JPH0215976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact joining method capable of obtaining a defect-free joint and a good fillet without using a brazing material or flux.

Conventionally, in the contact joining method for this type of electrical contact that requires drop-off resistance and wear resistance, the contact 1 and the base 3 are usually joined by brazing as shown in Fig. 1a and b. is being used. The surface of the contact 1 to be bonded is preliminarily lined with a silver layer 2.
is formed. In the brazing work, first insert the brazing material 4 and flux 5 between the contact 1 and the pedestal 3, sandwich the contact 1 and the pedestal 3 with electrodes, and apply electricity through the electrodes under a predetermined pressure. The brazing phenomenon progresses between the backing silver layer 2 and the pedestal 3 to form a brazing layer 8, and the eluted metal 9 forms a fillet-like shape between the pedestal 3 and the contact at the peripheral edge of the contact 1. is formed. However, in such brazing, large cavities, that is, large voids 10, frequently occur in the brazing layer 8, and the actual bonding area ratio between the contact 1 and the pedestal 3 is usually said to be 60% to 70%. ing. For this reason, the drop-off resistance and wear resistance of the contactor were extremely unstable.

On the other hand, as a means of producing mass-produced contacts,
Efficient spot welding methods are being tried. In this case, the contact 1 and the pedestal 3 are held between the electrodes 6 and 7, and the contact and the pedestal are joined by applying pressure and electricity, without using the brazing material 4 and the flux 5. In practical terms, the following disadvantages occurred. That is, as shown in FIG.
Welding defects 12 often occur and dust 13 is always generated. The welding defect 12 is a factor that makes the fall-off resistance and wear resistance of the contact unstable, and the dust 13 peels off during operation, leading to accidents such as poor insulation of the electric circuit. Therefore, the spot welding method, which has such disadvantages, has not been put into practical use.
Furthermore, a contact bonding method as shown in FIGS. 3a and 3b has recently been developed.

According to this, as shown in Figure 3a, the pedestal 3
After dropping water 14 through a nozzle 15 in advance around the joint of the contact 1 and the contact 1, a defect-free pressure contact 18 can be obtained by applying pressure and applying electricity in the same manner as brazing or spot welding. Note that a silver layer 2 is formed on the contact 1. In this case, although the eluted metal 9 does not take the form of dust 13 as in the case of spot welding, it does not take the form of a fillet-like well-fitted state as in the case of brazing. Eluted metal 9
It is necessary for the contactor to be formed into a fillet shape in terms of the properties of the contact and its strength against peeling due to thermal stress.

On the other hand, as a dripping liquid as shown in Figure 3b,
When the alcohol 16 is dropped from the nozzle 17, the eluted metal 9 is very stably formed into a fillet shape, but a pressure contact defect 19 may occur at the pressure contact portion 18.

A joining method similar to the joining method shown in FIGS. 3a and 3b is disclosed in JP-A-55-88216 ``Method of welding electrical contacts.'' There is a method to improve the heat balance during welding by continuously injecting a cooling liquid such as water or alcohol, and to improve arc resistance and service life. Or, there is a defect similar to b, and furthermore, continuous injection of cooling liquid makes it difficult to stabilize the temperature rise of the joint, making it difficult to form a uniform joint.

Therefore, as shown in an embodiment in FIG. 4a, this invention supplies water 14 and alcohol 16, for example, through nozzles 15 and 17 to the area around the joint between the contact and the pedestal, and then connects the contact and the pedestal to the upper part. By applying current while applying pressure from both sides through the electrode and the lower electrode, a defect-free joint can be obtained and a good fillet can be formed.

FIG. 4 explains the principle and effects of an embodiment of the contact bonding method of the present invention.
That is, in FIG. 4a, the contact 1 and the pedestal 3 are sandwiched between the electrodes 6 and 7, and water 14 and alcohol 16 are
After dropping both of them, pressure and electricity are applied between the electrodes 6 and 7. This synergistically exhibits both the effects of the characteristic actions of water and alcohol 16 described above, and satisfies both the condition of the pressure welding part 18 and the shape of the eluted metal 9, as shown in FIG. 4b. Good contacts can be stably obtained.

The bonding phenomenon caused by the combined use of water and alcohol can be considered as follows.

The reason why alcohol is necessary is that, for example, in the decomposition reaction of ethanol (ethyl alcohol) upon heating, it is thought to exhibit the following reducing effect.

MO+C ₂ H ₆ OH→M+CH ₃ CHO+H ₂ O In other words, MO (metal oxide) is reduced to pure M (metal) by ethanol C ₂ H ₆ OH. however,
Although the oxidation reaction becomes active in the atmosphere, the oxidation reaction can be suppressed by shielding the area around the joint from the atmosphere by some means.
In this invention, both water and alcohol are necessary to maintain the vapor shielding effect until the contact and the pedestal are bonded together. In other words, if water with a large heat of vaporization is mixed with alcohol, the heating temperature of the contact bonding,
For example, at 800°C, the boiling point is further raised than when using only alcohol, and the vapor shield can be extended until the bonding is completed. Therefore, at the bonding interface, it is interpreted that the eluted metal 9 is formed in a fillet shape in order to effectively prevent the occurrence of defects caused by the oxide layer and to clean the surface of the pedestal 3 around the contact 1. Ru.

Further, in this invention, after water and alcohol are supplied around the joint, the supply is cut off, and then electricity is passed between the two electrodes to heat them. This is due to the fact that the heating mechanism of the current-carrying joint between the contact and the pedestal is inherently unstable, but if a cooling liquid is additionally supplied during the current-carrying heating as in the above-mentioned Japanese Patent Application Laid-Open No. 55-88216, the temperature rise of the material to be joined increases. This is because fluctuations occur in the bonding temperature, resulting in a bonding result with insufficient heat input, and a uniform bonding cannot be obtained.

As explained above, the contact joining method of the present invention supplies water and alcohol around the joint between the contact and the pedestal to be joined together, and then connects the contact and the pedestal using the upper electrode and the lower electrode. Since the contact and the pedestal are joined by applying current while applying pressure from both sides, a defect-free joint can be obtained and a good fillet can be formed.

[Brief explanation of drawings]

Figures 1a and b are explanatory diagrams showing the conventional joining method by brazing and the state after joining, Figure 2 is an explanatory diagram showing the state after joining by the generally considered spot welding method, and Figure 3 FIGS. 4a and 4b are explanatory diagrams showing a joining method as a premise of the present invention, and FIGS. 4a and 4b are explanatory diagrams showing a joining method and a state after joining according to an embodiment of the present invention. In the drawing, 1 is a contact, 2 is a silver layer, 3 is a pedestal, 4 is a brazing material, 5 is a flux, 6 is an upper electrode, 7 is a lower electrode, 14 is water, 15 is a water supply nozzle, 16 is alcohol, 17 is alcohol supply nozzle, 18
19 is a pressure contact portion and 19 is a pressure contact defect. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. After supplying a predetermined amount of water and alcohol around the joint between the contact and the pedestal to be joined to each other, the contact and the pedestal are heated to a predetermined pressure from both sides by an upper electrode and a lower electrode. A contact bonding method in which the contact and the base are bonded by applying a predetermined current for a predetermined period of time while applying. 2. The contact joining method according to claim 1, characterized in that predetermined amounts of water and alcohol are supplied at the same time. 3. Claim 1, characterized in that after a predetermined amount of water has been supplied and a predetermined amount of time has elapsed, a predetermined amount of alcohol is supplied, and a predetermined current is applied while a predetermined pressure is applied. Contact joining method.