JPS6032773Y2 - airtight terminal - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an airtight terminal used in a stem for a semiconductor device such as a power transistor.

For example, general examples of power transistors are shown in Figures 1 and 2.
As shown in the figure, 1 is a stem and 2 is a metal cap.

The stem 1 has lead wires 5 made of iron-nickel alloy etc. inserted into lead sealing holes 4 drilled at key points in the iron-based stem substrate (metal ring) 3.
It is an airtight terminal with a hermetic seal structure in which the transistor is sealed with glass 6, and the transistor pellet 7 is placed on the top surface of the stem substrate 3.
is soldered, and the lead wire 5 is connected to the surface electrode of this pellet.
A metal wire assembly 8 is bonded to the two to electrically connect them.

Then, the pellet 7 and the lead wire 5 are covered, and the open end of the iron-based metal cap 2 is low-resistance welded to the upper surface of the stem substrate 3 to form an airtight terminal.

The glass lead wire of the stem 1 is sealed using a graphite sealing jig in a high-temperature atmosphere of about 1000°C. At this time, if the stem substrate 3 is also made of iron, the sealing process will be difficult. A carburizing phenomenon occurs in which carbon released from the tool enters the iron-based grain boundaries of the stem substrate 3 and lead wires 5.
The soldering properties of the pellets to the stem substrate 3 are poor, and the hosing of the thin metal wires 8 to the lead wires 5 is also poor.

Therefore, in order to solve this problem, the following plating process was conventionally performed.

That is, before the lead wire 5 is sealed with glass, the entire surface of the stem substrate 3 is electrolytically plated with nickel to prevent carburization during glass sealing.

However, in this case, there is a problem that electrolytic nickel plating is interposed at the sealing interface between the glass 6 and the stem substrate 3, which deteriorates the sealing properties of the glass 6 and deteriorates the airtightness. Ta.

In addition, as another plating process, before sealing the lead wire 5, the entire surface of the stem board 3 is plated with copper, which has good sealing properties with glass, and after sealing the glass, electrolytic nickel is further applied to eliminate the carburizing phenomenon. It has been proposed to prevent this and improve the sealing properties of the glass 6.

However, in the case of this copper plating, the metal cap 2 is
When low-resistance welding is performed on the stem board 3, if there is copper plating with good conductivity on this welding part, this copper plating will not melt.
Only the electrolytic nickel plating on the surface is likely to be welded to the cap 2, which poses a problem in welding strength.

On the other hand, if the welding current is increased to melt the copper plating, the heat during welding will cause the copper plating to melt, become hot water beads, scatter around, and adhere to the pellets, deteriorating the properties of the pellets 7. was there.

The present invention solves the above-mentioned conventional problems and provides an airtight terminal in which a welding ring is brazed to an iron-based metal ring whose entire surface has been previously plated with copper.

Hereinafter, the present invention will be explained with reference to examples.

For example, the example applied to the above transistor stem is shown in the third example.
As shown in the figure, the present invention applies copper plating 9 to the entire surface of the iron-based stem board 3 in advance, seals the lead wire 5 with glass, and then welds the iron-based stem board 3 to the welded part of the upper surface of the stem board 3. After the ring 10 is brazed, a finishing plating 11 such as electrolytic nickel plating or electroless nickel plating is formed on the entire surface of the stem 1'.

In this case, the soldering material used for brazing the welding ring 10 may be silver soldering material whose melting point is lower than the melting point of the glass 6, for example, about 780.degree.

Further, the welding ring 10 can be brazed to the stem substrate 3 at the same time as the glass 6 is sealed. In this case, a brazing material having a melting point close to the sealing temperature of the glass 6 (approximately 1000° C.), for example, a brazing material having a melting point of approximately A nickel-phosphorus alloy brazing material at 980°C is used.

In addition, when brazing the welding ring 10 at the same time as glass sealing, if the welding ring 10 is made of iron base, the welding ring 10
The carburization phenomenon occurs.

However, since the metal cap 2 is simply welded to the weld ring 10, there is no problem even if the metal cap 2 is carburized.

In addition, in order to prevent carburization of the welding ring 10, the welding ring 10 is coated with copper in advance and sealed with glass, and after the welding ring 10 is brazed to the stem board 3, the exposed copper plating is removed. You may also do so.

Further, the welding ring 10 can be brazed to the stem substrate 3 with a brazing material having a melting point higher than the sealing temperature of the glass 6 before the glass 6 is sealed.

FIG. 4 shows a modification of FIG. 3, in which a copper heat sink 13 is fitted and brazed into the through hole 12 at the pellet mounting location of the stem board 3, and the pellet 7 is soldered onto the heat sink 13. will be attached.

In the case of this type, it is sufficient to braze the welding ring 10 to the stem substrate 3 whose entire surface is coated with copper plating 9 at the same time as the heat sink 13 is brazed.

Note that the present invention is not limited to the above-mentioned embodiments, but can also be applied to a type of stem in which, for example, a copper heat sink plate is placed on a stem substrate and brazed.

Furthermore, the present invention is not limited to hermetic terminals for power transistor stems, but can be fully applied to hermetic terminals for other semiconductor devices and electronic components.

As explained above, according to the present invention, the carburization phenomenon is prevented by the copper plating on the surface of the metal ring, and since the copper plating is present at the sealing interface between the metal ring and the glass, the glass sealing property is improved. is improved, and an airtight terminal with good airtightness can be provided.

In addition, since the welding ring is brazed to the copper-plated iron metal ring and the metal cap is welded to this welding ring, there is no copper plating in the welding area, so welding current does not increase. This eliminates problems such as deterioration of pellet properties due to hot water beads during welding, and stabilizes the properties of semiconductor devices and the like.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of a general hermetic terminal (stem for power transistor), Fig. 2 is a side sectional view taken along line A-A in Fig. 1, and Figs. 3 and 4 are according to the present invention. It is a side sectional view showing each example of an airtight terminal. 1...Airtight terminal (stem), 3...Iron-based metal ring, 4...Lead sealing hole, 5...
...Lead wire, 6...Glass, 9...
Copper plating, 10...Welding ring, 11...
...Finish plating.

Claims (1)

[Scope of utility model registration request] An airtight device characterized by glass-sealing the lead wire into the lead sealing hole of an iron-based metal ring with copper plating on the entire surface, brazing a welding ring on the top surface of the metal ring, and applying finish plating to the entire surface. terminal.