JPH02117935A - Casting resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, having excellent casting properties, capable of exhibiting good insulating characteristics and high electrical properties in potting, etc., of electronic parts by blending a thermosetting resin with specific spherical fine silica. CONSTITUTION:The objective composition obtained by blending a thermosetting resin (preferably epoxy resin) with spherical fine silica having <=2mum, preferably 0.2-1.5mum average particle diameter and <=20m<2>/g, preferably <=10m<2>/g specific surface area. Furthermore, the amount of the blended above-mentioned silica is preferably 40-200 pts.wt. based on 100 pts.wt. resin. An acid anhydride is preferably used as a curing agent for the epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a casting resin composition suitable for, for example, manufacturing precision parts having a fine structure.

[Prior Art] In order to improve the physical properties of thermosetting resins, especially their electrical properties, hardness, thermal properties, etc., various fillers have been added to thermosetting resins. Improves various properties. However, increasing the filler content ω leads to an increase in resin viscosity, and both workability and casting processability decrease.

In addition, the resin viscosity is also related to the filler particle size, and as the filler particle size becomes smaller, the surface area of the filler increases.
When kneading the thermosetting resin, the interaction with the resin increases, and in some cases, this may lead to an extreme increase in resin viscosity. Therefore, from the point of view of resin viscosity, the larger the filler particle size is, the more preferable it is, but a large filler is problematic because it inevitably inhibits the resin from flowing into fine parts smaller than its maximum particle size. In other words, the filler used in the shell with an average particle size of 5 mm or more usually has a particle size distribution, and on the large particle size side there are particles of several tens of microseconds. The inflow of resin into the minute parts of the ten-powder is obstructed. On the other hand, ultrafine silica with a particle diameter of several hundred angstroms or less, generally called Aerosil, has the problem of extremely increasing the viscosity of the resin.

By the way, JP-A No. 63-234.056 describes an epoxy resin composition for casting in which a large amount of alumina powder and a small amount of finely divided filler are added to an epoxy resin. Alumina powder is required, and the aim is to improve the adhesive strength with metal electrodes. Also, Unexamined Japanese Patent Publication No. 6
Publication No. 3-207.815@ describes a casting resin composition in which an epoxy resin is filled with two types of glass fibers with different fiber lengths. Therefore, it cannot be said to be suitable for manufacturing precision parts with fine structures.

[Problem to be Solved by the Invention 1] The purpose of the present invention is to provide a casting resin composition that not only has excellent electrical properties, thermal properties, hardness, etc., but also has excellent workability and precision workability. There is a particular thing.

[Means for Solving the Problems] That is, the present invention provides a thermosetting resin having an average particle size of 2IJ.
This is a casting resin composition containing spherical fine silica having a specific surface area of 20 rd/g or less.

In the present invention, any resin such as epoxy resin and phenol resin can be used as the thermosetting resin, but uboxy resin is preferable. . When using an epoxy resin, a curing agent and a curing accelerator are usually used, and the curing agent is preferably an acid anhydride such as phthalic anhydride.

In the present invention, spherical fine silica having a particle size of 2 particles or less, preferably 0.2 to 1.5p, and a specific surface area of 20 m/g or less, preferably 10 m/y or less, is used as a filler. If the particle size is larger than 2 mm, molding of fine parts will be inaccurate, and if the specific surface area is larger than 20 mm/g, the viscosity will become too high and workability will decrease. Further, if the shape is not spherical, the same problem will still occur. Such spherical fine silica is published in Journal or Co11oid and In
surface 5science 26°62~69(
1968) by hydrolysis of silicon alkoxides in ammoniacal alcohol solution.

The blending amount of this spherical fine silica in the thermosetting resin is 20 parts by weight or more, preferably 4 parts by weight, per 100 parts by weight of the resin.
It is about 0 to 200 parts by weight.

[Example 1] Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples.

Examples 1 and 2 and Comparative Examples 1 and 2 100 parts by weight of an epoxy resin (trade name Epicoat 828EL manufactured by Yuka Shell Epoxy ■) and the silica shown in Table 1 were thoroughly kneaded, and then 40 parts by weight of phthalic anhydride was mixed. part and catalytic amount of methylimidazole, and at 120°C 201U
The flowability of the resin into the space was investigated. In addition, after curing the same material to the shape of Sea 1, an arc resistance test was conducted according to JIS K 6911 method, and the durability time was investigated. Results first
Shown in the table.

As is clear from the results in Table 1, in Examples 1 and 2, both the flowability into the 20IIIR space and the arc resistance are good, and especially in Example 2, in which the silica content is increased, the arc resistance is good. was significantly superior. On the other hand, in Comparative Example 1, although the arc resistance was good, the flowability into the 20p space was poor, and in Comparative Example 2, the resin viscosity increased due to the large specific surface area of Aerosil.
It was difficult to increase the blending amount to 20 parts by weight or more, and perhaps because of the high viscosity, the pourability into the 20 IU space was poor, and the arc resistance was also poor.

Table 1 [Effects of the Invention] According to the present invention, it has good flowability even in a narrow space of about 20 μs, and it does not show good insulation properties, so it can be used for botting of electronic parts and for bonding. Shows uniform and high electrical properties during mold sealing.

Patent applicant: Nippon Steel Chemical Co., Ltd.

Claims (3)

[Claims] (1) A casting resin composition characterized in that a thermosetting resin is blended with spherical fine silica having an average particle size of 2 μm or less and a specific surface area of 20 m^2/g or less. (2) The casting resin composition according to claim 1, wherein the thermosetting resin is an epoxy resin. (3) Claim 2, wherein the curing agent for the epoxy resin is an acid anhydride.
The casting resin composition described.