JPS6038289Y2 - airtight terminal - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an airtight terminal in which a lead wire is sealed in a through hole of a metal outer ring through a glass, and particularly relates to an improvement of a stem for a semiconductor device.

The can-sealed power semiconductor device is shown in Figures 1 and 2.
It has the structure shown in the figure.

In the figure, a is a stem made of an airtight terminal, and 1 is a rhombus-shaped stem board made of iron, which has mounting holes 2, 2 at both ends in the longitudinal direction for attaching to the chassis, etc., and has a lead near the center. It has sealing holes 3,3.

Reference numerals 4 and 4 denote lead wires made of iron-nickel alloy, which are hermetically sealed in the lead sealing holes 3.3 through glasses 5, 5.

Reference numeral 6 denotes semiconductor elements 7, 7 fixed to the surface of the stem substrate 1.
8 is a thin metal wire connecting the surface electrode of the semiconductor element 6 and the lead wires 4, 4, and 8 is an iron cap resistance welded to the stem substrate 1.

The stem a is manufactured as follows.

That is, in order to resist corrosion up to glass sealing, and to prevent the so-called carburization phenomenon in which free carbon in the graphite sealing jig intrudes into the iron grain boundaries of the stem substrate 1 during glass sealing, the third As shown in the figure, a copper plating layer 9 is formed on the entire surface of the stem board 1 in advance, and the lead wires 4,
After glass sealing in step 4, stem substrate 1 and lead wires 4, 4
A finishing electrolytic nickel plating layer 10 is formed on the exposed surface.

However, if the copper plating layer 9 is formed on the stem substrate 1, during resistance welding of the cap 8, metal grains from the melted copper plating layer 9 will adhere to the semiconductor element 6, deteriorating the characteristics of the semiconductor element 6. There was a problem.

For this reason, it has been considered to coat the surface of the semiconductor element 6 with a precoat resin, silicone rubber, etc., but no satisfactory results have been obtained.

This idea was proposed in consideration of these points,
It is an object of the present invention to provide an airtight terminal that is not adversely affected by molten metal particles during resistance welding of a cap.

Examples of this invention will be described below with reference to the drawings.

FIG. 4 shows a cross-sectional view of the stem b of the first embodiment, and in the figure, the same or corresponding parts as in FIG. 2 are given the same reference numerals and their explanations will be omitted.

The difference from Fig. 2 is that in Fig. 2, the lead wires 4, 4 are sealed directly to the lead sealing holes 3, 3 with glasses 5, 5, whereas in Fig. 4, iron eyelets are used. The lead wires 4, 4 are sealed with glass via 11.

In addition, an electrolytic nickel plating layer with a thickness of about 1 to 7 μm is applied in advance to the entire surface of the stem substrate 1, as shown in FIG. 12 is formed, and a finishing electrolytic nickel plating layer 13 having a thickness of about 2 to 10 μm is formed on the exposed surfaces of the stem substrate 1 and the lead wires 4, 4.

The stem substrate 1 and the eyelet 11 are fixed together by the following arbitrary method and process.

First, as a fixing method, there are a method using resistance welding and a method using brazing such as copper brazing or nickel phosphorous brazing.

Further, the fixing process can be carried out before the glass sealing of the lead wires 4.4, at the same time as the glass sealing, or after the glass sealing.

In particular, when sealing the stem substrate 1 and the eyelet 11 after glass sealing, the eyelet 1
If finish plating is applied to the surfaces of stem board 1 and lead wires 4 and 4, finish plating on stem board 1 can be omitted.

Furthermore, the eyelet can be formed by directly forming an oxide film on the surface of the iron base and sealing it with glass, or by forming a copper plating layer on the entire surface and then forming an oxide film and sealing it with glass.

In the case of glass sealing through a copper plating layer, the heat resistance temperature is improved by about 30 to 50°C compared to the case of direct glass sealing.

According to the above configuration, the eyelet 11 and the glass 6 are tightly and airtightly sealed together directly or via the copper plating layer, and since no copper plating layer is formed on the surface of the stem substrate 1, There is less possibility that molten metal particles during resistance welding of the cap 8 will adhere to the semiconductor element, and a semiconductor device with good characteristics can be obtained.

FIG. 6 shows a sectional view of the stem C of another embodiment of this invention.

The feature of this embodiment is that a heat sink fitting hole 14 is formed approximately in the center of the stem board 1.
4, a copper heat sink 15 is fitted onto it, mechanically caulked, and then brazed.

FIG. 7 shows a sectional view of the stem d of still another embodiment of this invention.

The feature of this embodiment is that a recess 16 for fitting a heat sink is formed approximately in the center of the stem board 1, and a copper heat sink 17 is fitted into this recess 16, mechanically caulked, and then brazed. .

In addition, as another embodiment of this invention, a copper heat sink may be brazed on the flat stem substrate 1, an intermediate metal plate such as molybdenum or tungsten may be brazed, or a ceramic plate may be brazed. You may also do so.

Further, this invention can be applied not only to the power semiconductor device stem shown in the illustrated example, but also to any airtight terminal for sealing an element by resistance welding a cap.

Furthermore, the material of the metal outer ring and the eyelet may be not only iron but also an alloy whose main component is iron.

As described above, this idea consists of an electrolytic nickel plating layer formed on the iron-based metal outer ring, an iron-based eyelet fixed to the through hole of the metal outer ring, and a lead wire inserted into the eyelet through the glass. Because it is a sealed airtight terminal, there is no copper plating layer with a low melting point on the metal outer ring, and when the metal cap is resistance welded to the metal outer ring, the metal grains from the molten copper plating layer will not reach the elements such as semiconductor devices. The lead wires do not adhere to the glass and deteriorate the characteristics of the device, and the lead wires are not sealed to the glass via the electrolytic nickel plating layer that reduces the sealing strength to the through hole of the stem board, resulting in improved airtightness and sealing strength. This has the effect that an airtight terminal with a high level of resistance can be obtained.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway plan view of a semiconductor device that is the background of this invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1,
3 is an enlarged sectional view of the main part of FIG. 2, FIG. 4 is a sectional view of a stem for a semiconductor device according to an embodiment of this invention, and FIG.
6 and 7 are enlarged sectional views of main parts in the figure, and sectional views of stems for semiconductor devices according to different embodiments of this invention. b, c, d... Airtight terminal (stem), 1.
...Metal outer ring (stem board), 3...Through hole, 4,4...Lead wire, 5,5...
Glass, 8...Metal cap, 11...
- Eyelet, 12.13...Electro nickel plating layer, 15. 17-----Heat sink.

Claims (1)

[Scope of utility model registration request] In airtight terminals, a lead wire is sealed to a through hole in an iron-based metal outer ring via glass, and a metal cap is resistance welded.
An airtight terminal characterized in that an electrolytic nickel plating layer is formed on the metal outer ring, an iron-based eyelet is fixed to the through hole, and a lead wire is sealed inside the eyelet through a glass.