreated 
film to form a printed circuit wiring board. The resultant wiring boards 
have excellent inter-layer adhesion and a dielectric constant of about 2.8 
when using E-type glass fiber cloth. Particularly preferred polyolefins 
comprise polyethylene. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention provides prepregs and laminates prepared from such prepregs. 
For example, the invention provides printed wiring boards having superior 
dielectric properties. The prepregs comprise fiberglass cloth reinforced 
with resins, and in particular, a mixture of a polynorbornene and a 
polyolefin. The printed circuit wiring boards comprise at least one of 
such prepregs, preferably more than one, laminated together with at least 
one layer of metallic film or foil. Preferably the metallic film is a 
copper foil which has been pretreated with an adhesion promotion agent. 
Silane compounds are particularly preferred adhesion promotion agents. 
The prepregs are derived from a dipping solution which comprises norbornene 
polymers dissolved in a solvent and polyolefin polymers dissolved or 
suspended in a solvent. The polyolefin polymers are fully conventional. 
Suitable polyolefins include polyolefins derived from monomers containing 
from 2-4 carbon atoms. For example, polyethylene (polyethene), 
polybutylene (polybutene) and polypropylene (polypropene) are particularly 
suitable polyolefins. Polyethylene is particularly preferred. However, 
throughout the specification, polyethylene is used in an illustrative 
sense. Thus, those of ordinary skill in the art will readily comprehend 
that polypropylene and polybutylene can readily be interchanged for 
polyethylene. Moreover, mixtures of the various polyolefins can be 
employed as well. 
The polynorbornene polymers are obtained from metathesis ring-opening 
polymerization of cycloolefin monomers having a norbornene functional 
group. 
These cycloolefin monomers are characterized by the presence of at least 
one norbornene moiety identified below, in its structure: 
##STR1## 
Suitable cycloolefin monomers include substituted and unsubstituted 
norbornenes, dicyclopentadienes, dihydrodicyclopentadienes, trimers of 
cyclopentadiene, tetracyclododecenes, hexacycloheptadecenes, ethylidenyl 
norbornenes and vinylnorbornenes. Substituents on the cycloolefin monomers 
include hydrogen, alkyl, alkenyl, and aryl groups of 1 to 20 carbon atoms, 
and saturated and unsaturated cyclic groups of 3 to 12 carbon atoms which 
can be formed with one or more, preferably two, ring carbon atoms. In a 
preferred embodiment, the substituents are selected from hydrogen and 
alkyl groups of 1 to 2 carbon atoms. Generally speaking, the substituents 
on the cycloolefin monomers can be any which do not poison or deactivate 
the polymerization catalyst. Examples of the preferred monomers referred 
to herein include 
dicyclopentadiene, 
methyltetracyclododecene, 
2-norbornene, 
and other norbornene monomers such as 
5-methyl-2-norbornene, 
5,6-dimethyl-2-norbornene, 
5-ethyl-2-norbornene, 
5-ethylidenyl-2-norbornene (or5-ethylidene-norbornene), 
5-butyl-2-norbornene, 
5-hexyl-2-norbornene, 
5-octyl-2-norbornene, 
5-phenyl-2-norbornene, 
5-dodecyl-2-norbornene, 
5-isobutyl-2-norbornene, 
5-octadecyl-2-norbornene, 
5-isopropyl-2-norbornene, 
5-phenyl-2-norbornene, 
5-p-toluyl-2-norbornene, 
5-.alpha.-naphthyl-2-norbornene, 
5-cyclohexyl-2-norbornene, 
5-isopropenyl-norbornene, 
5-vinyl-norbornene, 
5,5-dimethyl-2-norbornene, 
tricyclopentadiene (or cyclopentadiene trimer), 
tetracyclopentadiene (or cyclopentadiene tetramer), 
dihydrodicyclopentadiene (or cyclopentenecyclopentadiene co-dimer), 
methyl-cyclopentadiene dimer, 
ethyl-cyclopentadiene dimer, 
tetracyclododecene, 
hexacycloheptadecene, 
9-methyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, (or 
methyl-tetracyclododecene) 
9-ethyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, (or 
ethyl-tetracyclododecene) 
9-propyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, 
9-hexyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, 
9-decyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, 
9,10-dimethyl-tetracyclo[6,2,1,1.sup.3,6 0.sup.2,7 ]dodecene-4, 
9-methy1,10-ethyl-tetracyclo[6,2,1,1.sup.3,6 0.sup.2,7 ]dodecene-4, 
9-cyclohexyl-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, 
9-chloro-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4, 
9-bromo-tetracyclo[6,2,1,1.sup.3,6,0.sup.2,7 ]dodecene-4, 
9-fluoro-tetracyclo[6,2,1,1.sup.3,6,0.sup.2,7 ]dodecene-4, 
9-isobutyl-tetracyclo[6,2,1,1.sup.3,6,0.sup.2,7 ]dodecene-4, 
9,10-dichloro-tetracyclo[6,2,1,1.sup.3,6, 0.sup.2,7 ]dodecene-4. 
This invention especially contemplates the use of one or more monomers so 
as to provide either homopolymers or copolymers upon polymerization. 
Copolymers are defined as polymers composed of two or more monomers. 
Other monomers can form part of the polynorbornenes such as non-conjugated 
acyclic olefins, monocyclic olefins and diolefins. The non-conjugated 
acyclic olefins act as chain terminators. Hexene-1 is preferred while 
1-butene, 2-pentene, 4-methyl-2-pentene, and 5- (-N ethyl-3-octene are 
suitable also. They are typically used at a molar ratio of 0.001:1 to 
0.5:1 acyclic olefin to cycloolefin monomer. 
The polynorbornenes used in forming the printed wire boards of the present 
invention are obtained by solution polymerization in the presence of a 
catalyst, and preferably a co-catalyst. For solution polymerization, the 
catalyst preferably comprises molybdenum or tungsten salts and the 
co-catalyst preferably comprises dialkylaluminum halides, alkylaluminum 
dihalides, alkylalkoxy halides or a mixture of trialkylaluminum with an 
iodine source. 
Examples of useful molybdenum and tungsten salts include the halides such 
as chlorides, bromides, iodides, and fluorides. Specific examples of such 
halides include molybdenum pentachloride, molybdenum hexachloride, 
molybdenum pentabromide, molybdenum hexabromide, molybdenum pentaiodide, 
molybdenum hexafluoride, tungsten hexachloride, tungsten hexafluoride and 
the like. Other representative salts include those of acetylacetonates, 
sulfates, phosphates, nitrates, and the like. Mixtures of salts can also 
be used. The more preferred salts are the molybdenum halides, especially 
molybdenum pentahalides such as MoCl.sub.5. 
Specific examples of co-catalysts for ring-opening solution polymerization 
include alkyl-aluminum halides such as ethylaluminum sesquichloride, 
diethylaluminum chloride, diethylaluminum iodide, ethylaluminum diiodide, 
propylaluminum diiodide and ethylpropylaluminum iodide and a mixture of 
triethylaluminum and elemental iodine. 
For solution polymerization, the molybdenum or tungsten salt is generally 
employed at a level from about 0.01 to about 50 millimoles per mole of 
total monomer, preferably from about 0.5 to about 10 millimoles per mole 
of total monomer and, the organoaluminum compounds described above are 
generally used in a molar ratio of organoaluminum compound to molybdenum 
and/or tungsten salt(s) of from about 10/1 to about 1/3 preferably from 
about 5/1 to about 3/1. Both catalyst and co-catalyst for solution 
polymerization are normally added after the heating and at the time of 
polymerization. 
Suitable solvents used for the solution polymerization and in forming the 
dipping solution include aliphatic and cycloaliphatic hydrocarbon solvents 
containing 4 to 10 carbon atoms such as cyclohexane, cyclooctane and the 
like; aromatic hydrocarbon solvents containing 6 to 14 carbon atoms which 
are liquid or easily liquified such as benzene, toluene, xylene and the 
like; and substituted hydrocarbons wherein the substituents are inert such 
as dichloromethane, chloroform, chlorobenzene, dichlorobenzene and the 
like. Optionally present within the dipping solution are curing agents 
which initiate radical crosslinking such as the peroxides, di-t-butyl 
peroxide, or 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3. Antioxidants 
such as hindered phenol antioxidants (Ethyl 330) and polyunsaturated 
monomeric or oligomeric crosslinkers such as trimethylol propane 
triacrylate are also optional. The dipping solution has a solids content 
of preferably about 10% to about 40%. Dipping solutions having 
concentrations both above and below this range can be used in forming the 
laminates of the invention. 
The polyolefin is added to the dipping solution. Preferably it is added in 
powdered form. For example, polyethylene powder can be employed. 
Particularly suitable polyethylenes include MICROTHENE FN 524 and 
MICROTHENE FN 510, available from USI. It is also possible to employ 
polyolefin powder prepared from ground or otherwise finely divided 
polyolefin pellets. Powder particle sizes of 100 micron (0.1 mm) size or 
less are especially suitable. The polyethylene component is fully 
conventional, readily available and well-known to those of ordinary skill 
in the art. Other polyolefins are also fully conventional, readily 
available, and well known. 
Polynorbornene copolymers can be employed as the polynorbornene component. 
Preferred copolymers include, in a weight to weight ratio, those of 50% to 
75% methyltetracyclododecene, to 25% to 50% vinylnorbornenes, based on the 
total amount of poly-norbornene-type polymer employed. Most preferably, 
75% to 90% methyltetracyclo-dodecene to 10% to 25% vinylnorbornene, based 
on the total weight of norbornene-type polymer is employed. 
The polynorbornene-polyolefin blend is preferably employed in a weight 
ratio of from about 40:60 to about 90:10 of polynorbornene to polyolefin, 
more preferably from 45:55 to 65:35 polynorbornene to polyolefin. Blends 
of 50% polynorbornene and 50% polyolefin (1:1) have been found 
particularly suitable. 
Preferably, from about 40 wt.% to about 75 wt.% of polymer blend versus 
glass, based on the weight of finished prepreg, is present in the prepreg. 
More preferably from about 55 wt.% to about 70 wt.% is employed. Most 
preferably, about 65 wt.% polymer blend versus glass is employed based on 
the weight of the finished dry prepreg. 
The dipping solution, or suspension when the polyolefin is in a dispersed 
form, is impregnated into a non-cellulosic cloth, such as fiberglass to 
form a substrate layer, often referred to as a prepreg. The cloth may be 
woven or non-woven. Many glass cloth materials having a variety of surface 
characteristics are available commercially. In the present invention 
E-type fiberglass cloth, style 2116, having a surface finish type 642 or 
627 made by Burlington Industries is preferred. The glass cloth may be 
pretreated with a silane solution. A preferred class of pretreating agents 
is the styryl diamino silanes. This non-cellulosic cloth is impregnated by 
immersing it in the dipping solution, or suspension when the polyolefin is 
present in dispersed form, of the polynorbornene diluted in an organic 
solvent. This can be accomplished at ambient temperatures or at the 
temperatures above or below ambient temperatures. 
The prepreg so produced is typically dried at temperatures between ambient 
temperature and about 150 C. At the final stages of drying the temperature 
is preferably maintained above the glass transition temperature (Tg) of 
the polymer to permit the solvent to diffuse out. If curing agents are 
present, the temperature is kept sufficiently low to prevent activation of 
the radical crosslinking. 
Under typical conditions, for example, when a high molecular weight C.sub.2 
-C.sub.4 polymer is employed, it is not dissolved by the solvent of the 
dipping solution, but is suspended therein. For example, under most cases, 
the MICROTHENE powders employed form a suspension. Once impregnated into 
the prepreg and dried, the prepreg could show some opacity due to phase 
separation of the polymer components. Typical curing conditions involve 
placing the dried prepreg in a 180.C. oven and raising the temperature 
from 180.degree. C. to 220.degree. C. over a 25 minute period. The prepreg 
is then maintained at 220.degree. C. for another 25 minutes. Under these 
conditions, the C.sub.2 -C.sub.4 polyolefin phase is melted, and instead 
of the two-phase mixture which was present before curing, one phase 
develops. Subsequently, during final curing, a crosslinked product 
develops. 
Commercially, the drying is conducted in a continuous drying system, for 
example, a continuous drying tower as part of a treater having a 
temperature gradient from room temperature up to 220.degree. C. Treaters 
are well known to those of ordinary skill in the art, are fully 
conventional (they are employed in the production of conventional epoxy 
prepregs), and can be readily employed in the process of this invention, 
perhaps with a few routine optimization experiments. 
The laminates produced by the present invention incorporate a conductive 
film such as copper foil. This copper foil can be the surface layer of 
other metallic films. The copper surface layer is pretreated with a silane 
solution which increases the bond strength between the substrate and the 
copper surface layer. Preferably, copper foil of the type manufactured for 
printed wiring boards with a matte side for lamination to a prepreg is 
pretreated with such a solution of silane coupling agent before being 
laminated to the prepreg. Such copper foils are typically about 35 microns 
thick and have a dendritic bronze matte surface. 
According to the present invention several silanes were found to be 
preferred for bonding substrate layers of polynorbornene impregnated glass 
to copper layers. The silane coupling agent is preferably in solution at 
concentrations ranging from about 1% to 10% by weight. Suitable silanes 
include: 
3-methylacryloyloxypropyltrimethoxysilane, 
3-(N-styrylmethyl-2-aminoethylamino)propyltrimethoxysilane hydrochloride, 
3-(N-allyl-2-aminoethylamino)-propyltrimethoxy-silane hydrochloride, 
N-(styrylmethyl)-3-aminopropyltrimethoxysilane hydrochloride, 
N-2-aminoethyl-3-aminopropyltrimethoxysilane, and 
3-(N-Benzyl-2-aminoethylamino)-propyltrimethoxy silane hydrochloride. 
The laminates, such as printed wire boards, are finished by laminating the 
pretreated conductive layer to the substrate layer (prepreg). Lamination 
is accomplished in a heated press using pressures above about 700 psi, 
preferably above 1000-1100 psi and at temperatures between ambient 
temperature and 250.degree. C., but preferably between 170.degree. C. and 
190.degree. C. Preferably the temperature is above the glass transition 
temperature of the polynorbornene and sufficiently high to activate any 
peroxide curing agents. At such temperatures, any peroxide curing agent 
present in the polymer releases an oxygen free-radical which causes 
crosslinking. Crosslinking provides strength and chemical resistance to 
the boards. Generally a stack of prepregs may be pressed between a pair of 
pretreated copper foils. The pretreated bronze side of the copper foil is 
placed in contact with the prepreg.

The following examples are provided to illustrate preferred embodiments of 
the present invention. They are not intended to limit the scope of this 
disclosure to the embodiments exemplified therein. All percentages are by 
weight unless specified otherwise. 
EXAMPLE 1 
Step 1 
Preparation of 65/35 (wt/wt) Methyltetracyclododecene (MTD) 
Vinyl-Norbornene (VNB) Copolymer 
An unsaturated polynorbornene polymer was obtained in the following manner. 
Into a septum-capped vessel containing 30 g. of molecular sieves were 
added 81 g. of dry toluene, 10.22 g. of methyl tetracyclododecene, 5.73 g. 
vinyl norbornene and 4.90 g. hexene-1. The contents were mixed and this 
mixture was allowed to stand 30 minutes, then transferred to a second 
vessel by passing it through a micron filter under nitrogen pressure. The 
vessel was slightly pressurized with nitrogen. To the mixture 0.23 cc of a 
25% solution of ethyl-aluminum-sesquichloride (EASC cocatalyst) in dry 
toluene were introduced by syringe. To this mixture, 1.65 cc of a solution 
of 2 g. of molybdenum pentachloride catalyst in 39 g. of dry ethylacetate 
and 84 g. of dry toluene, were also introduced by syringe. Within one 
minute, an exothermic reaction of the mixture resulted and the mixture 
became a viscous liquid. After 15 minutes, 60 cc of a 88/12 (wt/wt) 
mixture of 2-propanol and water was added to the vessel and the contents 
shaken to inactivate the catalyst. The top layer containing mostly 
solvents, residual monomers and low molecular weight polymers was poured 
off. The semisolid bottom layer was redissolved in 100 cc of toluene, 
washed with water and dried by azeotropic distillation of part of the 
solvent. 
Polymerization was found to be 91% conversion of monomer as calculated by 
measuring the percent weight solids of the resulting polymer solution. The 
glass transition temperature (Tg) was found to be 118.degree. C. in the 
second heat, as calculated from a Differential Scanning Calorimetry curve 
of a sample of the polymer that was diluted in toluene, precipitated into 
methanol with stirring, filtered and dried. 
Step 2 
Preparation of Prepreg 
A dipping solution or suspension, to obtain prepregs, was prepared from the 
polymer solution above as follows. The polymer solution was dissolved in 
toluene containing 3.5 p.h.r. (parts per hundred resin) LUPERSOL 130 
peroxide (LUPERSOL 130 is a trademark of Lucidol, Division of Penwalt 
Corp.). To this solution a polyethylene fine powder was added (MICROTHENE 
FN 524 from USI of a melt index of 57 and density 0.925). The amount of 
polyethylene employed was equal to the amount of polynorbornene employed. 
An E-type glass cloth, Style 2116 having 642 finish (product of Burlington 
Industries) was impregnated with dipping solution and dried at room 
temperature until it was tack-free. The resulting prepreg was then 
transferred to a mechanical convection oven where drying was continued at 
successively higher temperatures, i.e., for 15 minutes at 50.degree. C., 
15 minutes at 100.degree. C. and 20 minutes at 130.degree. C. The value 
for polymer uptake versus glass was 65.8. 
Step 3 
Pretreatment of Copper Foil with a Silane 
A commercially available electrodeposited copper foil (product of Gould, 
Inc.) typically used for fabricating general purpose epoxy printed wiring 
boards was prepared for laminating to the prepreg. The foil, as purchased, 
weighed 1 oz. per ft..sup.2, was 35 microns thick and had a roughened 
matte bronze surface on one side. The treatment method used to roughen the 
surface is proprietary to Gould, Inc. Such copper foils are preferred, but 
not essential to the performance of the invention. 
The copper foil was dipped in a 10% solution of 
3-methacryloyloxypropyltrimethoxysilane (a product of Petrarch Systems, 
Inc.) in methanol for 30 minutes and was allowed to air dry at room 
temperature for 15 minutes, then transferred to an oven where drying was 
completed at 105.degree. C. for 5 minutes. 
Step 4 
Lamination of Cooper Foil to the Prepregs 
Two plies of prepregs were laminated and cured between pretreated copper 
foils at from 180.degree. C. to 220.degree. C. and 1,000 pounds of 
pressure per square inch for 30 minutes to provide a laminate. The 
increase in temperature was gradual at about 2 degrees per minute. 
Results 
The laminate exhibited a dielectric constant at 1 MHz of about 2.8 using 
E-type glass as measured on an electric bridge. (A Gen Rad 1687-B 
Megahertz LC Digibridge.) 
EXAMPLE 2 
Example 1 was repeated except the polymer employed was 100% polynorbornene 
polymer described in Step 1. The laminate exhibited a dielectric constant 
of 3.1. 
EXAMPLE 3 
Example 1 was repeated except that the C.sub.2 -C.sub.4 polyolefin employed 
was MICROTHENE FN 510 (melt index 4.5; density 0.924). There was a 69.7% 
uptake of polymer blend by the glass cloth during the prepregging stage. 
The laminate exhibited a dielectric constant of 2.8. 
EXAMPLE 4 
Example 3 was repeated in the absence of polyolefin, i.e., the polymer 
employed was 100% polynorbornene copolymer described in Example 1, Step 1. 
The prepreg had a polymer uptake of 70% versus glass and the resulting 
laminate exhibited a dielectric constant of 3.14. 
While this invention has been disclosed in this specification by reference 
to the details of preferred embodiments of the invention, it is to be 
understood that this disclosure is intended in an illustrative sense 
rather than in a limiting sense, as it is contemplated that modifications 
will readily occur to those skilled in the art, within the spirit of the 
invention and the scope of the appended claims.