Note: Descriptions are shown in the official language in which they were submitted.
~'~77579
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LAMINATES
The present invention pertains to laminates,
particularly electrical laminates.
Laminates have previously been prepared from
bisphenol A based epoxy resins. It is known that the
properties of a laminate can be improved by employing
multifunctional epoxy novolac resins in the
formulations. It is also known that just as
significant as the improvements in laminate properties
is the detrimental effect that multifunctional epoxy
resins have on processability. The tris(hydroxy-
phenyl)methane, tetra(hydroxyphenyl)ethane and phenol-
formaldehyde epoxy novolac resins have beenunsuccessful toward this end because to achieve a glass
transition temperature (Tg) of 150C or higher,
whencured with dicyandiamide, requires sufficient
quantities of the multifunctional epoxy resin to have
~dverse effects in the following areas: (l) varnish
reactivity, (2) prepreg reactivity, (3) prepreg
cosmetics, (4) reinforcement wetability, (5) laminate
pressing, (6) laminate post cure requirement and (7)
blister resistance oE the laminate.
33,261B-F -1-
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It has now been discovered that these
deficiencies can be overcome by the use of hydrocarbon-
phenol epoxy resins. They not only provide theelectrical laminates prepared therefrom an improvement
in electrical and moisture resistance properties, but
they also provide an improvement in one or more of the
0 above enumerated deficlencies.
The present invention concerns laminate which
has a Tg of at least 150C prepared from a cured
composition comprising
(A) at least one reinforcing material;
(B) at least one epoxy resin; and
(C) at least one curing agent for component
(B);
characterized by employing as at least a part of
component (B), at least one hydrocarbon-phenol epoxy
resin or halosenated hydrocarbon-phenol epoxy resin in
an amount such that at least 40, preferably from 90 to
lO0 percent of the epoxy groups present in component
(~) are contributed by said hydrocarbon-phenol epoxy
resin, halogenated hydrocarbon-phenol epoxy resin. or
combinatin thereof.
Suitable hydrocarbon-phenol epoxy resins which
can be employed herein include those disclosed by
Vegter et al in U.S. Patent 3,536,734, by Nelson in
U.S. Patent 4,390,680 and Nelson et al in U.S. Patent
4,394,497. Particularly suitable hydrocarbon-phenol
epoxy resins include those prepared by
dehydrohalogenating the reaction product of an
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epihalohydrin and the reaction product of an aro~atic
hydroxyl-containing compound with an unsaturated
hydrocarbon having from 4 to 55 carbon atoms. Suitable
aromatic hydroxyl-containing compounds which can be
employed herein include any such compounds which
contain one or two aromatic rings, at least one
phenolic hydroxyl group and at least one ortho or para
ring position with respect to a hydroxyl group
available for alkylation.
Particularly suitable aromatic hydroxyl-
containing compounds which can be employed herein
include, for example, phenol, chlorophenol,
bromophenol, methylphenol, hydroquinone, catechol,
resorcinol, guaiacol, pyrogallol, phloroglucinol,
isopropylphenol, ethylphenol, propylphenol, t-
butylphenol, isobutylphenol, octylphenol, nonylphenol,
cumylphenol, p-phenylphenol, o-phenylphenol, m-
phenylphenol, bisphenol A, dihydroxydiphenyl sulfone,
or mixtures thereof.
Suitable unsaturated hydrocarbons which, either
in a crude or purified state, can be employed herein
include, for example, butadiene, isoprene, piperylene,
cyclopentadiene, cyclopentene, 2-methylbutene-2,
cyclohexene, cyclohexadiene, methyl cyclopentadiene,
dicyclopentadiene, limonene, dipentene, linear and
cyclic dimers of piperylene, methyl dicyclopentadiene,
~0 dimethyl dicyclopentadiene, norbornene, norbornadiene,
ethylidine norbornene, and mixtures thereof. Also
suitable unsaturated hydrocarbons include the other
dimers, codimers, oligomers and cooligomers of the
aforementioned unsaturated hydrocarbons. Particularly
suitable unsaturated hydrocarbons which can be employed
herein include, for example, a dicyclopentadiene
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concentrate containing from 70 to lO0 percent by weight
of dicyclopentadiene; from 0 to 30 percent by weight of
C8-Cl2 dimers or codimers of C4-C6 dienes such as, for
example, cyclopentadieneisoprene, cyclopentadiene-
piperylene, cyclopentadienemethyl cyclopentadiene,and/or dimers of isoprene, piperylene, methyl
cyclopentadiene and the like; from zero to 7 percent by
weight of Cl2-Cl8 trimers of C4-C6 dienes and from zero
to lO percent by weight of aliphatic diolefins such as,
for example, piperylene, isoprene, l,5-hexadiene and
cyclic olefins such as cyclopentadiene, methyl
cyclopentadiene, cyclopentene and the like. Methods of
preparation for these dicyclopentadiene concentrates
and more detailed descriptions thereof can be found
collectively in U.S. ~atent No. 3,557,239 issued to
Gebhart et al and U.S. Patent No. 4,167,542 issued to
Nelson.
Also, particularly suitable unsaturated
hydrocarbons which can be employed herein include a
crude dicyclopentadiene stream containing from 20 to 70
percent by weight dicyclopentadiene, from 1 to lO
percent codimers and dimers of C4-C6 hydrocarbons
(described above), from zero to lO percent oligomers of
C4-C6 dienes and the balance to provide lO0 percent, C4-
C6 alkanes, alkenes and dienes.
Also, particularly suitable unsaturated
hydrocarbons which can be employed herein include a
crude piperylene or isoprene stream containing from 30
to 70 percent by weight piperylene or isoprene, zero to
ten percent by weight C8-C12 dimers and codimers of C4-
C6 dienes, and the balance to provide 100% C4-C6
alkanes, alkenes and dienes.
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Also, particularly suitable are hydrocarbon
oligomers prepared by polymerization of the reactive
components in the above hydrocarbon streams e.g.,
dicyclopentadiene concentrate, crude dicyclopentadiene,
crude piperylene or isoprene, individually or in
combination with one another or in combination with
high purity diene streams.
These hydrocarbon-phenol epoxy resins can be
employed alone or in admixture with other epoxy resins
such as the diglycidyl ethers of dihydric phenols such
as, for example, resorcinol, catechol, hydroquinone,
bisphenol A, bisphenol F, dihydroxybiphenyl, and
mixtures thereof. Also suitable are the polyglycidyl
ethers of phenolic materials having more than two
hydroxyl groups such as, for example, tris(hydroxy-
phenyl)methane, tetra(hydroxyphenyl)ethane, phenol-
aldehyde novolacs, and mixtures thereof. Also,
suitable are the halogenated derivatives, particularly
the brominated derivatives of the aforementioned epoxy
resins.
Suitablé curing agents which can be employed
herein include, for example, amines, acids or
anhydrides thereof, biguanides, imidazoles, urea-
aldehyde resins, melamine-aldehyde resins, phenolics,
halogenated phenolics, combinations thereof and the
like. These and other curing agents are disclosed in
Lee and Neville's Handbook of EpoxY Resins, McGraw-Hill
Book Co., 1967. Particularly suitable curing agents
include, for example, dicyandiamide, diaminodiphenyl-
sulfone, 2-methylimidazole, diethylene- toluenediamine,
bisphenol A, tetrabromobisphenol A, phenol-formaldehyde
33,261B-F -5-
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novolac resins, halogenated phenol-formaldehyde resins,
hydrocarbon-phenol resins and combinations thereof.
Suitable reinforcing materials which can be
employed herein include, for example, fiberglass,
aromatic polyamides, aramid resins, carbon, graphite,
quartz, synthetic fibers, and combinations thereof.
The reinforcing materials can be woven, matt, filament
or in the form of random ~ibers.
Suitable catalysts or promoters or accelerators
which can be employed in the preparation of the prepreg
materials from which the laminates are prepared
include, for example, tertiary amines, imidazoles,
phosphonium compounds, ammonium compounds, sulfonium
compounds, and mixtures thereof.
Suitable tertiary amines include, for example,
triethylenediamine, N-methylmorpholine, triethylamine,
tributylamine, benzyldimethylamine,
trisldimethylamino-methyl)phenol, and mixtures thereof.
Suitable imidazoles include, for example, 2-
methylimidazole, l-propylimidazole, and mixtures
thereof.
Suitable phosphonium compounds include, for
example, those clisclosed by Dante et al in U.S.
3,477,990, Perry in Canadian Patent 893,l9l and U.S.
3,948,855 and by Tyler, Jr. et al in U.S. 4,366,295.
Suitable quaternary ammonium compounds include,
for example, benzyl trirnethyl ammonium chloride, benzyl
trimethyl ammonium hydroxide, tetrabutyl ammonium
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chloride, tetrabutyl ammonium hydroxide, and mixtures
thereof.
Suitable solvents which can be employed to
prepare the electrical laminates include, for example,
glycol ethers, ketones, aromatic hydrocarbons,
alcohols, amides, and combinations thereof.
Particularly suitable solvents include, for example,
0 methyl ethyl ketone, acetone, methanol,
dimethylformamide, ethylene glycol methyl ether,
propylene glycol methyl ether, and combinations
thereof.
The laminates of the present invention are
suitable for use in electrical applications, structural
laminates or composites and the like. They are
particularly suitable for use in the manufacture of
printed circuit boards.
The printed circuit boards, of course, have an
outer layer oE an electrical conductive material such
as copper, gold, silver, platinum and the like.
The following examples are illustrative of the
invention, but are not to be construed as to limiting
the scope thereof in any manner.
EPoxy Resin A i8 a phenol-ormaldehyde epoxy novolac
resin having an average functionality of 3.8 and an
epoxide equivalent weight, EEW, of 200.
EpoxY Resin B is a glycidyl ether of tris-
(hydroxyphenyl~methane novolac (the reaction product of
hydroxybenzaldehyde with phenol in a molar ratio of 1
33,261B-F -7_
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to 4 respectively) having an average functionality of
5.9 and an epoxide equivalent weight, EEW, of 218.
Epoxy Resin C is the glycidyl ether of the reaction
product of phenol and a dicyclopentadiene concentrate
consisting of 83~ DCPD, 1.4% non-reactive light
hydrocarbons, and the remainder bein~ primarily a
mixture of codimers of C4-C6 dienes. This resin has an
0 average functionality of 3.2 and an epoxide equivalent
weight, EEW, of 279.
Resin Varnish Preparation Procedure
In the Example and Comparative Experiments, the
resin varnish was prepared from the indicated
formulation in the following manner.
The indicated amount of epoxy resin solution
was blended with the indicated amount of dicyandiamide
solution. 2-Methylimidazole was added, if necessary,
to adjust the varnish reactivity to approximately 200
seconds by stroke cure gel time. Additional acetone
was added, if necessary, to bring the overall varnish
viscosity to 21 seconds by a #2 Zahn cup.
The tests were performed according to the
following procedures. The relative blister resistance
was determined by placing three 2" ~ 4" ~50.8 mm x
101.6 mm3 unclad laminate coupons in a pressure pot at
15 psi (103 kPa) steam for 60 minutes and 120 minutes.
After this time the co~pons were removed, externally
dried and dipped in molten solder at 500F (260C) for
20 seconds. Each side of the 3 coupons was then
inspected for any delamination blisters. The results
were reported as the percent of number of sides with no
blisters. Degrees of cure were measured by glass
33,261B-F -8-
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transition temperatures and/or exotherms as evidenced
on a DuPont 1090 Thermal Analyzer with a 910
Differential Scanning Calorimeter (DSC). All gel times
were measured by stroke cure on a 171C hot plate.
The resin Elow is a measure of the amount of
resin that will be expelled during a pressing
operation. The ~ flow is measured by the following
procedure:
1. cut six 6" x 6" (152.4 mm x 152.4 mm) squares
f prepreg;
2. stack the 6 pieces and weigh to the nearest
i.01 gram;
3. put the stack between caul plates and place
into a preheated press at 340F (171.1C) and
apply a pressure of 200 psi (1379 kPa);
4. leave in the press for at least 10 minutes;
5. remove the pressed laminate and cut into a 4" x
3 4" (101.6 mm x 101.6 mm) piece;
6. weigh the 4" x 4" (101.6 mm x 101.6 mm) piece
to the nearest +.01 gram; and
7. the fol:Lowing calculation is used to determine
% flow:
% flow - initial weiqht/2 - final wei~ht
initial weight/2
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COMPARATIVE EXPERIMENT A
A. Formulation
A varnish was prepared employing the aforemen-
tioned procedure employing the following formulation.
4292 grams (18.241 equiv.) of an 85~ by weight
solution of Epoxy Resin A in methyl ethyl ketone.
2287 grams (10.95 equiv.) of a 10% by weight
solution of dicyandiamide in a 50/50 by weight solvent
blend of dimethylformamide and propylene glycol methyl
ether.
500 grams of acetone to adjust solution
viscosity.
B. Preparation of Preimpreqnated Substrate
Burlington style 7628 glass cloth with an I-617
finish was impregnated with the above varnish
formulation. The impregnation was done in a forced air
vertical treater having a total length of 36 feet
(10.97 m). The first 27 feet (8.23 m) were heated to
350F (176.7C). The last 9 feet (2.74 m) were not
heated. The treater was operated at rates of 11, 13,
15 and 17 feet per minute (55.88, 66.04, 76.2 and 86.36
mm/s). The resultant preimpregnated glass cloth had a
gel time of 124 seconds except for the one prepared at
11 ft./min. (55.88 mm/s) which gelled (0 gel time).
The resin content of the impregnated glass cloth was
37% by weight.
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C. Preparation of Laminate
A single opening Wabash press was preheated to
350F (176.7C). ~ight plys of 12" x 12" (304.8 mm x
304.8 mm) preimpregnated glass cloth prepared in (B)
above was placed between 2 steel plates and Teflon
pads. The above lay-up was placed into the press and a
minimal amount of pressure, 30 psig (206.844 kPa) was
applied to help control the laminate thickness and
resin flow. At 5 minutes, the pressure was increased
gradually to 500 psig (3447.4 kPa).
The results were as follows: (1) The varnish
gel time was 124 seconds. This is considerably faster
than the typical 200 second gel time especially since
there was no accelerator (2-methylimidazole) added.
(2) The prepreg cosmetics (uniformity of resin coating
on the glass) was in all instances very poor. The
surface was very rough and mottled. (3) The
impregnation of the glass (wetability) was very poor.
If properly wet out, the prepreg should be translucent.
In this instance, the prepreg was virtually opaque.
(4) ~he excessive resin flow during lamination, even
with an initial low pressure period, caused resin
starved areas in the laminate. (5) The very rapid
build in viscosity as evidenced by the dynamic
mechanical spectroscopy (DMS) cur~es caused
considerable air entrapment in the laminate. (6)
~0 During the typical 1 hour , 500 psig (3447.4 kPa) press
cycle at 350F (176.7C) the laminate did not reach full
cure. Even after a post bake cycle of 16 hours at
175C, the laminate was still not fully cured. (7) A
blister resistance test of 60 and 120 minutes exposure
to 15 psig (103.4 kPa) steam followed by immersion in
500F (260C) solder for 20 seconds was conducted and at
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60 min., 50% of the samples passed and at 120 min.,
none of the samples passed. (8) The dielectric
constant was 5.64 and the dissipation factor was
0.0080.
COMPARATIVE EXPERIMENT B
A. Preparation of Varnish
A varnish was prepared employing the procedure
in part A of Comparative Experiment A employing the
following formulation.
4301 grams (13.81 equiv.) of a 70~ by weight
solution of Epoxy Resin B in methyl ethyl ketone.
1740 grams (8.9 equiv.) of a 10% by weight
solution of dicyandiamide in a 50/50 by weight solvent
blend of dimethylformamide and propylene glycol methyl
ether.
No acetone was added, as no viscosity adjust-
ment was required.
B. Preparatlon of Preimpreqnated Substrate
The same glass cloth, vertical treater and
treater conditions were employed in this experiment as
in part B of Comparative Experiment A. The treater was
operated at 16 feet per minute (81.28 mm/s). The
resultant preimpregnated glass cloth had a gel time of
92 seconds. The resin content was 41% by weight.
C. Preparation of Laminate
The same press conditions and press cycle were
employed in this experiment as in part C of Comparative
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Experiment A. The results were as follows: (1) The
gel time of the varnish from which the laminate was
prepared was 147 seconds. This is considerably faster
than the typical 200 second gel time, especially since
there was no accelerator (2-methylimidazole) present.
(2) The prepreg cosmetics were very poor. The surface
was very rough and mottled. (3) The wet-out of the
glass cloth was very poor. The prepreg was virtually
opaque. (4) The excessive resin flow even during the
low pressure cycle caused resin starved areas. (5) The
rapid build in viscosity near the gel point (similar to
that of Comparative Experiment A) as evidence by the
DMS curves caused considerable air entrapment in the
laminate. (6) During the typical 1 hour, 500 psig
(3447.4 kPa), press cycle at 350F (176.7C), the
laminate did not reach full cure as evidenced by an
exotherm at 205~C during DSC analysis. Even after a 16
hour post cure at 175C, the laminate exothermed at
220C again indicating an incomplete cure. (7) A
blister resistance test of 60 and 120 minutes exposure
to 15 psig (103.4 kPa) steam Eollowed by immersion in
3 500F (260C) solder for 20 seconds was conducted and at
60 min., 100% of the samples passed and at 120 min.,
none of the samples passed.
EXAMPLE 1
A. PreParatio _of Varnish
A varnish was prepared employing the procedure
part A of Comparative Experiment A employing the
following formulation.
4939 grams (14.15 equiv.) of an 80~ by weight
solution of Epoxy Resin C in acetone.
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1782 grams (8.49 equiv.) of a 10~ by weight
solution of dicyandiamide in a 50/50 by weight solvent
blend of dimethylformamide and propylene glycol methyl
ether.
2.77 grams of 2-methylimidazole to adjust the
reactivity.
400 grams of acetone were added to adjust the
solution viscosity.
B. PreParation of Preimpreqnated Substrate
The same glass cloth, vertical treater and
treater conditions were employed in this experiment as
in part B of Comparative Experiment A. The treater was
operated at 8.5 feet per minute (43.18 mm/s). The
resultant preimpregnated glass cloth had a gel time of
150 seconds. The resin content was 40% by weight.
C. Preparation of Laminate
The same press conditions and press cycle were
3 employed in this example as in part C of Comparative
Experiment A. The results were as follows: (1) The
varnish formulation was accelerated with 2-imidazole to
obtain the typical 200 second gel time. (2) The
prepreg cosmetics were excellent. The surface was
very smooth and even. (3) The wetability of the glass
cloth was very good. The prepreg was translucent which
is indicative of good wet-out. (4) There were no resin
starved areas on the laminate even though the prepreg
had a longer gel time than that of Comparative
Experiment A. (5) There was no air entrapped in the
laminate. (6) Full cure of the laminate was achieved
in the 1 hour press cycle. The glass transition
33,261B-F -14_
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temperature (Tg) was 185C as determined by DSC,
differential scanning calorimetry. Following a 16 hour
post cure at 175C, there was no significant increase in
the Tg indicating that full cure is achieved in the l
hour press cycle. (7) A blister resistance test of 60
and 120 minutes exposure to 15 psig (103.422 kPa) steam
followed by immersion in 500F (260C) solder for 20
seconds was conducted and at 60 min., 83% of the
samples passed and at 120 min., 83% of the samples
passed. (8) The dielectric constant was 4.75 and the
dissipation factor was 0.00696.
The results of Comparative Experiments A and B
and Example 1 are tabulated in the following table.
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Comparative Example
Experiments
A B
Varnish Reactivity, seconds 124 147 200
Prepreg Reactivity, seconds 124 92 150
Prepreg Appearance Poor Poor Excellent
Glass Wetability Poor Poor Excellent
Resin Flow, % 60 50 25
Blister Resistance (120 min.)
Sides with no blisters0 0 83
5 ~ielectric Constant @ 1 KHZ5.645.25 4.75
*Residual Exotherm ~after 16
hours @ 175C) Yes Yes No
20 **Amount of 2-methylimidazole required
for reactivity adjustment 0 0 2.77
*Residual exotherm is an indication that the reaction
mixture was not totally cured, i.e. a reaction was
still taking place.
**Amount of 2-methylimidazole required to adjust the
reactivity so that the gel time of the reaction
mixture was approximately 200 seconds.
3o
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EXAMPLE 2
A. Preparation of Varnish
A varnish was prepared employing the procedure
of Comparative Experiment A, Part A from the following
components.
124 grams (0.46 epoxy equiv.) of Epoxy Resin C.
44 grams (0.16 phenolic hydroxyl equiv.) of
tetrabromobisphenol A.
62 grams (0.35 phenolic hydroxyl equiv.) of a
novolac resin prepared by reacting phenol with
a mixture consisting of 83% dicyclopentadiene,
1.4% non-reactive liqht hydrocarbons and the
remainder being primarily a mixture of codimers
of C4-C6 dienes. This resin had an average
functionality of 3.2 and a phenolic hydroxyl
equivalent weight of 176.9.
0.35 grams of 2-methyl imidazole.
92 grams of acetone.
31 grams of propylene glycol methyl ether.
B. Preparation f Preimpreqnated Substrate.
Strips of 6 in. (152.4 mm) wide 7628 style
fiberglass cloth were dipped into the above solution
and dried in a forced draft oven at 350F (176.6C) for
90 sec. The resultant preimpregnated substrate
material contained 41.8% resin, 58.2% glass and had a
gel time of 131 seconds at 345C.
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C. Preparation of Laminate
Eight layers of the above preimpregnated
substrate material were pressed in an electrically
heated press under the following conditions, each step
being sequential:
80~(26.7C~ to 290F (143.3C) at 12F/min
(0.1157C/sec.) at 35 psig (241.3 kPa);
290F!143.3C) to 350F (176.7C) at 12F/min
(0.1157C/sec.) and the pressure increased to 450 psig
(3102.7 kPa) at a rate of 140 psig/min (16.09 kPa/sec);
maintained at 350F (176.7C) and 450 psig (3102.7 kPa)
for 90 min.
cooled from 350F (176.7C) to 150F (65.6C) at
-20F/min (-0.185C/sec). and a pressure of 450
psig (3102.7 kPa).
The press was then opened and the laminate
removed. The laminate had the following properties.
Glass transition temp. (heated at 20C/min) ....167C.
Thickness......................................... 58 mils (0.147 mm)Resin
35 Flow.................................................................... 8%
Uniformly translucent over entire area. Dielectric
constant at 100 KHz .................................................. 4.5
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EXAMPLE 3
A. Preparation of Varnish
A varnish was prepared employing the procedure
of Compartive Experiment A, Part A employing the
following components.
121 grams (0.45 epoxy equiv.) of Epoxy Resin C.
50.6 grams (0.19 phenolic hydroxyl equiv.~ of
terabromobisphenol A.
24~5 grams (0.22 phenolic hydroxyl equiv.) of
phenol-formaldehyde novolac resin having
an average functionality of 5 and a
phenolic hydroxyl equivalent weight of
110 .
0.3 grams of 2-methyl imidazole.
112 grams of acetone.
2.5 grams of propylene glycol methyl ether.
B. Preparation of PreimPreqnated Substrate.
Strips of 6 in. (152.4 mm) wide 7628 style
fiberglass cloth were dipped into the above solution
and dried in a forced draft oven at 350F (176.6C) for
90 sec. The resultant preimpregnated substrate
material contained 42.4% resin, 57.6~ glass and had a
gel time of 107 seconds at 345C.
C. Preparation of Laminate
Eight layers of the above preimpregnated
substrate material were pressed in an electrically
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heated press under the following conditions, each step
being se~uential:
80F(26.7C) to 275F (135C) at 12F/min
(0.1157C/sec.) at 35 psig (241.3 kPa);
275F(135C) to 350F (176.7C) at 12F/min
(0.1157C/sec.) and the pressure increased to 350
psig (2413.2 kPa) at a rate of 160 psig/min (18.39
kPa/sec); maintained at 350F (176.7C) and 350 psig
(2413.2 kPa) for 90 min.
350F (176.7C) to 150F (65.6C) at -20F/min (-
0.185C/sec) and a pressure of 350 psig ((2413.2 kPa);
The press was then opened and the laminate
removed. The laminate had the following properties.
Glass transition temp. (heated at 20C/min)...... 175C.
Thickness.......................... 580 mils (0.127 mm)
Resin Flow......................................... 8%.
3o
Uniformly translucent over entire area.
Dielectric constant at 100 KHz ................... 4.6.
Blister
resistance...................................... 66.6%.
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