JPH0577688B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an epoxy resin composition for semiconductor encapsulation that has excellent solder stress resistance. (Prior art) Conventionally, electronic components such as diodes, transistors, and integrated circuits have been encapsulated with thermosetting resin, but especially for integrated circuits, o-cresol novolac epoxy resin, which has excellent heat resistance and moisture resistance, has been used. An epoxy resin cured with a novolac type phenolic resin is used. However, in recent years, as integrated circuits have become more highly integrated, chips have become larger and larger, and packages have become smaller than conventional ones.
The DIP type has been replaced by small, thin flat packages that are surface mounted, such as SOP, SOJ, and PLCC. That is, a large chip is enclosed in a small and thin package, and problems such as the occurrence of cracks due to stress and a decrease in moisture resistance due to these cracks are becoming more and more important. In particular, during the soldering process, rapid exposure to high temperatures of over 200°C has caused problems such as cracking of the package and deterioration of moisture resistance due to peeling of the resin and chip. It has been desired to develop a highly reliable encapsulating resin composition suitable for encapsulating these large chips. To solve these problems, thermoplastic oligomers have been added (Japanese Patent Laid-Open No. 115849/1982) and various silicone compounds have been added (Japanese Patent Laid-open No. 115850/1983) to alleviate thermal shock during soldering. Publication, 62−
116654 Publication No. 62-128162 Publication) and silicone modification (Japanese Patent Application Laid-open No. 136860/1983), but all of these techniques resulted in cracks in the package cage during soldering, resulting in poor reliability. However, it was not possible to obtain an epoxy resin composition for encapsulating a semiconductor. On the other hand, in order to obtain a heat-resistant epoxy resin composition with excellent solder stress resistance, the use of a polyfunctional epoxy resin as the resin system (Japanese Patent Application Laid-Open No. 168620/1983) has been considered; Although the use of epoxy resin increases the crosslinking density and improves heat resistance, the solder stress resistance is insufficient, especially when exposed to high temperatures such as 200°C to 300°C. (Problems to be Solved by the Invention) The present invention solves these problems by using a trifunctional epoxy resin as the epoxy resin, a dicyclopentadiene-modified phenol resin as the curing agent, and further using secondary agglomerated silica as the filler. By using the powder, it is possible to provide an epoxy resin composition for semiconductor encapsulation that has extremely excellent solder stress resistance. (Means for Solving the Problems) The epoxy resin composition of the present invention uses a trifunctional epoxy resin having a structure represented by the following formula () as an epoxy resin.

[Chemical formula] (In the formula, R ₁ to R ₁₁ are atoms or groups selected from hydrogen, halogen, and alkyl groups) The epoxy resin containing 50 to 100% by weight based on the total amount of epoxy resin and the curing agent are as follows. Dicyclopentadiene-modified phenolic resin with the structure shown by formula ()

[Chemical formula] (In the formula, R ₁ and R ₂ are atoms or groups selected from hydrogen, halogen, and alkyl groups.) A curing agent containing 40 to 100% by weight of the total amount of curing agent is used, and an inorganic As a filler, secondary agglomeration having a primary average particle diameter of 0.1 to 1 μm, a secondary average particle diameter of 2 to 60 μm, an apparent density of 0.1 to 1 g/cc, and a specific surface area of 1 to 10 m ² /g It is characterized by using an inorganic filler containing 20 to 100% by weight of silica powder based on the total amount of inorganic filler, and has extremely superior solder stress resistance compared to conventional epoxy resin compositions. be. By adjusting the amount of the trifunctional epoxy resin having the structure represented by the formula (), the solder stress resistance can be maximized. In order to obtain the effect of solder stress resistance, it is desirable to use the trifunctional epoxy resin represented by the formula () in an amount of 50% by weight or more, preferably 70% by weight or more of the total amount of epoxy resin. If it is less than 50% by weight, the crosslinking density will not increase and the solder stress resistance will be insufficient. Furthermore, R ₁ , R ₂ , R ₄ to _{R 7} , R ₁₀ , and R ₁₁ in the formula are hydrogen atoms, R ₃ ,
R ₈ and R ₉ are preferably methyl groups. In addition, if the epoxy resin is difunctional or less, the crosslinking density will not increase, the heat resistance will be poor, and the effect of solder stress resistance will not be obtained. The epoxy resin used in combination with the polyfunctional epoxy resin represented by formula () refers to any resin having an epoxy group. For example, it refers to bisphenol type epoxy resin, novolak type epoxy resin, triazine nucleus-containing epoxy resin, etc. The phenolic resin curing agent having the structure represented by the formula () has dicyclopentadiene in its main skeleton, and is a dicyclopentadiene-modified phenolic resin curing agent having flexibility and water repellency. The amount of this dicyclopentadiene-modified phenolic resin curing agent is:
By adjusting this, the solder stress resistance can be maximized. In order to achieve the effect of solder stress resistance, the dicyclopentadiene-modified phenolic resin curing agent shown by the formula () should be used in an amount of 40% by weight or more of the total amount of curing agent.
It is preferable to use 70% by weight or more. If it is less than 40% by weight, impact resistance and low water absorption will not improve.
Solder stress resistance is insufficient. Furthermore, R ₁ and R ₂ in the formula are preferably a hydrogen atom or a methyl group. If the number of carbon atoms in the alkyl group exceeds 2, the reactivity with the epoxy resin tends to decrease and the curability tends to deteriorate. It is necessary to use a value of n in the range of 0 to 5. When the value of n is greater than 5, fluidity decreases and moldability deteriorates. Examples of curing agents used in combination with the dicyclopentadiene-modified phenolic resin curing agent represented by formula () include phenol novolak resins, cresol novolak resins, and combinations of dicyclopentadiene-modified phenolic resins with phenol novolak and cresol novolak resins. Copolymers, paraxylene-modified phenol curing agents, acid anhydrides, amine curing agents, etc. can be used. In addition, the inorganic filler used in the present invention has a primary average particle size of 0.1 to 1 μm, a secondary average particle size of 2 to 60 μm, and an apparent density of 0.1 to 1 μm.
An inorganic filler containing 20 to 100% by weight of secondary agglomerated silica powder having a specific surface area of 1 to 10 m ² /g based on the total amount of inorganic filler is used. By adjusting the amount of secondary agglomerated silica powder used, the solder stress resistance can be maximized. In order to obtain the effect of solder stress resistance, it is preferable to use the secondary agglomerated silica powder in an amount of 20% by weight or more, more preferably 50% by weight or more of the total amount of inorganic filler. If it is less than 20% by weight, impact resistance will not improve and solder stress resistance will be insufficient. In addition, the average particle diameter of secondary agglomerated silica is 2 to 60μ
A range of m is preferred. If the secondary average particle diameter is less than 2 μm, impact resistance will decrease, and if it exceeds 60 μm, moldability will decrease, both of which are unfavorable. More preferably 2 to 10 μm considering fluidity.
is preferred. The primary average particle diameter is preferably in the range of 0.1 to 1 μm.
If the primary average particle diameter is less than 0.1 μm, fluidity will decrease, and if it exceeds 1 μm, impact resistance will decrease, both of which are not preferred. The apparent density is preferably in the range of 0.1 to 1 g/cc,
If it is less than 0.1 g/cc, fluidity will decrease, and if it exceeds 1 g/cc, impact resistance will decrease. Further, the specific surface area is preferably in the range of 1 to 10 m ² /g, more preferably 3 to 7 m ² /g. If the specific surface area is less than 1 m ² /g, the strength of the molded product will decrease and the solder stress resistance will decrease, and if it exceeds 10 m ² /g, the fluidity will decrease, both of which are unfavorable. Inorganic fillers that can be used in combination with secondary agglomerated silica powder include fused silica powder, fused spherical silica powder, porous silica powder, porous silica powder pulverized to the optimum particle size, alumina powder, and nitrided silica powder. Examples include general inorganic fillers such as silicon powder. The curing accelerator used in the present invention may be one that promotes the reaction between an epoxy group, a phenolic hydroxyl group, an acid anhydride, or an amino group of an amine curing agent.
A wide range of materials commonly used for sealing can be used, such as diazabicycloundecene (DBU), triphenylphosphine (TPP), dimethylbenzylamine (BDMA), and 2methylimidazole (2MZ). etc. may be used alone or in combination of two or more. The epoxy resin composition for sealing of the present invention contains an epoxy resin, a curing agent, an inorganic filler, and a curing accelerator as essential components. Various additives such as flame retardants such as antimony and hexabromobenzene, colorants such as carbon black and red iron, mold release agents such as natural wax and synthetic wax, and low stress additives such as silicone oil and rubber are appropriately blended. There is no problem. In addition, in order to produce the epoxy resin composition for sealing of the present invention as a molding material, the epoxy resin, curing agent, curing accelerator, filler, and other additives are sufficiently and uniformly mixed using a mixer or the like. After that, the mixture is further melt-kneaded using a hot roll or a kneader, cooled, and then crushed to obtain a molding material. These molding materials can be applied to sealing, covering, insulating, etc. electronic or electrical components. (Example) Example 1 12 parts by weight of trifunctional epoxy resin represented by the following composition formula ()

[Chemical] Orthocresol novolac epoxy resin
8 parts by weight Dicyclopentadiene-modified phenolic resin represented by the formula () 5 parts by weight

[Chemical] (N=1, 2, and the mixing ratio is n=1 to 2 and n=2 to 8.) Phenol novolac resin 5 parts by weight Secondary agglomerated silica powder ( Primary average particle diameter is 0.4μm,
Secondary average particle diameter is 3.5μm, apparent density is 0.7g/
cc, specific surface area 5 m ² /g) 35 parts by weight of fused silica powder 38.8 parts by weight triphenylphosphine 0.2 parts by weight Carbon black 0.5 parts by weight Carnauba wax 0.5 parts by weight were mixed at room temperature in a mixer, and heated to 70 to 100°C. The mixture was kneaded using a twin-screw roll, cooled, and then ground to obtain a molding material. The obtained molding material was made into a doublet, and a 6 x 6 mm chip was sealed in a 52p package for a solder crack test using a low-pressure transfer molding machine at 175°C, 70 kg/cm ² and 120 seconds. A 3 x 6 mm chip was sealed in a 16 pSOP package for moisture resistance testing. The following solder crack test and solder moisture resistance test were conducted on the sealed test device. Solder crack test: The sealed test element is
Processed for 72 hours in an environment of 85℃ and 85%RH,
After that, it was immersed in a solder bath at 250°C for 10 seconds, and the occurrence of external cracks was observed using a microscope. Solder moisture resistance test: 85 times the sealed test element
℃, 72hrs treatment under 85%RH environment,
After that, after immersing it in a soldering bath at 250℃ for 10 seconds, the pressure solder test (125℃, 100%
RH) to measure the oven failure of the circuit. The test results are shown in Table 1. Examples 2 to 7 Molding materials were obtained in the same manner as in Example 1 by blending according to the formulations in Table 1. A sealed molded article for testing was obtained using this molding material, and a solder crack test and a solder moisture resistance test were conducted in the same manner as in Example 1 using this molded article. The test results are shown in Table 1. Comparative Examples 1 to 8 Molding materials were obtained in the same manner as in Example 1 by blending according to the formulations in Table 1. Using this molded article, a solder crack test and a solder moisture resistance test were conducted in the same manner as in Example 1. The results are shown in Table 1.

【table】

[Table] (Effects of the invention) According to the present invention, it is possible to obtain an epoxy resin composition that has heat resistance and impact resistance that could not be obtained using conventional techniques. It has excellent solder crack resistance when subjected to heat stress, and also has good moisture resistance, so it is especially suitable for surface mount packages when used for sealing, covering, and insulating electronic and electrical components. Highly integrated large chip IC installed in
It is suitable for products that require high reliability.

Claims (1)

[Claims] 1 (A) Trifunctional epoxy having a structure represented by the following formula () (wherein R ₁ to _{R 11} are atoms or groups selected from hydrogen, halogen, and alkyl groups) Epoxy resin (B) containing 50 to 100% by weight based on the total amount of epoxy resin A dicyclopentadiene-modified phenol resin with a structure represented by the following formula () (in the formula, R ₁ and R ₂ are hydrogen, halogen, or an alkyl group) A curing agent (C) containing 40 to 100% by weight of (atoms or groups selected from among) based on the total amount of curing agent. , and the apparent density is 0.1~
Secondary agglomerated silica powder with a specific surface area of 1 g/cc and a specific surface area of 1 to 10 m ² /g is added to the total amount of inorganic filler.
An epoxy resin composition for semiconductor encapsulation that contains 100% by weight of an inorganic filler (D) and a curing accelerator.