JPH10340628A - Heat resistant conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable heat resistance and electric conductivity endurable to long-term use by arranging a barrier between Ni and Cu to prevent duffusion of Ni. SOLUTION: A Cr plating layer and an Ni plating layer are arranged in this order on an outer peripheral surface of a Cu conductor by electroplating or the like. This Cr plating layer operates as a barrier layer to mutual diffusion of Ni/Cu by entering an intermediate part of the Ni plating layer and the Cu conductor. Here, a thickness of the Cr plating layer is desirably set to 0.2 to 2 μm, and when it is thinner than this, an effect as a barrier becomes insufficent. The Ni plating layer also has the crack occurrence preventive action in the Cr plating layer besides the action as a heat resistant layer, and its thickness is desirable to be 1 to 5 μm. When this thickness is thinner than 1 μm, a crack preventive effect to the Cr plating layer becomes insufficent, and when its exceeds 5 μm, since electric conductivity of Ni itself is low, electric conductivity of a heat resistant conductor is reduced, and both are undesirable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant conductor for a heat-resistant insulated wire having both heat resistance and high conductivity.

[0002]

2. Description of the Related Art Conventionally, as a heat-resistant insulated wire, for example, a ceramic-coated wire or a glass winding has been known.
The ceramic coated wire is made by applying a ceramic coating to the surface of the heat-resistant conductor by a coating method such as a pyrolysis method or a sol-gel method, or a gas phase method such as a CVD method or a PVD method. It is made by winding fibers such as alumina.

[0003] Since a general metal Cu conductor reacts with oxygen in the air at a high temperature to form an oxide layer on its surface, which deteriorates the mechanical properties, the mechanical strength at such a high temperature decreases. Those with few are used as heat-resistant conductors. Specifically, metal conductors other than Cu, such as Ag wire, Ni wire, stainless steel (hereinafter referred to as SUS) wire, or Ni-plated Cu wire, Ni-clad Cu wire, SUS-clad Cu wire, etc. A conductor that forms a layer that blocks oxygen on the surface of Cu is
Exemplified as a heat-resistant conductor.

[0004] In recent years, these heat-resistant electric wires have been required to have more severe temperature conditions and electric characteristics than ever before, and have excellent heat resistance such that the decrease in mechanical strength is small even at a high temperature of 400 ° C and high electric conductivity. For a long period of time.

However, the above-mentioned conventional heat-resistant conductor does not sufficiently satisfy such requirements, and either heat resistance or conductivity is sacrificed according to the application. is there.

For example, among the conventional heat-resistant conductors described above, an Ag wire has a higher conductivity than a Cu wire,
When used for a long time at a high temperature, the material is softened and the mechanical strength is extremely reduced, so that there is a problem in heat resistance. Ni wire or SUS
Although the wire has excellent heat resistance even at a high temperature of about 400 ° C., an oxide layer is less likely to be formed on the surface, but the conductivity is much lower than that of the Cu wire, so it is not suitable for applications requiring high conductivity. Since the SUS clad Cu wire does not reach the inner Cu layer because oxygen in the atmosphere is blocked by the outermost SUS layer, there is no possibility that an oxidized layer is formed and the SUS clad Cu wire is conductive even in long-term use in a temperature range of about 400 ° C. The rate is hard to change.
However, it is difficult to reduce the thickness of the SUS layer to several tens μm or less due to the problem of workability.
By providing the US layer, the conductivity is lower than that of the Cu wire. Therefore, it is not very suitable for applications requiring high conductivity.

On the other hand, Ni-plated Cu wire or Ni-clad C
The u wire has a good heat resistance and a small decrease in electric conductivity compared to the Cu wire, and is generally used as a heat resistant conductor for heat resistant insulated wires.

[0008]

However, when Ni and Cu are in contact with each other, mutual diffusion is likely to occur, and when used at a temperature of 400 ° C. or more for a long time, N
The conductivity decreases due to the diffusion of i. Furthermore, if all of the Ni covering the surface of Cu diffuses into Cu, even if locally,
Comes into contact with the outside air and reacts with oxygen to react with CuO or Cu
An oxide layer such as ₂ O is formed, and in the worst case, the conductor is disconnected or the coating is peeled off. As described above, the Ni-plated Cu wire and the Ni-clad Cu wire have good heat resistance and conductivity, but have a drawback that they lack reliability enough to withstand long-term use.

As described above, the conventional heat-resistant conductor has advantages and disadvantages, and a material which satisfies all of the heat resistance, the electric conductivity, and the reliability for long-term use has not yet been obtained. The present invention has been made in view of the above circumstances to solve the problems of conventional heat-resistant conductors, and has as its object to provide a heat-resistant conductor that exhibits stable heat resistance and conductivity that can withstand long-term use. .

[0010]

The heat-resistant conductor according to the present invention comprises N
A barrier is provided between Ni and Cu to prevent the diffusion of i, and a Cr plating layer and a Ni plating layer are sequentially provided on the outer periphery of the Cu conductor.

In the present invention, the thickness of the Cr plating layer is
The thickness is preferably 0.2 to 2 μm, and if the thickness is less than 0.2 μm, the plating film tends to be relatively coarse and porous, and the effect as a barrier becomes insufficient, which is not preferable. On the other hand, the Cr plating layer is a very hard plating film, and if it is thicker than 2 μm, cracks easily occur at high temperatures, which is not preferable.

In the present invention, the Ni plating layer has a function of preventing the occurrence of cracks in the Cr plating layer in addition to the function as a heat-resistant layer, and preferably has a thickness of 1 to 5 μm. When the thickness of the Ni plating layer is thinner than 1 μm, the effect of preventing cracks on the Cr plating layer becomes insufficient. When the thickness exceeds 5 μm, the conductivity of the heat-resistant conductor decreases because the conductivity of Ni itself is low. Both are not preferred.

The heat-resistant conductor of the present invention can be easily obtained by sequentially providing a Cr plating layer and a Ni plating layer on the outer peripheral surface of a Cu conductor by electroplating or the like. According to the electroplating method, the plating thickness can be easily adjusted, and the resulting plating layer is porous but rich in flexibility because it does not form an alloy layer. When the Cr plating layer enters between the Ni plating layer and the Cu conductor, it functions as a barrier layer against Ni / Cu interdiffusion. In the present invention, the Cu conductor is not particularly limited, but the purity is 99.9%.
It is preferable to use one having the above high conductivity.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

Example 1 A 1 μm-thick Cr plating layer and a 2 μm-thick Ni plating layer were formed on a Cu wire having an outer diameter of 0.5 mm by electroplating to obtain a heat-resistant conductor of the present invention. When the conductivity was measured, a value of 98% was obtained when the Cu wire having the same outer diameter was taken as 100%.

Then, in order to examine the stability of the heat-resistant conductor at a high temperature, it was left in a thermostat at a temperature of 400 ° C. for 1000 hours, taken out, and measured for its conductivity. . Further, after being left in a constant temperature bath at 425 ° C. for 1000 hours, it was taken out and measured for the electrical conductivity. And 450 ° C
After leaving in a thermostat for 1000 hours, it was taken out and the conductivity was measured. As a result, no change was observed and it was 98%.

Example 2 A heat-resistant conductor of the present invention was obtained in the same manner as in Example 1 except that the thickness of the Cr plating layer was changed to 2 μm. Its conductivity is 97%
Met.

Then, the heat-resistant conductor was heated at a high temperature of 400 ° C., 425 ° C., and 450 ° C. in the same manner as in Example 1.
When the change in the electrical conductivity was examined by holding for 00 hours, the electrical conductivity did not change at each stage, and was 97%.

Example 3 The thickness of the Cr plating layer was 2 μm and the thickness of the Ni plating layer was 5 μm.
A heat-resistant conductor of the present invention was obtained in the same manner as in Example 1 except that the thickness was changed to μm. Its conductivity was 95%.

Then, the heat-resistant conductor was heated at a high temperature of 400 ° C., 425 ° C., and 450 ° C. in the same manner as in Example 1.
When the change in the electrical conductivity was examined by holding for 00 hours, the electrical conductivity did not change at each stage, and was 95%.

Comparative Example 1 The same procedure as in Example 1 was carried out except that neither Cr plating nor Ni plating was performed, and the electric conductivity of the example was set to 100%. When the stability at a high temperature was examined by the same method as that described above, the measurement was impossible due to oxidation by heating.

Comparative Example 2 A heat-resistant conductor was obtained in the same manner as in Example 1 except that the thickness of the Ni plating layer was changed to 3 μm without applying Cr plating. Its conductivity was 98%.

Then, the heat-resistant conductor was held at 400 ° C. for 1000 hours in the same manner as in Example 1 and the change in conductivity was examined. 10 minutes at 425 ° C
When holding for 00 hours, the measurement was terminated because Ni diffused into Cu.

Comparative Example 3 A heat-resistant conductor of the present invention was obtained in the same manner as in Example 1 except that the thickness of the Cr plating layer was 0.1 μm and the thickness of the Ni plating layer was 3 μm. Its conductivity was 98%.

When this heat-resistant conductor was held at 400 ° C. for 1,000 hours in the same manner as in Example 1, and the change in conductivity was examined, it was reduced to 82%. 10 minutes at 425 ° C
When holding for 00 hours, the measurement was terminated because Ni diffused into Cu.

Comparative Example 4 The thickness of the Cr plating layer was 5 μm, and the thickness of the Ni plating layer was 3
A heat-resistant conductor of the present invention was obtained in the same manner as in Example 1 except that the thickness was changed to μm. Its conductivity was 97%.

Then, the heat-resistant conductor was held at 400 ° C. for 1000 hours in the same manner as in Example 1 and the change in conductivity was examined. 10 minutes at 425 ° C
When holding for 00 hours, cracks were formed in the plating layer, and thus the measurement was terminated.

Comparative Example 5 The electrical conductivity of a heat-resistant conductor provided with a SUS clad having a thickness of 100 μm on a Cu wire having an outer diameter of 0.5 mm was measured and found to be as low as 50%.

Then, the heat-resistant conductor was heated at a high temperature of 400 ° C., 425 ° C., and 450 ° C. in the same manner as in Example 1.
When the change in the electrical conductivity was examined while being held for 00 hours, the electrical conductivity at each stage remained unchanged at 50%, and no change was observed.

The measurement results of these examples and comparative examples are shown in Table 1 below.

[0031]

[Table 1] As is evident from Table 1, the thickness of C
By providing the Ni plating layer after the formation of the r plating layer, the heat-resistant conductor of the present invention was able to stably exhibit properties of a heat-resistant temperature of 450 ° C. or more and a conductivity of 95% or more over a long period of time.

[0032]

As described above, according to the present invention,
A heat-resistant conductor exhibiting stable heat resistance and conductivity that can withstand long-term use can be provided. Therefore, it becomes possible to improve the heat resistance and the reliability in long-term use of a ceramic-coated wire, a glass winding, etc., which have conventionally depended on the heat resistance of the conductor.

[0033]

Claims (3)

[Claims] 1. A heat-resistant conductor comprising a Cu conductor and a Cr plating layer and a Ni plating layer sequentially provided on the outer periphery of the Cu conductor. 2. The thickness of the Cr plating layer is 0.2 to 2
2. The heat-resistant conductor according to claim 1, wherein said heat-resistant conductor has a thickness of μm. 3. The Ni plating layer has a thickness of 1 to 5 μm.
3. The heat-resistant conductor according to claim 2, wherein: