JPS5952031B2 - Cold welding method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a cold pressure welding method that improves pressure welding properties.

Conventionally, in lap cold welding, the objects to be welded are directly overlapped and welded together.

In this case, since the oxidized coating on the surface of the object to be pressed at the pressure welding portion impairs the pressability, the oxidized coating is mechanically removed by wire brushing or the like before the pressure welding. However, even if the oxide coating is removed by wire brushing, the oxide coating may be re-formed, or the oxide coating removal process may be incomplete, so the processing rate at the press-welded area must be extremely high (for example, 60% or more) to be satisfied. It is not possible to obtain an exponent junction. Moreover, under such a high processing rate, there is a drawback that the mechanical strength of the processed portion is significantly reduced. The present invention has been made in consideration of the above-mentioned circumstances, and it is an object of the present invention to perform cold welding by interposing a metal having lower ductility than the metal constituting the object to be welded in advance in the welding part, thereby obtaining a satisfactory joint with a small processing rate. The purpose of the present invention is to provide a cold welding method that enables the following. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment of a semiconductor exterior with reference to the drawings. A press-welded object 1 to be cold-welded is shown in FIGS. 1A and 1B.

As shown in this figure, the pressurized object 1 consists of two disk-shaped copper plates 2a and 2b of the same shape that are stacked on top of each other. A recess 3a3b is formed, and these plate bodies 2a, 2b
When the above-mentioned recesses 3a and 3b are overlapped with each other facing each other,
For example, a storage space 4 is formed to store semiconductors and the like. When storing semiconductor elements, the storage space 4 is required to be sealed against the outside air, so the cold welded portion 5 has an annular shape surrounding the recesses 3a and 3b. In this way, the exterior members are first manufactured using a nickel plating machine such as Wat Folk.
, 2b surface is plated with nickel to a thickness of 5 μm to 20 μm to form a thin nickel film.

As shown in FIG. 2, the plates 2a and 2b are then overlapped. At this time, the plating layer 8 is
a and 8b are simply in close contact. Next, cold pressure welding is performed using a cold pressure welding device. That is, as shown in FIGS. 3 and 4, as the cold welding progresses, the wedge-shaped dies 6a and 6b enter the plates 2a and 2b in the directions of arrows A and B, respectively, causing plastic deformation. As a result, as the cold welding progresses, the plated layers 8a and 8b are separated at the welded portion 5, and move along the welded interface 7 in the directions of arrows C and D with the plastic flow caused by the cold welding of the plates 2a and 2b. do. This is because copper, which is the constituent metal of the plates 2a and 2b, is more ductile than nickel, which is the constituent metal of the plating layers 8a and 8b (in other words, nickel has a lower breaking strength than copper), so cold This is because the plated layers 8a, 8b cannot follow the plastic flow of the plates 2a, 2b due to pressure welding, and reach a breaking point before the pressure welding is completed. As a result, after the plating layers 8a, 8b are separated and moved, each plate 2a,
The two new surfaces 2b, which are clean and free of oxide films, come into close contact with each other, and these new surfaces are completely joined by cold pressure welding. Furthermore, even if a thin oxide film is interposed between the plating layers 8a, 8b and the plate bodies 2a, 2b, such an oxide film will cause the plating layers 8a, 8
It moves following the division of b, and as above, a clean new surface is scoured, and both plates 2a and 2b can be completely joined. FIG. 5 is a metallurgical microscope photograph showing a cross section of the press-welded portion 5 of the object 1 to be press-welded after cold press-welding, which actually illustrates the above-mentioned situation. White linear eyelid in the center of the photo. It can be seen that the plated layer is separated and moved along the pressure-bonded interface, and that the two metals are completely joined at the pressure-bonded interface where the plated layer has moved. Since the above-mentioned new surface appears for the first time during the cold press bonding process, an oxide film is not formed by the outside air. stomach. Therefore, satisfactory cold pressure welding can be achieved without extremely high processing rates. FIG. 6 shows this. That is, the relationship between the welding length L in the radial direction across the welded part 5 that has been substantially completely cold welded and the processing rate shown in FIGS. 3 and 4 is the case when cold welding is performed after wire brushing. The plot also shows the case of nickel plating. Here, the processing rate is the change in the thickness of the object 1 to be pressed, expressed as a percentage. As can be seen from this figure, the oxide film on the surface of the pressurized object 1 is not completely removed just by wire brushing, and even after brushing, it is still exposed to the outside air, so a considerable amount of oxide film remains on the surface. are doing. This oxide coating acts to prevent metal bonding between the plates 2a and 2b at the welding interface 7 due to cold welding. FIG. 7 is a metallurgical micrograph of a cross-section of the press-welded portion 5 of the press-welded object 1 which was subjected to cold pressure welding without intervening a plating layer at the press-bond interface. Although the processing rate is higher than in the case of FIG. 5, the bonding is incomplete, and a black streak at the crimped interface indicating this fact remains near the center of the crimped portion 5. Therefore, in order to obtain the same bonding length L, the processing rate must be increased when wire brushing and cold pressure welding is performed compared to when nickel plating and cold pressure welding is performed. For example, to achieve a bond length L of 0.3 mm, wire brushing requires a processing rate of approximately 70%, while nickel plating requires a processing rate of approximately 40%. . As described above, in the cold welding method of the present invention, the surface of the object to be cold welded is coated in advance with a thin film of metal, and then cold welding is performed, and the processing rate is extremely high. As a result, it is possible to obtain a sufficiently satisfactory cold welded joint at a moderate processing rate without deteriorating the mechanical properties of the entire object to be welded.

In the above embodiments, the welded portion is annular, but the cold welding method of the present invention is not limited to this, and the cold welding method of the present invention can also be applied to linear or dotted welded portions.

In addition, in the above embodiment, cold welding is performed by pinching the objects to be welded from both sides with the dies 6a and 6b, but the invention is not limited to this, and cold welding with dies from only one side can also be performed. It is valid. In addition, the present invention is not limited to cold welding at room temperature as in the above embodiments, but also
Applicable to pressure welding at temperatures below about 400°C. moreover,
In the above embodiment, nickel was used as the plating layer, but any metal having lower ductility than copper, such as chromium, may be used. Furthermore, in addition to the cold welding of copper as exemplified in the above embodiments, cold welding between other non-ferrous metals such as aluminum (or aluminum alloy), cold welding between ferrous metals, and combinations thereof are also possible. It can also be applied to cold welding of dissimilar materials. In addition, in the above embodiment, a metal having lower ductility than the metal constituting the objects is coated on the pressure contact surface of each of the pair of objects to be welded, but metal is coated only on the pressure contact surface of one of the objects to be welded. You may let them. In other words, if the material to be pressed on one side that is not coated with metal does not form an oxide on its surface, such as gold, the same effect will be achieved as if it were coated on each pressure contact surface, and Even if the material to be welded on one side that is not bonded is oxidizing, the bonding strength will be slightly lower than if metal is bonded to both surfaces, but it should still be able to withstand practical use. I can do it. Furthermore, although the metal coating method was used in the above embodiments, the metal coating is not limited to this, and the metal coating may be formed by, for example, a vacuum evaporation method or a metal spraying method. In addition, various changes can be made without departing from the gist of the present invention.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1A and 1B are a plan view and a sectional view taken along line X-X of a pressurized object used in an embodiment of the present invention, and FIGS. 2 to 4 are an embodiment of the present invention. FIG. 5 is a sectional view of a main part for explaining the cold pressure welding method in the example, and FIG. Figure 6 is a diagram showing the relationship between processing rate and joining length in cold welding, and Figure 7 is a microscope showing a cross section of the welded part of the welded object after cold welding when no plating layer is interposed at the welding interface. It's a photo. 1: Pressure contact object, 5: Pressure contact portion, 8a, 8b: Plating layer.

Claims (1)

[Scope of Claims] 1. A step of depositing a metal layer having lower ductility than the metal constituting the welded objects on at least each pressure welding surface of the first and second objects to be cold-welded; a step of bringing the low ductility metal layers of the press-welded object to face each other;
cold welding the first and second objects to be welded by simultaneously applying pressure to separate and move the metal layer with low ductility on each pressure welding surface of the objects to be welded. Cold pressure welding method. 2. The cold pressure welding method according to claim 1, wherein the first and second objects to be welded are storage containers for accommodating semiconductors or the like. 3. The cold pressure welding method according to claim 1, wherein the metal layer with low ductility has a thickness of 5 μm to 20 μm. 4. The cold welding method according to claim 1, wherein cold welding is performed by applying pressure to a die so that the first and second objects to be welded enter the die while causing plastic deformation.