JPH0575774B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides an epoxy resin composition for semiconductor encapsulation that has excellent solder stress resistance and thermal shock resistance, and is also excellent in molding processability (mold stains, resin burrs, molding voids, and mold releasability). It is about things. (Prior Art) In recent years, epoxy resin compositions have been commonly used for resin encapsulation of semiconductor elements such as ICs, LSIs, transistors, diodes, and electronic circuits from the viewpoint of both properties and cost. However, with the trend toward mass production of electronic components, miniaturization, lightening, thinning, and increasing the degree of integration, requirements for sealing resins have become more severe, and improvements in solder stress resistance, thermal shock resistance, and moldability are particularly desired. Various plans have been proposed to solve these problems. The use of multifunctional epoxy resins (Japanese Patent Application Laid-Open No. 168620/1983) has been proposed to improve solder stress resistance, but the use of multifunctional epoxy resins increases crosslinking density and improves heat resistance. ,especially
When exposed to high temperatures such as 200 to 300°C, the solder stress resistance was insufficient. Furthermore, since the modulus of elasticity of the resin composition increases due to the improvement in crosslinking density, the use of polyfunctional epoxy resins has to be limited because of the disadvantage that thermal shock resistance is decreased. Also, in order to improve thermal shock resistance, the use of so-called silicone-modified resins in which epoxy resins and phenolic resin processing agents are modified with silicone compounds having reactive functional groups (Japanese Patent Laid-Open Publication No. 73725/1982).
However, simply using a silicone-modified resin lowers the resin modulus but does not significantly improve the strength, and is insufficient to improve thermal shock resistance. Furthermore, if a silicone-modified resin is used, the strength will be improved to some extent and the solder stress resistance will also tend to be improved, but the glass transition point (hereinafter referred to as Tg) due to silicone modification is lowered (5 to 50%).
(20°C), the effect was insufficient. Therefore, as a method to simultaneously improve solder stress resistance and thermal shock resistance, it has been proposed to obtain a resin composition by combining a multifunctional epoxy resin, a silicone-modified epoxy resin, and a silicone-modified phenol novolak resin. It has become possible to simultaneously improve stress resistance and thermal shock resistance to some extent. However, in the case of these methods, the moldability is insufficient and the thermal shock resistance (low stress resistance) is still insufficient to meet the current required level, and there is a strong desire to improve these drawbacks. ing. (Problems to be Solved by the Invention) The purpose of the present invention is to provide a highly resistant material that has excellent solder stress resistance, thermal shock resistance, and molding processability (mold stains, resin burrs, molding voids, and mold releasability). An object of the present invention is to provide a well-balanced epoxy resin composition for semiconductor encapsulation. (Means for Solving the Problems) The present inventors have proposed an epoxy resin for semiconductor encapsulation that has an excellent balance of solder stress resistance, thermal shock resistance, and moldability, which could not be overcome using conventional techniques. As a result of intensive research on compositions, we found that a polyfunctional epoxy resin represented by the formula [] has particularly good heat resistance and has the effect of improving solder stress resistance.

[C] (n is an integer, n = 1 to 10, R ₁ to _{R 7} : hydrogen,
Atoms or groups selected from halogens and alkyl groups) A system that combines a random copolymerized silicone-modified epoxy resin that has low elasticity and toughness and has the effect of improving thermal shock resistance, and has even lower stress properties. Semiconductor encapsulation that satisfies the desired properties by combining a silicone copolymer, which is a block copolymer of a random copolymerized silicone compound and polyalkylene oxide, silicone rubber, and synthetic rubber as an imparting agent and molding processability improver. The present invention was completed by discovering that an epoxy resin composition can be obtained. (Function) The polyfunctional epoxy resin having the structure represented by the formula [] used in the present invention has three or more epoxy groups in one molecule, and has the function of improving solder stress properties. R ₁ to _{R 7} shown in the formula may be any atoms or groups selected from hydrogen, halogen, and alkyl groups, and among them, R ₁ and R ₆ are methyl groups,
R ₂ and R ₇ are t-butyl groups, R ₃ and R ₄ are hydrogen atoms, R ₅
Those having a methyl group or a hydrogen atom are preferably used because they have good solder stress resistance due to the effect of reducing water absorption by introducing an alkyl group, and have good moldability due to the moderate amount of alkyl groups. Further, it is necessary to use a value of n between 1 and 10.
When the value of n is 0, the epoxy becomes a monofunctional epoxy, resulting in decreased curability and poor moldability. When the value of n is 11 or more, fluidity decreases and moldability deteriorates. Furthermore, if the epoxy resin has less than two functionalities, the crosslinking density will not increase, the Tg will decrease, and the effect of solder stress resistance will not be obtained. The random copolymerized silicone-modified epoxy resin used in the present invention has the function of improving thermal shock resistance. Organophorlysiloxane used as a raw material for random copolymerized silicone-modified epoxy resin has functional groups that can react with epoxy resins, and these functional groups include, for example, alkoxy groups, hydroxyl groups, amino groups, and hydrosilyl groups. The molecular structure of the organopolysiloxane may be either linear or branched. The epoxy resin to be reacted with these organopolysiloxanes may be any resin as long as it has two or more epoxy groups in one molecule, such as bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novo epoxy resin, etc. Examples include easy-type epoxy resins, cresol novolak-type epoxy resins, alicyclic epoxy resins, and modified resins thereof, and these epoxy resins may be used alone or in combination of two or more. Among these epoxy resins, the epoxy equivalent is
150-250, the softening point is 60-130℃, and Na ⁺ ,
It is preferable that the amount of ionic impurities such as Cl ^- is as small as possible. The reaction method of random copolymerized silicone-modified epoxy resin using these raw materials is not particularly limited, but for example, an organopolysiloxane having two or more amino groups is reacted with some epoxy groups of the epoxy resin. or a random copolymer with an alkenyl group-containing epoxy resin.
There is a method in which a random copolymer is obtained by reacting with an organopolysiloxane having more than one hydrosilyl group. The random copolymerized silicone-modified epoxy resin of the present invention is one in which organopolysiloxanes are randomly copolymerized, and the silicone domains are more uniformly dispersed than those obtained by simple block copolymerization, resulting in improved moldability, stampability, and moisture resistance. It has excellent durability and thermal shock resistance. Multifunctional epoxy resin, random copolymerized silicone-modified epoxy resin, and conventional epoxy resin may be mixed and used, but in these mixed systems, the total weight of the polyfunctional epoxy resin and random copolymerized silicone-modified epoxy resin is 50% by weight. % or more, and if it is less than 50% by weight, solder stress resistance and thermal shock resistance will decrease. In the combination of a polyfunctional epoxy resin and a random copolymerized silicone-modified epoxy resin, it is necessary that the weight of the polyfunctional epoxy resin/the weight of the random copolymerized silicone-modified epoxy resin is in the range of 0.3 to 3. If this ratio is less than 0.3, the solder stress resistance will be insufficient, and if it exceeds 3, the thermal shock resistance will be insufficient. The random copolymerized silicone-modified phenol resin used as component (B) in the present invention is effective in improving thermal shock resistance and functions as a curing agent. The organopolysiloxane used as a raw material for these random copolymerized silicone-modified phenolic resins has a functional group that can react with the phenolic resin, and examples of these functional groups include epoxy groups, alkoxy groups, and hydrosilyl groups. The molecular structure of the organopolysiloxane may be either linear or branched. Examples of the phenolic resin to be reacted with the organopolysiloxane include phenol novolak, cresol novolak, and modified resins thereof, and these may be used alone or in combination of two or more. The phenolic resin used has a hydroxyl equivalent of 80~
150, a softening point of 60 to 120°C, and a material containing as few ionic impurities as Na ⁺ and Cl ^- is preferable. These random copolymerized silicone-modified phenolic resins are obtained by reacting the aforementioned organopolysiloxane having a functional group with the aforementioned phenolic resin in the presence of a tertiary amine catalyst. The random copolymerized silicone-modified phenolic resin of the present invention is a product in which organopolysiloxane is randomly copolymerized, and the silicone domains are more uniformly dispersed than in a product that is simply block copolymerized, so it has better moldability and printing properties. , excellent moisture resistance and thermal shock resistance. In the present invention, the random copolymerized silicone-modified phenolic resin curing agent may be used alone or in a mixture with other phenol novolac type curing agents, but in these mixed systems, the random copolymerized silicone-modified phenolic resin is It is preferable to use 50% by weight or more of the curing agent system.
If it is less than 20%, thermal shock resistance will decrease. Inorganic fillers as component (C) used in the present invention include crystalline silica, fused silica, alumina,
Examples include calcium carbonate, talc, mica, glass fiber, etc., and these may be used alone or in combination of two or more. Among these, crystalline silica or fused silica is particularly preferably used. The SP value as the (D) component used in the present invention is 7
The silicone copolymers of ~9 are effective in improving the compatibility of trifunctional epoxy resins, random copolymerized silicone-modified epoxy resins, random copolymerized silicone-modified phenolic resins, and various low-stress agents, and improve moldability and stamping properties. In addition, lead frames and ICs
It also has the effect of improving solder stress resistance by improving the adhesion between the chip and the sealing resin. If the SP value of the silicone copolymer is less than 7, it will become too hydrophobic and the compatibility with the random copolymerized silicone-modified epoxy resin and phenol resin will decrease, and if it exceeds 9, it will become too hydrophilic and will not be compatible with the epoxy resin. The SP value of the silicone copolymer needs to be within the range of 7 to 9, since the compatibility with the random copolymerized silicone-modified phenolic resin is decreased. For silicone copolymers, the SP value is 7~
There is no particular restriction on the structure as long as it falls within the range of 9, but for example, the following:

[ka] (however A;

[Formula] B; - (CH ₂ ) _r - O - (C ₂ H ₄ O) _i - - (C ₃ H ₆ O) _j -
_-CH3R1 ~ _R6 ; _{-CH3 ,}

【formula】

[Formula] −CH=CH ₂ ,

[Formula] However, R ₁ to R ₆ may be the same group or may be different groups. ) copolymer of organopolysiloxane and alkylene oxide, or

[C] (However, R ₁ ~ _{R 4} ; −CH ₃ ,

【formula】

[Formula] −CH=CH ₂ ,

[Formula] However, R ₁ to R ₄ may be the same group or may be different groups. ) A copolymer of organopolysiloxane and styrene having a structure as shown in FIG. These silicone copolymers have a resin content (A+
It is used in an amount of 0.1 to 15% by weight based on B). If the amount of these additives is less than 0.1% by weight, the low stress agent will bleed, resulting in poor moldability, and the effect of improving solder stress resistance will be insufficient.
If it exceeds 15% by weight, moldability will decrease. Furthermore, the SP value used as component (E) of the present invention is 7 to 9.
The silicone rubber within the range of (F), the liquid synthetic rubber used as component (F), or the mixture of silicone rubber and liquid synthetic rubber used as component (G) has good compatibility with the silicone copolymer of component (D). It is a low-stress agent, and when used in combination with component (A), a multifunctional epoxy resin, random copolymerized silicone-modified epoxy resin, and component (B), random copolymerized silicone-modified phenol resin, it improves moldability and solder stress resistance. Both properties and thermal shock resistance are significantly improved. The reason for this is that the compatibility of the polyfunctional epoxy resin, random copolymerized silicone-modified epoxy resin (A), and random copolymerized silicone-modified phenol resin (B) with other sealing resin components is higher than that of the silicone copolymer (D). further improved by silicone rubber
By combining (E), liquid synthetic rubber (F), and a mixture of silicone rubber and liquid synthetic rubber (G), the compatibility is further improved, resulting in improved strength, toughness, and adhesion with lead frames and IC chips. This significantly improved moldability and solder stress resistance. Furthermore, by combining a random copolymerized silicone-modified epoxy resin, a random copolymerized silicone-modified phenol resin, and a silicone rubber, a liquid synthetic rubber, or a mixture of a silicone rubber and a liquid synthetic rubber, which have a stress-lowering effect, a remarkable reduction in stress can be achieved. It is thought that this will significantly improve thermal shock resistance. The silicone rubber used as component (E) of the present invention is three-dimensionally crosslinked and so-called cured, and there are no particular limitations as long as its SP value is in the range of 7 to 9. The shape of the silicone rubber is preferably spherical (with an aspect ratio of 1.5 or less) with an average particle size of 30 μm or less, and silicone rubber that is reactive or has an affinity for the epoxy resin component, the phenol resin component, or both of these resins. Preferably, these particles are spherical and have an average particle diameter of 15 μm or less. Examples of these silicone rubbers include spherical silicone rubbers obtained by interfacial polymerization of organopolysiloxanes having vinyl groups and organopolysiloxanes having hydrogen groups. These silicone rubbers are used in an amount of 1 to 25% by weight based on the resin content (A+B). If the amount added is less than 1% by weight, the effect of improving thermal shock resistance will be insufficient, and if it exceeds 25% by weight, the molding processability will decrease due to bleeding of silicone rubber, and the hot hardness during molding and moldability will decrease. The solder stress resistance decreases due to a decrease in the strength of the product. The liquid synthetic rubber used as component (F) of the present invention is preferably a diene-based rubbery polymer having one or more epoxy groups capable of reacting with a curing agent in the molecule, such as epoxidized polybutadiene rubber. These liquid synthetic rubbers have a resin content (A
+B) is used in a range of 0.5 to 20% by weight. If the amount added is less than 0.5% by weight, the effect of improving molding processability and thermal shock resistance will be insufficient, and if it exceeds 20% by weight, the molding processability will decrease due to bleeding of the synthetic rubber, and the heat resistance during molding will decrease. As a result, the solder stress resistance decreases due to a decrease in hardness and strength of the molded product. Furthermore, the mixture of silicone rubber and liquid synthetic rubber used as component (G) has a liquid synthetic rubber content of 20 to 100 parts by weight per 100 parts by weight of silicone rubber.
It is desirable to mix the components within the range of parts by weight in terms of performance balance, but it is possible to use them even if the ratio is slightly deviated from this range. In addition, the mixture of these silicone rubbers and liquid synthetic rubbers has a
It is used in a range of 0.5 to 15% by weight. If the amount added is less than 0.5% by weight, the effect of improving thermal shock resistance will be insufficient, and if it exceeds 15% by weight, molding processability will decrease due to bleeding of silicone rubber and liquid synthetic rubber, and heat resistance during molding will decrease. As a result, the solder stress resistance decreases due to a decrease in hardness and strength of the molded product. In addition, as necessary ingredients other than these
Tertiary amines such as BDMA, imidazoles,
A curing accelerator such as an organic phosphorus compound such as 1,8-diazabicyclo[5,4,0]undecene-7 and triphenylphosphine is used. In addition, mold release agents such as waxes, flame retardants such as hexabromobenzene, decabromo biphenyl ether, and antimony trioxide, coloring agents such as carbon black and red iron oxide, silane coupling agents, and other thermoplastic resins may be added as necessary. It can be added and blended as appropriate. A general method for manufacturing the epoxy resin composition for semiconductor encapsulation of the present invention is to thoroughly mix raw materials in a predetermined blending ratio using a mixer or the like;
Furthermore, it is melt-kneaded using rolls, kneaders, etc.
It can then be easily produced by cooling, solidifying, and pulverizing into an appropriate size. (Example) Example 1 Multifunctional epoxy resin (a) 45 parts by weight random copolymerized silicone-modified epoxy resin (c)
45 parts by weight Brominated bisphenol A type epoxy resin (epoxy equivalent: 370, softening point: 65°C, bromine content: 37%)
10 parts by weight - Cresol novolac resin (epoxy resin equivalent: 200, softening point 65°C) 10 parts by weight Random copolymerized silicone-modified phenolic resin (O)
60 parts by weight Phenol novolak resin (hydroxyl equivalent: 105, softening point 95°C) 5 parts by weight Fused silica 490 parts by weight Triphenylphosphine 2 parts by weight Random copolymerized silicone-modified polyalkylene oxide (x) 5 parts by weight Silicone rubber 10 parts by weight parts antimony trioxide 25 parts by weight silane coupling agent 2 parts by weight carnauba wax 3 parts by weight carbon black 3 parts by weight were thoroughly mixed at room temperature, and further kneaded at 95 to 100°C.
After cooling, it was pulverized to obtain a molding material, which was then made into tablets to obtain an epoxy resin composition for semiconductor encapsulation. This material was evaluated for mold stain resistance and resin burrs using a transfer molding machine (molding conditions: mold temperature 175°C, curing time 2 minutes), and the resulting molded product was molded at 175°C for 8 hours. After curing, voids inside the package, imprintability, thermal shock resistance, moisture resistance, and solder stress resistance were evaluated. Examples 2 to 9 Epoxy resin compositions for semiconductor encapsulation having the compositions shown in Table 1 were obtained in the same manner. Table 1 shows the evaluation results of this epoxy resin composition for semiconductor encapsulation. Comparative Examples 1 to 11 Epoxy resin compositions for semiconductor encapsulation having the compositions shown in Table 1 were obtained in the same manner. Table 1 shows the evaluation results of this epoxy resin composition for semiconductor encapsulation.

【table】

【table】

【table】

【table】

[Table] (Effects of the Invention) According to the present invention, it is possible to obtain an epoxy resin composition having high Tg, high flexibility, high strength, and high moldability that could not be obtained using conventional techniques. It has extremely high solder stress resistance and thermal shock resistance, and also has good moldability, so when used for sealing, coating, insulation, etc. of electronic and electrical parts,
It is particularly suitable for highly integrated large-chip ICs mounted on surface mount packages that require high reliability.

Claims (1)

[Claims] 1 (A)(i) A polyfunctional epoxy resin represented by the following formula [] (n is an integer, n = 1 to 10, R ₁ to R ₇ : hydrogen, halogen, Atoms or groups selected from alkyl groups) (ii) A silicone-modified epoxy resin obtained by reacting a random copolymerized silicone compound and an epoxy resin, and a polyfunctional epoxy resin (i) and a silicone-modified epoxy resin (ii) The weight mixing ratio (i)/(ii) is 0.3~
3, and the total of the polyfunctional epoxy resin (i) and silicone-modified epoxy resin (ii) is 50 to 100% by weight of the total epoxy resin amount (B) Random copolymerized silicone compound and phenol resin The silicone-modified phenolic resin obtained by reacting accounts for 50~50% of the total phenolic resin amount.
100% by weight phenolic resin curing agent (C) Inorganic filler (D) Silicone copolymer with an SP value of 7 to 9 (E) Silicone rubber with an SP value of 7 to 9 as an essential component, and the resin component [ (A)+(B)], the resin composition contains 0.1 to 15% by weight of a silicone copolymer component (D) and 1 to 25% by weight of a silicone rubber component (E). 2 In place of component (E) in patent claim 1
Using liquid synthetic rubber (F) with an SP value in the range of 7 to 9, liquid synthetic rubber (F) is used for resin components [(A) + (B)].
A resin composition containing 0.5 to 20% by weight of 3 In place of component (E) in patent claim 1
Using a mixture (G) of silicone rubber and liquid synthetic rubber with an SP value in the range of 7 to 9, the resin component [(A) +
(B)] and 0.5 to 15% by weight of a mixture (G) of silicone rubber and liquid synthetic rubber.