JPH05178965A - Resin composition for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain the title compsn. exhibiting a low stress and an excellent resistance to thermal shock and soldering heat by compounding an epoxy resin having a specified molecular structure and a specific rubber component as essential components. CONSTITUTION:An epoxy resin having a backbone of the formula (wherein R<1> to R<8> are each H, 1-4C alkyl, or halogen), an ethylene-propylene or ethylene- propylene-diene rubber, and a filter are compounded to obtain the title compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for encapsulating a semiconductor, which is (1) low in stress and excellent in thermal shock resistance, and (2) excellent in heat resistance in soldering in a soldering step during semiconductor mounting.

[0002]

2. Description of the Related Art As a method for sealing a semiconductor element, hermetic sealing using ceramics or the like or sealing with a thermosetting resin is known, but resin sealing is preferable because it is excellent in mass productivity and inexpensive. It is the mainstream.

This semiconductor encapsulating resin composition comprises, for example, cresol novolac type epoxy resin, bisphenol A type epoxy resin, aliphatic cyclic epoxy resin and other epoxy resins; phenol novolac resin and other curing agents; 3
Curing accelerators such as primary amines and imidazoles; inorganic fillers composed of inorganic fine powders such as silica and alumina; coupling agents such as silane coupling agents; release agents such as carnauba wax and stearic acid; carbon black, etc. It is composed of a colorant and the like.

In recent years, the degree of integration of semiconductor devices has remarkably advanced, the element size has increased, and the wiring has become finer. When such a semiconductor element is sealed with a thermosetting resin, the resin directly contacts the semiconductor element, so that strain stress occurs due to curing contraction during curing and thermal contraction during cooling, resulting in displacement of aluminum wiring or bonding wire. Failures due to strain stress such as cutting of the element and cracking of the element were observed.

Further, recently, in order to reduce the size and thickness of electronic parts, the semiconductor mounting method is shifting from the conventional pin insertion method to the surface mounting method. In this case, the semiconductor is processed at a high temperature such as being immersed in a solder bath during mounting, but a problem of solder heat resistance such as cracking of the sealing resin and deterioration of moisture resistance has been pointed out.

Of these, various studies have been made to solve the problem of strain stress reduction (reduction of stress).
Method of selecting the type of inorganic filler (Japanese Patent Publication No. 58-191
36, JP-A-60-202145), a method of making the stress and strain uniform by making the shape of the inorganic filler spherical or controlling the particle diameter (JP-A-60-171750, Japanese Patent Application Laid-Open). (Kaisho 60-17937) and the like.

[0007]

On the other hand, the examination of the problem of solder heat resistance has just begun, and after the semiconductor device is left under high temperature and high humidity, it is immersed in a solder bath to test for cracks (solder heat resistance). However, since this test is affected by many physical properties such as heat resistance and moisture resistance at the same time as strain stress, this test cannot be dealt with only by conventional crack generation preventing means.

As described above, due to high integration of semiconductor devices and changes in mounting method, a resin composition having smaller thermal stress than conventional encapsulating resin and excellent solder heat resistance during mounting is realized. Was desired.

[0009]

The above-mentioned problems are caused by the following formula (I)

[Chemical 2] (Wherein R ^{1 to} R ⁸ represent a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom) and a rubber selected from an ethylene propylene rubber or an ethylene propylene diene rubber. This can be solved by a resin composition for semiconductor encapsulation, which contains and as an essential component.

The structure of the present invention will be described in detail below.

The epoxy resin in the present invention has the following formula (I)

[Chemical 3] (However, it is important to use an epoxy resin having a skeleton represented by R ^{1 to} R ⁸ represents a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom.).

In the epoxy resin represented by the above formula (I), preferred examples of R ^{1 to} R ⁸ are hydrogen atom, methyl group, ethyl group, propyl group, i-propyl acid, butyl group and sec-butyl. Group, tert-butyl group, chlorine atom, bromine atom and the like.

Preferred specific examples of the epoxy resin in the present invention include 4,4'-bis (2,3-epoxypropoxy) biphenyl and 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, 4,4'-bis (2,3-epoxypropoxy)-
3,3 ', 5,5'-tetrabutylbiphenyl and the like can be mentioned.

The epoxy resin represented by the above formula (I) can be used in combination with other epoxy resins. Examples of the epoxy resin that can be used together include, for example, cresol novolac type epoxy resin, phenol novolac type epoxy resin, phenol novolac type epoxy resin, and the following formula (II).
Novolak type epoxy resin represented by

[Chemical 4] (However, n represents an integer of 0 or more.) Various novolac type epoxy resins synthesized from bisphenol A or resorcin, bisphenol A type epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic type Examples thereof include epoxy resin.

The epoxy resin represented by the above formula (I) must be contained in the total epoxy resin in an amount of usually 10 wt% or more, preferably 25 wt% or more, and an amount less than this amount is not sufficient.

In the present invention, the total epoxy resin content in the composition is usually 5 to 25 wt%.

The composition of the present invention usually contains a curing agent. The curing agent is not particularly limited as long as it reacts with the epoxy resin and is cured. For example, phenol novolac resin, cresol novolac resin, the following formula (I
Novolak resin represented by II)

[Chemical 5] (However, n represents an integer of 0 or more.) Various novolac resins synthesized from bisphenol A, resorcin, and the like, various polyhydric phenol compounds, acid anhydrides such as maleic anhydride, phthalic anhydride, and pyromellitic anhydride, Examples thereof include aromatic amines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone, but are not particularly limited.

In the present invention, the compounding amount of the curing agent in the composition is usually 2 to 15 wt%.

From the viewpoint of moisture resistance, it is preferable that the epoxy resin and the curing agent used in the present invention have sodium ions, chlorine ions, free acids, alkalis and impurities that may form them removed as much as possible. ..

The compounding ratio of the epoxy resin and the curing agent is such that the chemical equivalent ratio of the curing agent to the epoxy resin is 0.5 to 1.5, particularly 0.7 to 1.2 from the viewpoint of mechanical properties and heat resistance. It is preferably in the range.

In the present invention, ethylene propylene rubber (E) is used together with the epoxy resin represented by the above formula (I).
PM) or ethylene propylene diene rubber (EPD
It is important to include a rubber selected from M) as an essential component.

In particular, EPDM can further exhibit the effect of solder heat resistance when used in combination with a silicone rubber cross-linked product.

The amount of rubber compounded is usually 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the total amount of the composition. If the amount is small, the effect is small, and if the amount is large, the mechanical strength is significantly reduced. ..

Examples of the filler in the present invention include fused silica, crystalline silica, silicon nitride, silicon carbide, magnesium carbonate, calcium carbonate, alumina, clay, talc, calcium silicate, titanium oxide, asbestos, glass fiber, carbon fiber, Aramid fiber or the like can be used, and these can be used in combination of two or more kinds. Of these, fused silica is preferably used because it has a large effect of lowering the linear expansion coefficient and is effective in reducing stress. The fused silica can be used in a crushed form or in a spherical form, but it is particularly preferable to use fused silica as a filler and to make 40 wt% or more of the fused silica into crushed silica because it is effective for improving solder heat resistance.

The amount of filler here is 5 relative to the total composition.
0 to 90 wt%, preferably 60 to 80 wt%,
When the amount is small, the reliability is lowered, and when the amount is large, the formability is lowered.

In the present invention, a curing accelerator may be used to accelerate the curing reaction between the epoxy resin and the curing agent. The curing accelerator is not particularly limited as long as it accelerates the curing reaction. For example, imidazoles such as 2-methylimidazole and 2-phenylimidazole, benzyldimethylamine, amines such as 1,8-diazabicyclo (5,4,0) undecene-7 (abbreviated as DBU), triphenylphosphine, tetra Organic phosphorus compounds such as phenylphosphonium and tetraphenylborate are preferably used.

In the resin composition of the present invention, a release agent, a coloring agent, a coupling agent, a flame retardant and the like can be used if necessary.

The resin composition of the present invention is preferably melt-kneaded, and a known method can be used for melt-kneading. For example, Banbury mixer, kneader, roll,
Melt-kneading can be performed using a uniaxial or biaxial extruder, a co-kneader, or the like.

[0029]

According to the studies by the present inventors, the epoxy resin having the skeleton represented by the above formula (I) and EPM or EP
By using a resin composition containing a rubber selected from DM as an essential component, (1) low stress and excellent thermal shock resistance, and (2) excellent solder heat resistance during mounting, for semiconductor encapsulation. A resin composition can be realized.

The reason why the resin composition of the present invention exhibits the above-mentioned excellent properties is not clear, but it is EPM or EPD.
Due to M, the elastic modulus that is directly proportional to the strain stress has decreased, the epoxy resin having a biphenyl skeleton has reduced the crosslink density of the cured product, has improved toughness and moisture resistance, and that the biphenyl skeleton has heat resistance. It is thought to be due to the synergistic effect of.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Using the reagents shown in Table 1, the reagents were dry-blended with a mixer in the composition ratios shown in Table 2. This was heated and kneaded for 5 minutes using a mixing roll having a roll surface temperature of 110 ° C., then cooled and pulverized to obtain a resin composition.

Using this resin composition, a bending test piece (5 ″ × 1/2 ″ × 1/4 ″) and a simulated element were molded by molding under low pressure transfer molding at 175 ° C. for 4 minutes. 16 pin DIP (dual in-line package) and 44 pin FPP (flat plastic package) were obtained and post cured for 5 hours at 175 ° C. After the post cure, the physical properties of each resin composition were measured by the following physical property measuring methods.

Bending strength, elastic modulus: A using a bending test piece
It was measured according to the STM D-790 standard.

Thermal shock: 20 pieces of 16-pin DIP

[0036]

[Formula 1] Then, the number of cycles in which 10 cracks occurred was determined.

Solder heat resistance: 85 of 16 44-pin FPPs
After treatment at 85 ° C. and 85% RH for 168 hours, vapor phase reflow treatment was performed at 215 ° C. for 90 seconds, and the ratio of the number of cracked FPPs was calculated.

The results are shown in Table 2.

[0039]

[Table 1]

[Table 2] As shown in Examples 1 and 2, the resin composition of the present invention containing an epoxy resin having a biphenyl skeleton and a rubber selected from EPM or EPDM as essential components has a low flexural modulus and a low stress. It can be seen that the number of thermal shock cycles is large and the thermal shock resistance is excellent. Also,
Soldering heat resistance is also excellent with a small crack occurrence rate. Furthermore, as seen in Example 3, when silicone rubber is used in combination, thermal shock resistance and solder heat resistance are further improved. On the other hand, as seen in Comparative Examples 1 and 2, in the system containing no rubber, regardless of the presence or absence of the epoxy resin having the biphenyl skeleton, the flexural modulus was high, the stress was not lowered, and the thermal shock resistance was very high. bad. Also, the solder heat resistance is inferior. In addition, as seen in Comparative Example 3, the system in which only rubber is added has insufficient thermal shock resistance, and the solder heat resistance is rather lowered.

[0040]

According to the present invention, a resin composition having (1) low stress and excellent thermal shock resistance and (2) excellent solder heat resistance can be obtained. It is possible to provide an excellent resin composition for semiconductor encapsulation, which also solves the problem of resin cracks in the soldering process.

Claims (1)

[Claims] 1. A semiconductor encapsulating resin composition comprising an epoxy resin and a filler as main components, wherein the following formula (I): (Wherein R ^{1 to} R ⁸ represent a hydrogen atom, a C _{1 to} C ₄ lower alkyl group or a halogen atom) and a rubber selected from an ethylene propylene rubber or an ethylene propylene diene rubber. A resin composition for semiconductor encapsulation, which comprises and as an essential component.