JPS6057168B2 - composite contact - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to composite contacts that are used with relatively low contact pressures.

Conventionally, contacts made of noble metals and alloys thereof are well known as switching contacts, and in particular, contacts made of platinum (platinum, rhodium, ruthenium, etc.) of Au (gold) are often used.

Au-based contacts of Au and Au alloys have relatively low melting points and hardnesses, which allows the contact loads to be heavy (e.g. 20
When used in the case of V, IA), welding and deformation are likely to occur due to the arc heat generated when the contacts open and close, and when the contacts are in contact with each other and energized, the contacts may stick to each other and open. It was easy to cause so-called adhesion failure, which made it impossible to use the adhesive. However, on the other hand, Au-based contacts have excellent contact resistance and atmosphere resistance, and therefore, when used under light loads, the contact resistance does not increase and is relatively stable even as the number of times the contact opens and closes increases. It was hot. In addition, platinum-based contacts have a high melting point and hardness, so they do not cause welding, deformation, or adhesion problems when used under heavy loads, but when used under light loads, the insulating polymer unique to platinum-based contacts A certain thin film-like so-called brown powder is generated, and as a result, the contact resistance increases as the number of times the contact is opened and closed, resulting in poor connection (mistakes).Also, the initial contact resistance is high (50 mΩ or more). The disadvantage, particularly when used with low contact pressures, is the high initial contact resistance, for example in contacts for relays, which is a source of noise and has been a problem. The first invention was made in view of the above-mentioned circumstances, and its purpose is to eliminate welding deformation and adhesion during opening and closing under heavy loads, which are the weak points of Au-based contacts, and to improve initial contact. Its purpose is to provide contacts with low resistance, stability, and long life.

The present inventor investigated various Au-based materials as materials for contacts used with relatively low contact pressure, such as relay contacts, and found that an AuCu alloy of Au and Cu (Cu0
．． It has been found that a contact material using AuCu-based materials dispersed with composite particles and cross-linkers (1 to 1% by mass) is excellent in contact opening and closing under relatively heavy loads (e.g., 20 V, 1 A). However, the composite particles are required to have the following properties. That is, (1) hardness is extremely high.

(2) It has a high melting point.

(3) Stable against various corrosive gases in the atmosphere.

(4) High oxidation resistance.

(5) Be conductive.

is required.

Therefore, the present inventors conducted research on composite particles with such characteristics and found that tungsten carbide (W
C) The first invention was completed by discovering that the particles had the above-mentioned characteristics and were mass-producible and inexpensive.
That is, the first invention is characterized in that the contact surface is an alloy layer formed by dispersing tungsten carbide particles in an AuCu alloy, and by dispersing WC particles in the AuCu alloy, the AuCu alloy is As a result, a high-performance composite contact was obtained that is free from welding, adhesion, and deformation when opening and closing contacts under heavy loads, which are the weak points of Au-based contacts.

The particle size of the WC particles is preferably 10μ or less, and the amount of eutectoid is preferably 30 to 50 V01% (volume %),
The thickness of the AuCu-WC alloy layer is preferably 1 to 15 μm. In that case, the effect will be noticeable, and the most preferable is the particle size of the WC particles of 1 μm, the eutectoid content of 40%, and the layer thickness of 3 to 15 μm. It was found to be 5μ. and AuCu-W
The AuCu alloy that is the base material of the C alloy layer will be described. Pure Au is very soft (Vickers hardness Hv8O)
~90), has weak mechanical strength, and even if composite particles are eutectoided in the compacted Au to strengthen the composite, the effect is weak and welding failure may occur when the contacts are opened and closed under heavy loads. I understood. However, to the extent that the contact resistance does not increase significantly. It was necessary to increase the hardness and mechanical strength by alloying Au. Therefore, the inventors
An AuCu alloy whose hardness reaches a Vickers hardness of approximately HV2OO was selected by alloying Cu with Au. Figure 1 shows that the WC particle size is 1μ, and the weight of CUL is %AuC.
The relationship between the eutectoid amount (VOl%) of WC particles of a composite contact and the contact life N (contact opening/closing circuit) at 20 V and 1 A when the u-WC alloy layer thickness is 3 μm is shown. The vertical axis shows the contact life N1 and the horizontal axis shows the eutectoid amount V. In the figure, the eutectoid amount of WC is 40V01%, which indicates the longest life and high performance. However, it turned out to be the most preferable. Next, AuCu-W
An example of a method for manufacturing a C alloy contact surface will be described. for example,
The ALlCU-WC contact surface layer is formed by a composite plating method in which AuCu alloy is electrodeposited on the contact base material and WC is eutectoid. That is, WC particles are mixed into a plating solution, stirred thoroughly, and then energized to perform plating. This composite plating method allows W to be added into the AuCu alloy.
C particles are uniformly dispersed. An AuCu-WC contact surface layer could be obtained. The second invention will be described.

As a result of further research, the inventors of the present invention found that by forming a pure Au layer on top of a contact surface layer of AuCu-WC alloy on the contact base material, which is the first invention, a light load (for example, 100 mV , 1 mA), it was discovered that the contact resistance could be stabilized even as the number of opening/closing operations progressed, and the second invention was completed.

That is, the second invention is characterized in that a pure Au layer is formed on the surface of an alloy contact surface layer made by dispersing tungsten carbide particles in an AuCu alloy.
By forming a pure Au layer on the WC alloy layer, it is possible to prevent Cu from forming in the AuCu-WC alloy layer when the contact is opened and closed, thereby stabilizing the contact resistance of the contact.

Next, the pure Au layer will be described in detail. If the thickness of the pure Au layer is too small, the above effect will be reduced, and if the thickness is too large, the Au in the pure Au layer will diffuse into the AuCu-WC alloy layer due to arc heat when opening and closing the contacts under heavy loads. , the Cu concentration on the contact surface is relatively lowered, and therefore welding is likely to occur, causing deterioration of the contact life, which poses a problem. For this reason, the inventors of the present invention have conducted various studies and found that the thickness of the pure Au layer is preferably 0.1 to 0.5 μm, and most preferably 0.2 to 0.3 μm. Next, the third and fourth inventions will be described.

In the first and second inventions described above, in order to plate the AuCu-WC alloy layer on the contact base material (generally Fe-based material),
The adhesion was relatively poor, and as a result of research, the present inventor found that by interposing a base material between the contact base material and the AuCu-WC alloy layer, the bonding between the two could be greatly improved. I found it.

However, this base is required to have the following properties.
That is, (1) good adhesion with the AUCU-WC layer.

(2) It has a high melting point (the base is made of AuCu due to arc heat)
- It is expected that the melting point will be lowered by alloying with the WC layer). (3) High thermal conductivity (to prevent welding)
. (4) High conductivity. (5) High adhesion to the contact base material.

(6) The diffusivity of the contact base material component (Fe) must be low so that the contact base material component (Fe) does not precipitate on the contact surface due to diffusion.

is required.

Therefore, as a result of further research on the base material having such characteristics, the present inventors developed a two-layer structure for the base material, and formed a Cu layer and a Ni layer as the base layer on the contact base material in order to form AuCu-WC. It was discovered that the alloy layer and the contact base material can be strongly bonded. In other words, the Ni layer has good adhesion to the AuCu-WC layer constituting the contact surface portion, has a high melting point, and can prevent welding of the contact, and has good adhesion to the AuCu-WC layer that constitutes the contact surface, and has a high melting point to prevent welding of the contact.
etc., the diffusion rate is small.

However, the Ni layer has poor adhesion to the contact base material. Therefore, a Cu layer having good adhesion to the Ni layer and the contact base material was interposed between the Ni layer and the contact base material to bond them together.
Since the Cu layer has good thermal and electrical conductivity, it contributes to improving the welding resistance of the contact. Furthermore, since the Ni layer has a low diffusion rate, it also suppresses the diffusion of the Cu layer. That is, this two-layer structure base has all the characteristics required of the base described above. Let's talk about the base in detail. If the thickness of the Ni layer and Cu layer constituting the base is small, the above effect will be reduced. On the other hand, if the thickness is large, the cost will increase, especially for N.
The problem with the i-layer is an increase in contact temperature due to an increase in conductor resistance and low thermal conductivity. As a result of various studies, the inventors of the present invention have found that the thickness of the Ni layer and the Cu layer is preferably 1 to 5 microns, and most preferably 3 microns. That is, as described above, in the third invention, the Cu layer, the U1 layer and the A layer are sequentially formed on the contact base material.
It is a composite contact in which a uCu-WC alloy contact surface layer is formed, and in the fourth invention, a Cu layer, a Si layer, and an A layer are sequentially formed on the contact base material.
This is a composite contact formed with a uCu-WC alloy layer and a pure Au layer.

The figure shows an enlarged cross-sectional view of an embodiment of the composite contact configured in this manner. FIG. 2 is an enlarged sectional view of the composite contact of the third invention, and FIG. 3 is an enlarged sectional view of the composite contact of the fourth invention. In Fig. 2, 1 is a contact base material made of Fe-based material, 2 is a Cu layer, 3 is a Ni layer, and 4 is a contact base material made of Fe-based material.
Layer 3 is the base layer, 5 is AuCu- which constitutes the contact surface layer.
This is a WC alloy layer. This AuCu-WC alloy layer 5 is made of A
It is constructed by dispersing WC particles 5b in a uCu alloy 5a. In Fig. 3, 6 is a pure Au layer;
It is formed on the WC alloy layer 5. The first, second,
Both the third and fourth inventions have a common feature in that they use an AuCu-WC alloy layer formed by dispersing WC particles in an AuCu alloy.

In summary, in the composite contact of the first invention, since the surface layer of the contact is an AuCu-WC alloy layer in which WC particles are dispersed in the AuCu alloy, welding between the contacts and adhesion problems occur when the contacts are opened and closed under heavy loads. In addition, since WC particles are conductive, dispersing WC particles in AuCu alloy does not increase the contact resistance, but it becomes almost the same as AuCu alloy, so the initial contact resistance is low and stable. and
Since the WC particles cause less wear, contact resistance remains low and stable even as the number of times the contact opens and closes increases.

Therefore, the contact has a long life. The composite contact of the second invention has a pure Au layer formed by flashing (thin layer) pure Au on the surface layer of the AuCu-WC alloy with good contact resistance. Even if the process progresses, carrion products are not formed, and the Cu in the AuCu-WC alloy layer is not distributed, making the contact resistance low and stable, which is effective in preventing contact failure. has.

Moreover, the composite contact of the second invention has all of the effects 7 of the first invention, and the contact resistance is stable even when the number of times the contact opens and closes increases during contact opening and closing from heavy loads to light loads. , high capacity and dry contacts can be obtained. The composite contact of the third invention has a Cu layer and a Ni layer interposed as a base between the AuCu-WC alloy layer and the contact base material, so the contact has a long life and the AuCu
The u-WC alloy layer is tightly fixed to the contact material, and the base material suppresses diffusion of the contact base material, thereby improving corrosion resistance.

The composite contact of the fourth invention includes a Cu layer and an S layer on the contact base material.
Since the i-layer, the AuCu-WC alloy layer, and pure AuW are formed, all of the effects of the first, second, and third inventions described above are obtained.

In other words, even when the contact opens and closes from heavy loads to light loads, the contact resistance remains low and stable even if the number of times the contact opens and closes increases, and problems such as welding, adhesion, and deformation do not occur, and the contact base material and AuCu - The WC alloy layer is tightly fixed, diffusion of the contact base material is suppressed, corrosion resistance is improved, and the life of the contact can be extremely extended. Next, an example will be explained.

(Example of the first invention) [Example 1] In order to increase the mechanical strength of Au, the AuCu-WC alloy layer is made by dissolving 1% by weight of Cu in Au and using this A
WC particles are eutectoid in a uCu alloy.

These were obtained by electrolytic deposition using a composite plating method. That is, using an AuCu alloy plating liquid (product name: Neutronex 240, manufactured by Nippon Electroplating Engineers), WC particles are mixed into the liquid, composite plating is performed, and the plating is applied onto the contact base material. AuCu-
A WC alloy layer was formed. The particle size of the WC particles is about 1μ, and they are very finely dispersed in the AuCu alloy.The amount of eutectoid is measured by the WC eutectoid amount measurement method described later. The eutectoid amount of WC particles in the AuCu alloy is controlled by increasing or decreasing the amount of WC particles mixed in, and
Layer thickness is controlled by plating time. did. The eutectoid amount of WC particles was about 27 1%, and the layer thickness was 3 microns. The compound plating conditions are as follows. Composite plating conditions Current density: 0.5 A/d bath temperature: 65°C Amount of WC particles mixed: 15 g/' Plating time: 1 powder or more The desired composite contact was obtained.

[Example 2] The eutectoid amount of WC particles was approximately 40V01% (WC
A composite contact was obtained in the same manner as in the example except that the amount of particles mixed in was 25y/f).

[Example 3] The eutectoid amount of WC particles was approximately 50V01% (WC particle mixed amount;
A composite contact was obtained in the same manner as in Example 1 except that the contact point was 35y/').

[Example 4] A composite contact was obtained in the same manner as in Example 2, except that the thickness of the AuCu-WC alloy layer was 1 μm (plating time: 4 minutes).

[Example 5] A composite contact was obtained in the same manner as in Example 2, except that the thickness of the AuCu alloy layer was 5 μm (plating time: 16” minutes).

(Example of the second invention) [Example 6] A pure Au layer with a layer thickness of 0.1μ was formed on the AuCu-WC alloy layer of the composite contact obtained in Example 2 by electrodeposition to achieve the objective. A composite contact point was obtained.

The layer thickness was controlled by the plating time. The plating solution and plating conditions are as follows. Plating liquid: Gold plating liquid (Product name: Neutronex 21 manufactured by Nippon Electroplating Engineers Co., Ltd.)
Plating conditions [:-:. Example 7 A composite contact was obtained in the same manner as in Example 6, except that the thickness of the pure Au layer was 0.2 μm (plating time: 5 times).

[Example 8] The thickness of the pure Au layer was 0.3μ (plating time;
A composite contact was obtained in the same manner as in Example 6, except that the contact point was changed to 1.

[Example 9] The thickness of the pure Au layer was 0.5μ (plating time:
A composite contact was obtained in the same manner as in Example 6 except that the heating time was 125 seconds).

(Example of the third invention) [Example 10] <Formation of Cu layer> A 1μ thick layer was formed on the contact base material (Fe material) by electrolytic deposition using the following plating bath composition and plating conditions. A Cu layer was formed.

Layer thickness was controlled by plating time. Bath composition...Copper sulfate; 220f1/e Sulfuric acid; 45g/
f Plating conditions: Bath temperature: 300C Electrolytic density: 3A/Dd Plating time: 2. Formation of Ni Layer with Disappearance> Next, a Ni layer with a thickness of 1 μm was formed on the Cu layer by electrolytic deposition using the following plating bath composition and plating conditions.

Layer thickness was controlled by plating time. Bath composition: Nickel sulfate; 270g/I? Nickel chloride;
60y/e Boric acid; 45y/E l,3,6 naphthalene sulfonic acid sodium; 3y Plating conditions: Bath temperature: 45°C Current density A/Dd PH: 4.5±2 Plating conditions: 1. Formation of confusing AuCu-WC alloy layer> On the U1 layer, an AuCu-WC alloy layer with a thickness of 3 μm and a WC eutectoid content of 40V01% was formed under the plating conditions of Example 1.

In the above manner, the desired composite contact point was obtained. [Example 11] The thickness of the Cu layer was 3 μ (plating time: 7.0 mm), N
A composite contact was obtained in the same manner as in Example 10, except that the thickness of the i-layer was 3 μm (plating time: 3 minutes).

[Example 12] The thickness of the Cu layer was 5μ (plating time: 12.5 minutes), and the thickness of the Ni
A composite contact was obtained in the same manner as in Example 10, except that the layer thickness was 5 μm (plating time: 7 layers).

(Example of the fourth invention) [Example 13] On the AuCu-WC alloy layer of the composite contact obtained in Example 10, a thick pure Au layer was deposited by electrolytic deposition under the plating conditions of Example 7. A pure Au layer with a thickness of 0.2 μm was formed to obtain the desired composite contact.

[Example 14] On the AuCu-WC alloy layer of the composite contact obtained in Example 11, a pure Au layer with a thickness of 0.2μ was deposited by electrolytic deposition under the conditions for plating the hardened Au layer in Example 7. The desired composite contact was obtained.

[Example 15] On the AuCu-WC alloy layer of the composite contact obtained in Example 12, a pure Au layer with a thickness of 0.2μ was deposited by electrolytic deposition under the conditions for plating the hardened Au layer in Example 7. The desired composite contact was obtained.

[Example 16] The eutectoid amount of WC particles in the AuCu-WC alloy layer was 27■o1
A composite contact was obtained in the same manner as in Example 14, except for the percentage.

[Example 17] A composite contact was obtained in the same manner as in Example 14, except that the amount of eutectoid WC particles in the AuCu-WC alloy layer was 50V01%.

[Example 18] A composite contact was obtained in the same manner as in Example 14, except that the thickness of the AuCu-WC alloy layer was 2 μm.

[Example 19] Example 1 except that the thickness of the AuCu-WC alloy layer was 5 μm.
A composite contact was obtained in the same manner as in 4.

[Example 20] A composite contact was obtained in the same manner as in Example 14, except that the thickness of the pure Au layer was 0.5 μm (plating time: 125 seconds).

[Example 20] A Cu layer with a thickness of 1 μm was formed on the contact base material under the conditions of Example 10.
Formed a Cu layer with a layer thickness of 3μ and a WC eutectoid content of 40■o1%.
An AuCu-WC alloy layer was formed on the Cu layer under the same conditions as the AuCu-WC alloy layer of Example 1 except for the layer thickness of 0.2μ, and the pure Au layer of Example 6 was used except for the layer thickness of 0.2μ. A pure Au layer was formed under the same conditions as in the above to obtain the desired composite contact.

Here, a method for measuring the eutectoid amount of WC particles in the AuCu-WC alloy layer will be described.

(WC eutectoid measurement method) After protective plating (N1) is applied to the composite contact, it is cut and its cross section is mirror-finished with emery paper and buff.

Then, the cross section of the obtained AuCu-WC alloy layer was enlarged using a metallurgical microscope, and the area ratio of the AuCu alloy part and the WC part was determined using a video analyzer to obtain the eutectoid amount of WC. The composite contacts obtained in the above examples were tested for contact life (heavy load, light load), adhesion, initial contact resistance, and adhesion between each plating layer.

1-contact life test The contact life was tested by dividing the load level into heavy load and light load.

<Heavy load> The load level is 20V, 1A, and the contact is opened and closed at a frequency of 2.8 times per second in the atmosphere, and the number of times the contact opens and closes when the contact resistance becomes 4Ω or more or when welding occurs. It showed the lifespan.

In this case, each test was conducted w times using 10 samples. The average contact life at that time is shown in the attached table. Note that the number of openings and closings ends after 1.5 million times, and 15 times indicates the maximum contact life. <Light load> Set the load level to 1007n. ■The contact is opened and closed at a frequency of 100 times per second under a load of 17n, A, and when the contact resistance during the opening and closing operation becomes 30Ω or more, it is detected as a contact failure.
The contact life was determined by the number of times the contact opened and closed when it occurred.

In this case, each test was conducted w times using 10 samples. The average contact life at that time is shown in the attached table. In addition, the number of opening and closing times is 50 million times, and 500 million times.
The number 00,000 times indicates that there were no contact failures, indicating the maximum contact life. Change in Contact Resistance> FIGS. 4 and 5 show the relationship between the number of times of contact opening/closing (N) and the contact resistance (R) in Example 14.

Fig. 4 shows a case where the load level is 100m. The graph at light load when V, 1 mV, Figure 5 shows the load level 20, A.
, 1V under heavy load. In the figure, the vertical axis is the contact resistance (R; mΩ), and the horizontal axis is the number of openings and closings (N
; times), and both axes are logarithmic. 2. Adhesive Test Contacts were set to ON state, current was applied, and adhesive performance was evaluated based on the time it took for the contacts to adhere to each other and become impossible to separate.

The results are shown in the attached table. In addition, the adhesion test was conducted for 50 seconds (
The end of H) and 500 hours indicates that there was no adhesion for 50 hours, indicating the maximum adhesion performance in the test.

3 Initial Contact Resistance Test The initial contact resistance of the contacts was measured. W samples were used for each, and the average was shown in the attached table.

4 Adhesion Test The adhesion test was conducted by conducting a bending test at 180'C and examining the state of peeling between each plated layer.

The test was conducted in Examples 13 to 20, and as a result, no delamination was observed in any of the Examples, and the results were good.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the eutectoid amount of WC particles and contact life in an embodiment of the present invention, FIG. 2 is an enlarged sectional view explaining the basic principle of an embodiment of the third invention, and FIG. 3 is an enlarged sectional view explaining the basic principle of an embodiment of the fourth invention, FIG. 4 is a diagram showing the change in contact resistance under light load in embodiment 14, and FIG.
The figure is a diagram showing the change in contact resistance under heavy load in Example 14. 1...Contact base material, 2...CU layer, 3.
...Ni layer, 4...Base, 5...
・AUCU-WC alloy layer, 5a...AuCu alloy, 5b...WC particles, 6...Pure A
U layer.

Claims (1)

[Scope of Claims] 1. A composite contact characterized in that the contact surface is an alloy layer formed by dispersing tungsten carbide particles in an AuCu alloy. 2. A composite contact in which the eutectoid amount of WC according to item 1 is 30 to 50 Vol%. 3. A composite contact characterized in that a pure Au layer is formed on the surface of an alloy contact surface layer made by dispersing tungsten carbide particles in an AuCu alloy. 4. The composite contact according to item 3, wherein the pure Au layer has a thickness of 0.1 to 0.5 μ. 5 Cu layer, Si layer and AuCu layer are sequentially formed on the contact base material.
- A composite contact characterized by forming a WC alloy contact surface layer. 6. The composite contact according to item 4, wherein the Cu layer and the Ni layer each have a thickness of 1 to 5 μm. 7 Cu layer, Si layer, AuCu-WC on the contact base material
A composite contact characterized by forming an alloy layer and a pure Au layer.