Note: Descriptions are shown in the official language in which they were submitted.
~0;~4030
EPO~Y RESIN IMPRE:GNATED GhASS CLOTEI SHl~ET
EL~VING AD~ESIVE LAYER
FIELD OF THE INVENTION
This invention relates to an epoxy resin-impregnated
glass cloth sheet having an adhesive layer, and more
particularly to a heat-resistant, flame-retardant epoxy
resin-impregnated glass cloth sheet having an adhesive layer
which has no fluidity, is excellent in such characteristics
as adhesion, soldering heat resistance, flexibility, etc. and
is highly flame-retardant.
BACKGROUND OF THE INVENTION
-
Fig. 1 and Fig. 2 show the cross-sectional views of
embodiments of substrates for LSI, which are directly loaded
with LSI chips. Such substrate for carrying LSI chips can be
prepared in the following manner. An electrical conductor 3
is laminate-bonded onto the adhesive layer 2 of an epoxy
resin-impregnated glass cloth sheet 1 by means of heated
rollers, etc., and a copper foil of the electrical conductor
3 is then chemically etched to form a predetermined circuit.
If desired, through-holes having electrical conductivity may
be optionally formed. Subsequently, LSI chips 4 are placed
and bonded by means of an adhesive 5 for die bond, and LSI
chips 4 arq then connected to the circuit by means of bonding
wires 6 ,to form a module.
~03~30
As adhesives conventionally used for such substrates
for carrying LSI chips, there are known epoxy-novolak resins,
nitrile-phenol resins, nylon-epoxy resins, polyester resins,
acrylic resins. As circuit designs have been highly
complicated in recent years, it has been demanded to provide
high-performance adhesives having more higher reliability,
particularly adhesives which have scarcely fluidity during
the course of copper cladding and exhibit high adhesion
between the substrate and copper foil under high-temperature
conditions.
Further, adhesives having flame retardance in
addition to the above-described characteristics have been
required from the viewpoint of safety of electrical
apparatuses. To obtain flame-retarded adhesives, flame-
retardant fillers or flame-retardant resin components singly
or in combination have been conventionally used. However,
there is a problem that when the flame-retardant fillers are
blended, a lowering in the adhesion of metallic foil is
caused. Further, there are problems that when the flame-
retardant resin components are used, heat-resistance is
generally lowered and a lowering in adhesion between the
substrate and the metallic foil under high-temperature
conditions is caused.
Epoxy resin-impregnated glass cloth sheets are
already known as substrates for carrying LSI chips. ~owever,
it is demanded to provide epoxy resin-impregnated glass cloth
~0;~ 103~
sheets which have more higher reliability and are excellent
in heat resistance and flame retardance.
The present inventors have eagerly made studies to
solve the above-mentioned problems associated with the prior
art and found that the above-mentioned problems can be solved
by providing an adhesive layer comprising a specific curable
epoxy resin composition on an epoxy resin-impregnated glass
cloth sheet formed by impregnating glass cloth with a
specific curable epoxy resin composition and curing it.
SUM~RY OF THE INVENTION
An object of the present invention is to provide an
epoxy resin-impregnated glass cloth sheet having an adhesive
layer, which has an excellent performance as a substrate for
carrying LSI chips.
Another object of the present invention is to provide
an epoxy resin-impregnated glass cloth sheet having an
adhesive layer, said adhesive layer being provided on a
substrate which is excellent in heat resistance and flame
retardance and the adhesive of said adhesive layer being
scarcely fluidized during bonding and being excellent in
adhesion to a metallic foil under high-temperature conditions
and highly flame retardant.
Other objects and effects of the present invention
will be apparent from the following description.
The present invention provided an epoxy resin-
impregnated glass cloth sheet having an adhesive layer
;~03~030
provided on at least one side of the surface thereof,
characterized in that (A) said epoxy resin-impregnated glass
cloth sheet is formed by impregnating glass cloth with a
curable epoxy resin composition and curing it, said curable
epoxy resin composition comprising an epoxy resin represented
by the following structural formula (I~, a brominated epoxy
resin and a curing agent for epoxy resin in such an amount
that the content of the epoxy resin represented by the
following structural formula (I) is 5 to 50% by weight based
on the amount of the entire epoxy resins and the content of
bromine atom is 14 to 30% by weight based on the combined
amount of the entire epoxy resins and the curing agent for
the epoxy resin; and (B) said adhesive layer is composed of a
curable epoxy resin composition comprisîng an epoxy resin
represented by the following structural formula (I), a
brcminated epoxy resin, an acrylonitrile/butadiene copolymer
having carboxyl groups in its molecule which is a solid at
room temperature and a curing agent for epoxy resin in such
an amount that the content of the epoxy resin represented by
the following structural formula (I) is 5 to 70% by weight
based on the amount of the entire e,poxy resins, the content
of said acrylonitrile/butadiene copolymer is 20 to 70 parts
by weight based on lO0 parts by weight of the entire epoxy
resins and the content of bromine atom is lO to 30% by weight
based on'the combined amount of the entire epoxy resins, the
;~03~030
acrylonitrile/butadiene copolymer and the curing agent for
the epoxy resin.
C ~ -CH-CH2O ~ ~ OCH2-C~ / H2
C~-CH (I)
~ ~ OCH2-C\-/ H2
O . O
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. 1 and 2 show each the cross-sectional view of
an embodiment of a substrate for carrying LSI chips. In
Figs., numeral 1 represents an epoxy resin-impregnated glass
cloth sheet, 2 represents an adhesive layer, 3 represents an
electrical conductor, 4 represents LSI chip, 5 represents an
adhesive for die bond, and 6 represents bonding wire.
DETAILED DESCRIPTION OF THE INvENTION
In the present invention, the curable epoxy resin
composition for use in impregnating glass cloth and the
curable epoxy resin composition for the adhesive layer to be
provided on the epoxy resin-impregnated glass cloth sheet
contain the epoxy resin represented by the structural formula
(I). The epoxy resin (I) is commercially available, for
example, under trade name of Epikote 1031S or Epikote 1031
(products of Yuka Shell Epoxy KK). Accordingly, the present
;~();~4030
invention can be carried out by using such commercially
available products.
In the above-described two kinds of the curable epoxy
resin compositions according to the present invention, the
amount of the epoxy resin (I) to be blended should be 5 to
50% by weight based on the amount of the entire epoxy resins
when the epoxy resin (I) is used for the curable epoxy resin
composition for used in impregnating glass cloth, and the
amount of the epoxy resin (I) to be blended should be 5 to
70% by weight based on the amount of the entire epoxy resins
when the epoxy resin (I) is used for the curable epoxy resin
composition for the adhesive layer. When the amount of the
epoxy resin (I) in the epoxy resin composition for
impregnating glass cloth is less than 5% by weight, the heat
resistance of the sheet per se of the produced epoxy resin-
impregnated glass cloth sheet is deteriorated. When the
amount of the epoxy resin (I) in the epoxy resin composition
for the adhesive layer is less than 5% by weight, the heat
resistance of the adhesive layer itself is deteriorated,
while when the amount is more than 70% by weight, flame
retardance is poor.
In the present invention, the epoxy resin composition
for use in impregnating glass cloth as well as the epoxy
resin composition for the adhesive layer contain the
brominated epoxy resin as an essential component. Examples
of the brominated epoxy resin which can be used in the
;~0;~030
present invention include brominated bisphenol A type epoxy
resins and brominated novolak type epoxy resins. These
brominated epoxy resins may be used either alone or in
combination of two or more of them.
The amount of the brominated epoxy resin to be
blended in the present invention is 14 to 30% by weight, in
terms of the content of bromine atom, based on the combined
amount of the entire epoxy resins and the curing agent for
the epoxy resin when the brominated epoxy resin is used for
the epoxy resin composition for impregnating glass cloth.
The amount of the brominated epoxy resin to be blended is 10
to 30~ by weight, in terms of the content of bromine atom,
based on the combined amount of the entire epoxy resins, the
acrylonitrile/butadiene copolymer and the curing agent for
the epoxy resin when the brominated epoxy resin is used for
the epoxy resin composition for the adhesive layer. When the
brominated epoxy resin is blended in such an amount that the
content of bromine atom becomes less than the lower limits
described above, the sheet itself of the produced epoxy
resin-impregnated glass cloth sheet and the adhesive layer
have poor flame retardance. When the content of bromine atom
exceeds 30~ by weight, the heat resistance of the adhesive
layer itself is deteriorated when the brominated epoxy resin
is used for the epoxy resin composition for the adhesive
layer.
~034~30
In addition to the epoxy resin (I) and the brominated
epoxy resin, the epoxy resin composition for impregnating
glass cloth and the epoxy resin composition for the adhesive
layer, according to the present invention, may optionally
contain other epoxy resins in an amount which has ar, adverse
effect on the contents of said epoxy resin (I) and bromine
atom as described above. Examples of such epoxy resins which
may be used in combination with the epoxy resin (I) and the
brominated epoxy resin include bisphenol A type epoxy resins,
bisphenol F type epoxy resins, novolak type epoxy resins,
alicyclic epoxy resins, glycidyl ester type epoxy resins,
glycidylamine type epoxy resins, heterocyclic epoxy resins
and urethane-modified epoxy resins. These epoxy resins may
be used either alone or in combination of two or more of
them.
In the present invention, the epoxy resin composition
for impregnating glass cloth and the epoxy resin composition
for the adhesive layer contain a curing agent for epoxy
resin. Examples of the curing agent for epoxy resin include
amine curing agents, polyaminoamide curing agents, acids and
acid anhydrides, dicyandiamide, basic active hydrogen
compounds such as organic acid hydrazides, imidazoles, amine-
imides, Lewis acids, Br~nsted acid salts and phenolic resins,
These compounds may be used either alone or in a combination
of two o'r more of them.
4 t~30
The epoxy resin composition for the adhesive layer
according to the present invention contain an
acrylonitrile/butadiene copolymer having carboxyl group in
its molecule which is a solid at room temperature (20C).
Examples of the copolymer include copolymers obtained by
carboxylating the terminal of an acrylonitrile/butadiene
copolymer and terpolymers obtained by copolymerizing
acrylonitrile with butadiene and a monomer having carboxyl
group such as acrylic acid. The copolymers have an
acrylonitrile content of 10 to 50% by weight, preferably 15
to 35% by weight, a carboxyl group content of 2.0 to 3.5% by
weight, a specific gravity (25/25C) of 0.94 to 1.02, a
molecular weight from 8,000 to 80,000 and a Mooney viscosity
MLl,4 (100 C) of from 10 to lO0, preferably from 40 to 80 and
are preferably a solid having no fluidity at room
temperature. A typical example of such copolymer ~hich is
commercially available is Nipol 1072 (a produce of Nippon
Zeon Co., Ltd.) and T-4633 (a produce of Japan Synthetic
Rubber Co., Ltd.).
The content of the acrylonitrile/butadiene copolymer
in the epoxy resin composition for~the adhesive layer
according to the present invention is 20 to 70 parts by
weight, preferably 30 to 65 parts by weight based on lO0
parts by weight of the amount of the entire epoxy resins.
When the amount of the copolymer is too small, the adhesive
is greatly fluidized and there are caused troubles that the
_ g _
)30
adhesive flows out from the adhesive layer into device hole
part when a metallic foil is bonded to substrates having
various shapes, such as a substrate having device hole.
Further, adhesion to the metallic foil is lowered. On the
other hand, when the amount of the copolymer is too large,
adhesion at elevated temperatures is lowered.
In the present invention, the epoxy resin composition
for impregnating glass cloth and the epoxy resin composition
for the adhesive layer may contain various additives
according to the use of the epoxy resin-impregnated glass
cloth sheet. Examples of such additives include inorganic
powders such as calcium carbonate, titanium oxide, zinc
oxide, silica, alumina, hydrated alumina and bentonite;
coupling agents such as silicone coupling agent and titanate
coupling agent; flame retarder; coloring material, etc.
The epoxy resin-impregnated glass cloth sheet having
an adhesive layer according to the present invention can be
prepared by various methods. A typical embodiment thereof is
illustrated below.
First, the curable epoxy resin composition for
impregnating glass cloth is dissolved in an appropriate
solvent such as acetone, methyl ethyl ketone, toluene, methyl
cellosolve or dimethylformamide or a mixed solvent of two or
more of them, and the components of the composition are
thoroughly mixed to prepare varnish. Glass cloth is then
impregnated with the resulting varnish and dried to remove
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- ;~034030
the solent. The impregnated glass cloth is heated under
pressure to cure the resin composition. Alternatively, the
resin composition is cured while drying the solvent to obtain
an epoxy resin-impregnated glass cloth sheet having flame
retardance. The drying of the solvent is carried out at a
temperature of room temperature to 130C for 1 to 60 minutes.
Curing is carried out at a temperature of 80 to 200C for lO
minutes to one day. Pressure is 1 to lO0 kgf/cm2 when curing
is carried out under pressure.
Subsequently, the epoxy resin composition for the
adhesive layer is dissolved in the solvent described above,
and the components of the composition are thoroughly mixed to
prepare varnish. The resulting varnish is coated on the
epoxy resin-impregnated glass cloth sheet prepared in the
manner mentioned above, and the solvent is removed by drying
to thereby obtain an epoxy resin-impregnated glass cloth
sheet having an adhesive layer according to the present
invention. The drying of the solvent is carried out at a
temperature of room temperature to 170C for 1 to 60 minutes.
The adhesive layer of the epoxy resin-impregnated
glass cloth sheet of the present invention is scarcely
fluidized and is excellent in adhesion, soldering heat
resistance, flexibility and flame retardance, and the sheet
per se is excellent in heat resistance and flame retardance.
The epoxy resin-impregnated glass cloth sheet of the
present invention is now illustrated in greater detail by
X034~)30
reference to the following preparative examples, examples
and comparative examples which, however, are not to be
construed as limiting the present invention in any way.
Parts given below are by weight otherwise stated.
PreParative Examples A to C
Preparation of e~oxY resin-impreqnated qlass cloth sheets_A
to C
Varnish of each epoxy resin composition indicated in
Table 1 was prepared. Glass cloth of 0.2 mm in thickness was
impregnated with each of the resulting varnish. The
impregnated glass cloth was dried in an oven at 120C for 20
minutes and then cured in an oven at 170C for 30 minutes.
The flame retardance of each of the resulting epoxy resin-
impregnated glass cloth sheets is shown in Table 1.
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;~03f~030
Table 1
Epoxy resin-impregnated
alass cloth sheet
A B
Composition of epoxy resin varnish
(parts)
Epikote 1031S *1 10 30 30
Epikote 5050 *2 30 `30
Bren . *3 30 10 30
Epikote *4 30 30 40
Dicyandiamide 5 5 5
lB2MZ *5 0.5 0.5 0.5
Methyl ethyl ketone 60 60 60
Methyl cellosolve 20 20 20
Bromine atom content (wt.%) *6 24.5 17.6 10.2
Flame resistance test *7 result of 94V-0 94V-0 94-1
produced epoxy resin-impregnated or below
glass cloth sheet
Notes (in Table 1~
*1: Trade name (a product of Yuka Shell Epoxy KK), epoxy
equivalent: 195, epoxy resin represented by the
formula (I).
*2: Trade name (a product of Yuka Shell Epoxy KK),
bromine content: 50 wt.%, epoxy equivalent: 440.
*3: Trade name (a product of Nippon Kayaku Co., Ltd.),
bromine content: 36 wt.%, epoxy equivalent: 285.
*4: Trade name (a product of Yuka Shell Epoxy KK), epoxy
equivalent: 460, general purpose epoxy resin.
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;~)3~030
*5: Trade name (a product of Shikoku Xasei Kogyo KK),
imidazole type curing agent.
*6: Content (wt.~) based on the combined amount of the
entire epoxy resins and the curing agent for epoxy
resin.
*7: Flame resistance test was carried out according to
UL-94.vertical method (Underwriter~' Laboratories
Inc. Standard Test).
Examples 1 to 6 and ComParative ExamPles 1 to 5
Varnish of each epoxy resin composition for the
adhesive layer was prepared by using each blend indicated in
Table 2.
Each of the resulting varnish was coated on the epoxy
resin-impregnated glass cloth sheet A prepared in the
aforesaid Preparative Example A in such an amount as to give
a dry thickness of 20 ~m. The coated sheet was dried in an
oven at 140C for 5 minutes. A copper foil of 35 ~m in
thickness was then laminated onto the adhesive-coated surface
of the sheet by using rollers under such conditions that a
roller temperature was 160C, velocity was 1 m/min and
pressure was 1 kg/cm. The laminat~e was heated in an oven at
170C for one hour to cure the epoxy resin composition, thus
preparing each copper-clad substrate.
The characteristics of each of the resulting copper-
clad substrates are shown in Table 2.
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~)34030
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a~ ~
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u ~ ~ z ~ m x a m
~ ()3~030
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V ~ o ~ o ~
.
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E~ ~ ~I v ~ r
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-- 16 --
~(334030
Notes (in Table 2):
*1: Trade name (a product of Yuka Shell Epoxy RK), epoxy
equivalent: 195, epoxy resin represented by the
formula (I).
*2: Trade name (a product of Nippon Kayaku Co., Ltd.),
brominated novolak type epoxy resin, bromine content:
36 wt.%, epoxy equivalent: 285.
*3: Trade name (a product of Yuka Shell Epoxy KK),
brominated bisphenol A type epoxy resin, bromine
content: 50 wt.%, epoxy equivalent: 440.
*4: Trade name (a product of Yuka Shell Epoxy XK),
bromine content: 22 wt.%, epoxy equivalent: 480.
*5: Trade name (a product of Yuka Shell Epoxy KK), epoxy
equivalent: 470.
*6: Trade name (a product of Nippon Zeon Co., Ltd.),
acrylonitrile/butadiene copolymer having carboxyl
group which is a solid at room temperature, carboxyl
group content: 3.35 wt.%.
*7: Trade name (a product of Goodrich Co.),
acrylonitrile/butadiene copolymer having carboxyl
group which is liquid at room temperature, carboxyl
group content: 2.40 wt.%.^
*8: Trade name (a product of Shikoku Kasei Kogyo KK),
imidazole type curing agent.
*9; BF3 monoethylamine complex.
Z034030
*10: Bromine content (wt~) based on the combined amount
of the entire epoxy res.ins, the acrylonitrile/-
butadiene copolymer and the curing agent for epoxy
resin.
*11: Test method was as follows:
A hole of 10 mm squaxe was punched out of the epoxy
resin-impregnated glass cloth sheet having an
adhesive layer. A metal foil was put on the upper
surface of the adhesive layer of the holed substrate.
Laminating was carried out at 160C under a roll
pressure of 1 kg/cm, and the laminate was heated at
170C for one hour to effect curing thus obtaining a
metal foil-clad substxate. The flowed-out width
R (mm) of the adhesive which flowed out from the
adhesive layer into the hole part of the metal foil-
clad substrate was measured. The measurement was
made for the 4 sides of the hole. The mean value was
referred to as fluidity.
*12: Measurement was made according to JISC-6481.
*13: Flame resistance test was carried out according to
VL-94 vertical method (Underwriters' Laboratories
Inc. Standard Test).
It is apparent from Table 2 that the epoxy resin-
impregnated glass cloth sheets having an adhesive layer of
Examples are superior to those of Comparative Examples in the
-
03()
fluidity of the adhesive layer during roll press bonding, the
peeling strength of copper foil, particularly peelinq
strength during heating and flame retardance on the whole.
Example 7 and ComParative E ample 6T
Varnish of the epoxy resin composition prepared in
Example 2 was coated on the epoxy resin impregnated glass
cloth sheet B or C in such an amount as to give a dry
thickness of 20 ~m. A copper-clad substrate was then
prepared in the same way as in Example 2.
The characteristics of each of the resulting copper-
clad substrates were measured in the same way as in
Example 2.
The results are shown in Table 3.
Table 3
Ex.7 Com~.Ex. 6
Epoxy resin-impregnated glass cloth B C
sheet used
Characteristics of copper-clad
substrate
Fluidity during roll pressing (mm) <0.1 <0.1
Normal peeling strength of copper
foil (kgf/cm)
25C 1.8 1.8
150C 1.2 1.2
Flame resistance 94V-0 94V-l or
test result below
-- 19 --
;~0~030
It is apparent from Table 3 that the sheet of Example
7 is scarcely fluidized during roll press bonding, has a high
copper foil peeling strength particularly at elevated
temperatures and is superior in flame retardance, while the
sheet of Comparative Example 6 is inferior in flame
retardance.
While the present invention has been described in
detaii and with reference to specific embodiments thereof, it
is apparent to one skilled in the art that various changes
and modification can be made therein without departing from
the spirit and the scope of the present invention.
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