JPS6253035B2 - - Google Patents

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 Au, Ag, and Pd have been used as conductive powders in this type of conductive paint. Generally, Ag paint is mixed with a thermosetting resin such as phenolic resin, epoxy resin, or xylene resin, and a solvent such as ethyl carbitol using Ag as the conductive powder, and is screen printed on a phenolic resin substrate. After being applied by this method, it is cured by heating and used as electrodes for variable resistors and printed wiring conductors 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. The interaction between atmospheric moisture and the DC electric field causes a phenomenon in which Ag paint migrates between electrodes, so-called migration, resulting in a short circuit.
It is often a major cause of trouble. In order to compensate for such shortcomings of Ag paint,
Conductive paints using Ag-Pd powder are commercially available, but they are not yet perfect. Also, Ag―Pd
Conductive paint using powder is extremely disadvantageous in terms of economic efficiency in the recent situation where the price of Pd is extremely high compared to the price of Ag, and the price of precious metals, especially Ag, has skyrocketed in recent years. For the reasons mentioned above, there is a desire for an inexpensive conductive paint with good migration resistance. The present invention was 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-Sn-Cu alloy powder as 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. The conductive paint according to the present invention is characterized in that the conductive powder is an Ag-Sn-Cu alloy powder containing at least 10 to 70% by weight of Ag, 1 to 10% by weight of Sn, and the balance being Cu. It is sex paint. Desired conditions for the conductive powder of this type of resin-curing conductive paint include: a) electrical conductivity; and b) thermal oxidation resistance during heat curing. Cu, which is a component of alloy powder, is a metal with excellent electrical conductivity, but it cannot be said to have good heat resistance, oxidation resistance, and corrosion resistance. Therefore, a large amount of oxide scale is generated on the surface of the Cu powder, and sufficient conductivity of the cured paint film cannot be obtained. These drawbacks of Cu powder can be improved by adding Ag as an alloying element. However, from the point of view of migration resistance, since Cu is less likely to cause migration, Ag-Cu alloy powder is
Although it tends to be improved compared to powder, sufficient migration resistance cannot be obtained. like this
The drawbacks of Ag--Cu alloy powder can be greatly improved by adding Sn 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 Sn itself is difficult to cause migration.
The fact that Sn is an extremely base metal compared to Ag is thought to be the reason why the Ag--Sn--Cu alloy powder exhibits excellent migration resistance when used as a conductive paint. Furthermore, the addition of Sn as an alloying element also tends to improve the thermal oxidation resistance of Ag--Cu alloy powder. This is presumed to be due to the semiconducting properties of Sn oxide in terms of conductivity. Furthermore, due to the environmental resistance of Sn itself, the addition of Sn is thought to provide corrosion resistance effects. The alloy composition in which the Ag--Sn--Cu alloy powder can find the above-mentioned advantages is 10 to 70% by weight of Ag, 1 to 10% by weight of Sn, and the balance is Cu. The lower limit of the amount of Ag is determined by the thermal oxidation resistance of the alloy powder, and the upper limit is determined by economic efficiency. Further, the lower limit of the amount of Sn is a small amount at which the effect of its addition can be found, and the upper limit is an amount that is restricted from the viewpoint of alloy production. As described above, conductive paint using Ag-Sn-Cu alloy powder has good conductivity and migration resistance. However, generally
Just as the corrosion resistance of Cu and Cu-based alloys is not necessarily good in excessively corrosive environments, the alloy powder of the present invention also does not necessarily have satisfactory corrosion resistance when left in such an atmosphere. However, these drawbacks can be solved by immersing the alloy powder in a solution of 1,2,3-benzotriazole dissolved in an organic solvent such as acetone.
This problem can be solved by drying (hereinafter referred to as benzotriazole 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-Sn-Cu alloy powder or Ag-Sn-Cu alloy powder treated with benzotriazole
Cu alloy powder is kneaded with thermosetting resin and solvent to create conductive paint. This conductive paint is applied to a phenolic resin substrate by a method such as screen printing in the same way as regular Ag paint, and then
It is heated and hardened in the atmosphere and used as electrodes and conductive paths. The particle size of the alloy powder is in the range of 0.05 to 10μ, preferably about 0.5 to 5μ. When the thickness exceeds 10μ, printability during screen printing deteriorates, and sheet resistance after final heat curing increases. Next, examples will be described in detail in order to make the present invention more concrete. Ag--Sn--Cu alloy powder according to the present invention was produced as follows. In accordance with the composition according to the invention,
Each material of Ag, Sn, and Cu was weighed and the total amount was 1 kg. This was dissolved in nitrogen gas and further pulverized by a molten metal spray method. Nitrogen gas was used as the spray medium and cooled by cooling it in water. The particle size of the obtained alloy powder is about 5 to 100μ, but this is powdered again using a mechanical crusher, and the average particle size is about 2μ.
And so. A portion of the alloy powder obtained by the above method was treated with benzotriazole. The benzotriazole treatment was carried out in the following manner.
1,2,3-benzotriazole 10mg in acetone
The alloy powder was dissolved in 100 ml, and 10 g of the alloy powder was immersed in this solution and thoroughly dispersed. After this, the alloy powder was separated and dried. 2 g of the alloy powder obtained by the above method or 2 g of the benzotriazole-treated alloy powder was kneaded with 1 g of xylene resin and 0.2 g of ethyl carbitol using a Hubermala. Kneading with a Hubermala was carried out with a load of 100 pounds and 40 rotations 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. for 10 minutes in the atmosphere. Based on the results of measuring the resistance value between both ends of the above printed pattern, and furthermore,
The following table shows the results measured after being left for 120 hours. The table also includes commercially available Ag powder and Cu powder for reference.
The results are also shown when the powder is a conductive powder.

[Table] In addition, as a migration resistance test, the paint prepared above was screen printed in a pattern with a gap of 0.5 mm on a phenol resin substrate, and after curing by heating, 0.2 ml of pure water was dropped into the gap. In this state, a voltage of 3 V DC was applied to the gap and the current flowing through the gap was measured.
The current values after the elapse of time were about 10 μA in all cases. On the other hand, when a similar test was conducted on a paint using conductive Ag powder, Ag migration was observed in the gap 1 minute after voltage application, 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 Ag paint. As is clear from the above explanation and table, although the conductive paint according to the present invention is somewhat inferior in terms of conductivity and corrosion resistance compared to conventional Ag paint, it has sufficient characteristics for practical use. In particular, it has excellent migration resistance and can be economically produced at a much lower cost than conventional Ag paints, so it has great industrial value.

Claims (1)

[Claims] 1. A composite powder consisting of conductive powder, resin, and solvent, where the conductive powder contains at least 10 to 70% by weight of Ag, 1 to 10% by weight of Sn, and the balance is Cu. A conductive paint characterized by: 2. The alloy powder according to claim 1, characterized in that the alloy powder is giblets obtained by immersing in a solution of 1,2,3-benzotriazole dissolved in an organic solvent, separating it from the solution, and drying it. conductive paint.