JPS62253675A - Electrically conductive coating - Google Patents

Abstract

PURPOSE:To obtain the titled inexpensive coating outstanding in terms of resistivity, with high adhesivity of the resultant coating film to copper foil surface, by dispersing metallic copper powder in a system comprising melamine resin, polyol and polyester resin. CONSTITUTION:The objective coating can be obtained by blending (A) 100pts.wt. of metallic copper powder, (B) 15-50pts.wt. of a resin blend made up of (i) 20-60wt% of melamine resin and (ii) 8.0-40wt% of polyol plus polyester resin and/or alkyd resin and (C) 1-8pts.wt. of a saturated or unsaturated fatty acid or a metal salt therefrom. This coating is outstanding in electrical conductivity of the resultant coating film and in adhesivity of said film to copper foil surface, forming jumper circuit serving as a by-pass of printed circuit, also being capable of additional correction of copper foil printed circuit board obtained by chemical etching process to enable said board to be effectively utilized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a conductive paint in which metallic copper powder is dispersed in a melamine resin, a polyol, a polyester resin, or/and an alkyd resin, and more specifically, A resist film is applied to the entire unconnected circuit part between the copper foil circuits of the printed circuit formed on the copper-clad laminated insulating substrate, and the copper foil circuits to be connected are connected from above the resist film. This invention relates to conductive paint that forms bypass jumper circuits using screen printing methods.

(Prior art) Conventionally, W4-clad laminated insulating substrates have been stacked as printed circuits for mounting ICs, MSISLSI, etc., but in order to form printed circuits from these substrates, photoreactive resin is placed on the copper-clad laminated insulating substrate. After coating, a mask is applied to form a predetermined conductive circuit by light irradiation, unreacted resin is removed, and then chemical etching is performed to dissolve and remove the fl foil layer to form a printed circuit.

In such a printed circuit, the conductive circuit is formed by a chemical etching method, and therefore, once the printed circuit is formed, it is difficult to make additional modifications to the conductive circuit. However, in reality, in order to make effective use of the obtained printed circuit board, or if necessary, a bypass jumper circuit is often provided on the printed circuit.

A method for forming this jumper circuit is to use an insulated wire for internal wiring, with the insulation coating on both ends peeled off to expose the conductor, and solder it to the copper foil surface of the required conductive circuit. However, this method requires a soldering process to provide the jumper circuit on a mass-produced printed circuit board, and the thickness of the board increases, making it difficult to make it compact.

As a way to improve this problem, conductive root paint (hereinafter referred to as
Taking advantage of the fact that silver paste (referred to as silver paste) has good adhesion to the copper foil surface, a resist film is applied to the entire unconnected circuit portion between the copper foil circuits of the obtained printed circuit, and after curing, the resist film is A bypass jumper circuit is formed between the copper foil circuits to be connected from above the film by screen printing using silver paste. However, although the silver paste has a specific resistance of to-'Ω·cm and has good conductivity, silver powder is expensive, and when a large amount is used, the material cost is a non-negligible problem.

(Problems to be Solved by the Invention) Recently, a specific resistance of 10-3 to 10' that can be substituted for silver paste has been developed.
-'A variety of inexpensive conductive copper paints (hereinafter referred to as copper pastes) of Ω 0111 class have been published, but these copper pastes use thermosetting phenolic resin as a binder, so copper There is a problem in that it has poor adhesion to the foil surface and cannot be used as a bypass jumper circuit for printed circuits.

The present invention aims to solve such technical problems, and provides a conductive paint containing metallic copper powder that has good adhesion to a copper foil surface, is inexpensive, and has excellent specific resistance. It's about doing.

(Means for Solving the Problems) The present inventors have completed extensive studies to solve the above problems, and the composition of the conductive paint is 100% by weight of metallic copper powder. 15 to 50 parts by weight of a resin mixture (resin mixture consisting of 20 to 60% by weight of melamine resin and 80 to 40% by weight of polyol and polyester resin or/and alkyd resin) and saturated fatty acid or unsaturated fatty acid or It is characterized by comprising 1 to 8 parts by weight of these metal salts.

Here, the metallic copper powder used in the present invention may be in any shape such as flake, dendritic, spherical, or irregular shape.
The particle size is preferably 100 μm or less, particularly 1 to 30 μm.
It is preferable to modify m.

Particles with a particle size of less than 1 μm are undesirable because they are easily oxidized and the conductivity of the resulting coating film decreases.

The amount of metallic copper powder used is always 100 parts by weight.

The melamine resin in the resin mixture is an alkylated melamine resin, and at least one selected from methylated melamine, butylated melamine resin, etc. is used. The melamine resin binds the metallic copper powder and other components in the conductive paint according to the present invention.

The amount of melamine resin in the resin mixture depends on the amount of polyol used as other binder and polyester resin or/and
and alkyd resin, it is used in a range of 20 to 60% by weight, preferably 30 to 50% by weight.

If the blending amount of the melamine resin is less than 20% by weight, the metallic copper powder cannot be sufficiently bound, and the three-dimensional network structure of the melamine resin becomes unstable, which significantly reduces the conductivity of the coating film, so it is preferable. do not have. On the other hand, when it exceeds 60% by weight, it is also not preferable because it significantly reduces the conductivity of the coating film.

The polyol in the resin mixture is a polyester polyol represented by the following chemical structural formula, and is crosslinked with the melamine resin.

The polyol used has a total hydroxyl value and acid value of 10.
It is 0 mg/g or more, preferably 130 B/g or more. If the sum of the hydroxyl value and acid value is less than 100 B/g, the conductivity will be lost, which is not preferable.

The blending amount of the polyol in the resin mixture is in the range of 50 to 95% by weight, preferably 60 to 90% by weight in blending the polyol with the polyester resin or/and alkyd resin.

If the amount of polyol is less than 50% by weight, the conductivity of the coating film will not be good, and if it exceeds 95% by weight, good adhesion of the coating film will not be obtained.

The polyester resin and/or alkyd resin in the resin mixture has a moderating or suppressing effect on the condensation reaction between the melamine resin and the polyol, and serves as a vehicle to improve the properties of the coating film.

The average molecular weight of the polyester resin or alkyd resin used is preferably 5,000 or more, preferably 8,000 or more. It is not preferable to use a polymer having an average molecular weight of less than 5,000 because it significantly reduces the adhesion of the coating film.

The blending amount of polyester resin or/and alkyd resin in the resin mixture is 5 to 50% in the blending amount of polyol and polyester resin or/and alkyd resin.
Used in a range of 10 to 40% by weight, preferably 10 to 40% by weight.
It is.

When the amount of polyester resin and/or alkyd resin is less than 5% by weight, the adhesion of the coating film is unfavorable, and when it exceeds 50% by weight, the conductivity of the coating film is significantly reduced, which is undesirable. .

Here, the blending amount of polyol and polyester resin or/and alkyd resin in the resin mixture is 80 to 40! when blended with melamine resin. f%, preferably 70 to 50% by weight.

Next, the resin mixture used in the present invention (melamine resin 20
~60% by weight and a resin mixture consisting of 80 to 40% by weight of polyol and polyester resin or/and alkyd resin), the blending amount is based on 100 parts by weight of metallic copper powder.
It is used in a range of 15 to 50 parts by weight, preferably 20 to 50 parts by weight.
It is 40 parts by weight.

The saturated fatty acid, unsaturated fatty acid, or metal salt thereof used in the present invention is a dispersant for dispersing metallic copper powder in a resin mixture, and the saturated fatty acid has 16 carbon atoms.
Palmitic acid, stearic acid, arachidic acid, etc. with ~20 carbon atoms, or unsaturated fatty acids with 16 to 18 carbon atoms, such as seamaric acid, oleic acid, lylunic acid, etc., and their metal salts with sodium, potassium, etc. , salts with metals such as copper, zinc, and aluminum.

The amount of the saturated fatty acid or unsaturated fatty acid or metal salt thereof is 1 to 1 to 100 parts by weight of metallic copper powder.
It is used in an amount of 8 parts by weight, preferably 2 to 6 parts by weight.

If the amount of the dispersant is less than 1 part by weight, it will take time to knead to finely disperse the metallic copper powder into the resin mixture, and if it exceeds 8 parts by weight, the conductivity of the coating film will be affected. This is not preferable because it lowers the temperature.

A conventional organic solvent can be appropriately used in the conductive paint according to the present invention in order to adjust the viscosity. For example, known solvents such as cellosolve acetate and butyl cellosolve acetate 1.

(Examples) Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples, but the present invention is not limited only to these Examples.

Dendritic metal copper powder with a particle size of 5 to 10 μm, dispersants of stearic acid, oleic acid, inic acid and olefinic acid, and resin mixtures of melamine resin, polyester polyol, polyester resin, and alkyd resin, respectively, were added to the first layer. The mixture was mixed in the proportions shown in the table (parts by weight), a small amount of butyl cellosolve acetate was added as a solvent, and the mixture was kneaded with a three-wheel roll for 20 minutes to prepare a lead-it paint.This was applied to glass epoxy resin by screen printing. Width 21111 on the board
Five conductive circuits with a thickness of 30±5 prns and a length of 1001 were formed, and the coating was cured by heating for 130 to 10 to 60 minutes, and the conductivity of the coating was measured.

On the other hand, after cleaning the copper foil surface of the copper-clad laminated insulating board, a screen printing method was used to print 50×50ms on the copper foil surface.
After forming a coating film and curing the coating film by heating in the same manner as above, parallel lines with an interval of 1111111 perpendicular to each other were drawn on the coating film in accordance with the base grain test of JIS K5400 (1979). When cuts were made in the shape of 100 squares in the substrate, peeling of the coating film from the copper foil surface was visually observed.

Table 1 shows the results of examining these characteristics. The electrical conductivity of a coating film is a value obtained by measuring the volume resistivity of a heat-cured coating film.

As can be seen from the results, in Examples 1 to 7, the specific compounded materials used in the present invention were appropriately combined, so properties such as the conductivity of the coating film and the adhesion between the copper foil surface and the coating film were improved. becomes good. Therefore, the conductive paint according to the present invention may be used to form a bypass jumper circuit on the printed circuit board, depending on the effective use or necessity of the copper-clad laminated printed circuit board.

However, looking at the comparative examples, Comparative Example 1 has a large amount of butylated melamine resin, polyester polyol, and polyester resin, so the conductivity of the coating film is significantly reduced and the adhesion of the coating film is also not favorable. In Comparative Example 2, the polyester polyol used had a low hydroxyl value, so no conductivity was obtained at all.

In Comparative Example 3, the average molecular weight of the alkyd resin used was 5.
000 or less, the adhesion of the coating film will not be favorable. Comparative Example 4 contains a large amount of metallic copper powder and contains no polyester resin or/and alkyd resin, so the conductivity of the coating film decreases and the adhesion of the coating film is also unfavorable.

(Effects of the Invention) As explained above, the conductive paint according to the present invention is less expensive than the paste and has favorable properties in terms of conductivity of the paint film and adhesion of the paint film to the surface of the copper foil. A resist film mask is applied to the entire unconnected circuit part between the printed circuits,
A bypass jumper circuit can be formed between the copper foil printed circuits to be connected from on the resist film by screen printing or the like, and the copper foil printed circuit board obtained by chemical etching can be additionally modified. The substrate can be effectively utilized and has high industrial utility value.

Claims (2)

[Claims] (1) Resin mixture (melamine resin 20-60% by weight, and polyol and polyester resin or/and alkyd resin 8.0-40% by weight per 100 parts by weight of metallic copper powder)
(resin mixture consisting of 15 to 50 parts by weight) and 1 to 10 parts by weight of saturated or unsaturated fatty acids or metal salts thereof
8 parts by weight of a conductive paint. (2) The blending of the polyol and the polyester resin or/and alkyd resin is as follows: (polyol)/(polyester resin or/and alkyd resin) = (95-50)/(5-50) The conductive paint according to claim 1, characterized in that: