JPS6242707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method of soldering by heating and melting a soldering material on which solder has been placed in advance. The purpose of this is to solder so that no air bubbles remain at the solder joint interface, and in particular, superconducting stranded wires and It is effective when used in soldering with the stabilizing material.

Generally, when soldering materials to be soldered,
Air bubbles caused by flux, air that adheres to the surface of the soldering material, air bubbles that occur when atmospheric air is drawn into the solder, or air bubbles that are caused by gas contained in the solder itself. When the solder remains on the joint interface of the soldering material and solidifies, it may form voids and impair soldering performance. For example, when creating a composite superconducting conductor by soldering a stabilizing material to conventional stranded superconducting wires,
A method of incorporating superconducting stranded wires into the grooves of the stabilizing material and immersing them in a solder bath, or a method of incorporating pre-soldered superconducting stranded wires into the grooves of the stabilizing material and heating them while pressurizing them. There is also a method of incorporating superconducting twisted wires into the grooves of the stabilizing material, heating them, and injecting molten solder from above. However, in these soldering methods, when the material to be soldered is immersed in a solder bath, the molten solder flows into the groove from the top of the groove of the stabilizing material, making it difficult for air and gas from the twists of the stranded wire to escape to the outside. Moreover, since all these soldering processes use flux, air bubbles due to the decomposition of flux remain between the strands or between the bottom of the groove in the stabilizing material and the superconducting strands, and X-ray radiographs show that the bubbles cannot be seen during soldering. Many voids are often observed in the area.

The present invention is a soldering method that improves the above-mentioned drawback that air bubbles at the solder joint interface are difficult to be discharged to the outside. That is, when another soldering material is introduced into a long groove-shaped soldering material having an opening at the top and the two are soldered, at least the bonding interface between the soldering materials With solder attached to one side in advance or with solder interposed between the interfaces, heat is applied from the side farthest from the side where air bubbles existing at the interface to be soldered are discharged to the outside from the upward opening of the groove. This is a soldering method characterized by sequentially melting the solder. Further, an example of soldering when making a composite superconducting conductor will be explained in detail with reference to the drawings as follows. FIG. 1a is a side view showing an embodiment of the invention, FIG. 1b is a plan view thereof, and FIG. 2 is a front view of the grooved copper material. First, as a stabilizing material, a small amount of solder is poured into the bottom of the groove of the high-purity copper strip 1 having a concave cross section, or a solder 2 is interposed therebetween. A shaped superconducting stranded wire 3 having a rectangular cross section is inserted into the groove from the upper part of the groove by roll processing, and the copper strip is inserted into the heating zone 4.
Since the solder poured into the groove bottom begins to melt, the superconducting strands are gradually immersed in the molten solder and incorporated into the groove of the stabilizing material, as shown by the arrow. Go in the direction. On the other hand, the heating zone from the bottom of the copper strip is divided into several parts, 4, 5, 6, and 7, and is arranged so that the heating range reaches the top in order, so that the stranded wire is connected to the molten solder at the bottom of the groove. The molten solder is gradually immersed in the groove, and the molten solder is heated from the groove bottom toward the upward opening of the groove from the groove bottom, that is, the upper opening, which is opposite to the dipping direction of the superconducting stranded wire, which is the soldering material. As the superconducting strands rise up in the direction of 5', 6', and 7', air bubbles generated at the solder joint interface between the superconducting strands and the stabilizing material are trapped in the groove and do not remain, but rise up. The molten solder is discharged to the outside from the upper opening, allowing void-free soldering.

Next, examples will be described. 15 2.3mmφ superconducting wires coated with solder are stranded and formed.
Formed strands of 4.3mm x 17mm, passed through a solder bath,
By squeezing with a die, we created a solder-formed stranded wire with the wire gap of 4.3 mm x 17.1 mm filled with solder. Next, a grooved copper material with a concave groove shape of 4.4 mm x 17.2 mm was prepared as a stabilizing material, and in order to incorporate the superconducting molded stranded wire into the groove, a small amount of groove was added to the bottom of the copper material in advance. With solder grains interposed, the copper material is gradually introduced into the heating zone from one end. The heating zone is gradually expanded to the upper part by electric heating. In such a case, the solder grains at the bottom of the groove of the copper material begin to melt and at the same time are immersed to incorporate the formed stranded wire into the solder grains. The bonding interface with the stranded wire portion is filled with bubble-free solder. Subsequently, the composite superconducting conductor of the copper material and the formed stranded wire sequentially enters the next heating zone. As the solder starts to melt from the bottom, it releases gas as it melts to the top, and the stranded wire is completely installed in the groove, and the excess solder still remains at the top of the groove, with a very small amount of air bubbles remaining. After more bubbles spilled out and there were almost no remaining air bubbles in the soldered area, the soldering work was completed by heating for a certain period of time. When the composite superconducting conductor thus soldered was examined using transmitted X-rays, no voids were observed between the formed strands and the grooves and between the strands.

As described above, according to the present invention, there are no voids at the joint interface of the soldered materials, the heat transfer of the solder joint is good, the joint strength is excellent, and excellent soldering with stable quality can be achieved. .

[Brief explanation of the drawing]

FIG. 1a is a side view showing an embodiment of the invention, FIG. 1b is a plan view thereof, and FIG. 2 is a front view of the grooved copper material. 1: Grooved stabilizing material, 2: Solder, 3: Superconducting molded stranded wire, 4: Heating zone, 5: Heating zone, 6: Heating zone,
7: heating zone, 5': molten solder, 6': molten solder, 7': molten solder.

Claims (1)

[Claims] 1. When sequentially introducing other soldering materials into a long groove-shaped soldering material having an opening at the top and soldering both materials, it is necessary to minimize the bonding interface between the soldering materials. Attach solder to one side in advance,
Or, with solder interposed between the interfaces, bubbles generated at the interface to be soldered are heated from the side farthest from the side discharged to the outside from the upper opening of the groove, and the solder is sequentially melted. Soldering method.