JPH0577687B2 - - 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The DIP type has been replaced by small, thin flat packages that are surface mounted, such as SOP, SOJ, and PLCC.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 crosslinking density and improves heat resistance, 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 and a dicyclopentadiene-modified phenol resin as the curing agent, thereby significantly improving solder stress resistance. It is an object of the present invention to provide an excellent epoxy resin composition for encapsulating semiconductors. (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.) An epoxy resin containing 50 to 100% by weight based on the total amount of epoxy resin, and a curing agent. Dicyclopentadiene-modified phenolic resin curing agent with the structure shown by the following formula ()

A curing agent containing 40 to ₁₀₀ % by _weight of the total amount of curing agent is used. It has extremely superior solder stress resistance compared to conventional epoxy resin compositions. 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. Further, R ₁ , R ₂ , R ₄ to _{R 7} , R ₁₀ , and R ₁₁ in the formula are preferably hydrogen atoms, and 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 trifunctional 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. By adjusting the amount of phenol resin used, 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 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, and solder stress resistance will be 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 the curing agent used in combination with the dicyclopentadiene-modified phenolic resin curing agent represented by formula () include phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenolic resin, phenol novolak, and cresol novolak resin. Copolymers of, paraxylene-modified phenol curing agents, acid anhydrides, amine curing agents, etc. can be used. Inorganic fillers used in the present invention include fused silica powder, spherical silica powder, crystalline silica powder, secondary agglomerated silica powder, porous silica powder, silica powder obtained by crushing secondary agglomerated silica powder or porous silica powder, and alumina powder. Dissolved silica powder is particularly preferred. The curing accelerator used in the present invention may be one that promotes the reaction between the epoxy group and the phenolic hydroxyl group, and a wide variety of those commonly used in sealing materials can be used, such as diaza. Bicycloundecene (DBU), triphenylphosphine (TPP), dimethylbenzylamine (BDMA)
and 2-methylimidazole (2MZ) are 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 manufacture 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 Composition below Trifunctional epoxy resin represented by formula ()
12 parts by weight

[Chemical] Orthocresol novolac epoxy resin
8 parts by weight Dicyclopentadiene-modified phenolic resin represented by the formula () 6 parts by weight

[Chemical] (n = 1, 2, and the mixing ratio is n = 1: 2, n = 2: 8) Phenol novolak resin 5 parts by weight Fused silica powder 68.8 parts by weight 0.2 parts by weight of triphenylphosphine, 0.5 parts by weight of carbon black, and 0.5 parts by weight of carnauba wax were mixed at room temperature in a mixer, kneaded with a twin-screw roll at 70 to 100°C, cooled, and then pulverized 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 resistance test: The sealed test element was
After processing for 48 hours and 72 hours in an environment of 85% RH and 85% RH, the product 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: sealed test element at 85℃,
Processed for 48hrs and 72hrs in an 85%RH environment, then immersed in a 250℃ solder bath for 10 seconds, then subjected to a pressurization test (125℃, 100%RH)
We conducted a test to measure the oven failure of the circuit. The test results are shown in Table 1. Examples 2 to 5 Molding materials were obtained in the same manner as in Example 1 by blending according to the formulations in Table 1. A solder crack test and a solder moisture resistance test were conducted in the same manner as in Example 1 using molded articles sealed for testing with this molding material. The test results are shown in Table 1. Comparative Examples 1 to 4 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 results are shown in Table 1.

[Table] (Effects of the Invention) According to the present invention, it is possible to obtain an epoxy resin composition that has heat resistance, low water absorption, and impact resistance that could not be obtained using conventional techniques. It has excellent solder crack resistance when subjected to heat stress due to temperature changes, and also has good moisture resistance, so it is especially useful when used for sealing, coating, insulation, etc. of electronic and electrical components. It is suitable for highly integrated large-chip ICs mounted on surface mount packages 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 an atom or group selected from the following based on the total amount of curing agent (C) An inorganic filler (D) An epoxy resin for semiconductor encapsulation that contains a curing accelerator as an essential component. Composition.