JPH01121319A - Epoxy resin composition for sealing semiconductor and resin-sealed type semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the title composition, having a low linear expansion coeffi cient and elastic modulus and excellent fluidity with hardly any generated thermal stress by blending a reaction product of an amino group-containing polydimethylsiloxane with an anhydrous acid as a modifying agent in an epoxy resin. CONSTITUTION:The aimed composition obtained by blending a reaction product of a polydimethylsiloxane having amino group with an anhydrous acid (e.g. itaconic anhydride) as a modifying agent in an epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an epoxy resin composition for semiconductor encapsulation which has a small coefficient of linear expansion, a small modulus of elasticity, generates little thermal stress, and has excellent fluidity.

[Conventional technology]

In order to reduce the thermal stress of epoxy resin compositions for semiconductor encapsulation, there are two methods: adding a filler with a small coefficient of linear expansion to reduce the coefficient of linear expansion, and adding a rubber component to reduce the modulus of elasticity. Two methods are known. However, if the amount of filler added is increased in order to reduce the coefficient of linear expansion, a problem arises in that the modulus of elasticity increases, and there is a limit to the amount of filler added. In addition, the elastic modulus can be reduced by adding a rubber component, but the rubber component may seep onto the surface of the molded product during molding, causing mold stains, etc., or the addition of a rubber component may cause sealing. The fluidity of the material decreased, resulting in poor moldability.

[Problem that the invention seeks to solve]

Epoxy resin compositions are currently widely used for semiconductor encapsulation because they generally have excellent dielectric properties, electrical properties such as volume resistivity, and mechanical properties such as bending strength and impact strength. But epoxy resin.

Since it is generally a hard resin, when it is used to seal a semiconductor device, it gives a large mechanical stress to the device. As a result, the element may not function properly, - a part of the element may be destroyed, or - cracks may occur in the passivation film formed on the surface of the element.

Alternatively, the wiring on the element may be cut or misaligned, causing a decrease in reliability. In addition, semiconductor devices are becoming larger as the degree of integration increases.

Wiring is becoming increasingly finer, denser, and multilayered. On the other hand, package dimensions are becoming smaller and thinner, and the encapsulation resin layer is becoming thinner and thinner.

Cracks tend to occur in the sealing resin layer due to mechanical stress. One of the causes of such mechanical stress is the difference in linear expansion coefficient between the semiconductor element and the sealing material, and the difference in shrinkage rate after molding. Semiconductor elements have very small linear expansion coefficients and contraction rates, but sealing materials have large values.The difference in linear expansion coefficient and contraction rate between the two is due to molding,
Aftercure or subsequent various thermal histories can impart large thermal stress to semiconductor elements, encapsulating materials, or other constituent materials.

Therefore, as the dimensions of semiconductor elements become larger and the thickness of encapsulating materials becomes increasingly thinner, reducing such thermal stress will become an extremely important issue in improving the reliability of semiconductors. ing.

What is the thermal stress applied to a resin-sealed semiconductor element?

It can be determined approximately according to the following formula.

ct = k ・Er ・(αr−αs)(Tg T
o) However, σ: Thermal stress k applied to the element: Constant Er: Elastic modulus of the sealing material αr: Linear expansion coefficient αS of the sealing material Linear expansion coefficient Tg of the two-semiconductor element: Glass transition temperature To of the sealing material :In order to reduce thermal stress at room temperature, there are methods to lower the glass transition temperature (Tz) of the sealing material, methods to reduce the linear expansion coefficient (αr) of the sealing material, and methods to reduce the elastic modulus (Er) of the sealing material.
) can be considered. However, the method of lowering the glass transition temperature of the encapsulating material cannot be applied to semiconductor encapsulating materials because it reduces the heat resistance and moisture resistance of the semiconductor and impairs reliability. A known method for reducing the coefficient of linear expansion is to add a specific inorganic filler with a small coefficient of linear expansion, but in an attempt to further reduce the coefficient of linear expansion, the amount of filler added is increased. This causes a problem that the fluidity decreases due to the increase in the viscosity of the sealing material, resulting in poor workability. Therefore, attempts have been made to reduce the increase in viscosity of the sealing material by using a spherical filler, but a problem arises in that the modulus of elasticity increases as the amount of filler added increases. Therefore, in order to suppress the increase in elastic modulus caused by such an increase in filler and further improve the effect of reducing thermal stress, rubber is added to the resin as a flexibility imparting agent such as butadiene-acrylonitrile copolymer or silicone polymer. Methods have been considered to reduce the elastic modulus of the sealing material by adding components. However, when such a flexibility imparting agent is added, there are problems in that during molding, the rubber component oozes out onto the surface of the molded product and adheres to the surface of the mold, and the fluidity of the sealing material is reduced.

In the future, as the degree of integration of semiconductor devices increases, these problems will become more important as thermal stress is further reduced.

This is an important issue.

In the present invention, regarding an epoxy resin composition particularly useful for semiconductor encapsulation, the glass transition temperature is the same as that of conventional epoxy resins, and the linear expansion coefficient is the same as that of conventional epoxy resins.

The object of the present invention is to provide an epoxy resin composition for semiconductor encapsulation that has a small elastic modulus, lowers thermal stress than conventional epoxy resin cured products, and has excellent moldability.

[Means for solving interlayer points]

It is believed that the above object can be achieved by increasing the amount of filler blended and further stably dispersing a flexibility imparting agent (hereinafter abbreviated as flexibilizing agent). Therefore, the present inventors investigated the relationship between various physical properties of cured products when flexibilizing agents having various functional groups and having various molecular weights were added to epoxy resin compositions for semiconductor encapsulation6. As a result, by adding silicone polymers with various functional groups to epoxy resin, the elastic modulus and fluidity of the encapsulant change significantly, and especially when silicone polymers have amino groups as functional groups and acid anhydrides. It has been found that the reactive type of the compound and the one added as a flexibilizing agent lower the elastic modulus of the molded product and provide excellent fluidity during molding.

When an amino-modified silicone polymer that does not react with acid anhydrides is used as a flexibilizing agent, the epoxy resin in the matrix reacts with the amino groups, shortening the melt viscosity and gelation time of the molding material. Liquidity will deteriorate. In addition, when a silicone polymer having hydroxyl or epoxy groups as functional groups is used, the elastic modulus of the molded product does not decrease much, and the flexibilizing agent seeps onto the surface of the molded product during molding, causing mold stains. It was found that the workability deteriorated significantly. Furthermore, the molecular weight of the amino-modified silicone polymer is 1
If the molecular weight is less than 000, gelation occurs due to reaction with an acid anhydride, making it difficult to use as a flexibilizing agent.The molecular weight of the amino-modified silicone polymer is preferably 1000 or more.

In addition, when a high molecular weight 7-mino-modified silicone polymer is used, the decrease in elastic modulus is not so large, and the molecular weight of the amino-modified silicone polymer is 1000 to 50.
,000 is particularly desirable.

The compounding amount of the reaction product of amino-modified silicone polymer and acid anhydride as a flexibilizing agent can be 2 to 40 parts by weight per 100 parts by weight of epoxy resin, but it is especially important for heat resistance and moisture resistance. 2 The range for good mechanical properties is 5 to
It is preferable to add 20 parts by weight.

The reaction between the amino-modified silicone polymer and the acid anhydride can be carried out by adding the acid anhydride directly into the amino-modified silicone polymer, or by dispersing the amino-modified silicone polymer in the resin in advance and then adding the acid anhydride to the amino-modified silicone polymer. The reaction may be carried out in the resin by adding an acid anhydride.

Furthermore, these reaction methods can be varied depending on the type of amino-modified silicone polymer and acid anhydride used. Furthermore, these silicone polymers can be blended simultaneously with other materials, and can also be used after being melt-mixed or pre-reacted with epoxy resins, curing agents, etc.

The acid anhydride used in the present invention is itaconic anhydride.

An acid anhydride having two or more functional groups that reacts with the amino group of the flexibilizing agent and also reacts with the resin of the matrix, such as citraconic anhydride and maleic anhydride, can be used. Epoxy resins include cresol novolac type epoxy resin and phenol novolac type epoxy resin.

Bisphenol A type epoxy resins, which are currently commonly used as molding materials for semiconductor encapsulation, are used, and novolac resins such as phenol novolac and cresol novolac are used as hardening agents.

The desired composition is prepared by using acid anhydrides such as pyromellitic anhydride and benzophenone anhydride, and further adding curing accelerators, fillers, coupling agents, coloring agents, flame retardants, mold release agents, etc. Obtainable.

This epoxy resin composition can be produced in exactly the same manner as conventional molding materials for semiconductor encapsulation, and can also be encapsulated in semiconductors in exactly the same manner. That is, each material is kneaded using twin-screw rolls or an extruder heated to 70°C to 100°C, and then heated to a mold temperature of 160°C using a transfer press.
℃～190℃.

Molding pressure 30-100)cgloo)c, curing time 30
It can be molded in seconds to 180 seconds.

[Effect]

By adding a reaction product of an amino-modified silicone polymer and an acid anhydride to an epoxy resin as a deforming agent, the elastic modulus of the molded product can be reduced and thermal stress can be reduced without impairing the fluidity of the molded material. Can be done. Here, the acid anhydride suppresses the reactivity of the amino group by reacting with the 7-mino group of the amino-modified silicone polymer and forming an imide.
Furthermore, another functional group of the acid anhydride reacts with the matrix, allowing the silicone polymer to be stably dispersed in the matrix as rubber particles. Therefore, the elastic modulus of the molded amount can be reduced without the silicone component seeping onto the surface of the molded product during molding, resulting in good molding workability and less thermal stress caused by various thermal histories. It becomes possible to improve reliability such as temperature cycle resistance, heat resistance, and moisture resistance.

〔Example〕

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

[Examples 1 to 6 and Comparative Examples 1 to 8] Using various silicone polymers and reactants shown in Table 1 as modifiers, epoxy resin compositions having the compositions shown in Table 2 were prepared.
The mixture was kneaded for about 10 minutes using twin-screw rolls heated to about 80°C.

Transfer molding was performed using the obtained composition, and 180'
After curing for 6 hours, spiral flow, flexural modulus, and glass transition temperature were measured. As a result, the spiral flow of the obtained cured product becomes shorter when an untreated amino-modified silicone polymer is added, and the fluidity of the molding material decreases, but these react with acid anhydrides. It was found that the liquidity could be significantly improved by letting the liquid flow.

Further, the elastic modulus of the cured product increases in the order of the reaction product of unreacted amino-modified silicone polymer hydroxyanhydride and silicone polymer, silicone polymer having hydroxyl group and epoxy group. Since the glass transition temperature hardly changes even when these modifiers are added, a reaction product of an acid anhydride and an amino-modified silicone polymer is suitable, considering the two points of composition and reduction of thermal stress. I understand that.

Furthermore, using these resin compositions, a semiconductor element having aluminum acid wires on the surface was sealed, and a temperature of -55°C/30+in.
The crack resistance of the sealing layer and the connection reliability of leads, gold wires, and aluminum wiring were evaluated in a thermal cycle test of 150° C./30 m1n (a case where the resistance value changed by 50% or more was determined to be defective).

The results of the crack resistance test are shown in Table 3, and the results of the connection reliability test are shown in Table 4. It can be seen that the developed semiconductor device has extremely good crack resistance in thermal cycle tests and wiring connection reliability.

Table 1 Table 3 Table 4 〔Effect of the invention〕

Claims (1)

[Scope of Claims] 1. An epoxy resin composition for semiconductor encapsulation, characterized in that a reactant of polydimethylsiloxane having an amino group and an acid anhydride is blended as a modifier in the epoxy resin. 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein a reaction between polydimethylsiloxane having an amino group and an acid anhydride is carried out in the resin. 3. A resin-sealed semiconductor device, characterized in that it is encapsulated with an epoxy resin composition containing a reactant of polydimethylsiloxane having an amino group as a modifier and an acid anhydride.