JPH03103425A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in heat resistance and adherability, useful for fixed resistors, variable resistors, circuit substrates, etc., by dispersing electrically conductive powder in a resin composition comprising a specific synthetic resin and a specified amount of a bisphenol type epoxy resin. CONSTITUTION:The objective composition based on electrically conductive powder-resin can be obtained by dispersing (A) electrically conductive powder in (B) a resin composition prepared by incorporating (1) 100 pts.wt. of a synthetic resin having a structure of the formula [R1 is CH2, C(CH3)2 or alkylene; R2 and R3 are each methylol or a group formed by etherification of methylol with an alcohol and resol-type phenolic resin] with (2) 5-50 pts.wt. of a bisphenol-type phenolic resin <5000 in epoxy equivalent.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a fixed resistor. The present invention relates to a conductive resin composition based on a conductive powder/resin composition used in variable resistors and their circuit boards, etc., and aims to provide a conductive resin composition with particularly excellent heat resistance and adhesion. It is something.

Conventional technology Generally, conductive resin assemblies or materials used in electrode parts and resistor parts of resistors, circuit boards, etc. are made of conductive powder such as metal powder or carbon powder and phenol resin. It is used by applying a conductive paint made from a thermosetting resin binder such as melamine resin or epoxy resin and a solvent onto an insulating substrate by a method such as printing and baking it.

As a resin binder, resol type phenolic resin has traditionally been used because it has superior film strength and printability compared to Ike's resin, and also has good adhesion to phenolic resin laminates and epoxy resin laminates. Characteristics, heat resistance properties are 1
In order to improve these points, the basic structure ▲ has more reaction points and good curing performance (▲ is the structural formula CH2 + C(CH5)2 or apkylene, R2
rR5 is a methylol group, or a bisphenol type alkylphenol resin obtained by etherifying and modifying a methylol group with an Aμcol and a resol p-type phenol resin (the same applies hereinafter).

Problems to be Solved by the Invention However, in recent years, with the miniaturization and increase in density of electronic devices, reliability requirements for conductive resin composite materials have become stricter, and the basic structure has become more difficult for environmental resistance, especially heat resistance. The rate of change in resistance value was unsatisfactory when using a conductive resin made of a mixture of resin and a conductive resin in which, for example, carbon powder or the like was dispersed. Furthermore, when the conductive resin composition is formed on a ceramic substrate, which is a highly reliable substrate, there is a drawback that the adhesion is significantly deteriorated in a moisture-resistant environment.

The present invention maintains the excellent moisture resistance, film strength, printability, etc. of the synthetic resin consisting of the basic groove structure, while also improving heat resistance and adhesion, which were disadvantageous in the past. The purpose of this invention is to provide a conductive resin composition.

Means for Solving the Problems In order to solve the above problems, the present invention provides an epoxy 4315
The binder is a resin composition in which 6 to 50 parts by weight of a bisphenol type epoxy resin having a molecular weight of less than 0.000 is added to 100 parts by weight of a synthetic resin having the basic structure ▲, and conductive powder is dispersed therein.

Function: The conductive resin composition in which conductive powder is dispersed using the above-mentioned resin composite as a binder component is a conductive resin composition that uses only the synthetic resin with the basic structure ▲ without the addition of bisphenol type epoxy resin as the binder component. Compared to resin composites, environmental durability is improved without deterioration in film strength or printability, and in particular, heat resistance properties can be greatly improved. Furthermore, it is possible to prevent deterioration in adhesion to a ceramic substrate after being left in a humidity-resistant environment.

Example 1 mol of bisphenol ▲ and 4.6 mol of 38% hopmarin are reacted in an alkaline solution, and after neutralization and washing with water, a solution mainly consisting of methylolated bisphenol ▲ is produced. To 9 parts by weight of this solution, 1 part by weight of resol li phenol resin and 2 parts by weight of n-propyl alcohol/I/2 were added, and after complete dissolution, they were reacted to form a resin mainly composed of etherified and modified methylolated bisphenol ▲. obtain. Various amounts of bisphenol-type epoxy resins having various epoxy equivalents were added to this resin, and finally benzyl alcohol was added to adjust the solid content to 60% to produce various resin compositions.

Using these various resin compositions as resin binders, 100 parts by weight of resin solids, 30 parts by weight of acetylene black,
5 parts by weight of artificial graphite powder was added and milled using a three-roll mill to obtain a conductive paint. This coating material was applied onto an alumina substrate by screen printing and cured by baking at 216° C. for 30 minutes to obtain a conductive film. The resistance value of the film is 3KΩ/mouth ~ 6K
It was in the range of Ω/mouth. For comparison, a conductive film was obtained in the same manner using etherified modified methylolated bisphenol N▲ to which no bisphenol tv'fJl epoxy resin was added as a resin binder. The moisture resistance of these conductive films is 801:l:, 90~
After being left at 96%RH for 1,000 hours, the heat resistance is 85℃.
, the change in resistance value after being left for 1000 hours was measured. In addition, regarding adhesion, humidity-resistant environment (SO℃, 90-96%RH)
, 1,000 hours), a cross-cut test using cellophane tape was conducted.

These results are shown in Table 1.

(Leaving space below) As is clear from Table 1, when the amount of bisphenol-type epoxy resin added is as small as 6 parts by weight, the improvement in heat resistance, which is the objective of the present invention, is small, and the deterioration of adhesion in a humid environment is prevented. I can't. If the amount is more than 60 parts by weight, the compatibility with the phenol resin is considered to be poor, but foaming and surface unevenness of the coating film occur during coating, making it impossible to maintain good printing workability. The film became brittle, and the environmental resistance and heat resistance did not improve.
Furthermore, a significant deterioration in moisture resistance is observed. As for the epoxy equivalent of the added epoxy resin, it is thought that the compatibility with the phenol resin deteriorates even if the amount added is within the appropriate range when the epoxy equivalent becomes so large. The strength of the resulting film is also brittle, making it impossible to obtain a highly reliable conductive resin composition.

The conductive powder used inside is metal powder such as silver powder or gold powder,
It was confirmed that the material can be arbitrarily selected from carbon powder such as carbon plaque and graphite, and other conductive oxides, nitrides, and carbide powders.

Effects of the Invention As described above, the conductive resin composition of the present invention provides good heat resistance and adhesion without impairing the conventional excellent moisture resistance, film strength, and printing workability. It is extremely useful industrially as a highly reliable conductive sealing composition.

Claims (1)

[Claims] For 100 parts by weight of a synthetic resin having basic structure A, (A
is the structural formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and in the above formula A, R_1 is CH_2, C(CH_3)_2 or alkylene, R_2 and R_3 are methylol groups, or methylol groups are combined with alcohols and resol type phenolic resin. A conductive resin composition characterized in that conductive powder is dispersed in a resin composition to which 5 to 50 parts by weight of a bisphenol type epoxy resin having an epoxy equivalent of less than 5000 is added.