JPS60155224A - Sealing resin composition - Google Patents

Abstract

PURPOSE:The titled composition having excellent moisture and thermal cycling resistance, a low stress and good molding workability, comprising a specified epoxy resin, a novolak phenolic resin, a polyvinyl acetal synthetic resin, and an inorganic filler. CONSTITUTION:At least one epoxy resin having at least two epoxy groups in the molecule is mixed with a novolak phenolic resin at a molar ratio of the epoxy groups of component A to the phenolic hydroxyl groups of component B of 0.1- 10. This mixture is melt-blended with 0.1-30wt% polyvinyl acetal resin of the formula (wherein R is H or alkyl and n>=1), 25-90wt% inorganic filler (e.g., silica powder of alumina) and, optionally, a mold release, flame retardant, colorant, silane coupling agent and cure accelerator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a resin composition for encapsulating electronic components that has excellent moisture resistance and low stress.

[Technical problems with the invention and its problems 1 Conventionally, electronic components such as diodes, transistors, and integrated circuits have been sealed using a thermosetting resin. This resin sealing is widely put into practical use because it is economically advantageous compared to hermetic sealing methods using glass, metal, or ceramic. Among thermosetting resin compositions, epoxy resin compositions are most commonly used as sealing resin compositions in terms of reliability and cost.

Epoxy resin compositions use curing agents such as acid anhydrides, aromatic amines, and novolac-type phenolic resins. Among these, epoxy resin compositions using novolac-type ethanol resin as a curing agent have excellent moldability and moisture resistance, are non-toxic, and are inexpensive compared to those using other curing agents. Widely used as a semiconductor encapsulation material. However, epoxy resin compositions using novolac type phenolic resin as a curing agent have the disadvantage that they shrink during molding and curing, stress is applied to semiconductor elements, and reliability is poor. When a molded article using such a resin composition is subjected to a partial cycle test, open bonding wires, resin cracks, and pellet cracks occur, resulting in the problem that the molded article cannot function as an electronic component.
For these reasons, it has been desired to develop a sealing resin composition that maintains the advantages of the conventional epoxy resin compositions and has low stress.

[Object of the invention] The object of the invention was made in view of the above circumstances, and
The object of the present invention is to provide a resin composition for sealing that has excellent moisture resistance and partial cycle resistance, and has low stress.

"Summary of the Invention" As a result of extensive research to achieve the above object, the present inventors have discovered that by blending a polyvinyl acetal synthetic resin having the general formula described below, the conventional sealing resin composition can be improved. It has been discovered that a resin composition for sealing can be obtained which has superior moisture resistance and thermal cycling properties, and has low stress compared to the conventional method.

That is, the present invention provides (A) an epoxy resin, (B) a novolac type phenolic resin, and (C) a polyvinyl aretal-based synthetic resin represented by the general formula (wherein R is a hydrogen atom or an alkyl group, and n is an integer of 1 or more. (D) An inorganic filler is an essential component, the polyvinyl acetal synthetic resin is 0.1 to 30% by weight based on the resin composition, and the inorganic filler is 25 to 90% by weight based on the resin composition. % of the sealing resin composition.

As long as the epoxy resin (A) used in the present invention is a compound having at least two epoxy groups in its molecule,
There are no particular restrictions on the molecular structure, molecular weight, etc., and a wide range of commonly used ones can be included. Examples include aromatic resins such as bisphenol type, alicyclic resins such as cyclohexane derivatives, and epoxy novolak resins represented by the following general formula.

(In the formula, R1 represents a hydrogen atom, a halogen atom, or an alkyl group, R2 represents a hydrogen atom or an alkyl group, and n represents an integer of 1 or more.) These epoxy resins may be used alone or in combination of two or more. used.

The (B) novolak type phenolic resin used in the present invention includes novolak type phenol resins obtained by reacting phenols such as phenol and alkylphenols with formaldehyde or paraformaldehyde, and modified resins thereof such as epoxidized or butylated novolacs. Examples include type phenolic resins. The blending ratio of the novolak type phenolic resin is determined by the molar ratio of the epoxy I (a) of the (A) epoxy resin and the phenolic water 11 (b) of the (B) novolac type phenol resin [(
a)/(b)] is required to be within the range of 0.1 to 10. If the molar ratio is less than 0.1 or more than 10, the moisture resistance, molding workability and electrical properties of the cured product will be poor (all of which are unfavorable). Therefore, it is limited within the above range.

Examples of the polyvinyl acetal synthetic resin (C) used in the present invention include polyvinyl formal, polyvinyl acetal, polyvinyl butyral, and the like. The blending ratio of the polyvinyl acetal synthetic resin needs to be 0.1 to 30% by weight based on the resin composition. If the proportion is less than 0.1% by weight, it will not be effective in low stress and partial cycle resistance, and if it exceeds 30% by weight, it will have low stress and poor moldability, making it unsuitable for practical use. Polygonyl acetal-based synthetic resins have good compatibility with epoxy resins and phenolic resins, and are thought to impart flexibility to the resin composition and relieve stress, resulting in low stress.

In addition, the (D) inorganic filler used in the present invention includes:
Silica powder, alumina, antimony trioxide, talc, calcium carbonate, titanium white, clay, asbestos,
Examples include mica, red iron oxide, glass fiber, carbon lli fiber, and silica powder and alumina are particularly preferred. The blending ratio of the inorganic filler needs to be 25 to 90% by weight of the resin composition. If the amount is less than 25% by weight, it has no effect on moisture resistance, heat resistance, mechanical properties and moldability, and if it exceeds 90% by weight, the bulk becomes large and moldability is poor, making it unsuitable for practical use.

The sealing resin composition of the present invention contains an epoxy resin, a novolak type phenol resin, a polygonyl acetal type synthetic resin, and an inorganic filler as essential components, but may optionally include natural waxes, synthetic waxes, synthetic waxes, etc. Metal salts of straight chain fatty acids, acid amides, esters, mold release agents such as paraffins, chlorinated paraffins, bromotoluene, hexabromobenzene.

Flame retardants such as antimony trioxide, colorants such as carbon black and red iron oxide, silane coupling agents, various curing accelerators, etc. can also be appropriately added and blended.

Typical methods for producing the sealing resin composition of the present invention as a molding material include epoxy resin, novolak phenol resin, polyvinyl acetal synthetic resin,
After mixing the inorganic filler and the raw material composition in a predetermined composition ratio sufficiently in a mixer, etc., it is further melted and mixed using hot rolls, or mixed using a kneader, etc., and then cooled. It can be solidified and pulverized to an appropriate size to be used as a molding material.

A molding material made of the encapsulating resin composition according to the present invention can be applied to encapsulating, covering, insulating, etc. electronic or electrical components.

[Effects of the Invention] The encapsulating resin composition of the present invention is a composition that has excellent moisture resistance and partial cycle, has low stress, and has good molding workability.
When used for sealing, covering, insulating, etc. electronic and electrical parts, sufficiently reliable products can be obtained.

[Examples of the Invention] The present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

In the Examples and Comparative Examples below, "%" means "% by weight".

Example 1 Cresol novolak epoxy resin (epoxy m2
15) 18%, novolak type phenolic resin (phenol equivalent: 107) 9%, polyvinyl formal 3%
, and 70% fused silica powder were mixed at room temperature, and further 9
After kneading and cooling at 0 to 95°C, the mixture was pulverized to obtain a molding material. The obtained molding material was transfer-injected into a mold heated to 170° C. and cured to obtain a molded article. This molded article was tested for various properties such as moisture resistance and stress, and the results are shown in Table 1.

Example 2 Cresol novolac epoxy resin (epoxy equivalent weight 21
5) 16%, novolac type phenolic resin (1.107% per phenol) 8%, polyvinyl acetal 6%
, and 70% of fused silica powder were mixed, kneaded and pulverized in the same manner as in Example 1 to obtain a molding material. Molded articles were then obtained in the same manner, and these molded articles were tested for various properties such as moisture resistance and stress in the same manner as in Example 1. The results are shown in Table 1.

Comparative example Cresol novolac epoxy resin (epoxy equivalent: 21
5) In the same manner as in the example, a molding material was obtained by adding 20%, 10% of novolak type phenol resin (phenol equivalent: 107), and 70% of silica powder. This molding material was used to make a molded article, and the various properties of the molded article were tested in the same manner as in the Examples, and the results are shown in Table 1.

Table 1 *1 The number of cracks is determined by embedding a 25x25x 3mm copper plate in the bottom of a 30x25x5mm molded product at -40°C.
The resin was placed in a constant temperature bath at +200°C for 30 minutes each, and cracks in the resin were investigated after 15 cycles.

*2 An electrical component having two aluminum wirings was transfer-molded using the sealing resin composition (molding fee) at 170°C for 3 minutes, and then cured at 180°C for 8 hours. Regarding the 100 sealed electrical components obtained in this way,
A moisture resistance test was conducted in high-pressure steam at 120° C., and the time required for 50% wire breakage (occurrence of defects) due to aluminum corrosion was evaluated.

*3 A commercially available strain gauge was adhered to the island portion of a DIP16 bin lead frame, and the strain was then measured at 180° C. for 8 hours.

As is clear from Table 1, the sealing 1F tree composition of the present invention has excellent moisture resistance and low stress.

Claims (1)

[Scope of Claims] 1 (A) Epoxy resin (B) Novolac type phenol resin (C) Polyvinyl acetal synthetic resin represented by the general formula (wherein R is a hydrogen atom or an alkyl group, and 0 is one or more (represents an integer) (D) An inorganic filler is an essential component, the polyvinyl acetal synthetic resin is 0.1 to 30% by weight based on the resin composition, and the inorganic filler is 25 to 30% by weight based on the resin composition. A sealing resin composition characterized by containing 90% by weight. 2 Molar ratio of the epoxy group (a) of the epoxy resin and the phenolic hydroxyl group (b) of the novolac type phenolic resin [
(a)/(b)] is within the range of 0.1 to 10, the sealing resin composition according to claim 1.