JPS58104970A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To provide a paint having excellent corrosion resistance and migration resistance and suitable as a conductor of a printed circuit for electronic use, at a low cost, by mixing electrically conductive alloy powder treated with a specific solvent, a resin and a solvent. CONSTITUTION:Electrically conductive alloy powder composed of 10-70(wt)% Ag, 0.1-4% Si and remaining part of Cu, is immersed in a solution of 1,2,3- benzotriazole, separated from the solution, and dried. The treated powder is kneaded with a thermosetting resin (e.g. phenolic resin) and a solvent (e.g. ethyl carbitol) to obtain the objective composition. The composition is applied to a phenolic resin board, etc. by screen printing, etc., and cured with heat.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paint, and an object of the present invention is to provide a conductive paint that is inexpensive, has excellent conductivity, and has excellent migration resistance.

Conventionally, this type of conductive paint contains A as a conductive powder.
Noble metal powders such as u, Ag, and Pd have been used. Generally, Aq is used as conductive powder, and Ag paint is mixed with a thermosetting resin such as phenol resin, epoxy resin, or xylene resin, and a solvent such as ethyl calpitol, and screen printing is performed on a phenolic resin base plate. After being applied by a method such as the above, it is cured by heating and used as an electrode for variable resistors or as a printed wiring conductor for electronic circuits.

However, in recent years, as electronic devices have become smaller and larger in size, there has been a strong demand for smaller electronic components. The interaction between Aq or atmospheric moisture and a DC electric field causes a phenomenon in which gradient paint moves between electrodes, so-called migration, which causes short circuits and is often a major cause of trouble.

In order to compensate for these drawbacks of Ag paint, Aq-P
Conductive paints using D powder are commercially available, but they are still not perfect. In addition, conductive paint using Aq-Pd powder is extremely economical due to the fact that the price of Pd is extremely high compared to the price of Aq, and in recent years the price of precious metals, especially Aq, has skyrocketed. It is disadvantageous.

For the above-mentioned reasons, there is a desire for an inexpensive conductive paint with good migration resistance.

The present invention has been made in view of these points, and as a result of research and study on alloy powders whose main components are base metals, the inventors have developed a conductive powder using Ag-8i-Cu alloy powder as a conductive powder. It has been discovered that the paint has excellent migration resistance and satisfies a considerable level of conductivity.

Next, the configuration of the present invention will be explained in detail.

In the conductive paint according to the present invention, the conductive powder is an Ag-8i-Cu alloy powder containing at least A (Jl 0 to 70 weight factor and sio, 1 to 4 weight factor), and the balance being Cu. This is a conductive paint with special characteristics.

The conditions desired for the conductive powder of this type of resin-curing conductive paint are: a) conductivity; and b) resistance to thermal oxidation during heat curing.

Cu, which is one component of the alloy powder, is a metal with excellent electrical conductivity, but it cannot be said to have good thermal oxidation resistance and corrosion resistance. Therefore, due to the heating during the paint curing process, large oxide scales are often generated on the surface of the Cu powder, making it impossible to obtain sufficient electrical conductivity of the cured paint film. C like this
The disadvantages of U powder can be improved by adding Aq as an alloying element.

However, in terms of migration resistance, since Cu is less likely to cause migration, Ag-
Although Cu alloy powder tends to be improved compared to Aq powder, sufficient migration resistance cannot be obtained. Such drawbacks of the A g -Cu alloy powder can be greatly improved by further adding Si as an alloying element. It is not clear why alloying brings about such an improvement in migration resistance, but the fact that Si itself is difficult to cause migration and the fact that Si is an extremely base element compared to AqKW makes it difficult for Ag- It is presumed that the 3t-Cu alloy powder exhibits excellent migration resistance when used as a conductive paint. In addition, the addition of St as an alloying element
It also tends to improve the thermal oxidation resistance of alloy powder.

This is presumably because Si oxide prevents excessive oxidation of the alloy powder. Furthermore, due to the environmental resistance of Si itself, it is thought that the addition of Si provides corrosion resistance effects. However, if the amount of St added exceeds an appropriate amount, the conductivity of the alloy powder itself decreases, making it impossible to obtain desirable characteristics.

The alloy composition in which Ag-8i-Cu alloy powder can find the above-mentioned advantages as a conductive powder for conductive paint is Ag10.
~70 weight ratio, Sio, 1~4 weight ratio, balance Cu. The lower limit of the amount of Aq is determined by the heat oxidation resistance of the alloy powder, and the upper limit is determined by economic efficiency.

Further, the lower limit of the amount of Si is the minimum amount at which the effect of its addition can be found, and the upper limit is the amount restricted from the viewpoint of the conductivity of the alloy.

As described above, the conductive paint using Ag-5t-Cu alloy powder has practically sufficient performance in terms of conductivity and migration resistance. However, in general, the corrosion resistance of Cu and Cu-based alloys is not necessarily good in excessively corrosive environments, and the alloy powder of the present invention does not necessarily have satisfactory corrosion resistance when left in such an atmosphere. isn't it. However, these drawbacks can be overcome by a process in which alloy powder is immersed in a solution of 1,2,3-benzotriazole dissolved in an organic solvent such as acetone, and then the solution is separated and dried (hereinafter referred to as benzotriazole). This problem can be solved by triazole treatment (referred to as triazole treatment). It is presumed that the benzotriazole treatment described above forms a thin chelate compound film on the surface of the alloy powder, thereby exerting an anticorrosive effect.

According to the present invention, Ag-8t-Cu alloy powder, or
Ag-8t-Cu alloy powder treated with benzotriazole is kneaded with a thermosetting resin and a solvent to form a conductive paint. This conductive paint, like ordinary Aq paint, is applied to a phenol resin substrate by a method such as screen printing, and then heated and cured in the atmosphere.
Used as electrodes and conductive paths. Alloy grain size is 0.0
A range of 5 to 10 μm, preferably about 0.5 to 6 μm is good. If it exceeds 10μ, the printability during screen printing will deteriorate and the surface resistance after final heat curing will increase.

Next, examples will be described in detail in order to make the present invention more concrete.

Ag-8i-Cu alloy powder according to the present invention was produced as follows. Ag, S according to the alloy composition according to the present invention
Each material of i and Cu was weighed, and the total amount was 1 kg (Si
was added by Cu-3t master alloy).

This was dissolved in nitrogen gas and further pulverized by a molten metal spray method. Nitrogen gas was used as a spray medium, and the mixture was cooled in water. The particle size of the obtained alloy powder was about 6 to 100 μm, but this was powdered again using a mechanical crusher to have an average particle size of about 2 μm.

In some of the alloy powders obtained by the above method,
Benzotriazole treatment was performed. The be/citriazole treatment was carried out in the following manner. 1゜Dissolve 1 oq of 2.3-Hensotria/- in 100 mA' of acetone,
Ten pieces of alloy powder were immersed in this solution and thoroughly dispersed. After that, the alloy powder and the solution were separated, and the alloy powder was dried.

Alloy powder 2y obtained by the above method or alloy powder 2no treated with benzotriazole was kneaded with xylene resin IP and 0.2y of ethylcarpitol using a Hubermala.

For kneading with a Hoover Mala, the load is 100 lbs., 40 lbs.
Rotation was repeated four times.

The conductive paint prepared above was printed in a predetermined shape on a phenolic resin substrate using a screen printing method, and then cured by heating at 190''C in the atmosphere for 10 minutes.

The results of measuring the resistance value between both ends of the above printed pattern,
The following table shows the measurement results after being left in a constant temperature and humidity chamber at 40°, 096% RH for 120 hours. For reference, the table also shows the results when commercially available Ag powder and Cu powder were used as conductive powder.

(See Margin 2 below.) Also, as a test for migration resistance, the paint prepared above was screen printed with a pattern with a gap of 0.6 mm on a phenolic resin substrate, and after curing by heating, a pattern was printed in the gap. With 0.2ml of pure water dropped, a DC voltage of 3V was applied to the gap, and the current flowing through the gap was measured.The current values 2 hours after voltage application were both IQlt. It was grade A.

On the other hand, when a similar test was conducted on a paint in which Ag powder was applied as a conductive powder, a gradient shift was observed in the gap portion one minute after the voltage was applied, and a short circuit occurred. Therefore, it can be said that the conductive paint according to the present invention has extremely superior migration resistance compared to the conventional A9 paint.

As is clear from the above description and table, although the conductive paint according to the present invention is somewhat inferior in terms of conductivity and corrosion resistance compared to conventional Aq paint, it has sufficient characteristics for practical use. It has particularly excellent migration resistance, and economically, it can be produced at a much lower cost than conventional Aq paints, so it has great industrial value.

Claims (1)

[Claims] (1) consisting of conductive powder, resin, and solvent;
The conductive powder contains at least 10 to 70% Ag, Si0
．． A conductive paint characterized by being an alloy powder containing 1 to 4% by weight, with the remainder having a composition of Cu1). (2) Claim (1) characterized in that the alloy powder is obtained by immersing in a solution of 1j2,3-benzotriazole dissolved in an organic solvent, separating the solution and drying it. Conductive paint as described.