JPS58101168A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To prepare an electrically conductive paint having excellent migration resistance as well as electrical conductivity, and useful as the conductor of a printed circuit for electronic part, etc., at a low cost, by using powder of a specific Ag-Al-Cu alloy as electrically conductive powder in combination with a resin and a solvent. CONSTITUTION:Powder of an alloy composed of 10-70wt% Ag, 0.1-10wt% Al and the remaining part of Cu is used as electrically conductive powder. The powder is preferably immersed in an organic solvent solution of 1,2,3-benzotriazole, and dried after separating the solution. The electrically conductive powder is kneaded together with e.g. a thermosetting resin and a solvent to obtain the objective paint.

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, noble metal powders such as MuU, MuG, and Pd have been used as conductive powders in this type of conductive paint. Generally, 5g of conductive powder is used, phenolic resin,
Ag paint, which is mixed with thermosetting resin such as epoxy resin or xylene resin and a solvent such as ethyl calpitol, is applied to a phenolic resin substrate by a method such as screen printing, and then heated and cured to produce variable resistors, etc. It has been used as an electrode for electronic circuits or as a printed wiring conductor for electronic circuits.

However, in recent years, as electronic devices have become smaller and thinner, there has been a strong demand for smaller electronic components. Interaction with a DC electric field causes a phenomenon in which Ag paint migrates between electrodes, so-called migration, which results in short circuits and is often a major cause of trouble.

In order to compensate for these drawbacks of Ag paint, Mug-P
Conductive paints using D powder are commercially available, but they are still not perfect. In addition, the price of Pd is extremely high compared to the price of Mug, and the price of precious metals, especially Mug, has been rapidly increasing in recent years. This is extremely disadvantageous in this respect.

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 component is base metal, the inventors have found that Mug-Mu-1-Cu alloy powder is used as conductive powder. It has been discovered that the conductive paint has excellent migration resistance and satisfies the electrical conductivity at a considerable level.

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

In the conductive paint according to the present invention, the conductive powder contains at least 10 to 7% by weight of Mug and 11 to 10% by weight of Mu1O.
Ag-mul-C with a composition of CU and the remainder CU
This is a conductive paint characterized by being made of U alloy powder.

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

Cu, which is a 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, heating in the paint curing process often generates a large amount of oxide scale on the surface of the Cu powder, making it impossible to obtain sufficient electrical conductivity of the cured paint film. This more C
The disadvantages of U powder can be improved by adding Ag as an alloying element. However, in terms of migration resistance, 5g-Cu alloy powder tends to be improved compared to mug powder because CU is less likely to cause migration, but sufficient migration resistance cannot be obtained. This disadvantage of the stiff Ag--Cu alloy powder can be greatly improved by further adding A/ as an alloying element. It is not clear why alloying brings about such an improvement in migration resistance, but it is important to note that Al itself is difficult to cause migration and that it is highly resistant to migration.
The fact that A is an extremely base metal compared to Ag
It is presumed that the g-mu1-ICu alloy powder exhibits excellent migration resistance when used as a conductive paint. Furthermore, the addition of A/ as an alloying element tends to improve the thermal oxidation resistance of the mug-Cu alloy powder. This is presumed to be because the mu-e oxide prevents excessive oxidation of the alloy powder.

Furthermore, it is thought that the addition of these substances will have an effect on corrosion resistance, depending on the environmental resistance of each person.

However, if the amount of mulch 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 Mug-kl-Cu alloy powder can find the above-mentioned advantages as a conductive powder for conductive paint is as follows:
Mug 10-70% by weight, Mulo 1-10% by weight.

The remaining Cu. The lower limit of the amount of magnesium is determined by the heat oxidation resistance of the alloy powder, and the upper limit is determined by economic efficiency. In addition, the lower limit of the amount of AJ is the minimum amount that can find the effect of its addition.
The upper limit is the amount limited by the electrical conductivity of the alloy powder.

As described above, the conductive paint using the Mu-4-Cu alloy powder can be found to have practically sufficient performance in terms of conductivity and migration resistance. However, in general, the corrosion resistance of Cu and Cu-based composites is not necessarily good in an excessively corrosive environment, and the alloy powder of the present invention does not necessarily have satisfactory corrosion resistance when left in such an atmosphere. It's not a thing. However, these drawbacks can be solved by a process (hereinafter referred to as benzotriazole) 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. (called processing). 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 anticorrosion effect.

According to the present invention, Mug-J-Cu alloy powder, or
The benzotriazole-treated Ag-1-Cu alloy powder is kneaded with a thermosetting resin and a solvent to form a conductive paint. This conductive paint is applied to a phenolic resin substrate or the like by a method such as screen printing in the same way as ordinary 5G paint, and then heated and cured in the atmosphere to be used as electrodes or conductive paths. The particle size of alloy powder is 0.05-1
A range of 0μ, preferably about 0.5 to 6μ is good. 10
If it exceeds μ, the printability during screen printing will deteriorate and the surface resistance after final heat curing will increase.

Next, examples will be described in detail to further embody the present invention.

Mug-mu 1-Cu alloy powder according to the present invention was produced as follows. Depending on the alloy composition according to the invention, Ag,
Each of the materials, Mul and Cu, was weighed to give a total weight of 1 kg. 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 give an average particle size of about 2 μm.

For some of the alloy powder obtained by the above method,
Benzotriazole treatment was performed. Benzo) IJ azole treatment was performed in the following procedure.

1.2.3-benzotriazole 1oIRg was dissolved in acetone 10011/, and alloy powder 10p was immersed in this solution and sufficiently dispersed. After that, the alloy powder and the solution were separated, and the alloy powder was dried.

The alloy powder 2y obtained by the above method or the alloy powder 2f treated with benzotriazole was kneaded with 'F silene m fat 1f and ethyl carpitol 0.29 using a Hubermala.

For kneading with a Hooper Mala, the load is 10 lbs.

40 rotations were 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 in the atmosphere for 190'010 minutes.

The results of measuring the resistance value between both ends of the above printed pattern,
Furthermore, the results of measurements after being left in a constant temperature and humidity chamber of 40'095 SRH for 120 hours are shown in the following table. For reference, the table also shows the results when commercially available mug powder and Cu powder were used as conductive powder.

In addition, as a migration resistance test, the paint prepared above was placed on a phenolic resin substrate with a gap of 0.5
After screen printing the fl pattern and curing it by heating, we applied a DC voltage of 3V to the gap and measured the current flowing through the gap for 1 hour with 0.2 liters of pure water dripped into the gap. The current values 1 minute after voltage application were about 10 μA in both cases. On the other hand, when we conducted a similar test on paint using mug powder as conductive powder, we found that
One minute after voltage application, migration of Ag was observed in the gap, causing a short circuit. Therefore, it can be said that the conductive paint according to the present invention has extremely superior migration resistance compared to conventional mug paint.

As is clear from the above description and table, the conductive paint according to the present invention has some disadvantages in terms of conductivity and corrosion resistance compared to conventional mug paint, but it can be put to practical use. It exhibits characteristics, particularly excellent migration resistance, and economically, it can be produced at a much lower cost than conventional mug paint, so it has great industrial value.

Claims (2)

[Claims] (1) Consisting of conductive powder, resin, and solvent, wherein the conductive powder contains at least 10 to 70% by weight of Ag and 1 to 1% of Aeo.
1. A conductive paint characterized by being an alloy powder containing 0% by weight of Cu and the remainder being Cu. (2) After immersing the alloy powder in a solution of 1,2,3-benzotriazole dissolved in an organic solvent,