JPH07254656A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent rusting of copper by bringing an electrode into contact with the flat peripheral part of a stem on the stem side and with the flange of a cap on the cap side and then sealing the stem and cap by electric welding. CONSTITUTION:A substantially rectangular electrode 1 conforming with the peripheral profile of a stem is brought into contact with the periphery of the stem 3 on the stem side and brought into contact with the flange 7a of a tubular electrode 2 conforming with the profile of a cap 7 on the cap 7 side. In this regard, the electrode 1 is prevented from coming into contact with the part 5 of the stem 3 having a copper underlying layer. The stem 3 and the cap 7 are brought into contact with each other under that state and then they are sealed by electric welding. Since the underlying material is not subjected to any machining and the electrode 1 touches the stem 3 at a flat part on the outside thereof, no discharge takes place and thereby no copper is exposed thus protecting the copper against rusting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a technique effective when applied to a method of sealing a semiconductor element with a metal material.

[0002]

2. Description of the Related Art Among semiconductor device sealing methods, the can type, which generally uses a metal stem and a cap, is sealed by electric welding. Among these, there is one in which a hole is once bored in the stem, a copper plate or molybdenum is fitted, and a nickel plating is further applied on the stem to improve heat conduction efficiency in the stem on which the chip is mounted. Examples of such products are "Mounting Technology and Reliability Improvement of Surface Mount LSI Package" published on November 16, 1988, published by Applied Technology Publishing, supervised by Moto Murakami, pages 4 to 8.

[0003]

Although not described in the above-mentioned publicly known example, as a result of examination by the present inventor, in the technique described above, a hole is formed in the central portion of the stem, and a copper plate or the like is used. It was found that there is a problem that the flatness of the central part of the stem is lowered because the material of (1) is embedded. Such a decrease in flatness causes a non-contact portion between the electrode and the stem during sealing, and if there is a non-contact portion between the center of the stem and the electrode, which has poor flatness, discharge occurs during sealing. The problem is that the nickel plating formed on the stem is crushed and the embedded material such as copper is exposed to generate rust, which may cause a defect.

An object of the present invention is to solve the above problems and to provide a can type semiconductor device in which copper rust does not occur.

[0005]

The typical means of the invention disclosed in the present application will be described below.

That is, in connecting and sealing a substantially rectangular stem having a semiconductor element mounted at a desired position and a cylindrical cap by electric welding, the electrode is substantially flat on the periphery of the stem on the side of the stem. A good part is brought into contact with the brim of the cap on the side of the cap, and sealing is performed by electric welding.

[0007]

According to the above-mentioned means, since the electrode at the time of welding and sealing comes into contact with the portion of the stem having good flatness, there is no non-contact portion and no discharge occurs. Therefore, the plating does not collapse, and the material such as copper under the plating is not exposed, so that rust does not occur.

[0008]

1 is a schematic perspective view for explaining a sealing method according to an embodiment of the present invention, and FIG. 2 is a partial sectional side view for explaining a contact state of electrodes during sealing. is there.

As shown in FIG. 1, the semiconductor device of interest in the present application is a can type semiconductor device in which a semiconductor element is sealed with a metal stem and a cap, for example, a TO-3P type.

The stem 3 used in this embodiment is made of an iron material and has a substantially rectangular shape. After making a hole in the center, copper plate 5 is used to improve the heat transfer efficiency.
Is embedded and its upper surface is plated with nickel. External leads 4 are attached to both sides of the portion where the copper plate 5 is embedded by penetrating the stem 5 with a glass material. Although not shown, a semiconductor element is attached to the cap attachment surface and is connected to each lead 4 by a wire.

The cap 7 has a cylindrical shape, has a collar 7a for sealing, and is made of iron.

The electrode 1 in this embodiment is on the stem side, and is formed in a substantially rectangular shape so as to match the outer peripheral shape of the substantially rectangular shape of the stem 5. The electrode 2 on the cap side has a circular shape according to the outer shape and the collar of the cap 5.

Next, the sealing will be described. In this embodiment, first, the semiconductor element is attached, and the substantially rectangular stem 5 and the cap 7 which have been wire-bonded to the leads are prepared.

Next, positioning is carried out by a positioning jig (not shown), the cylindrical electrode 2 corresponding to the cap shape is brought into contact with the collar 7a on the cap 7 side, and the stem 3 side is of a substantially rectangular shape conforming to the peripheral shape of the stem. The electrode 1 is brought into contact with the peripheral edge of the stem 3. At this time, the electrode 1 does not come into contact with the portion 5 of the stem 3 whose base is made of copper.
In this state, the cap 7 and the stem 3 are brought into contact with each other, an electric current is caused to flow, and the cap 7 and the stem 3 are connected and sealed by electric welding.

At this time, since the electrode 1 on the side of the stem 3 is in contact with the outside of the stem 3 at a portion having a high flatness because the material under plating is not specially processed, no discharge occurs.

Although the invention of the present application has been described above based on the technique which is the background of the present application, the present application is not limited to the above-described embodiments, and various modifications can be made without departing from the technique. There is no end.

That is, in this embodiment, the electrode using the substantially rectangular electrode has been described, but other shapes may be adopted depending on the shape of the stem. Various changes can be made according to various shapes of the stem. The material to be embedded in the stem is not limited to copper but may be molybdenum or the like, which has high conductivity.

[0018]

The effects of typical ones of the inventions disclosed in this application will be described below.

That is, the electrode is brought into contact with the stem portion having high flatness, and since there is no non-contact portion between the electrode and the electrode, discharge is not generated and copper is not exposed, so that a semiconductor device in which rust is not generated can be provided.

[Brief description of drawings]

FIG. 1 is a schematic perspective view for explaining a sealing method that is an embodiment of the present invention.

FIG. 2 is a partial cross-sectional side view for explaining a contact state of electrodes at the time of sealing.

[Explanation of symbols]

 1. ． Electrode (stem side) 2. ． Electrode (cap side) 3. ． Stem 4. ． Lead 5. ． Copper plate 6. ． Hole 7. ． Cap 7a. ． Brim

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, wherein a semiconductor element attached at a desired position on a stem is covered with a cap, the stem and the cap are connected by electric welding, and the semiconductor element is sealed. Is in contact with a portion of the stem having good flatness, and is in contact with an outer flange of the cap on the cap side, and is connected and sealed by electric welding. 2. A method of manufacturing a semiconductor device, wherein a semiconductor element attached at a desired position on a stem is covered with a cap having a collar, the stem and the cap are connected by electric welding, and the semiconductor element is sealed. A method for manufacturing a semiconductor device, wherein the electrode is brought into contact with substantially the peripheral edge of the stem on the stem side, and is brought into contact with the brim of the cap on the cap side, and is connected and sealed by electric welding.