JPS6348364B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing an electrical contact.

It is well known that the electrical characteristics of electrical contacts used in various electrical circuits are greatly influenced by the surface condition of the contact parts, and in conventional electrical contacts, the contacts are resistance welded or caulked to a spring or plate. After processing, the surface of the contact is generally pressed to form a flat surface in order to adjust the surface condition of the contact.

However, in this method, impurities tend to adhere to the surface of the contact metal, and the contact resistance is therefore unstable. Therefore, in order to improve the electrical characteristics of electrical contacts that require high contact reliability,
In many cases, manufacturing was performed in a clean room and repeated cleaning was performed after each manufacturing process. However, even in a clean room, it is impossible to completely prevent dust from adhering to the surface, and cleaning with liquid often ends up contaminating the surface of the electrical contact due to aging of the liquid. There was no cleaning effect, and it was basically impossible to remove impurities that adhered during the contact material manufacturing process and welding dust generated during contact welding, making it difficult to obtain electrical contacts with stable electrical characteristics. .

For this reason, various methods have been tried in the past to improve the electrical characteristics of electrical contacts.

Among the mechanical methods, there is a method of polishing the contact surface with brushing or sandpaper, but in this method, abrasive grains generate polishing powder that adheres to or embeds on the contact surface, causing the electrical contact It has the disadvantage of unstable physical characteristics, especially contact resistance, and cannot be used in locations where reliability is required.

Additionally, an electrolytic polishing method has been attempted as an electrical method, but this method electrochemically activates the surface and keeps the electrical properties stable, but on the other hand, due to the activation, the surface is not exposed to air during use. It easily adsorbs dust and abrasion powder inside, and since it uses an electrolyte, it is difficult to manage the liquid and clean up the liquid that adheres to the electrical contact.Furthermore, because it is activated, the surface tends to stick during contact operation. It has drawbacks such as irregular opening/closing operations and malfunctions, and cannot necessarily be said to be good in terms of long-term reliability.

Dry honing has also been attempted, in which abrasives such as glass beads are sprayed onto the contact surface of an electrical contact to remove surface impurities and form a uniform uneven surface. The formation of an uneven surface stabilizes the contact resistance, dispersing the contact load and preventing sticking.However, small electrical contacts, especially electrical contacts with thin plates, may be deformed during honing. It is difficult to process, the abrasive material is easily embedded, and furthermore, impurities that have been removed once circulate together with the abrasive material, are sprayed again, and re-attached.

As described above, all conventional methods have their advantages and disadvantages, and there is no optimal manufacturing method.For this reason, manufacturing is generally performed in a clean room, with careful cleaning after each step, and the mechanical, electrical, etc. Contact surfaces are cleaned using one of these methods, but as material management and quality control for each intermediate process are required, process control is complicated and production costs are high. The final quality of the product is determined by the accumulation of variations, so as the number of processes increases, the variation in quality tends to increase.

It is an object of the present invention to overcome the above-mentioned drawbacks and to provide a manufacturing method capable of obtaining an electrical contact with stable and uniform electrical characteristics.

Examples of the present invention will be described below.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 shows an embodiment of the manufacturing method of the present invention, in which a contact material is fixed to a spring or plate by resistance welding or caulking, and then the contact is formed into a flat surface. Irradiate the surface with a laser beam. When irradiated with a laser beam, impurities (oil, fat, dust, etc.) attached to the contact surface melt and evaporate and are removed from the contact surface, and when irradiated with a stronger laser beam, oxides, etc. evaporate and the contact surface layer melts. When this solidifies again, as shown in Figure 2, a countless number of uniform fine uneven surfaces are formed on the contact surface, resulting in stable contact resistance and an electrical contact with stable electrical characteristics and less adhesion. can get. The intensity of the laser beam irradiation is appropriately selected depending on the material of the contact material, the amount of deposits, the desired degree of uneven surface formation, and the like. To irradiate the contact surface with a laser beam, you can focus it with a lens and irradiate a part of the contact surface while scanning to irradiate the entire contact surface, or you can widen the irradiation area and irradiate the entire contact surface at once. , Avoid irradiating plates or springs to which contacts are fixed. Although the case in which the laser beam is irradiated after forming the contacts in FIG. 1 has been described, this order may be reversed.

Figure 3 shows Au electrical contacts used in relays.
Laser oscillator (oscillation wavelength 6943Å) is mounted on the movable contact surface of
[Normal temperature], peak output 150MW, beam opening angle
A micrograph (100x magnification) of the contact surface state when irradiated with a laser beam at 5mrad., ruby 12.5mmφ x 100mm, oscillation repetition 4 times per minute).

Figure 3a shows the case where the laser beam is weakly irradiated, and b
c is the case of moderate irradiation, and c is the case of strong irradiation. This intensity was controlled by adjusting the distance between irradiations or the irradiation time. This revealed that after intense irradiation, countless unevenness was uniformly formed on the contact surface.

Also, almost the same results were obtained when the fixed contacts were irradiated with a laser beam under the same conditions. Figure 4 shows a micrograph (100x magnification).

In this experiment, the deposits (mainly organic matter) on the contact surface were melted and evaporated by moderate irradiation, and the surface was cleaned.
Intense irradiation removes remaining deposits (organic matter,
metal oxides, metal impurities, etc.) evaporate,
It was confirmed that the contact metal surface layer also melted and countless fine uniform irregularities were formed on the surface. In the above experiment on the movable contact, the surface roughness of the contact was measured using a stylus type surface roughness meter, and the roughness was approximately 2.5μ.
It was m. In addition, we have measured contact resistance by incorporating laser beam irradiation into successor electric appliances, but almost all products
It was found that the contact resistance was less than 50 mΩ, lower than any conventional electrical contact method, and that there was no variation among each product. This is thought to be due to the fact that impurities were removed by the laser beam irradiation and the contact surface was cleaned, and the uniform uneven surface provided multi-point contact. In addition, with conventional electrical contacts, the adhesion of the contacts during contact operation can cause disturbances in opening/closing operation or inability to operate, which is a major problem when used for high-speed switching. It turned out to be less. This is thought to be because the numerous fine irregularities caused multiple points of contact, increasing the contact area and dispersing the contact load.

As explained above, the present invention provides the following effects.

(a) Adhesive matter on the contact surface can be easily removed by laser beam irradiation. Moreover, conventional methods such as cleaning, electrolytic polishing, and dry honing can cause aging of the liquid.
Alternatively, cleaning may be insufficient due to problems such as redeposition of impurities, but according to the present invention, impurities are melted and evaporated, so complete cleaning can be achieved in a short period of time.

(b) Since a uniform uneven surface is formed on the surface, the contact area of the electrical contact becomes multi-point contact and the contact area increases.This, together with the cleaning by removing impurities mentioned above, results in stable electrical contact with low contact resistance. Furthermore, since the contact load is dispersed and the sticking phenomenon can be reduced, it is possible to obtain an electrical contact with high reliability and stable electrical characteristics.

(c) When irradiating the laser beam, it is necessary to irradiate only the parts that require processing, so there is no risk of loss of strength or deformation of other parts, and processing is easy.

(d) Even if there is any deposit on the contact surface, it can be easily and completely removed by laser beam irradiation, which eliminates complicated work such as material management and cleaning after each intermediate process, and also improves product quality. Since the finish is no longer affected by the control status of intermediate processes as in the past, there is less variation in the product.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing an example of the manufacturing method of the present invention, Fig. 2 is a sectional view showing the surface condition of the contact of the electric contact according to the present invention, and Fig. 3 is irradiation of a laser beam onto the surface of the movable contact. Figure 4 is a micrograph of the surface of the movable contact when the laser beam is irradiated weakly, b is moderately irradiated, and c is strongly irradiated. It's a photo.

Claims (1)

[Claims] 1 A laser beam is irradiated only on the contact point of the electric contact to melt and evaporate the deposits on the surface of the contact point, and further irradiation is applied to melt the contact surface, and the solidification after melting of the contact surface causes fine particles to be formed. A method for manufacturing an electrical contact, which comprises forming unevenness on a contact surface.