JPH0325912B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermocompression welding electrode for joining materials to be joined by thermocompression welding.

(Prior art) Electrodes for thermo-compression welding, which join parts of materials to be joined by thermo-compression welding, are made of metals with high resistance and high melting point, such as tungsten (W), molybdenum (Mo), tantalum (Ta), etc. electrodes are known. With this electrode, the electrode itself generates resistance heat, so even if the material to be bonded is copper, copper alloy, or other highly conductive material,
That is, even materials that are considered unsuitable for resistance welding due to resistance heat generation of the materials to be joined can be joined without any problems.

(Problems to be Solved by the Invention) In order to join materials to be joined, such as conductors of electric wires, using the above electrode, as shown in FIG. The electrodes 100 and 110 are attached to the electrodes 100 and 110 so as to face each other, and the joint portion 31 of the electric wire 30 is set between these electrodes 100 and 110, and the joint portion 31 is sandwiched between the electrodes 100 and 110. While applying pressure (approximately 200Kg to 300Kg), electrode 1
It is conceivable to apply electricity between the electrodes 100 and 110 to cause the electrodes 100 and 110 to generate resistance heat, and to use the heat to join the joint portion 31.

In the above joining, the electrode 100,
The corner portions 101, 111 side of the electrode 110 (the portion surrounded by the dotted line in FIG. 3) are just the electrodes 100,
The heat-affected part in contact with 110 and the electrodes 100, 11
This becomes the boundary with the non-heat-affected area which deviates from 0. However, in this boundary area, one heat-affected area is at a high temperature, while the other non-heat-affected area is not so high, resulting in a large temperature difference between the two. There was a problem that stress was easily concentrated and the mechanical strength of this part decreased after joining.

This invention was made to solve the problems of the prior art described above, and its purpose is to:
It is an object of the present invention to provide an electrode for thermo-pressure welding that does not concentrate stress on materials to be joined during a joining operation and does not cause a risk of deterioration of mechanical strength of materials to be joined and reliability of joining.

[Effects of the Invention] (Means for Solving the Problems) In order to achieve the above object, in this invention, a material to be welded is arranged between a pair of electrodes facing each other, and the electrodes are pressed against the material to be welded. , an electrode for thermo-pressure welding that joins the materials to be welded by energizing the electrode, which has ceramic pressing plates closely attached to both left and right outer surfaces of each electrode, and It is characterized in that the end surface that comes into contact with the material to be joined is formed into a smooth circular arc shape or tapered shape toward both outer sides.

(Function) The pressure plate is made of ceramic and has insulation and heat insulation properties. Even if electricity is applied between the electrodes during the bonding operation, only the electrodes will rise in temperature due to resistance heat generation, whereas the pressure plate The inner surface portion in contact with the electrode is heated and the temperature rises slightly, and the outer surface portion in contact with the outside air has a temperature approximately equal to that of the outside air. That is, it is possible to alleviate stress concentration at the boundary between the heat-affected zone and the non-heat-affected zone due to a temperature gradient occurring at the press plate.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show an example of an electrode for thermocompression welding according to the present invention, and reference numerals 10 and 11 in the figures are electrodes made of, for example, tungsten (W), molybdenum (Mo), tantalum (Ta), etc. are attached to the ends of electrode holders 20 and 21 made of copper alloy so as to face each other, but the important point here is that a pressing plate 40 made of ceramic is attached to the side surface thereof.

In this embodiment, as shown in FIG.
A dovetail groove 40a is formed on the inner surface of the electrode 0, and dovetail grooves 10a and 11a are formed on the outer surface of the electrodes 10 and 11.
The press plate 40 presses the electrode 1 through engagement with the electrodes 1a and 11a.
It is detachably attached to both the left and right outer surfaces of 0 and 11.

Further, the end surface 40b of the press plate 40 that contacts the material to be welded 30 is formed into a smooth circular arc shape facing outward on both sides.

Note that the end surface 40b of the press plate 40 that comes into contact with the material to be welded 30 may be formed into a tapered shape that expands outward.

When the ceramic pressing plates 40 are attached to both the left and right outer surfaces of the electrodes 10 and 11 in this way, when the materials 30 to be welded such as electric wires are joined, the heat-affected zone in contact with the electrodes 10 and 11 is removed from the electrodes 10 and 11. It is possible to alleviate stress concentration at the boundary between the heat-affected zone and the non-heat-affected zone.

That is, while applying pressure while sandwiching the joint portion 31 of the material 30 between the electrodes 10 and 11,
When electricity is applied between the electrodes 10 and 11, the electrodes 10 and 11
Only the pressure plate 4 rises in temperature due to resistance heat generation.
0 is made of ceramic and has insulating and heat insulating properties, so it does not generate resistance heat, and the inner surface that contacts the electrodes 10 and 11 is heated by the electrodes 10 and 11, causing a slight temperature rise. The temperature of the outer surface that is in contact with the outside air is almost the same as that of the outside air. In other words, during the bonding operation, a temperature gradient occurs inside the press plate 40, and the temperature gradient is relaxed so that the temperature does not change rapidly between the heat-affected zone and the non-heat-affected zone. Therefore, the stress generated at the boundary between the two is alleviated.

On the other hand, regarding the electrodes 10 and 11, heat due to resistance heating is efficiently transmitted to the joining portion 31 by the press plate 40 without being radiated to the outside, and reliable joining can be achieved.

Therefore, there is no problem that the mechanical strength of the bonded portion 31 decreases after bonding, and the reliability of bonding can be improved, and the efficiency of bonding work can be improved.

The structure and effects of the present invention will be further explained by giving test examples below.

(Test example) Size: AVS (thin-walled low-voltage wire for automobiles) with a cross-sectional area of 0.5 mm ² (strand diameter 0.32 mm x 7 strands), the heat resistance of the present invention shown in Figures 1 and 2 was measured. Thermal pressure welding was carried out using a pressure welding electrode.

In other words, the electrode size is 10 mm in total width x 3 mm in total depth x 10 mm in total height, the width of the ceramic press plate is 3 mm, the depth is 3 mm, and the height is 7 mm.
Similarly, the contact end surface with the electric wire is tapered 1 mm outward on both sides, and the pressure during thermo-pressure welding is:
The conditions of 200Kg/mm ² , current: 6100A, and time: 0.5 seconds were adopted.

For electric wires thermocompressed under the above conditions, we measured the adhesion force (tensile breaking strength) until breaking when parallel tensile force was applied from both sides of the joint, and the average of 100 shots was 14.25 Kgf. The value was shown.

Furthermore, the coefficient of variation (dispersion in tensile strength at break) was evaluated for 5 shots, and the result was 1.54%, indicating that a reliable bond with little variation was obtained.

On the other hand, for comparison, we omitted the use of the ceramic press plate mentioned above and set the electrode size to 4 mm in total width x 3 mm in total depth x 10 mm in total height, and wires were joined under the same conditions as above. As a result, the adhesion force (tensile strength at break) of the bonded wire was not only inferior to that of the present invention, which was 12.39 Kgf on average over 100 shots, but also the coefficient of variation (dispersion in tensile strength at break) at 5 shots was 4.36%. The variation was large, resulting in a lack of bonding reliability.

As is clear from the above results, the effect of employing the ceramic press plate in the present invention is extremely significant.

[Effects of the Invention] As explained above, according to the thermocompression welding electrode of the present invention, the left and right outer surfaces thereof have smooth arcuate or tapered edges with the end surfaces in contact with the materials to be joined facing outward. Since the ceramic press plate is removably attached, stress will not be concentrated on the materials to be joined during the joining operation, and there is no risk of reducing mechanical strength. Furthermore, since the heat of the electrodes is not radiated to the outside, reliable bonding can be achieved.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of the present invention, with Figure 1 being a side view, Figure 2 being a plan view of the electrode portion, and Figure 3 being a side view showing the prior art. be. 10, 11...electrode, 40...pressing plate.

Claims (1)

[Claims] 1 A thermocompression welding electrode for joining the materials to be joined by arranging the materials to be joined between a pair of electrodes facing each other, pressing the electrodes against the materials, and applying electricity thereto, the electrodes comprising: Ceramic pressing plates are closely attached to both the left and right outer surfaces of each electrode, and the end surfaces of the pressing plates that come into contact with the material to be welded are shaped outwardly into a smooth arc or taper. An electrode for thermocompression welding, characterized in that: