JPS5818945A - Cap sealing of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent bubbles at the time of welding from scattering to a pellet and to prevent short circuit and a decrease in dielectric strength by a method wherein a border between the cylindrical wall section of a cap and a flange is welded after temporary pressing. CONSTITUTION:A border 18 between the cylindrical wall 1 of a metal cap 13 and a flange 12 is temporarily attached by coil welding on a substrate 1 by an internal punch 19. Next, an electrode 20 is went down by turns and the cap 13 is welded and sealed. Suitable welding can be done by making the ring projection of the flange 12 with slight inclination. This composition intercepts the space in a cap 13 from external part when the projection 22 is melted by pressure energizing and bubbles will not adhere to a pellet 8. Sufficient current is concentrated into the projection 22 by temporary fixing and no deviation of position occurs. Furthermore, the border section 8 may be temporarily fixed after fixing and connecting the pellet. Therefore, contamination by pellet 8 atmosphere can be prevented and yield is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camp sealing method for a can case type semiconductor device, and particularly to measures against the generation of hot water beads during camp welding. ′ Traditionally, can case-type semiconductor devices have superior air-tight sealing properties of semiconductor pellets (hereinafter simply referred to as pellets) than resin-sealed semiconductor devices, so they have a high withstand voltage and a fast switching action. It is still used in electronic equipment for government use that requires reliability, as well as control systems installed in various automatic control devices. Therefore,
If the structure of a can case type semiconductor device is represented by a power transistor, as shown in FIG. 1, a through hole 2.
Lead wires 6 and 7 are inserted through glass 4.5 and hermetically sealed in 3, and a power transistor pellet 8 near these sealed portions is fixed via solder S.
The upper base electrode and emitter electrode, and the tops 6' of the lead wires 6 and 7, ? 'And the internal money JIII! 9.10, and connect these main parts to the ceiling cylindrical wall part 11 and the flange part 1.
A hunt-shaped metal camp 13 consisting of two parts is covered and sealed by welding. Then, in this power transistor, the metal cap 13 is welded and sealed [Hl As shown in FIG. Then, current is applied while applying pressure with a pressure welding electrode (not shown), and the tip 16 of the ring-shaped protrusion 15 is melted by heat generated by current concentration, thereby performing ψ projection welding.

However, in the projection welding work of the camp 13 and the substrate 1 described above, when melting the ring-shaped protrusion 15, a large current of several thousand A/- is concentrated on the ring-shaped protrusion 15, so it is certain that the temperature exceeds its melting point. While it is heated to a high temperature, it also overheats the surrounding metal parts, scattering fine molten poles or hot water beads even into the inside of the cap 13, and adhering to the pellet 13, causing a short circuit between the electrodes. In some cases, the inconvenience of significantly lowering the withstand voltage may occur. In order to avoid this inconvenience, it is generally necessary to apply precoat resin R for insulation protection, which is indicated by a broken line, to pellet B.
Although VC is applied, it is not a means to fundamentally prevent the intrusion of hot water beads into the interior of the cap 13, and it is not recognized as having a sufficient effect.

Therefore, the applicant previously proposed the cylindrical wall portion 11 of the cat/13 as shown in FIG. Although countermeasures such as providing an annular insulating shielding member 17 on the inner surface of the cap 13 have been proposed, the number of materials increases, resulting in higher costs, and the welding workability of the cap 13 is poor.
However, in the actual implementation, Vct reached Mψ and the defect remained.

As a result of studying and considering the above-mentioned circumstances, this invention proposes a method that is different from the previous method.The main purpose of this invention is to This method employs a method in which the flange portion and the substrate are welded and sealed after being temporarily crimped onto the substrate in advance. Examples of practical application of this invention will be introduced below.

4 to 7 are a sectional view and an enlarged sectional view of a main part of a case-type power transistor in a camp sealing process, relating to a first practical example of the present invention. The same figure numbers as the conventional ones shown have the same names. Now,
In the first embodiment, as shown in FIG. 4, the steps of fixing the pellet 8 and covering the metal cap 13 are carried out in the conventional manner.

Next, in the first embodiment, as is clear from FIG. 5, which is an enlarged view of the circle A section, the boundary section 18 between the i-wall section 11 and the inner wall section 12 of the metal camp 13 is lowered. The inner cylinder is a crimping punch 19 that is pressed onto the substrate 1 and cold-welded at room temperature to the recrystallization temperature of the cap member. As shown in Fig. 6, a double cylinder 21 whose outer cylinder is a welding electrode 20 that descends alternately with a crimping punch 19, pressurizes the flange portion 12, energizes it, and seals it by projection welding is used to form a metal camp. 13 is welded and sealed. therefore,
The ring-shaped protrusion of the flange portion 12 of the metal camp 13 used in the first embodiment has the figure number 22, as shown in
As shown in the figure, welding can be performed suitably by changing the angle to a slightly inclined one.

In the first embodiment described above, the boundary portion 18 is temporarily crimped in advance, so when the ring-shaped protrusion 22 is melted by applying pressure and electricity, the internal space 23 of the metal cap 12 is completely shielded from the outside, and the molten water does not form. There is no risk of it adhering to the pellets 8.

Moreover, since the metal cap 13 is only temporarily fixed by temporary crimping, when pressurizing the welding electrode on the outer cylinder, the temporarily fixed part will come off or the contact resistance will be large and the ring-shaped protrusion 22 will be insufficient. When the ring-shaped protrusion 22 is melted by concentrated current heating, the gold camp 13 is unlikely to be displaced from the intended sealing position of the substrate l, and reliable cap positioning is achieved. Of course, in the first embodiment, the pre-coat resin R used conventionally can be abolished.
In addition, the boundary portion 18 may be firmly fixed on the bere 1 or temporarily fixed immediately after the internal wiring, so that it is possible to prevent the pellet 8 from being contaminated by the atmosphere.

The first example above is a case where a double cylinder is used to weld the flange part after the temporary pressure system at the boundary part of the camp. , a step is provided between the solid main part 23 of the pellet 8 and the welded part 24 of the outer edge, and a means is adopted for forcibly fitting and crimping the fixing main part 23 to the kiyaknob 13. It has the same effect as the example.

Excellent effects that do not cause pressure drop, contribute to improving the reliability and yield of can case type semiconductor devices, are inexpensive as there is no need to increase the number of parts, and are easy to implement as the camp positioning is good. play.

[Brief explanation of the drawing]

1 and 3 are cross-sectional views M of a conventional can nurse type semiconductor device, FIG. 2 is an enlarged sectional view of the main part of the camp in FIG. 1, and FIGS. 4 and 6 are cross-sectional views of a can case-type semiconductor device in the cap sealing process, FIG. 5 is an enlarged cross-sectional view of both parts A in FIG. 4, and FIG. FIG. 8 is a cross-sectional view of a main part of a can case-type semiconductor device according to a second embodiment of the present invention. l... Board, 6.7... External lead (lead wire), 8...
... Semiconductor pellet, 11 ... Cylindrical wall part, 12 ... Flange part, 13 ... Camp, 18 ... Boundary part. Figure 8' 15 too

Claims (1)

[Claims] A main part including the pellet of a structure formed by fixing a semiconductor pellet on a substrate and internally wiring it with an external lead-out lead,
In the camp sealing method of covering the cap with a flange and sealing it by welding, the boundary between the cylindrical wall portion of the cap and the flange portion is temporarily crimped onto the substrate, and then the flange portion and the substrate are welded. Features: Camp sealing method for semiconductor devices.