Semiconductor device-encapsulating epoxy resin composition

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 silicaCrushed fused silica Spherical fused silica Crushed fusedRatio by Mean particle Ratio by Mean particle silica/Sphericalweight *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 95/5Example 2 0/100/0/0/0 5.3 0/100/0 2.1 95/5Example 3 0/100/0/0/0 5.3 0/100/0 2.1 95/5Example 4 100/0/0/0/0 3.4 100/0/0 0.2 90/10Example 5 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 6 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 7 100/0/0/0/0 3.4 100/0/0 0.2 80/20Example 8 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 9 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 10 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 11 0/0/0/100/0 8.9 100/0/0 0.2 90/10Example 12 0/0/70/0/30 9.2 0/100/0 2.1 90/10Example 13 0/100/0/0/0 5.3 100/0/0 0.2 80/20Example 14 0/0/0/100/0 8.9 0/70/30 3.6 80/20Example 15 0/100/0/0/0 5.3 100/0/0 0.2 80/20Example 16 50/0/0/50/0 6.3 50/50/0 0.9 80/20Example 17 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 18 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 19 50/0/05/0/0 6.3 50/50/0 0.9 80/20Example 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 agentEpoxy 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 0.2Example 2 9.4 0.0 0.0 6.3 0.0 0.2Example 3 0.0 8.5 0.0 7.2 0.0 0.2Example 4 8.8 0.0 0.0 5.9 0.0 0.2Example 5 8.1 0.0 0.0 5.6 0.0 0.2Example 6 0.0 7.2 0.0 6.5 0.0 0.2Example 7 8.1 0.0 0.0 5.6 0.0 0.2Example 8 6.7 0.0 1.7 5.3 0.0 0.2Example 9 0.0 5.0 3.3 5.4 0.0 0.2Example 10 0.0 6.0 0.0 0.0 7.7 0.2Example 11 7.6 0.0 0.0 5.1 0.0 0.2Example 12 7.6 0.0 0.0 5.1 0.0 0.2Example 13 7.6 0.0 0.0 5.1 0.0 0.2Example 14 7.6 0.0 0.0 5.1 0.0 0.2Example 15 0.0 6.7 0.0 6.0 0.0 0.2Example 16 7.1 0.0 0.0 4.6 0.0 0.2Example 17 7.1 0.0 0.0 4.6 0.0 0.2Example 18 0.0 6.1 0.0 5.6 0.0 0.2Example 19 3.3 3.3 0.0 5.1 0.0 0.2Example 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 0.3Example 2 79 0.7 2.3 1.5 0.3 0.3Example 3 79 0.7 2.3 1.5 0.3 0.3Example 4 80 0.7 2.3 1.5 0.3 0.3Example 5 81 0.7 2.3 1.5 0.3 0.3Example 6 81 0.7 2.3 1.5 0.3 0.3Example 7 81 0.7 2.3 1.5 0.3 0.3Example 8 81 0.7 2.3 1.5 0.3 0.3Example 9 81 0.7 2.3 1.5 0.3 0.3Example 10 81 0.7 2.3 1.5 0.3 0.3Example 11 82 0.7 2.3 1.5 0.3 0.3Example 12 82 0.7 2.3 1.5 0.3 0.3Example 13 82 0.7 2.3 1.5 0.3 0.3Example 14 82 0.7 2.3 1.5 0.3 0.3Example 15 82 0.7 2.3 1.5 0.3 0.3Example 16 83 0.7 2.3 1.5 0.3 0.3Example 17 83 0.7 2.3 1.5 0.3 0.3Example 18 83 0.7 2.3 1.5 0.3 0.3Example 19 83 0.7 2.3 1.5 0.3 0.3Example 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 2/16Example 2 2/16 2/16Example 3 3/16 0/16Example 4 0/16 2/16Example 5 0/16 0/16Example 6 0/16 0/16Example 7 0/16 2/16Example 8 4/16 2/16Example 9 6/16 2/16Example 10 0/16 0/16Example 11 0/16 0/16Example 12 2/16 1/16Example 13 0/16 0/16Example 14 3/16 0/16Example 15 0/16 0/16Example 16 1/16 0/16Example 17 0/16 0/16Example 18 2/16 0/16Example 19 0/16 0/16Example 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__________________________________________________________________________Comparative 0/100/0/0/0 5.3 0/100/0 2.1 95/5Example 1Comparative 0/0/0/100/0 8.9 100/0/0 0.2 90/10Example 2Comparative 0/100/0/0/0 5.3 0/0/0 -- 100/0Example 3Comparative 0/100/0/0/0 5.3 0/0/0 -- 100/0Example 4Comparative 100/0/0/0/0 3.4 0/70/30 3.6 90/10Example 5Comparative 0/0/0/0/100 14.0 0/100/0 2.1 90/10Example 6Comparative 0//0/100/0/0 6.5 0/100/0 2.1 80/20Example 7Comparative 0/0/0/100/0 8.9 0/0/100 6.5 90/10Example 8Comparative 0/0/100/0/0 6.5 0/100/0 2.1 40/60Example 9Comparative 0/0/100/0/0 6.5 0/100/0 2.1 60/40Example 10__________________________________________________________________________ *1 Mean particle diameter of crushed 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 5__________________________________________________________________________Epoxy Resin Compositions (wt %)__________________________________________________________________________ Epoxy resin Curing agent Ortho-cresol Phenol 4,4'-Bis(2,3- novolac type novolac resin epoxypropoxy)- epoxy resin of a hydroxyl Curing 3,3', 5,5'- 1,6-Di(2,3- of an epoxy group catalyst tetramethyl epoxypropoxy)- equivalent of equivalent of Triphenyl- biphenyl naphthalene 200 107 phosphine__________________________________________________________________________Comparative Example 1 12.9 0.0 0.0 8.7 0.3Comparative Example 2 0.0 0.0 11.0 6.7 0.2Comparative Example 3 9.4 0.0 0.0 6.3 0.2Comparative Example 4 0.0 8.5 0.0 7.2 0.2Comparative Example 5 8.8 0.0 0.0 5.9 0.2Comparative Example 6 8.1 0.0 0.0 5.6 0.2Comparative Example 7 0.0 0.0 8.4 5.3 0.2Comparative Example 8 7.6 0.0 0.0 5.1 0.2Comparative Example 9 6.4 0.0 0.0 4.4 0.1Comparative Example 10 1.8 0.0 0.0 2.0 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 4 methoxysilane 36 wt % trioxide black wax__________________________________________________________________________Comparative 73 0.7 2.3 1.5 0.3 0.3Example 1Comparative 77 0.7 2.3 1.5 0.3 0.3Example 2Comparative 79 0.7 2.3 1.5 0.3 0.3Example 3Comparative 79 0.7 2.3 1.5 0.3 0.3Example 4Comparative 80 0.7 2.3 1.5 0.3 0.3Example 5Comparative 81 0.7 2.3 1.5 0.3 0.3Example 6Comparative 81 0.7 2.3 1.5 0.3 0.3Example 7Comparative 82 0.7 2.3 1.5 0.3 0.3Example 8Comparative 84 0.7 2.3 1.5 0.3 0.3Example 9Comparative 91 0.7 2.3 1.5 0.3 0.3Example 10__________________________________________________________________________
TABLE 6______________________________________Results of evaluation Heat resistance of solder Dipping in solder at 260.degree. C. Solder reflow at 215.degree. C. (Fraction defective) (Fraction defective)______________________________________Comparative 16/16 16/16Example 1Comparative 16/16 16/16Example 2Comparative 11/16 10/16Example 3Comparative 16/16 12/16Example 4Comparative 9/16 15/16Example 5Comparative 16/16 9/16Example 6Comparative Melt-kneading evaluation impossibleExample 7 was impossible;Comparative 14/16 11/16Example 8Comparative 16/16 12/16Example 9Comparative Melt-kneading evaluation impossibleExample 10 was impossible;______________________________________
TABLE 7______________________________________Results of evaluation Heat ressitance of solder Dipping in solder at 260.degree. C. After 50-hour After 75-hour humidification humidification (Fraction defective) (Fraction defective)______________________________________Example 5 0/16 0/16Example 7 0/16 0/16Example 10 0/16 0/16Example 11 0/16 4/16Example 12 2/16 6/16Example 13 0/16 0/16Example 14 3/16 6/16Example 15 0/16 0/16Comparative 16/16 16/16Example 2Comparative 16/16 16/16Example 6Comparative 14/16 16/16Example 8______________________________________
EXAMPLES 21 to 38, COMPARATIVE EXAMPLES 11 to 16
Using the styrene type block copolymers each shown in Table 8 and the fused silica of each of the compositions shown in Table 9, blending of the reagents was carried out at their mixing ratios shown in Table 10, by using a mixer. Epoxy resin compositions were produced as in Examples 1 to 20.
Using the compositions, test devices were molded according to the low-pressure transfer molding method to evaluate the heat resistance of solder and reliability on moisture resistance after thermal cycling.
Evaluation of Heat Resistance of Solder
Sixteen 80-pin QFP were molded and post cured at 180.degree. C. for 5 hours, followed by humidification at 85.degree. C./85% RH for 48 hours, which were then dipped into a solder bath heated at 260.degree. C. for 10 seconds. Those QFP with occurrence of cracking were judged defective.
Evaluation of Reliability on Moisture Resistance After Thermal Cycling
Twenty 16-pin DIP (package size, 19.times.6.times.3 mm) mounting a test element with aluminum wiring were molded and cured at 180.degree. C. for 5 hours, followed by 100-time repetition of the thermal cycle from -55.degree. C. to 150.degree. C., which were then subjected to PCT at the condition of 143.degree. C./100% RH. Then, the lifetime of the properties was determined in Weibull distribution.
The results are shown in Table 11.
As shown in Table 11, the epoxy resin compositions with the styrene type block copolymers added, in accordance with the present invention (Examples 21 to 34), have improved heat resistance of solder together with considerably improved reliability on moisture resistance after thermal cycling, compared with those compositions without styrene type block copolymers added (Examples 35 to 38).
All of the composition with the mean particle diameter of spherical fused silica greater than the size of crushed fused silica (Comparative Example 11), the composition without containing the spherical fused silica (Comparative Example 12), the compositions without containing the epoxy resin composition of the present invention (Comparative Examples 13 and 14), and the compositions of the mean particle diameter of crushed or spherical fused silica being outside the range of the present invention (Comparative Examples 15 and 16), even though the above compositions all contain styrene type block copolymers, have much poorer heat resistance of solder and reliability on moisture resistance after thermal cycling, in contrast to the epoxy resin compositions of the present invention.
TABLE 8__________________________________________________________________________ Polymerized ratio ofPolystyrene copolymers Solutiontype block Butadiene or viscositycopolymer Copolymerized composition Styrene isoprene (cps) 25.degree. C.__________________________________________________________________________I Polystyrene/polybutadiene/polystyrene 40 60 2,500*.sup.1 triblock copolymerII Hydrogenated polystyrene/polybutadiene/ 29 71 550*.sup.2 polystyrene triblock copolymerIII Hydrogenated polystyrene/polybutadiene/ 13 87 1,100*.sup.2 polystyrene triblock copolymerIV Polystyrene/polyisoprene/polystyrene 21 79 1,300*.sup.1 triblock copolymerV Hydrogenated polystyrene/polyisoprene 37 63 1,260*.sup.3 diblock copolymer__________________________________________________________________________ *.sup.1 25 wt % toluene solution *.sup.2 20 wt % toluene solution *.sup.3 15 wt % toluene solution
TABLE 9__________________________________________________________________________Compositions of fused silica Crushed fused silica Spherical fused silica Crushed fused Ratio by Mean particle Ratio by Mean particle silica/Spherical weight *1 diamerter weight *2 diameter fused silica (I/II/III/IV/V) (.mu.m) (VI/VII/VIII) (.mu.m) Ratio by weight__________________________________________________________________________Example 21 0/0/100/0/0 6.5 100/0/0 0.2 95/5Example 22 30/0/70/0/0 6.0 50/50/0 0.9 95/5Example 23 100/0/0/0/0 3.4 100/0/0 0.2 90/10Example 24 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 25 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 26 0/0/0/100/0 8.9 0/100/0 2.1 70/30Example 27 0/0/0/100/0 8.9 100/0/0 0.2 90/10Example 28 0/0/0/100/0 8.9 100/0/0 0.2 90/10Example 29 0/0/0/100/0 8.9 0/70/30 3.6 90/10Example 30 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 31 0/0/0/100/0 8.9 0/100/0 2.1 80/20Example 32 0/0/0/100/0 8.9 0/100/0 2.1 80/20Example 33 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 34 0/0/100/0/0 6.5 0/100/0 2.1 80/20Comparative Example 11 100/0/0/0/0 3.4 0/70/30 3.6 90/10Comparative Example 12 0/0/0/100/0 8.9 0/0/0 -- 100/0Comparative Example 13 0/0/0/100/0 8.9 100/0/0 0.2 90/10Comparative Example 14 0/0/0/100/0 8.9 0/100/0 2.1 70/30Comparative Example 15 0/0/0/0/100 14.0 0/100/0 2.1 80/20Comparative Example 16 0/0/0/100/0 8.9 0/0/100 6.5 80/20Example 35 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 36 0/0/0/100/0 8.9 100/0/0 0.2 90/10Example 37 0/0/0/100/0 6.5 0/100/0 2.1 70/30Example 38 0/0/0/100/0 8.9 0/100/0 2.1 80/20__________________________________________________________________________ *1 Mean particle diameter of crushed 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 10__________________________________________________________________________Epoxy Resin Compositions (wt %)__________________________________________________________________________ Epoxy resin Curing agent Ortho-cresol Phenol 4,4'-Bis(2,3- novolac type novolac resin epoxypropoxy)- epoxy resin of a hydroxyl Curing 3,3', 5,5'- 1,6-Di(2,3- of an epoxy group catalyst Fused silica tetramethyl- epoxypropoxy)- equivalent of equivalent of Triphenyl- in biphenyl naphthalene 200 107 phosphine Table__________________________________________________________________________ 9Example 21 9.8 0.0 0.0 5.9 0.2 78Example 22 10.4 0.0 0.0 6.3 0.2 78Example 23 10.4 0.0 0.0 6.3 0.2 78Example 24 5.9 0.0 3.9 5.9 0.2 78Example 25 0.0 5.6 3.7 6.4 0.2 78Example 26 7.9 0.0 0.0 4.8 0.2 79Example 27 9.1 0.0 0.0 5.6 0.2 79Example 28 4.4 4.4 0.0 5.9 0.2 79Example 29 0.0 7.7 0.0 6.0 0.2 80Example 30 7.9 0.0 0.0 4.8 0.2 80Example 31 7.9 0.0 0.0 4.8 0.2 81Example 32 0.0 7.2 0.0 5.5 0.2 81Example 33 0.0 6.6 0.0 5.1 0.2 82Example 34 7.2 0.0 0.0 4.5 0.2 83Comparative Example 11 10.4 0.0 0.0 6.3 0.2 78Comparative Example 12 9.1 0.0 0.0 5.6 0.2 79Comparative Example 13 0.0 0.0 9.3 5.4 0.2 79Comparative Example 14 0.0 0.0 8.1 4.6 0.2 79Comparative Example 15 0.0 7.2 0.0 5.5 0.2 81Comparative Example 16 7.9 0.0 0.0 4.8 0.2 81Example 35 0.0 6.3 4.2 7.2 0.2 78Example 36 10.4 0.0 0.0 6.3 0.2 79Example 37 9.8 0.0 0.0 5.9 0.2 80Example 38 0.0 8.3 0.0 6.4 0.2 81__________________________________________________________________________ Flame Retardant Tetrabromo- bisphenol A type epoxy resin with an Silane epoxy coupling equivalent Flame Styrene type agent of 400 and a retardant block .gamma.-Glycidoxy- total bromine assistant Release agent copolymer propyltri- content of Antimony Colorant Carnauba of Table 8 methoxysilane 49 wt % trioxide Carbon black wax Type/Quantity__________________________________________________________________________Example 21 0.5 1.5 1.5 0.3 0.3 I: 2.0Example 22 0.5 1.5 1.5 0.3 0.3 V: 1.0Example 23 0.5 1.5 1.5 0.3 0.3 IV: 1.0Example 24 0.5 1.5 1.5 0.3 0.3 V: 2.0Example 25 0.5 1.5 1.5 0.3 0.3 V: 2.0Example 26 0.5 1.5 1.5 0.3 0.3 II: 4.0Example 27 0.5 1.5 1.5 0.3 0.3 III: 2.0Example 28 0.5 1.5 1.5 0.3 0.3 III: 2.0Example 29 0.5 1.5 1.5 0.3 0.3 III: 2.0Example 30 0.5 1.5 1.5 0.3 0.3 III: 3.0Example 31 0.5 1.5 1.5 0.3 0.3 V: 2.0Example 32 0.5 1.5 1.5 0.3 0.3 V: 2.0Example 33 0.5 1.5 1.5 0.3 0.3 II: 2.0Example 34 0.5 1.5 1.5 0.3 0.3 II: 1.0Comparative Example 11 0.5 1.5 1.5 0.3 0.3 IV: 1.0Comparative Example 12 0.5 1.5 1.5 0.3 0.3 III: 2.0Comparative Example 13 0.5 1.5 1.5 0.3 0.3 III: 2.0Comparative Example 14 0.5 1.5 1.5 0.3 0.3 II: 4.0Comparative Example 15 0.5 1.5 1.5 0.3 0.3 V: 2.0Comparative Example 16 0.5 1.5 1.5 0.3 0.3 V 2.0Example 35 0.5 1.5 1.5 0.3 0.3 0.0Example 36 0.5 1.5 1.5 0.3 0.3 0.0Example 37 0.5 1.5 1.5 0.3 0.3 0.0Example 38 0.5 1.5 1.5 0.3 0.3 0.0__________________________________________________________________________
TABLE 11______________________________________Results of evaluation Reliability on moisture Heat resistance of solder resistance Dipping in solder PCT after at 260.degree. C. thermal cycling (Fraction defective) (hr)______________________________________Example 21 0/16 300Example 22 0/16 310Example 23 0/16 300Example 24 1/16 290Example 25 1/16 290Example 26 1/16 320Example 27 0/16 330Example 28 0/16 300Example 29 1/16 280Example 30 0/16 310Example 31 0/16 330Example 32 0/16 310Example 33 0/16 300Example 34 0/16 280Comparative 13/16 150Example 11Comparative 14/16 140Example 12Comparative 16/16 140Example 13Comparative Melt-kneading evaluation impossibleExample 14 was impossible;Comparative 16/16 90Example 15Comparative 16/16 110Example 16Example 35 5/16 220Example 36 2/16 210Example 37 2/16 210Example 38 1/16 200______________________________________
EXAMPLES 39 to 55, COMPARATIVE EXAMPLES 17 to 22
Using the copolymers (E) shown in Table 12, and the fused silica with the compositions shown in Table 13, blending of the reagents was carried out at their mixing ratios shown in Table 14, by using a mixer, to produce epoxy resin compositions as in Examples 1 to 20.
Using the compositions, test devices were molded according to the low-pressure transfer molding method, which were then subjected to the evaluation of heat resistance of solder and reliability on moisture resistance after dipping in solder.
Evaluation of Heat Resistance of Solder
Sixteen 80-pin QFP were molded and cured at 180.degree. C. for 5 hours, followed by humidification at 85.degree. C./85% RH for 48 hours, which were then dipped into a solder bath heated at 260.degree. C. for 10 seconds. Those QFP with occurrence of cracking were judged defective.
Evaluation of Reliability on Moisture Resistance After Dipping in Solder
A test element with aluminum wiring was mounted on a 80-pin QFP and molded. The resulting test device was cured at 180.degree. C. for 5 fours, followed by humidification at 85.degree. C./85% RH for 48 hours, which was then dipped in a solder bath heated at 260.degree. C. for 10 seconds. The test device after dipping in solder was subjected to PCT at the condition of 143.degree. C./100% RH, whether or not cracking occurred in the test device. Then, the lifetime of the properties was determined in Weibull distribution.
The results are shown in Table 15 and Table 16.
As shown in Table 15, the epoxy resin compositions with the copolymers (E) being added, in accordance with the present invention (Examples 39 to 51), have improved heat resistance of solder together with considerably improved reliability on moisture resistance after solder dipping, compared with those compositions without copolymers (E) added (Examples 52 to 55).
All of the compositions without containing the epoxy resin composition of the present invention (Comparative Examples 17 and 21), the composition with the mean particle diameter of spherical fused silica greater than the size of crushed fused silica (Comparative Example 18), the compositions of the mean particle diameter of crushed or spherical fused silica being outside the range of the present invention (Comparative Examples 19 and 20), and the composition in which the ratio of spherical fused silica used is outside the range of the present invention (Comparative Example 22), even though the above compositions all contain the copolymers (E) have much poorer heat resistance of solder and reliability on moisture resistance after solder dipping.
Even when using 28-pin SOP instead of 80-pin QFP as test device and changing the testing condition as follows, the epoxy resin compositions of the present invention have been found to have excellent heat resistance of solder and reliability on moisture resistance after solder dipping, as is shown in Table 16.
Evaluation of Heat Resistance of Solder
A test element with aluminum wiring was mounted on a 28-pin SOP and molded. The resulting test device was cured at 180.degree. C. for 5 hours, followed by humidification at 85.degree. C./85% RH for 72 hours, which was then dipped in a solder bath heated at 260.degree. C. for 10 seconds. Those SOP with the occurrence of cracking were judged defective.
Evaluation of Reliability on Moisture Resistance After Dipping in Solder
SOP after the evaluation of heat resistance of solder was subjected to PCT at the condition of 121.degree. C./100% RH, whether or not cracking occurred therein. Then, it was determined the time at which the cumulative failure rate reached 50%.
TABLE 12______________________________________Copolymer (E) Ratio Melt by indexSymbols Copolymerized composition weight (g/10 min)______________________________________I Ethylene/ethyl acrylate 75/25 50II Ethylene/acrylic acid 95/5 20III Ethylene/ethyl acrylate/ 68/30/2 40 maleic anhydrideIV Ethylene/methyl methacrylate 85/15 300V Ethylene/glycidyl methacrylate 90/10 10______________________________________
TABLE 13__________________________________________________________________________Compositions of fused silica Crushed fused silica Spherical fused silica Crushed fused Ratio by Mean particle Ratio by Mean particle silica/Spherical weight *1 diamerter weight *2 diameter fused silica (I/II/III/IV/V) (.mu.m) (VI/VII/VIII) (.mu.m) Ratio by weight__________________________________________________________________________Example 39 0/100/0/0/0 5.3 100/0/0 0.2 95/5Example 40 0/100/0/0/0 5.3 0/100/0 2.1 95/5Example 41 100/0/0/0/0 3.4 100/0/0 0.2 90/10Example 42 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 43 0/0/0/100/0 8.9 0/70/30 3.6 80/20Example 44 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 45 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 46 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 47 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 48 0/0/0/100/0 8.9 0/100/0 2.1 70/30Example 49 50/0/0/50/0 6.3 50/50/0 0.9 80/20Example 50 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 51 0/0/0/100/0 8.9 0/70/30 3.6 70/30Comparative Example 17 0/0/0/100/0 8.9 0/100/0 2.1 70/30Comparative Example 18 100/0/0/0/0 3.4 0/70/30 3.6 80/20Comparative Example 19 0/0/0/100/0 8.9 0/0/100 6.5 80/20Comparative Example 20 0/0/0/0/100 14.0 0/100/0 2.1 70/30Comparative Example 21 0/0/0/100/0 8.9 0/100/0 2.1 70/30Comparative Example 22 0/0/100/0/0 6.5 0/100/0 2.1 40/60Example 52 0/0/100/0/0 6.5 0/100/0 2.1 90/10Example 53 0/0/100/0/0 6.5 0/100/0 2.1 80/20Example 54 0/0/100/0/0 6.5 0/100/0 2.1 70/30Example 55 0/0/0/100/0 8.9 0/100/0 2.1 70/30__________________________________________________________________________ *1 Mean particle diameter of crushed 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 14__________________________________________________________________________Epoxy Resin Compositions (wt %)__________________________________________________________________________ Epoxy resin Curing agent Ortho-cresol Phenol 4,4'-Bis(2,3- novolac type novolac resin epoxypropoxy)- epoxy resin of a hydroxyl Curing 3,3', 5,5'- 1,6-Di(2,3- of an epoxy group catalyst Fused silica tetramethyl- epoxypropoxy)- equivalent of equivalent of Triphenyl- in biphenyl naphthalene 200 107 phosphine Table__________________________________________________________________________ 9Example 39 9.2 0.0 0.0 6.0 0.2 78Example 40 9.2 0.0 0.0 6.0 0.2 79Example 41 8.5 0.0 0.0 5.7 0.2 79Example 42 7.9 0.0 0.0 5.3 0.2 80Example 43 7.2 0.0 0.0 5.0 0.2 80Example 44 0.0 7.0 0.0 6.2 0.2 80Example 45 6.4 0.0 1.6 5.2 0.2 81Example 46 0.0 6.1 1.5 5.6 0.2 81Example 47 7.2 0.0 0.0 5.0 0.2 81Example 48 6.0 0.0 0.0 4.2 0.2 81Example 49 3.1 3.1 0.0 5.0 0.2 82Example 50 0.0 5.5 0.0 4.8 0.2 83Example 51 4.7 0.0 0.0 3.5 0.2 86Comparative Example 17 0.0 0.0 8.7 5.5 0.2 77Comparative Example 18 7.2 0.0 0.0 5.0 0.2 80Comparative Example 19 7.2 0.0 0.0 5.0 0.2 80Comparative Example 20 7.2 0.0 0.0 5.0 0.2 81Comparative Example 21 0.0 0.0 6.2 4.0 0.2 81Comparative Example 22 0.0 5.5 0.0 4.8 0.2 83Example 52 0.0 8.3 0.0 6.9 0.2 80Example 53 0.0 6.5 1.6 6.1 0.2 81Example 54 8.5 0.0 0.0 5.7 0.2 81Example 55 8.5 0.0 0.0 5.7 0.2 81__________________________________________________________________________ Flame Retardant Brominated phenol novalac type epoxy resin with an Silane epoxy coupling equivalent Flame agent of 270 and a retardant .gamma.-Glycidoxy total bromine assistant Release agent Copolymer of propyltri- content of Antimony Colarant Carnauba Table 12 methoxysilane 36 wt % trioxide Carbon black wax Type/Quantity__________________________________________________________________________Example 39 0.7 2.3 1.0 0.3 0.3 V: 2.0Example 40 0.7 2.3 1.0 0.3 0.3 II: 1.0Example 41 0.7 2.3 1.0 0.3 0.3 IV: 2.0Example 42 0.7 2.3 1.0 0.3 0.3 III: 2.0Example 43 0.7 2.3 1.0 0.3 0.3 II: 3.0Example 44 0.7 2.3 1.0 0.3 0.3 III: 2.0Example 45 0.7 2.3 1.0 0.3 0.3 III: 1.0Example 46 0.7 2.3 1.0 0.3 0.3 III: 1.0Example 47 0.7 2.3 1.0 0.3 0.3 V: 2.0Example 48 0.7 2.3 1.0 0.3 0.3 IV: 4.0Example 49 0.7 2.3 1.0 0.3 0.3 II: 2.0Example 50 0.7 2.3 1.0 0.3 0.3 I: 2.0Example 51 0.7 2.3 1.0 0.3 0.3 V: 1.0Comparative Example 17 0.7 2.3 1.0 0.3 0.3 IV: 4.0Comparative Example 18 0.7 2.3 1.0 0.3 0.3 II: 3.0Comparative Example 19 0.7 2.3 1.0 0.3 0.3 III: 2.0Comparative Example 20 0.7 2.3 1.0 0.3 0.3 V: 2.0Comparative Example 21 0.7 2.3 1.0 0.3 0.3 IV: 4.0Comparative Example 22 0.7 2.3 1.0 0.3 0.3 I: 2.0Example 52 0.7 2.3 1.0 0.3 0.3 0.0Example 53 0.7 2.3 1.0 0.3 0.3 0.0Example 54 0.7 2.3 1.0 0.3 0.3 0.0Example 55 0.7 2.3 1.0 0.3 0.3 0.0__________________________________________________________________________
TABLE 15______________________________________Results of evaluation Reliability on moisture Heat resistance of solder resistance Dipping in solder PCT after at 260.degree. C. dipping in solder (Fraction defective) at 260.degree. C. (hr)______________________________________Example 39 0/16 310Example 40 1/16 300Example 41 0/16 320Example 42 0/16 320Example 43 0/16 300Example 44 0/16 310Example 45 2/16 320Example 46 1/16 290Example 47 0/16 340Example 48 0/16 330Example 49 0/16 350Example 50 0/16 290Example 51 2/16 300Comparative 16/16 50Example 17Comparative 14/16 90Example 18Comparative 16/16 70Example 19Comparative 16/16 60Example 20Comparative Melt-kneading was impossible; evaluation impossibleExample 21Comparative 10/16 110Example 22Example 52 0/16 220Example 53 4/16 190Example 54 2/16 240Example 55 2/16 230______________________________________
TABLE 16______________________________________Results of evaluation Reliability on moisture Heat resistance of solder resistance Dipping in solder PCT after at 260.degree. C. dipping in solder (Fraction defective) at 260.degree. C. (hr)______________________________________Example 47 0/20 350Example 51 0/20 350Comparative 11/20 50Example 20______________________________________

Number	Date	Country
2-90018	Apr 1990	JPX
2-159231	Jun 1990	JPX
2-159233	Jun 1990	JPX
2-339721	Nov 1990	JPX

Semiconductor device-encapsulating epoxy resin composition

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