JP2843247B2 - Epoxy resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation which is excellent in resistance to soldering stress in surface mounting of semiconductor devices.

[0002]

2. Description of the Related Art Conventionally, electronic components such as diodes, transistors, and integrated circuits are sealed with a thermosetting resin. In particular, in the case of integrated circuits, an O-cresol novolac type epoxy resin having excellent heat resistance and moisture resistance is used. An epoxy resin cured with a novolak type phenol resin is used. However, in recent years, the chip has been gradually increased in size with the increase in the degree of integration of integrated circuits, and the package has been reduced in size from the conventional DIP type to a small and thin QFP, SOP, SOJ, TJ.
SOP, TQFP and PLCC are changing. That is, a large chip is sealed in a small and thin package, and cracks are generated due to stress, and problems such as a decrease in moisture resistance due to these cracks have been greatly highlighted. Especially in the soldering process,
Exposure to a high temperature of 00 ° C. or more causes a problem that the moisture resistance is deteriorated due to cracking of the package or separation of the resin and the chip. Development of a highly reliable sealing resin composition suitable for sealing these large chips has been desired. In order to analyze these problems, use of an epoxy compound represented by the formula (1) as an epoxy compound (Japanese Patent Application Laid-Open No. 61-259552) has been studied. By using the epoxy compound represented by the formula (1), the viscosity of the resin system can be reduced. Therefore, by blending a larger amount of fused silica powder, it is possible to reduce the thermal expansion and water absorption after molding the composition, thereby improving the resistance to water. Improvement of solder stress property was achieved. However, an increase in the modulus of elasticity due to the incorporation of a large amount of the fused silica powder is another adverse effect, and it is necessary to further improve the solder stress resistance.

[0003]

SUMMARY OF THE INVENTION The present invention solves such a problem by using an epoxy resin represented by the formula (1) as an epoxy compound and achieving a reduction in stress due to a decrease in elastic modulus as a curing agent. Another object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation in which the use of a phenolic resin curing agent represented by the formula (2) significantly improves the solder stress resistance of a semiconductor package during mounting on a substrate.

[0004]

The epoxy resin composition of the present invention comprises: (A) an epoxy compound represented by the following formula (1):

[0005]

Embedded image (Wherein R ₁ and R ₂ are the same or different atoms or groups selected from lower alkyl groups)

(B) a phenol resin curing agent represented by the following formula (2):

[0007]

Embedded image (Wherein R ₁ and R ₂ are the same or different atoms or groups selected from hydrogen and a lower alkyl group, n = 0 to
5)

[0008] 30 to 10 in the total phenolic resin curing agent
An epoxy resin composition for semiconductor encapsulation containing a curing agent containing 0% by weight, (C) an inorganic filler and (D) a curing accelerator as essential components. Solder stress resistance superior to conventional epoxy resin compositions It has.

The hydroquinone-based epoxy compound represented by the structure of the formula (1) is a bifunctional epoxy compound having two epoxy groups in one molecule, and has a lower melt viscosity than conventional polyfunctional epoxy resins, and transfer molding. Excellent fluidity at the time. Therefore, a large amount of the fused silica powder of the composition can be blended, an epoxy resin composition having low thermal expansion and low water absorption, and having excellent solder stress resistance can be obtained. By adjusting the amount of the hydroquinone-based epoxy compound used, the solder stress resistance can be maximized. In order to achieve the effect of resistance to solder stress, it is desirable to use the hydroquinone-based epoxy compound represented by the formula (1) in an amount of 30% by weight or more, preferably 50% by weight or more of the total epoxy resin amount. If it is less than 30% by weight, low thermal expansion and low water absorption cannot be obtained, and the solder stress resistance is insufficient. Further, R ₁ and R ₂ in the formula are preferably —C (CH ₃ ) ₃ groups among lower alkyl groups. R ₁ , R
_{If 2} is a small atomic group such as a hydrogen atom, the reactivity is high, and the flowability during transfer molding tends to decrease, and moldability tends to deteriorate.

Other epoxy resins used in combination with the hydroquinone-based epoxy compound represented by the formula (1) include all polymers and oligomers having an epoxy group. For example, trifunctional epoxy resins such as biphenyl type epoxy resin, bisphenol type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin, triphenolmethane type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, and triazine nucleus It refers to contained epoxy resin and the like. These may be used alone or as a mixture.

The curing agent represented by the molecular structure of the formula (2) is
It is obtained by a condensation reaction using a compound of phenol and para-xylenes. This use can lower the elastic modulus near the soldering temperature, improve the adhesion to the lead frame and the semiconductor chip, and achieve low water absorption, as compared with the use of a conventional phenol novolak resin curing agent or the like. Therefore, it is effective for preventing a reduction in stress generated due to a thermal shock at the time of soldering and a peeling failure with a semiconductor chip, a lead frame and the like accompanying the thermal shock. By adjusting the amount of the phenol resin curing agent of the formula (2), the solder crack resistance can be maximized. In order to obtain the effect of the solder stress resistance, it is desirable to use the phenolic resin curing agent represented by the formula (2) in an amount of 30% by weight or more, more preferably 50% by weight or more based on the total amount of the curing agent. If the content is less than 30% by weight, low elasticity, low water absorption, etc., and insufficient adhesion to the lead frame and semiconductor chip cannot be expected to improve solder stress resistance. Further, R _{1 to} R ₄ in the formula are preferably small atomic groups such as a hydrogen atom and a methyl group in order to obtain sufficient curability during transfer molding. The value of n is 0-5. n
Exceeds 5, the fluidity during transfer molding tends to decrease, and moldability tends to deteriorate.

The other phenolic resin used in combination with the phenolic resin curing agent represented by the formula (2) mainly refers to polymers and oligomers having mainly phenolic hydroxyl groups. For example, phenol novolak resin, cresol novolak resin, dicyclopentadiene-modified phenol resin, copolymer of dicyclopentadiene-modified phenol resin with phenol novolak and cresol novolak resin, triphenolmethane resin, condensation of phenol and cresol with salicylaldehyde Things can be used.

The inorganic filler used in the present invention includes fused silica powder, spherical silica powder, crystalline silica powder, secondary aggregated silica powder, porous silica powder, secondary aggregated silica powder or silica obtained by grinding porous silica powder. Examples thereof include powder, alumina, and the like, and particularly preferred are fused silica powder, spherical silica powder, and a mixture of fused silica powder and spherical silica powder. The amount of the inorganic filler is preferably 80 to 93% by weight in the total composition in view of the balance between solder stress resistance and moldability.

The curing accelerator used in the present invention may be any one which promotes the reaction between an epoxy group and a hydroxyl group, and those generally used as a sealing material can be widely used. 8-diazabicycloundecene, triphenylphosphine, benzyldimethylamine and 2-
Methylimidazole and the like may be used alone or in combination. The epoxy resin composition for encapsulation of the present invention contains an epoxy compound, a curing agent, an inorganic filler and a curing accelerator as essential components, but if necessary, a silane coupling agent, a brominated epoxy resin, and trioxide. Various additives such as flame retardants such as antimony and hexabromobenzene, coloring agents such as carbon black and red iron oxide, release agents such as natural wax and synthetic wax, and low stress additives such as silicone oil and rubber are appropriately blended. No problem. In addition, in order to manufacture the epoxy resin composition for sealing of the present invention as a molding material, an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and other additives are sufficiently uniformly mixed by a mixer or the like. Alternatively, the mixture may be melt-kneaded with a hot roll or a kneader, cooled and pulverized to obtain a molding material. These molding materials can be applied to sealing, coating, insulating and the like of electronic parts or electric parts.

Hereinafter, the present invention will be described specifically with reference to Examples.

【Example】

 Example 1 The following composition: 2.6 parts by weight of an epoxy compound represented by the formula (3) (softening point: 138 ° C., epoxy equivalent: 184 g / eq)

[0016]

Embedded image

Orthocresol novolak type epoxy resin (softening point 55 ° C., epoxy equivalent 200 g / eq) 4.8 parts by weight Flexible phenol resin curing agent represented by the formula (4) (softening point 75 ° C., hydroxyl equivalent 175 g) / Eq) 1.6 parts by weight

[0018]

Embedded image (A mixture of n = 1 to 4, where n = 1 is 4 by weight ratio)
0, n = 2 = 30, n = 3 = 20, n = 4 = 10).

Phenol novolak resin curing agent (softening point 90 ° C., hydroxyl equivalent 105 g / eq) 3.0 parts by weight Fused silica powder 86.8 parts by weight Triphenylphosphine 0.2 parts by weight Carbon black 0.5 parts by weight Carnauba wax 0.5 parts by weight was mixed at room temperature with a mixer, kneaded at 70 to 100 ° C. with a biaxial roll, cooled, and pulverized to obtain a molding material. The obtained molding material is formed into a tablet, and a 6 × 6 mm chip is sealed in a 52p package for a solder crack test under a condition of 175 ° C., 70 kg / cm ² , and 120 seconds using a low-pressure transfer molding machine. A 3 × 6 mm chip was sealed in a 16 pSOP package for a sex test. The sealed test element was subjected to the following solder crack test and solder moisture resistance test.

Solder crack test: The sealed test element was subjected to 48 hours and 72 hours at 85 ° C. and 85% RH.
After the treatment, it was immersed in a solder bath at 260 ° C. for 10 seconds, and external cracks were observed with a microscope. Solder Moisture Resistance Test: Sealed test element was tested for 72 hours at 85 ° C. and 85% RH.
After performing the Hr treatment, and then immersing in a solder bath at 260 ° C. for 10 seconds, a pressure cooker test (125 ° C., 2.3 atm, 100% RH) was performed to measure the open failure of the circuit. Table 1 shows the test results. Examples 2 to 5 Compounded according to the formulation shown in Table 1, and a molding material was obtained in the same manner as in Example 1. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 1. Table 1 shows the test results. Comparative Examples 1 to 5 Compounded according to the formulation shown in Table 1, and a molding material was obtained in the same manner as in Example 1. A sealed molded product for a test was obtained from this molding material, and a solder crack test and a solder moisture resistance test were performed using this molded product in the same manner as in Example 1. Table 1 shows the test results.

[0021]

[Table 1]

[0022]

According to the present invention, an epoxy resin composition having solder stress resistance, which cannot be obtained by the prior art, can be obtained. When used for encapsulation, coating, insulation, etc. of electronic and electrical components, especially for highly integrated large chip ICs mounted on surface mount packages because of their excellent crack resistance and excellent moisture resistance This is suitable for products that require extremely high reliability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI H01L 23/31 (58) Fields investigated (Int.Cl. ⁶ , DB name) C08G 59/24 C08G 59/62 C08L 63/00 -63/10 H01L 23/29

Claims (1)

(57) [Claims] (A) an epoxy compound represented by the following formula (1): (R) wherein R ₁ and R ₂ are the same or different atoms or groups selected from lower alkyl groups in an amount of 30 to 100% by weight in the total epoxy resin amount; (B) an epoxy resin having the following formula (2) A phenolic resin curing agent represented by (Wherein R ₁ and R ₂ are the same or different atoms or groups selected from hydrogen and a lower alkyl group, n = 0 to
5) 30 to 100% by weight in the total phenolic resin curing agent
An epoxy resin composition for semiconductor encapsulation, comprising, as essential components, a curing agent containing (C) an inorganic filler and (D) a curing accelerator.