JP3060709B2 - Method and apparatus for manufacturing electrical contact material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, industrial equipment,
The present invention relates to a method and an apparatus for manufacturing a material for electrical contacts used for electrical contacts such as wiring connection terminals, relays, and switches mounted on automobiles and the like.

[0002]

2. Description of the Related Art An electrical contact that is electrically connected to a conductive member by contact with the conductive member has a base material made of copper and a copper-based alloy such as brass. In order to improve the corrosion resistance and the contact characteristics, a film of a metal such as gold, nickel and tin is formed on the surface. Of these, tin (Sn)
In general, a tin film is formed on the surface of a base material by a so-called wet process (wet process) such as an electrolytic plating method, an electroless plating method, and a hot dipping method.

[0003]

In such an electrical contact, the base material constituent elements (Cu,
The problem is that Zn) diffuses into the tin film. In particular, when the use environment temperature is high and exceeds 100 ° C., the above-mentioned diffusion phenomenon appears remarkably. For example, copper of the base material diffuses to the tin film side, and an alloy is formed by copper and tin. This alloy of copper and tin has a high hardness, and deteriorates adhesion when contacting a conductive member to increase contact resistance. Further, when the zinc element of the base material is diffused, it deposits on the surface of the tin film to form zinc oxide having low conductivity on the surface of the tin film, and the contact characteristics are deteriorated, for example, the contact resistance is increased as described above. As described above, the conventional electrical contact is inferior in heat resistance. For example, diffusion occurs at the periphery of the engine of an automobile having a high use environment temperature, and the contact characteristics are deteriorated.

On the other hand, a technique has been developed in which a zinc diffusion barrier layer made of pure copper is formed between a base material and a tin film, and the diffusion of the constituent elements of the base material is suppressed by the barrier layer. However, also in this case, an alloy having high hardness similar to the above is formed due to the interdiffusion between copper of the barrier layer and tin of the tin film, and the contact characteristics are not deteriorated. In particular, when the alloying of pure copper and tin progresses and the alloy layer reaches the interface with the base material, the alloy layer promotes the diffusion of the zinc element in the base material, and the zinc element is abundantly deposited on the tin film surface. It precipitates and degrades the contact characteristics as described above.

<Analysis of Conventional Products> On the basis of a conventional example, an electrical contact having pure copper as a zinc diffusion barrier layer and an electrical contact having no barrier layer were formed, and a thermal aging test was performed on each of these electrical contacts. By analyzing the diffusion of the constituent elements of the base material by X-ray photoelectron spectroscopy (XPS), the following points were confirmed and assumed.

First, electrical contacts without a barrier layer include:
A tin oxide film is formed on the outermost surface of the tin film, and diffusion of zinc as a constituent element of the base material is suppressed by the tin oxide film,
The diffusion of zinc stops slightly inside the outermost surface of the tin film. This is considered to be because the tin oxide film has a dense structure, and the layer prevents the diffusion and deposition of zinc. Further, also in the electric contact having the barrier layer, a tin oxide film is formed on the outermost surface, and the growth of the alloy layer due to the interdiffusion between tin and pure copper is prevented by the tin oxide film. This is considered that the diffusion of copper is suppressed by the tin oxide film.

[0007]

In view of these points and the fact that tin oxide is an oxide having a high conductivity (10 ⁻⁴ Ωcm), a diffusion barrier is provided between the base material and the tin film. It is thought that the electrical contact with the tin oxide film interposed as a layer can suppress the diffusion of the base metal constituent element even at high temperature by the tin oxide film, but the tin oxide film and the tin film are adhered with sufficient strength In the state, how to achieve such a structure,
Conventionally, it did not exist.

The present invention has been made in view of the above viewpoints, and has an electric structure having a structure in which a tin oxide film is interposed between a base material and a tin film, and having excellent adhesion between the films. It is an object of the present invention to provide a method and an apparatus for manufacturing a material for electrical contacts that can form a material for contacts.

[0009]

According to the first aspect of the present invention,
In order to achieve the above object, a step of preparing a base material substantially made of copper or a copper-based alloy, a step of forming a tin oxide film by a dry process on the surface of the base material, and, on the tin oxide film, Forming a tin film by a dry process.

According to a second aspect of the present invention, there is provided a film forming apparatus for forming a tin film by depositing tin on a surface of a base material substantially made of copper or a copper-based alloy. An oxygen supply means connected to the film forming apparatus for supplying oxygen at the initial stage of the tin film formation to form a tin oxide film.

[0011]

According to the first aspect of the present invention, a tin oxide film is formed on a base material by a dry process, and a tin film is formed on the tin oxide film by a dry process. Therefore, it has a structure in which a tin oxide film is interposed between a base material and a tin film, and furthermore, each film is formed by a dry process, so that a material for electrical contact with excellent adhesion of each film can be formed. .

According to the second aspect of the present invention, there is provided a film forming apparatus for depositing tin on a base material by vapor deposition or spraying, and supplying oxygen at an initial stage of forming a tin film. Then, an oxygen supply means for forming a tin oxide film is provided, so that a tin film is formed on the base material via the tin oxide film, and the tin oxide film is interposed between the base material and the tin film. Each of the films has a mounted structure, and each film is formed by vapor deposition, so that it is possible to form a material for electrical contact with excellent adhesion of each film.

[0013]

【Example】

<First Embodiment> FIG. 1 is a structural view showing a sputtering apparatus to which an apparatus for manufacturing a material for electrical contacts according to a first embodiment of the present invention is applied. As shown in FIG. 1, in a chamber 1, an electrode (cathode) 2 for a target is disposed at an upper portion, and an electrode 3 for a base material is disposed at a lower portion. The electrode 3 is grounded, and a high-frequency voltage is applied to the target electrode 2 by the power supply 4. In this case, a DC voltage may be applied to the electrode 2. Further, an argon gas introducing means 5 for introducing argon (Ar) gas is connected to the chamber 1, and an oxygen gas introducing means (oxygen supplying means) 6 for introducing oxygen (O ₂ ) gas is connected to the chamber 1. Connected, and further connected to an evacuation unit 7 for evacuating the chamber 1.

Then, tin (Sn) 10 is set as a target on the electrode 2, and a base material 11 made of, for example, brass made of copper or a copper-based alloy is set on the electrode 3. In this state, the inside of the chamber 1 is evacuated to a high vacuum by the vacuum evacuation means 7, and argon gas and oxygen gas are introduced into the chamber 1 by the argon gas introduction means 5 and the oxygen gas introduction means 6. A high frequency voltage is applied between the three. Thereby, the target (10) and the base material 1
A plasma of an argon gas and an oxygen gas is generated between them, and argon ions in the plasma collide with the target 10 to strike out target particles (tin particles).
Further, the target particles and the oxygen gas plasma are
The tin oxide (Sn) reacts in the gas phase or on the surface of the base material.
O ₂ ) is formed, and the tin oxide is deposited on the upper surface of the base material 11.

Thus, a predetermined amount (0.2 μm or more) of tin oxide is deposited on the upper surface of the base material 11 to form a tin oxide film 12 as a diffusion barrier layer.

When the deposition of tin oxide is completed, the supply of oxygen gas by the oxygen gas introducing means 6 is stopped while the supply of argon gas is continued.

The tin particles beaten out by the argon gas plasma are deposited on the upper surface of the tin oxide film 12 to form a tin film 13.

As a result, as shown in FIG.
Is formed on the upper surface of the substrate with the tin film 13 formed with the tin oxide film 12 therebetween.

The material for electrical contact thus formed is:
It has a structure in which the tin oxide film 12 is interposed between the base material 11 and the tin film 13. Since the tin oxide film has a dense structure, the base material constituent element ( C
u, Zn, etc.) to the tin film 13 side is suppressed, and the heat resistance is excellent.

The tin oxide film 12 and the tin film 13
Is formed by a dry process such as a sputtering method.
In general, the film-forming (tin oxide film 12, tin film 13) particles can be formed in a small and small structure with a small particle size, and a large adhesion area of each of the films 12, 13 to the base material 11 or the like can be secured. For this reason,
The films 12 and 13 have excellent adhesiveness. For example, even if the material for electrical contact is subjected to plastic deformation during forming into a switch or a terminal, film peeling does not occur. Furthermore, since each of the films 12 and 13 can be formed in a dense structure, also in this respect, the diffusion of the constituent elements of the base material can be more reliably suppressed.

Further, since the tin oxide film 12 and the tin film 13 are continuously formed by introducing and stopping the oxygen gas,
The continuity of both films 12 and 13 is ensured, and the adhesion between both films 12 and 13 is excellent.

Further, since inexpensive tin is used as a coating material for the base material 11, the cost can be reduced.

<Second Embodiment> FIG. 3 shows an ion beam mixing apparatus to which an apparatus for manufacturing a material for electrical contacts according to a second embodiment of the present invention is applied. As shown in the figure,
In the chamber 21, a sample holder 22 for holding the base material 31 is disposed at an upper portion thereof, and a crucible 23 for an evaporation source is disposed at a lower portion. Further, the chamber 21 is provided with oxygen supply means 24. The oxygen supply means 24 includes an oxygen gas supply means 25 and an oxygen gas ion source 26. The oxygen gas supplied from the oxygen gas supply means 25 is ionized by the oxygen gas ion source 26 to The upper base material 31 is configured to be irradiated in a beam shape. Further, the chamber 21 is connected to an evacuation unit 27 for evacuating the inside thereof, and a heating unit (not shown) for heating the evaporation source in the crucible 23 and the base material 31 on the sample holder 22. ) Are provided.

Next, in this apparatus, a tin oxide film 32 as a diffusion barrier layer is formed on one side of a base material 31 as shown in FIG.
The case where two layers a and 32b are formed will be described.

First, a base material 31 made of, for example, brass made of copper or a copper-based alloy is set in the sample holder 22, and tin (Sn) is accommodated in the crucible 23 as an evaporation source. In this state, the chamber 21 is evacuated by the evacuation unit 27.
The inside is evacuated to a high vacuum, and the base material 31 and the evaporation source (tin) are heated by the respective heating means. Thereby, the tin of the evaporation source is evaporated, and the tin particles are converted into the base material 3.
1 is irradiated with oxygen gas ions from the oxygen supply means 24 to one side of the base material 31 while vapor deposition is performed on one side of the base material 3.
Reacting tin and oxygen on 1 to form tin oxide,
The tin oxide is deposited on one surface of the base material 31.

In this way, a predetermined amount (0.2 μm or more) of tin oxide is deposited on the base material 31 to form the first tin oxide film 32a.

When the deposition of tin oxide is completed, the irradiation of oxygen gas ions by the oxygen supply means 24 is stopped while the evaporation of tin continues.

Thus, the tin particles evaporated from the evaporation source are deposited on one surface of the base material 31 to form a tin film 33a.

Next, in the same manner as above, tin was added to the base material 31.
Irradiation of oxygen gas ions by the oxygen supply unit 24 is resumed while the second tin oxide film 32b having a thickness of 0.2 μm or more is formed on the tin film 33a.

Subsequently, the irradiation of oxygen gas ions is stopped, and the tin film 3 is formed on the second tin oxide film 32b in the same manner as described above.
3b is formed.

As shown in FIG. 4, the tin oxide films 32a and 32b for suppressing the diffusion of the constituent elements
A layered electrical contact material is formed.

In the electrical contact material formed in this way, the diffusion of the constituent elements of the base material is suppressed by the two layers of tin oxide films 32a and 32b. Even so, the diffusion of the constituent elements of the base material can be suppressed more reliably, and the heat resistance is further improved. In addition, each film 32
Since a, 33a, 32b, and 33b are formed by a dry process such as an ion beam mixing method, the adhesion is excellent, and the occurrence of film peeling or the like can be prevented. Further, by supplying / stopping the oxygen by the oxygen supply means 24, each film 32a,
Since the layers 33a, 32b, and 33b are formed continuously, continuity between the films is ensured.
a, 33a, 32b, 33b.

<Modification> In the above embodiment, the case where the tin oxide film is formed directly on the base material has been described. However, as shown in FIG. 5, pure copper is formed on the base material 51 made of brass by a wet process. Copper layer (zinc diffusion barrier layer) 54
May be formed, and a tin oxide film 52 and a tin film 53 may be formed on the copper layer 54 in the same manner as in the above embodiment.

In this electrical contact material, the diffusion of the zinc element in the base material 51 is suppressed by the barrier layer 54 and the tin oxide film 52, and the copper and tin films 53 of the barrier layer 54 are suppressed.
Is suppressed by the tin oxide film 52. Further, the copper layer 54 made of pure copper also has a function of preparing an underlying substrate, and by forming the copper layer 54,
The surface is flattened, and the adhesion of the tin oxide film 53 is further improved.

In the above embodiment, the case where one or two tin oxide films are formed has been described. However, three or more tin oxide films may be formed.

Although the tin oxide film and the tin film are formed by a dry process such as a sputtering method and an ion beam mixing method, other dry processes such as a vacuum deposition method and an ion plating method are used. vapor deposition, thermal CVD, plasma-enhanced CVD, more chemical vapor deposition method such as light CVD, it is also possible to form the tin oxide film and the tin layer.

Hereinafter, for reference, an experimental example regarding the heat resistance and the like of the electrical contact material formed based on the above-described embodiment will be shown.

<Experimental Example> A tin oxide film (SnO ₂ ) of 0.2 μm was formed on one surface of a base material made of brass (Cu, Zn) in the same manner as in the first embodiment, and further thereon. An electrical contact material was formed by forming a tin film on the substrate. And the contact resistance value with respect to the load of the contact material was measured. Further, after the electric contact material is heated at 200 ° C. for 24 hours, the contact resistance value with respect to the load is measured, and X
The element distribution in the contact material was measured by X-ray photoelectron spectroscopy (XPS). Figure 6 shows the change in contact resistance before heat treatment.
FIG. 7 shows a change in contact resistance after the heat treatment, and FIG. 8 shows a distribution of elements in the material by XPS. In this case, in the graphs of FIGS. 6 and 7, the load (gr) is plotted on the horizontal axis.
am), and the vertical axis indicates contact resistance (ohm). In the graph of FIG. 8, the horizontal axis indicates the etching time (minute) corresponding to the depth position from the surface, and the vertical axis indicates the abundance (%) of each element measured by XPS. Open squares indicate copper, solid black circles indicate zinc, x indicates tin, and white circles indicate oxygen.

As a reference example, a conventional method
That is, the surface of the base material made of brass was coated with a tin film by an electrolytic plating method to form an electrical contact material. Then, the change in contact resistance with respect to the load of the contact material was measured.
Further, after the electrical contact material was subjected to a heat treatment at 200 ° C. for 24 hours, a change in contact resistance with respect to a load was measured, and an element distribution in the material was measured by XPS. FIG. 9 shows the contact resistance change before the heat treatment, and FIG. 10 shows the contact resistance change after the heat treatment.
The element distribution by XPS is shown in the graph of FIG.

First, when comparing the change in contact resistance, the material for electric contact (FIGS. 6 and 7) according to the embodiment generally has a lower contact resistance value than the conventional material (FIGS. 9 and 10). It can be seen that the contact characteristics are excellent. further,
In the contact material of the example, almost no variation was recognized, whereas in the conventional contact material, much variation was recognized, indicating that the quality of the contact material of the example was stable.

Further, in the contact material according to the embodiment, the respective contact resistance values after the heat treatment (FIG. 7) hardly change compared with those before the heat treatment (FIG. 6), and they are excellent in heat resistance. I understand. On the other hand, in the conventional example, comparing each contact resistance value after the heat treatment (FIG. 10) with that before the heat treatment (FIG. 9),
It can be seen that the variation is large and high and the heat resistance is poor.

As for heat resistance, FIG. 8 and FIG.
Also from the element distribution of No. 1, it can be determined that the electrical contact materials of Examples are excellent.

That is, as shown in FIG. 8, in the electric contact material of the embodiment, the etching time is from the surface of the tin film of 0 minute to the boundary portion between the tin film and the base material at around 15 minutes, that is, in the tin film. Contains a large amount of a tin element (marked with x) and almost no copper element (open square) or zinc element (closed circle) as a base material constituent element. This is presumably because the diffusion of the constituent elements of the base material was suppressed, and the precipitation of the zinc element on the surface of the tin film and the formation of an alloy of copper and tin were both prevented. As described above, it can be seen that the electrical contact material of the example can suppress the diffusion of the base material constituent element which causes the deterioration of the contact characteristics even at a high temperature of 200 ° C., and is excellent in heat resistance.

On the other hand, in the conventional contact material shown in FIG. 11, first, the etching time is about 0 minute on the tin film surface.
It can be confirmed that the zinc element (solid circle) as a constituent element of the base material is already present together with oxygen (open circle). This is considered to be because zinc element diffused from the base material diffuses toward the tin film side and precipitates on the tin film surface to form zinc oxide having low conductivity. Further, conventionally, the etching time is zero.
It is confirmed that a large amount of the copper element (open squares) is present together with the tin element (marked by x) in the tin film and the boundary portion between the base film and the tin film at about 18 minutes to 18 minutes. This is considered to be due to the fact that a large amount of copper diffuses from the base material into the tin film, forming an alloy having high hardness with copper and tin. Thus, it can be seen that the conventional material for electric contacts has a remarkable diffusion of the base material constituent element which causes the deterioration of the contact characteristics at a high temperature, and is inferior in heat resistance.

In the contact materials according to the examples, the appearance was visually observed before and after the heat treatment. As a result, the tin oxide film and the tin film were not peeled off at all, and the adhesion of each film was excellent. Was confirmed.

[0046]

As described above, according to the method for producing an electrical contact material according to the first aspect, a tin oxide film is formed on a base material by a dry process, and the tin oxide film is formed on the tin oxide film by a dry process. Since a tin film is formed, it has a structure in which a tin oxide film is interposed between the base material and the tin film, and furthermore, each film is formed by a dry process, and an electric contact with excellent adhesion between the films is provided. The effect that the contact material can be formed is obtained.

According to the second aspect of the present invention, there is provided a film forming apparatus for depositing tin on a base material by vapor deposition or spraying, and supplying oxygen at an initial stage of forming a tin film. Then, an oxygen supply means for forming a tin oxide film is provided, so that a tin film is formed on the base material via the tin oxide film, and the tin oxide film is interposed between the base material and the tin film. This has the effect that a material for electrical contacts having a structure in which the films are mounted and in which each film is formed by vapor deposition and having excellent adhesion between the films can be formed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a sputtering apparatus to which an apparatus for manufacturing a material for electrical contacts according to a first embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part showing a material for an electric contact manufactured by the manufacturing apparatus of the first embodiment.

FIG. 3 is a configuration diagram illustrating an ion beam mixing apparatus to which an apparatus for manufacturing a material for electrical contacts according to a second embodiment of the present invention is applied.

FIG. 4 is an enlarged sectional view of a main part showing a material for an electric contact manufactured by the manufacturing apparatus of the second embodiment.

FIG. 5 is an enlarged sectional view of a main part showing a material for an electric contact according to a modification of the present invention.

FIG. 6 is a graph showing a change in contact resistance of a material for an electric contact before heat treatment based on an example.

FIG. 7 is a graph showing a change in contact resistance after heat treatment of an electrical contact material according to an example.

FIG. 8 shows X after heat treatment of the electrical contact material according to the embodiment.
It is a graph which shows the element distribution by PS.

FIG. 9 is a graph showing a change in contact resistance before heat treatment of a material for electrical contact based on a conventional example.

FIG. 10 is a graph showing a change in contact resistance of a conventional electrical contact material after heat treatment.

FIG. 11 is a graph showing the element distribution by XPS after heat treatment of the electrical contact material based on the conventional example.

[Explanation of symbols]

 6 Oxygen gas introduction means 11, 31, 51 Base material 12, 32a, 32b, 52 Tin oxide film 13, 33a, 33b, 53 Tin film 24 Oxygen supply means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H01H 1/04 H01H 1/04 E 11/04 11/04 F (58) Investigated field (Int.Cl. ⁷ , DB name) C23C 14/00-14/58 C23C 28/00 H01H 1/04 H01H 11/04

Claims (2)

(57) [Claims] A step of preparing a base material substantially made of copper or a copper-based alloy; a step of forming a tin oxide film on a surface of the base material by a dry process; and a dry process on the tin oxide film. Forming a tin film by using the method. 2. A film forming apparatus for forming a tin film by depositing tin on a surface of a base material substantially made of copper or a copper-based alloy; and a tin film forming apparatus connected to the film forming apparatus. An apparatus for producing an electrical contact material, comprising: oxygen supply means for supplying oxygen at an early stage of time to form a tin oxide film.