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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an epoxy resin composition having good heat
resistance of solder and further having excellent reliability.
2. Description of the Prior Art
Epoxy resins have excellent heat resistance, moisture resistance,
electrical characteristics and adhesion properties, and they can acquire
various characteristics on modifying the recipes thereof. Accordingly,
therefore, epoxy resins are used in paints, adhesives, and industrial
materials such as electrically insulating materials.
As methods of encapsulating electronic circuit parts such as semiconductor
devices, there have been proposed a hermetic encapsulating method using
metals or ceramics, and a resin encapsulating method using phenolic resin,
silicone resin, epoxy resin or the like. From the view point of balancing
economy, productivity and physical properties, however, the resin
encapsulating method using an epoxy resin is mainly adopted.
On the other hand, integration and automated processing have recently been
promoted in the step of mounting parts to a circuit board, and a "surface
mounting method" in which a semiconductor device is soldered to the
surface of a board has been frequently employed in place of the
conventional "insertion mounting method" in which lead pins are inserted
into holes of a board. Packages are correspondingly in a transient stage
of from conventional dual inline package (DIP) to thin-type flat plastic
package (FPP) suitable for integrated mounting and surface mounting.
As with the transition to the surface mounting method, the soldering
process which conventionally has not attracted attention has now come to
be a serious problem. According to the conventional pin insertion-mounting
method, only a lead part is partially heated during soldering, whereas
according to the surface mounting method a package in its entirety is
dipped and heated in a heated solvent. As the soldering method for the
surface mounting method, there are used solder-bath dipping method, solder
reflow method in which heating is carried out with inert-liquid saturated
vapor and infrared ray, and the like. By any of the methods, a package in
its entirety is to be heated at a high temperature of 210.degree. to
270.degree. C. Accordingly, in a package encapsulated with a conventional
encapsulating resin, a problematic cracking of the resin portion occurs at
the soldering step, whereby the reliability is lost, and hence, the
obtained product cannot be practically used.
The occurrence of cracking during the soldering process is regarded due to
the explosive vaporization and expansion, at heating for soldering, of the
moisture absorbed in the time period from procuring to the mounting
process. For the countermeasure, there is employed a method to completely
dry up a post-cured package and enclose it in a hermetically sealed
container for shipping.
The improvement of encapsulating resins has been investigated in a wide
variety of ways. For example, heat resistance of solder can be improved by
a method of adding an epoxy resin having a biphenyl skeleton and a rubber
component (Japanese Unexamined Patent Publication No. 251419/1988), but it
is not sufficient. The method of adding an epoxy resin having a biphenyl
skeleton and microparticles in powder of a particle diameter less than 14
.mu.m (Japanese Unexamined Patent Publication No. 87616/1989) does not
yield a satisfactory level of heat resistance of solder.
Alternatively, there has been proposed the addition of spherical fused
silica microparticles (Japanese Unexamined Patent Publication No.
263131/1989), whereby only the fluidity of encapsulating resins is
improved and the heat resistance of solder is not sufficient.
SUMMARY OF THE INVENTION
One of the objects of the present invention is to solve the problem
concerning the occurrence of cracking during the soldering process, namely
to provide an epoxy resin composition having excellent heat resistance of
solder.
Another object of the present invention is to provide an epoxy resin
composition having both of excellent heat resistance of solder and
reliability after thermal cycles.
Other object of the present invention is to provide an epoxy resin
composition having both excellent heat resistance of solder and
reliability after solder-bath dipping.
Such objects in accordance with the present invention can be achieved by a
semiconductor device-encapsulating epoxy resin composition comprising
(i) an epoxy resin (A) containing as the essential component thereof at
least one of a bifunctional epoxy resin (a1) having a biphenyl skeleton
and a bifunctional epoxy resin (a2) having a naphthalene skeleton,
(ii) a curing agent, and
(iii) a filler containing a fused silica (C) consisting of 97 to 50 wt % of
crushed fused silica (C1) of a mean particle diameter not more than 10
.mu.m and 3 to 50 wt % of spherical fused silica (C2) of a mean particle
diameter not more than 4 .mu.m, wherein the mean particle diameter of the
spherical fused silica is smaller than the mean particle diameter of the
crushed fused silica, and the amount of the filler being 75 to 90 wt % of
the total of the composition. The objects can be achieved by further
allowing the composition to contain a styrene type block copolymer (D), or
a copolymer (E) of (1) at least one compound selected from the group
consisting of ethylene and .alpha.-olefin and (2) at least one compound
selected from the group consisting of unsaturated carboxylic acid and
derivatives thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the present invention, it is important that an epoxy
resin (A) contains as the essential component thereof at least one of a
bifunctional epoxy resin (a1) having a biphenyl skeleton and a
bifunctional epoxy resin (a2) having a naphthalene skeleton, and that a
filler containing a fused silica (C) is contained at 75 to 90 wt % to the
total of the composition. The fused silica (C) consists of 97 to 50 wt %
of crushed fused silica (C1) of a mean particle diameter not more than 10
.mu.m and 3 to 50 wt % of spherical fused silica (C2) of a mean particle
diameter not more than 4 .mu.m wherein the mean particle diameter of the
spherical fused silica is smaller than the mean particle diameter of the
crushed fused silica. Due to the bifunctionality of the epoxy resins (a1)
and (a2), crosslinking density can be lowered. Biphenyl and naphthyl
skeletons with high resistance to heat are contained, whereby there are
obtained the effect of reducing the water absorption potency of the cured
epoxy resin, as well as the effect of making the cured epoxy resin tough
at a higher temperature (a solder-treating temperature). The through-out
use of the fused silica of a smaller particle diameter can prevent the
localization of internal stress imposed on the cured epoxy resin. By
making the spherical fused silica of a smaller mean particle diameter
present among the crushed silica of a small mean particle diameter, the
internal stress being imposed on the cured epoxy resin can be reduced more
greatly. Consequently, there is obtained an effect of improving the
strength of the cured epoxy resin, in particular the strength at a high
temperature (at the solder-treating temperature). According to the present
invention, the independent effects of the epoxy resin and the silica are
simultaneously brought about to produce a synergistic, remarkable effect
on heat resistance of solder, far beyond expectation.
The epoxy resin (A) to be used in accordance with the present invention
contains as the essential component thereof at least one of a bifunctional
epoxy resin (a1) having a biphenyl skeleton and a bifunctional epoxy resin
(a2) having a naphthalene skeleton.
The effect of preventing the occurrence of cracking during the soldering
process cannot be exhibited in cases where the epoxy resins (a1) and (a2)
are not contained.
The epoxy resin (a1) of the present invention includes a compound
represented by the following formula (I) :
##STR1##
wherein R.sub.1 through R.sub.8 independently represent hydrogen atom,
halogen atom or a lower alkyl group having 1 to 4 carbon atoms.
As preferred specific examples of R.sup.1 through R.sup.8 in the
above-mentioned formula (I), there can be mentioned hydrogen atom, methyl
group, ethyl group, propyl group, i-propyl group, n-butyl group, sec-butyl
group, tert-butyl group, chlorine atom and bromine atom.
As preferred examples of the epoxy resin (a1), there can be mentioned
4,4'-bis(2,3-epoxypropoxy)biphenyl, 4,4'-bis(2,3
-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl,
4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethyl-2-chlorobiphenyl,
4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethyl-2-bromobiphenyl,
4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetraethylbiphenyl, and
4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetrabutylbiphenyl.
As particularly preferable examples, there can be mentioned
4,4'bis(2,3-epoxypropoxy)biphenyl, and
4,4'-bis(2,3-epoxypropoxy)-3,3',5,5'-tetramethylbiphenyl.
In accordance with the present invention, the epoxy resin (a2) includes a
compound represented by the following formula (II) :
##STR2##
wherein two of R.sup.9 to R.sup.16, independently represent a group
represented by
##STR3##
and those remaining independently represent hydrogen atom, halogen atom or
a lower alkyl group having 1 to 4 carbon atoms.
Those among R.sup.9 to R.sup.16, excluding the two representing the group
##STR4##
independently represent hydrogen atom, halogen atom or a lower alkyl group
having 1 to 4 carbon atoms. As specifically preferable examples, there can
be mentioned hydrogen atom, methyl group, ethyl group, propyl group,
t-propyl group, n-butyl group, sec-butyl group, tert-butyl group, chlorine
atom and bromine atom.
As preferred specific examples of the epoxy resin (a2), there can be
mentioned 1,5-di(2,3-epoxypropoxy)naphthalene,
1,5-di(2,3-epoxypropoxy)-7-methylnaphthalene, 1,6-di(2,3
-epoxypropoxy)naphthalene, 1,6-di(2,3-epoxypropoxy)-2-methylnaphthalene,
1,6-di(2,3-epoxypropoxy)-8-methylnaphthalene,
1,6-di(2,3-epoxypropoxy)-4,8-dimethylnaphthalene,
2-bromo-1,6-di(2,3-epoxypropoxy)naphthalene,
8-bromo-1,6-di(2,3-epoxypropoxy)naphthalene,
2,7-di(2,3-epoxypropoxy)naphthalene, etc. As particularly preferred
examples, there can be mentioned 1,5-di(2,3-epoxypropoxy)naphthalene,
1,6-di(2,3-epoxypropoxy)naphthalene and
2,7-di(2,3-epoxypropoxy)naphthalene.
The epoxy resin (A) of the present invention can contain epoxy resins other
than the epoxy resins (a1) and (a2), in combination with the epoxy resins
(a1) and (a2). As the other epoxy resins concurrently usable, there can be
mentioned cresol-novolac type epoxy resin, phenol-novolac type epoxy
resin, various novolac type epoxy resins synthesized from bisphenol A,
resorcine, etc., bisphenol A type epoxy resin, linear aliphatic epoxy
resin, alicyclic epoxy resin, heterocyclic epoxy resin, halogenated epoxy
resin, etc.
There is no specific limitation to the ratio of the epoxy resins (a1) and
(a2) to be contained in the epoxy resin (A), and the effects of the
present invention can be exerted only if the epoxy resin. (a1) or (a2) is
contained as the essential component. In order to exert the effects more
sufficiently, either one or both of the epoxy resins (a1) and (a2) should
be contained in total at 50 wt % or more in the epoxy resin (A),
preferably 70 wt % or more in the epoxy resin (A).
In accordance with the present invention, the compounding amount of the
epoxy resin (A) is generally 4 to 20 wt %, preferably 6 to 18 wt % to
total of the composition.
No specific limitation is imposed on the curing agent (B) in accordance
with the present invention, so long as the agent reacts with the epoxy
resin (A) and cures the resin. As specific examples of them, there can be
mentioned phenol type curing agents including phenol-novolac resin,
cresol-novolac resin, various novolac resins synthesized from bisphenol A,
resorcine, etc., phenol alkylallylic resin represented by the following
formula:
##STR5##
wherein n is an integer not less than 0; R is hydrogen atom or a lower
alkyl group having 1 to 4 carbon atoms, all Rs being not necessarily
identical, trihydroxyphenyl methane, etc.; acid anhydrides including
maleic anhydride, phthalic anhydride, pyromellitic anhydride, etc.;
aromatic amines including methaphenylene diamine, diaminodiphenyl methane,
diaminodiphenyl sulfone, etc. For encapsulating a semiconductor device,
there is preferably used a phenolic curing agent from the viewpoint of
heat resistance, moisture resistance and storage stability; there are
particularly preferably used phenol-novolac resin, phenol alkylallylic
resin, trihydroxyphenyl methane, etc. Depending on the use, two or more
curing agents may be used in combination.
According to the present invention, the mixing amount of the curing agent
(B) is generally 3 to 15 wt %, preferably 4 to 10 wt % to the total of the
composition. In view of mechanical properties and moisture resistance. The
compounding amount of the epoxy resin (A) and the curing agent (B) is such
that the chemical equivalent ratio of the curing agent (B) to the epoxy
resin (A) is in the range of 0.7 to 1.3, preferably in the range of 0.8 to
1.2.
In the present invention, a curing catalyst may be used for promoting the
curing reaction between the epoxy resin (A) and the curing agent (B). Any
compound capable of promoting the curing reaction can be used in the
present invention without specific limitation. For example, there can be
included imidazole compounds such as 2-methylimidazole,
2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,
2-phenyl-4-methylimidazole, 2-heptadecylimidazole; tertiary amine
compounds such as triethylamine, benzyldimethylamine,
.alpha.-methylbenzyldimethylamine, 2-(dimethylaminomethel)phenol,
2,4,6-tris(dimethylaminomethyl)phenol, and
1,8-diazabicyclo(5,4,0)undecene-7; organic metal compounds such as
zirconium tetramethoxide, zirconium tetrapropoxide,
tetrakis(acetylacetonate)zirconium and tri(acetylacetonate)aluminum; and
organic phosphine compounds such as triphenylphosphine,
trimethylphosphine, triethylphosphine, tributylphosphine,
tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine. From the
viewpoint of moisture resistance, an organic phosphine compound is
preferable, and triphenylphosphine in particular is preferably used. A
combination of two or more of these curing catalysts may be used,
depending on the use. Preferably, the curing catalyst is incorporated in
an amount of 0.5 to 5 parts by weight per 100 parts by weight of the epoxy
resin (A).
In the present invention, the filler contains the fused silica (C).
The fused silica (C) in accordance with the present invention consists of
90 to 50 wt % of crushed fused silica of a mean particle diameter not more
than 10 .mu.m and 3 to 50 wt % of spherical fused silica of a mean
particle diameter not more than 4 .mu.m, wherein the mean particle
diameter of the spherical fused silica is smaller than the mean particle
diameter of the crushed fused silica. Preferably, the fused silica (C) in
accordance with the present invention consists of 97 to 60 wt % of crushed
fused silica of a mean particle diameter not more than 10 .mu.m and 3 to
40 wt % of spherical fused silica of a mean particle diameter not more
than 4 .mu.m, wherein the mean particle diameter of the spherical fused
silica is smaller than the mean particle diameter of the crushed fused
silica. The crushed fused silica of a mean particle diameter exceeding 10
.mu.m cannot yield satisfactory heat resistance of solder. There is no
specific limitation to the crushed fused silica herein, as long as its
mean particle diameter is not more than 10 .mu.m. Crushed fused silica of
a mean particle diameter 3 .mu.m or more and 10 .mu.m or less is
preferably used, from the viewpoint of heat resistance of solder. A
crushed fused silica of a mean particle diameter of not less than 3 .mu.m
and less than 7 .mu.m is specifically preferably used. When the mean
particle diameter of crushed fused silica comes to be 10 .mu.m or less,
two or more types of crushed fused silica, with different mean particle
diameters, may be used in combination. The spherical fused silica of a
mean particle diameter exceeding 4 .mu.m cannot yield satisfactory heat
resistance of solder. There is no specific limitation to the spherical
fused silica, as long as its mean particle diameter is not more than 4
.mu.m, but a spherical fused silica of a mean particle diameter of 0.1
.mu.m or more and 4 .mu.m or less is preferably used, in view of heat
resistance of solder. When the mean particle diameter of spherical fused
silica comes to be 4 .mu.m or less, two or more types of spherical fused
silica, with different mean particle diameters, may be used in
combination. The mean particle diameter referred to herein means the
particle diameter (median size) at which the cumulative weight reaches 50
wt %. As the measuring method of particle diameter, a particle diameter
distribution measuring method of laser diffraction type is employed. As
laser diffraction type measurement, there is used, for example, a Laser
Granulometer Model 715 manufactured by CILAS Co., Ltd. In the fused silica
(C), it is also important that the mean particle diameter of spherical
fused silica is smaller than the mean particle diameter of crushed fused
silica. In the case that the mean particle diameter of spherical fused
silica is greater than the mean particle diameter of crushed fused silica,
a composition with excellent heat resistance of solder cannot be obtained.
The mean particle diameter of spherical fused silica smaller than the mean
particle diameter of crushed fused silica is permissible, and preferably,
the mean particle diameter of spherical fused silica is two-thirds or less
of the mean particle diameter of crushed fused silica, more preferably
half or less. Furthermore, in the case that the ratio of crushed fused
silica to spherical fused silica is not in the above-mentioned range, a
composition with excellent heat resistance of solder cannot be obtained.
In the present invention, the ratio of the fused silica (C) is at least 80,
preferably at least 90 wt % to the total amount of the filler. The ratio
of the filler is 75 to 90 wt %, more preferably 77 to 88 wt % to the total
amount of the composition. When the ratio of the filler is less than 75 wt
% or exceeds 90 wt % to the total amount of the composition or when the
ratio of the fused silica (C) is less than 80 wt % to the total amount of
the filler, heat resistance of solder is not sufficient.
To the epoxy resin composition of the present invention may be added, as
filler, crystalline silica, calcium carbonate, magnesium carbonate,
alumina. magnesia, clay, talc, calcium silicate, titanium oxide, antimony
oxide, asbestos, geass fiber, etc., besides fused silica (C).
In accordance with the present invention, a polystyrene type block
copolymer (D) is preferably used. The polystyrene type block copolymer (D)
includes linear, parabolic or branched block copolymers comprising blocks
of an aromatic vinyl hydrocarbon polymer having a glass transition
temperature of at least 25.degree. C., preferably at least 50.degree. C.,
and blocks of a conjugated diene polymer having a glass transition
temperature not higher than 0.degree. C., preferably not higher than
-25.degree. C.
As the aromatic vinyl hydrocarbon, there can be mentioned styrone,
.alpha.-methylstyrone, o-methylstyrene, p-methylstyrene,
1,3-dimethylstyrene, vinylnaphthalene, etc., and among them, styrone is
preferably used.
As the conjugated diene, there can be mentioned butadiene (1,3-butadiene),
isoprene (2-methyl-1,3-butadiene), methylisoprene
(2,3-dimethyl-1,3-butadiene), 1,3-pentadiene, etc., and of these
conjugated dienes, butadiene and isoprene are preferably used.
The proportion of the blocks of the aromatic vinyl hydrocarbon, which are
blocks of the glass phase, in the block copolymer, is preferably 10 to 50
wt %, and the blocks of the conjugated diene polymer, which are blocks of
the rubber phase, is preferably 90 to 50 wt %.
A great number of combinations of the blocks of the glass phase and the
blocks of the rubber phase are usable and any of these combinations can be
adopted. A diblock copolymer comprising a single block of rubber phase
bonded to a single block of glass phase, and a triblock copolymer
comprising blocks of the glass phase bonded to both ends of the
intermediate block of the rubber phase are preferably used. In this case,
the number averaged molecular weight of the block of the glass phase is
preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and the
number averaged molecular weight of the block of the rubber phase is
preferably 5,000 to 200,000, more preferably 10,000 to 100,000.
The polystyrene type block copolymer (D) can be prepared by the known
living anion polymerization process, but the preparation thereof is not
limited to this polymerization process. Namely, the polystyrene type block
copolymer (D) can be produced also by a cationic polymerization process
and a radical polymerization process.
The polystyrene type block copolymer (D) includes also a hydrogenated block
copolymer formed by reducing parts of unsaturated bonds of the
above-mentioned block copolymer by hydrogenation.
In this case, preferably not more than 25% of the aromatic double bonds of
the blocks of the aromatic vinyl hydrocarbon polymer is hydrogenated, and
not less than 80% of aliphatic double bonds of the blocks of the
conjugated diene polymer is hydrogenated.
As preferable examples of the polystyrene type block copolymer (D), there
can be mentioned polystyrene/polybutadiene/polystyrene triblock
copolymer(SBS), polystyrene/polyisoprene/polystyrene triblock
copolymer(SIS), hydrogenated copolymer of SBS(SEBS), hydrogenated
copolymer of SIS, polystyrene/isoprene diblock copolymer and hydrogenated
copolymer of the polystyrene/isoprene diblock copolymer (SEP).
The amount of polystyrene type block copolymer (D) incorporated is
generally 0.2 to 10 wt %, preferably 0.5 to 5 wt % to total of the
composition. The effect of improving the heat resistance of solder and
reliability on moisture resistance are not sufficient in case of less than
0.2 wt %, whereas the amount exceeding 10 wt % is not practical because
molding gets hard due to the lowered fluidity.
In the case that polystyrene type block copolymer (D) is additionally used
in the present invention, heat resistance of solder is thereby improved,
and the reliability after thermal cycling is more improved. The reason is
assumed to be in the synergistic action of the following two effects;
(1) Polystyrene type block copolymer (D) makes the cured epoxy resin
hydrophobic.
(2) Over a wide temperature range, the block of the conjugated diene
copolymer in the polystyrene type block copolymer reduces the internal
stress generating between semiconductor chips and the cured epoxy resin.
In the present invention, it is preferred to use the copolymer (E) of (1)
at least one compound selected from the group consisting of ethylene and
.alpha.-olefin and (2) at least one compound selected from the group
consisting of unsaturated carboxylic acid and derivatives thereof.
As a compound selected from the group consisting of the ethylene and
.alpha.-olefin in the copolymer (E), there can be mentioned ethylene,
propylene, butene-1, pentene-1, 4-methylpentene-1, octene-1, etc, and of
these, ethylene is preferably used. Two or more species of ethylene or
.alpha.-olefin may be concurrently used, depending on the use. As the
unsaturated carboxylic acid, there can be mentioned acrylic acid,
methacrylic acid, ethyl acrylic acid, crotonic acid, maleic acid, fumaric
acid, itaconic acid, citraconic acid, butene dicarboxylic acid, etc. As
the derivative thereof, there can be mentioned alkyl ester, glycidyl
ester, acid anhydride or imide thereof. As specific examples, methyl
acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl
methacrylate, ethyl methacrylate, glycidyl acrylate, glycidyl
methacrylate, glycidyl ethyl acrlylate, diglycidyl itaconate ester,
diglycidyl citraconate ester, diglycidyl butene dicarboxylate ester,
monoglycidyl butene dicarboxylate ester, maleic anhydride, itaconic
anhydride, citraconic anhydride, maleic imide, N-phenylmaleic imide,
itaconic imide, citraconic imide, etc., and of these, acrylic acid,
methacrylic acid, glycidyl acrylate, glycidyl methacrylate, maleic
anhydride are preferably used. These unsaturated carboxylic acids and the
derivatives thereof may be used in combination with two or more.
In view of heat resistance of solder and moisture resistance, the
copolymerizing amount of a compound selected from the group consisting of
unsaturated carboxylic acid and derivatives thereof is preferably 0.01 to
50 wt %.
Preferably, the melt index of the copolymer (E), measured according to
ASTM-D1238, is 0.1 to 5,000, more preferably 1 to 3,000, from the
viewpoint of moldability and heat resistance of solder.
In view of heat resistance of solder and moisture resistance, the added
amount of the copolymer of (E) is generally 0.1 to 10 wt %, preferably 0.5
to 5 wt %, more preferably 1 to 4 wt % to the total of the composition.
The copolymer (E) may be preliminarily made into powder, by means of
grinding, crosslinking, and other means, in accordance with the present
invention.
The copolymer (E) can be compounded by appropriate procedures. For example,
there can be mentioned a method in which the copolymer is preliminarily
melt mixed with the epoxy resin (A) or the curing agent (B) followed by
addition of other components, a method in which the copolymer is
compounded simultaneously with the epoxy resin (A), the curing agent (B)
and other components.
In the case that the copolymer of (E) is used in the present invention,
heat resistance of solder is thereby further improved and the reliability
after dipping in a solder bath is much more improved. The reason is
assumed to be due to the synergistic action of the following two effects;
(1) The copolymer makes the cured epoxy resin hydrophobic.
(2) Parts of the unsaturated carboxylic acid or a derivative thereof in the
copolymer reacts with the epoxy resin or the curing agent to render the
cured epoxy resin tough.
In view of the reliability, preferably the filler such as fused silica (C)
is preliminarily surface treated with coupling agents including silane
coupling agent and titanate coupling agent. Preferably, silane coupling
agents such as epoxysilane, aminosilane, mercaptosilane, etc., are
preferably used as the coupling agent.
A flame retardant such as a halogenated epoxy resin or phosphorus
compounds, a flame retardant assistant such as antimony trioxide, a
colorant such as carbon black or iron oxide, an elastomer such as silicone
rubber, modified nitrile rubber, modified polybutadiene rubber, erc., a
thermoplastic resin such as polyethylene, a release agent such as
long-chain fatty acid, metal salt of long-chain fatty acid, ester of
long-chain fatty acid, amide of long-chain fatty acid, paraffin wax,
modified silicone oil, etc., and a crosslinking agent such as organic
peroxide can be added to the epoxy resin composition of the present
invention.
The epoxy resin composition of the present invention is preferably
melt-kneaded. For example, the epoxy resin composition can be prepared by
carrying out the melt-kneading according to a known kneading method using
a Banbury mixer, a kneader, a roll, a single-screw or twin-screw extruder
or a cokneader.
The present invention will now be described in detail with reference to the
following examples.
EXAMPLES 1 to 20
Using fused silica of each of the compositions shown in Table 1, blending
of the reagents was carried out at their mixing ratios shown in Table 2,
by using a mixer. The blend was melt-kneaded using a twin-screw extruder
having a barrel-preset temperature maintained at 90.degree. C., and then
cooled and pulverized to prepare an epoxy resin composition.
Using the composition, a test device was molded according to the
low-pressure transfer molding method to evaluate the heat resistance of
solder under the conditions described below.
Evaluation of Heat Resistance of Solder
Thirty-two each of 80-pin QFP (package size, 17.times.17.times.1.7 mm;
silicone chip size, 9.times.9.times.0.5 mm) were molded and cured at
180.degree. C. for 5 hours, followed by humidification at 85.degree.
C./85% RH for 50 hours. Then, sixteen of 80-pin QFP each was dipped into a
solder bath heated at 260.degree. C. for 10 seconds, while another sixteen
of 80-pin QFP each was placed into a VPS (vapor phase solder reflow)
furnace heated at 215.degree. C. for 90 seconds. Those QFP with occurrence
of cracking were judged defective.
The results are shown in Table 3.
As is shown in Table 3, the epoxy resin compositions of the present
invention (Examples 1 to 20) have excellent heat resistance of solder.
TABLE 1
__________________________________________________________________________
Compositions of fused silica
Crushed fused silica Spherical fused silica
Crushed fused
Ratio by Mean particle
Ratio by
Mean particle
silica/Spherical
weight *1 diameter
weight *2
diameter
fused silica
(I/II/III/IV/V)
(.mu.m)
(VI/VII/VIII)
(.mu.m)
Ratio by weight
__________________________________________________________________________
Example 1
0/100/0/0/0
5.3 100/0/0 0.2 95/5
Example 2
0/100/0/0/0
5.3 0/100/0 2.1 95/5
Example 3
0/100/0/0/0
5.3 0/100/0 2.1 95/5
Example 4
100/0/0/0/0
3.4 100/0/0 0.2 90/10
Example 5
0/0/100/0/0
6.5 0/100/0 2.1 90/10
Example 6
0/0/100/0/0
6.5 0/100/0 2.1 90/10
Example 7
100/0/0/0/0
3.4 100/0/0 0.2 80/20
Example 8
0/0/100/0/0
6.5 0/100/0 2.1 80/20
Example 9
0/0/100/0/0
6.5 0/100/0 2.1 80/20
Example 10
0/0/100/0/0
6.5 0/100/0 2.1 90/10
Example 11
0/0/0/100/0
8.9 100/0/0 0.2 90/10
Example 12
0/0/70/0/30
9.2 0/100/0 2.1 90/10
Example 13
0/100/0/0/0
5.3 100/0/0 0.2 80/20
Example 14
0/0/0/100/0
8.9 0/70/30 3.6 80/20
Example 15
0/100/0/0/0
5.3 100/0/0 0.2 80/20
Example 16
50/0/0/50/0
6.3 50/50/0 0.9 80/20
Example 17
0/0/100/0/0
6.5 0/100/0 2.1 70/30
Example 18
0/0/100/0/0
6.5 0/100/0 2.1 70/30
Example 19
50/0/05/0/0
6.3 50/50/0 0.9 80/20
Example 20
0/0/0/100/0
8.9 0/100/0 2.1 70/30
__________________________________________________________________________
*1 Mean particle diameter of curshed fused silica (.mu.m) [I: 3.4 II: 5.3
III: 6.5, IV: 8.9, V: 14.0
*2 Mean particle diameter of spherical fused silica (.mu.m) [VI: 0.2, VII
2.1, VIII: 6.5
TABLE 2
__________________________________________________________________________
Epoxy Resin Compositions (wt %)
__________________________________________________________________________
Curing agent
Epoxy resin Phenol
Ortho-cresol
Phenol alkylallylic
4,4'-Bis(2,3- novolac type
novolac resin
resin of a
epoxypropoxy)- epoxy resin
of a hydroxyl
hydroxyl
Curing
3,3', 5,5'-
1,6-Di(2,3-
of an epoxy
group group catalyst
tetramethyl-
epoxypropoxy)-
equivalent of
equivalent of
equivalent of
Triphenyl-
biphenyl
naphthalene
200 107 173 phosphine
__________________________________________________________________________
Example 1
9.4 0.0 0.0 6.3 0.0 0.2
Example 2
9.4 0.0 0.0 6.3 0.0 0.2
Example 3
0.0 8.5 0.0 7.2 0.0 0.2
Example 4
8.8 0.0 0.0 5.9 0.0 0.2
Example 5
8.1 0.0 0.0 5.6 0.0 0.2
Example 6
0.0 7.2 0.0 6.5 0.0 0.2
Example 7
8.1 0.0 0.0 5.6 0.0 0.2
Example 8
6.7 0.0 1.7 5.3 0.0 0.2
Example 9
0.0 5.0 3.3 5.4 0.0 0.2
Example 10
0.0 6.0 0.0 0.0 7.7 0.2
Example 11
7.6 0.0 0.0 5.1 0.0 0.2
Example 12
7.6 0.0 0.0 5.1 0.0 0.2
Example 13
7.6 0.0 0.0 5.1 0.0 0.2
Example 14
7.6 0.0 0.0 5.1 0.0 0.2
Example 15
0.0 6.7 0.0 6.0 0.0 0.2
Example 16
7.1 0.0 0.0 4.6 0.0 0.2
Example 17
7.1 0.0 0.0 4.6 0.0 0.2
Example 18
0.0 6.1 0.0 5.6 0.0 0.2
Example 19
3.3 3.3 0.0 5.1 0.0 0.2
Example 20
6.0 0.0 0.0 3.8 0.0 0.1
__________________________________________________________________________
Flame
Retardant
Brominated
phenol
novolac
type epoxy
resin with an
Silane epoxy
coupling
equivalent
Flame
agent of 270 and a
retardant Release
Fused silica
.gamma.-Glycidoxy-
total bromine
assistant
Colorant
agent
in propyltri-
content of
Antimony
Carbon Carnauba
Table 1 methoxysilane
36 wt %
trioxide
black wax
__________________________________________________________________________
Example 1
79 0.7 2.3 1.5 0.3 0.3
Example 2
79 0.7 2.3 1.5 0.3 0.3
Example 3
79 0.7 2.3 1.5 0.3 0.3
Example 4
80 0.7 2.3 1.5 0.3 0.3
Example 5
81 0.7 2.3 1.5 0.3 0.3
Example 6
81 0.7 2.3 1.5 0.3 0.3
Example 7
81 0.7 2.3 1.5 0.3 0.3
Example 8
81 0.7 2.3 1.5 0.3 0.3
Example 9
81 0.7 2.3 1.5 0.3 0.3
Example 10
81 0.7 2.3 1.5 0.3 0.3
Example 11
82 0.7 2.3 1.5 0.3 0.3
Example 12
82 0.7 2.3 1.5 0.3 0.3
Example 13
82 0.7 2.3 1.5 0.3 0.3
Example 14
82 0.7 2.3 1.5 0.3 0.3
Example 15
82 0.7 2.3 1.5 0.3 0.3
Example 16
83 0.7 2.3 1.5 0.3 0.3
Example 17
83 0.7 2.3 1.5 0.3 0.3
Example 18
83 0.7 2.3 1.5 0.3 0.3
Example 19
83 0.7 2.3 1.5 0.3 0.3
Example 20
85 0.7 2.3 1.5 0.3 0.3
__________________________________________________________________________
TABLE 3
______________________________________
Results of evaluation
Heat resistance of solder
Dipping
in solder at 260.degree. C.
Solder reflow at 215.degree. C.
(Fraction defective)
(Fraction defective)
______________________________________
Example 1
2/16 2/16
Example 2
2/16 2/16
Example 3
3/16 0/16
Example 4
0/16 2/16
Example 5
0/16 0/16
Example 6
0/16 0/16
Example 7
0/16 2/16
Example 8
4/16 2/16
Example 9
6/16 2/16
Example 10
0/16 0/16
Example 11
0/16 0/16
Example 12
2/16 1/16
Example 13
0/16 0/16
Example 14
3/16 0/16
Example 15
0/16 0/16
Example 16
1/16 0/16
Example 17
0/16 0/16
Example 18
2/16 0/16
Example 19
0/16 0/16
Example 20
4/16 0/16
______________________________________
COMPARATIVE EXAMPLES 1 to 10
Using fused silica of each of the compositions shown in Table 4, blending
of the reagents was carried out at their mixing ratios shown in Table 5,
by using a mixer. Epoxy resin compositions were produced as in Examples 1
through 20, and the compositions were subjected to the evaluation of heat
resistance of solder.
The results are shown in Table 6 and Table 7.
As is shown in Table 6, all of the compositions with the incorporated
amounts of fused silica being outside the range of the present invention
(Comparative Examples 1 and 10), the compositions without containing the
epoxy resin of the present invention (Comparative Examples 2 and 7), the
compositions with the incorporated amounts of spherical fused silica being
outside the range of the present invention (Comparative Examples 3, 4 and
9), the composition with the mean particle diameter of spherical fused
silica being greater than the mean particle diameter of crushed fused
silica (Comparative Example 5), and the compositions with the mean
particle diameter of crushed fused silica or spherical fused silica being
outside the range of the present invention (Comparative Examples 6 and 8),
have much poorer heat resistance of solder in contrast to the epoxy resin
compositions of the present invention.
As is shown in Table 7, more excellent heat resistance of solder can be
obtained even at more strict conditions for evaluating heat resistance of
solder, in the case that the mean particle diameter of crushed fused
silica of the present invention is less than 7 .mu.m (Examples 5, 7, 10,
13 and 15) than in the case that the mean particle diameter of crushed
fused silica is 7 to 10 .mu.m (Examples 11, 12 and 14) .
TABLE 4
__________________________________________________________________________
Compositions of fused silica
Crushed fused silica
Spherical fused silica
Crushed fused
Ratio by Mean particle
Ratio by
Mean particle
silica/Spherical
weight *1
diameter
weight *1
diameter
fused silica
(I/II/III/IV/V)
(.mu.m)
(VI/VII/VIII)
(.mu.m)
Ratio by weight
__________________________________________________________________________
Comparati | | |
