JPS598066B2 - Manufacturing method of stud base for semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method of manufacturing a stud base for a semiconductor device.

In general, bases for semiconductor devices are made of a composite metal material consisting of a lower metal layer with good conductivity and an upper metal layer with good weldability, and this processed material is extruded to form a bulge on which a semiconductor pellet is to be mounted. It was manufactured by forming a stud on the top surface as well as a stud which would later be threaded to attach the base to the mounting plate.

After the upper surface of the bulge is cut off to expose the lower metal layer, a molybdenum plate is brazed to the bulge, and a semiconductor pellet is mounted on the molybdenum plate. However, the disadvantage of this conventional technology is that when brazing molybdenum plates, the studs, which have been work-hardened by extrusion molding, are annealed by the heating of the wax, making the studs brittle and the tightening torque of the screws being small. There was a risk of damage if the bolts were forcibly tightened. An object of the present invention is to provide a method of manufacturing a stud base for a semiconductor device that can increase the tightening torque of the stud.

Embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1 to 5 show the manufacturing method of the present invention in the order of steps.

First, as shown in FIG. 1, a composite metal consisting of a thick lower metal layer 12 with good conductivity such as copper or zirconium copper and a thin upper metal layer 14 with good weldability such as nickel or Cypronickel is processed. Prepare material 10. This processed material is formed by punching out a composite metal plate into a disk shape. The composite metal plate may be either one in which the upper metal layer 14 is silver-brazed to the lower metal layer 12 or a clad plate in which these metal layers 12 and 14 are clad-bonded. Next, this processed material is extruded by a rear extrusion molding machine so as to form a bulge 16 on the upper surface, as shown in FIG. At this time, the outer periphery of the material is formed into a polygonal shape, and an annular projection IT used for projection welding the shell is formed on the upper surface around the bulge. Thereafter, as shown in FIG. 3, the processed material is cut horizontally at the bulge at the position indicated by dotted line a in FIG. 2 so that the lower metal layer 12 is exposed on the upper surface of the bulge 16. Next, a molybdenum plate 18 is soldered with silver to the upper surface of the bulge 16 where the lower metal layer 12 is exposed (FIG. 4), and subjected to an aging treatment.

This aging treatment is carried out at 400°C to 50°C when the lower metal layer is zirconium copper and the upper metal layer is Cypronickel.
This is carried out at 0°C for over 1 hour. Finally, the material is back-extruded to form studs 20 on its underside, as shown in FIG.

An example of a rear extruder 22 is shown in FIG. This molding machine consists of a lower mold 24 having a hole 24a into which the bulging portion 16 is inserted and an upper mold 126 having a mold hole 26a into which the stud 20 is to be extruded.The lower mold 24 is placed on a base (not shown). The upper die 26 is attached to a press ram (not shown). In addition, upper mold 2
Above 6, there is a square hole 28a surrounded by a holder 28 into which the workpiece 10 is inserted. When the material is inserted into the molding machine 22 as shown and the ram is lowered with an impact, a part of the material flows into the mold hole 26a of the upper mold 26 and the stud 20 is formed (Fig. 6). (see dotted line). Since the molybdenum plate 18 is inserted downward into the hole 24a of the lower die, it will not be damaged by the impact during this poor stud extrusion. This stud 20 will later be threaded by thread rolling.
Since this stud 20 is work-hardened during molding, it will become hardened again even if it is annealed when the molybdenum plate 18 is brazed. Therefore, the screw tightening torque for this stud 20 becomes significantly large. According to experiments, the permissible tightening torque for studs with the stud base of the prior art was as small as 40k9, but with the stud base of the present invention, it was 80kg.
I was able to make it bigger.

This is because in the conventional technology, the molybdenum plates are brazed after the studs are formed, so the work-hardened stud material is annealed by the heat during brazing the molybdenum plates, but in the present invention, the studs are brazed after the molybdenum plates are brazed. This is because the stud material remains work-hardened during molding. According to the present invention, as described above, the permissible tightening torque of the stud is significantly increased, so it is particularly suitable as a base for a large-capacity semiconductor device.Also, since the stud is formed by backward extrusion, the molybdenum plate is not used during molding. No impact is applied and no damage occurs.

[Brief explanation of the drawing]

Figures 1 to 5 are vertical cross-sectional views of materials showing the method for producing stud bases of the present invention in the order of steps, and Figure 6 is a vertical cross-sectional view of a part of a backward extrusion molding machine for backward extrusion of studs. . DESCRIPTION OF SYMBOLS 10...Processing material, 12...Lower metal layer, 14...Upper metal layer, 16...Bulging portion, 18... Molybdenum plate, 20...
・Stud, 22... Rear extrusion molding machine.

Claims (1)

[Claims] 1. A composite metal processing material consisting of a lower metal layer with good conductivity such as copper or zirconium copper and an upper metal layer with good weldability such as nickel or cypronic is prepared, and the processing material is extruded to form a base body. A method for manufacturing a stud base for a semiconductor device, wherein the base body has a bulge portion on the upper surface to which a molybdenum plate to which a semiconductor pellet is to be mounted is brazed, and a screw stud on the lower surface to which the base is to be attached to a mounting plate. forming the bulge on the upper surface of the processed material by backward extrusion molding;
a step of cutting off the upper surface of the bulge so that the lower metal layer is exposed on the upper surface of the bulge; and a step of brazing and aging the molybdenum plate on the exposed surface of the lower metal layer of the bulge. A method for manufacturing a stud base for a semiconductor device, comprising the steps of: and then forming the threaded stud on the lower surface of the processed material by backward extrusion molding.