JPH0758236A - Hermetic semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a semiconductor device having a hermetic structure in which the cap is not deformed upon joining the cap and a uniform welded seal portion is formed between the cap and the tower mounting portion. provide. A nickel plating layer 51 is formed on the entire surface of the cap body 40 of the cap 4 having a joint surface 40c with the stem 1.
Are formed. Gold plating 52 is formed on the entire surface of the cappy main body 40 except for the bonding surface 40c. When the joint surface 40c of the cap body 40 is pressed against the stem 1 and a current is passed from the upper electrode 5 to the lower electrode 6, the current flows through the gold plating layer 52 and reaches the lower end position. This current is discharged mainly from the lower end position of the gold plating layer 52 to the stem 1 side, and the outer edge side of the joint surface 40c is heated,
A uniform welded seal portion 53 is formed in this portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a hermetic structure in which a semiconductor element mounted on a tower mounting portion is hermetically sealed by a cap.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a state in which a conventional semiconductor device having a hermetic structure is assembled. In the figure, reference numeral 1 is a stem as a tower mounting portion in which the outer edge portion 1a has a thin disk shape and the central portion 1b is a thick wall portion protruding upward. The stem 1 is made of an iron-nickel alloy, and a gold plating layer (not shown) is formed on the outer peripheral surface thereof. Reference numeral 2 is a semiconductor element mounted on the central portion 1b of the stem 1, 3 is a terminal for the semiconductor element 2 which penetrates the stem 1 downward through a glass seal, and 4 is a stem 1 which covers the upper side of the stem 1. A cap 5 for hermetically sealing and protecting the upper semiconductor element 2 is a cylindrical upper electrode for press-bonding the cap 4 to the side of the stem 1 for joining, and 6 is provided on the lower surface side of the stem 1, Lower electrode sandwiching the lower part of the electrode with the upper electrode 5, 7 is the stem 1, the semiconductor element 2, the terminal 3
And a cap 4 is a semiconductor device.

The cap 4 will be described in more detail. The reference numeral 40 designates a flange portion 40 that extends downward in a conical cylindrical shape.
a, and a cap body having a substantially U-shaped cross section having an opening 40b at the upper end surface, 41 is the opening 4 of the cap body 40
0b is a transparent glass plate that is used for sealing laser light from the semiconductor element 2 and the like. The lower surface side of the flange portion 40a of the cap body 40 (including the lower side of the end surface of the flange portion 40a) is a joint surface 40c that is pressed and joined to the upper surface side of the outer edge portion 1a of the stem 1. A nickel plating layer 51 having a predetermined thickness is formed on the outer surface of the cap body 40.

Next, the operation when the cap 4 is joined to the stem 1 and the semiconductor element 2 on the stem 1 is hermetically sealed will be described. After the stem 1 is positioned and placed on the lower electrode 6, the cap body 40 is positioned and placed on the stem 1 so that the joint surface 40c side of the cap body 40 contacts the outer edge portion 1a of the stem 1. . Next, the upper electrode 5 is lowered and its lower end surface 5a
Then, the upper surface of the flange portion 40a of the cap body 40 is pressed to sufficiently bring the joint surface 40c of the cap body 40 into close contact with the upper surface side of the outer edge portion 1a of the stem 1.

Subsequently, a current is passed from the upper electrode 5 side to the lower electrode 6 side. Since a contact resistance is generated at the contact portion between the joint surface 40c of the cap body 40 and the upper surface of the outer edge portion 1a of the stem 1, heat is generated by passing an electric current through this contact portion, and the nickel plating layer 51 of the joint surface 40c and The gold plating layer on the outer edge portion 1a of the stem 1 is melted to form a welded seal, and the cap body 40 and the outer edge portion 1a of the stem 1 are joined. As a result, the cap 4 is attached to the side of the stem 1 and the semiconductor element 2 mounted on the stem 1 is mounted.
Is hermetically sealed by the cap 4.

[0006]

However, in the conventional semiconductor device described above, since the nickel plating layer 51 is formed so as to be exposed to the entire cap body 40, the lower end surface 5a of the upper electrode 5 and the flange portion 40a. A contact resistance is also formed at the contact portion between the upper surface and the upper surface. Therefore, when the cap 4 is joined to the stem 1, the contact portion is also heated, and the heat generated here and the heat generated on the joint surface 40c side of the cap body 40 cause the flange portion of the cap body 40 to join. There is a problem that the entire 40a is heated and softened, and the outer shape of the flange portion 40a is deformed.

Further, in this semiconductor device, an electric current flows through the entire contact portion between the cap body 40 and the stem 1 which is formed when the flange portion 40a of the cap body 40 is pressed by the upper electrode 5, and this contact portion is It is welded. Therefore, the center of the cap 4 and the center of the upper electrode 5 do not coincide with each other, and the cap 4 receives an unbalanced load due to the upper electrode 5 and the cap body 40
If the contact portion between the stem 1 and the stem 1 is not formed uniformly, there is a problem that a uniform welded seal portion cannot be obtained in the circumferential direction of the cap body 40.

The present invention has been made in order to solve the above problems, and does not cause deformation of the cap when joining the caps, and forms a uniform welded seal portion between the cap and the tower mounting portion. It is an object of the present invention to provide a semiconductor device having a hermetic structure.

[0009]

According to another aspect of the present invention, there is provided a hermetically structured semiconductor device in which a nickel plating layer is formed on a cap body of a cap having a joint surface with a mounting portion so that the nickel plating layer is exposed at the joint surface. The gold plating layer is formed so as to be exposed except for the bonding surface.

[0010]

According to the present invention, the joint surface of the cap body is pressed toward the tower mounting portion side, and a current is passed from the cap body side to the tower mounting portion side through the electrode to melt and bond the cap and the tower mounting portion. In this case, the electric current flows through the gold plating layer of low resistance formed on the cap body except for the bonding surface,
While reaching from the lower end of the exposed gold plating layer to the tower mounting part side, a part of the current reaches the mounting part side through the nickel plating layer exposed from the lower end of the exposed gold plating layer. Therefore, the outer edge side of the joint surface of the cap body is heated by the discharge. Further, when a part of the electric current passes through the contact portion between the joint surface and the tower mounting portion, heat is generated due to the contact resistance of the contact portion. Then, the nickel plating layer on the outer edge side of the joint surface is fusion-bonded to the tower mounting side.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. 1 is a sectional view showing a state in which a cap of a hermetic structure semiconductor device according to a first embodiment of the present invention is attached, and FIG. 2 is a welding seal of a cap of a hermetic structure semiconductor device according to a first embodiment of the present invention. It is an expanded sectional view showing the circumference of a part. In the figure, the same or corresponding parts as those of the conventional semiconductor device having a hermetic structure shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, 52 is a gold-plated layer of a predetermined thickness formed on the entire outer surface of the cap body 40 except for the joint surface 40c of the cap body 40, and 53 is the cap 4
The nickel seal layer 51 and the gold coat layer of the stem 1 are fused to form a welded seal portion. The other structure of the semiconductor device 7 of the first embodiment is the same as that of the semiconductor device 7 shown in FIG.

Next, the operation of attaching the cap 4 having the gold-plated layer 52 to the stem 1 by welding will be described. After the stem 1 is positioned and mounted on the lower electrode 6, the cap body 40 is positioned and mounted on the stem 1 so that the joint surface 40c side of the cap body 40 contacts the outer edge portion 1a of the stem 1. Next, the upper electrode 5 is lowered, and the lower end surface 5a of the upper electrode 5 lowers the cap body 40.
The upper surface of the stem 1 to press the joint surface 40c to the outer edge 1a
Adhere to the top side sufficiently. Then, a current i is passed from the upper electrode 5 side to the lower electrode 6 side.

This current i flows through the gold plating layer 52 of the cap body 40 having the smallest electric resistance, and the gold plating layer 52
Reach the lower end position (a) closest to stem 1. Then, this current i reaches from the lower end position a of the gold plating layer 52 to the stem 1 side by discharge, and the joining surface 40c of the cap body 40
The outer edge side of is heated. Further, a part of the current i reaches the stem 1 side from the lower end position a of the gold plating layer 52 through the nickel plating layer 51, and at that time, the nickel plating layer 5
The contact portion is heated by the heat generated by the contact resistance of the contact portion between the stem 1 and the stem 1. At this time, this current i is mainly discharged from the lower end position (i) of the gold plating layer 52 to the stem 1 side, and the outer edge side of the joint surface 40c of the cap body 40 is heated by this discharge, and the nickel plating layer 51 and the stem of this outer edge part. The first gold-plated layer is melted, and a uniform welded seal portion 53 is formed on the outer edge of the joint surface 40c. Then, the cap 4 and the stem 1 are integrally joined by the welded seal portion 53, and the semiconductor element 2 inside is hermetically sealed.

As described above, according to the first embodiment, the gold plating layer 52 having a small electric resistance is formed so as to be exposed except the bonding surface 40c of the cap body 40, and the nickel plating is performed so as to be exposed at the bonding surface 40c. Since the layer 51 is formed, upon welding the cap 4 to the stem 1 side, the current i from the upper electrode 5 flows in the gold plating layer 52 and hardly flows in other parts of the cap body 40. Therefore, the joining surface 40 of the cap body 40 is
The portion other than the c side is not heated, and unlike the conventional semiconductor device 7, the flange portion 40a is not heated to its upper surface side and is not deformed.

Further, most of the current i from the upper electrode 5 reaches the stem 1 side by discharge from the lower end position a of the gold plating layer 52, so that the joining surface 40c of the cap body 40 is
The outer edge of is mainly heated by the discharge of the current i. Therefore, the welded seal portion 53 has the joining surface 40.
It is formed uniformly along the outer edge of c. In this case, the flange portion 40a of the cap body 40 is pressed by the upper electrode 5 in an eccentric state, and even if the contact portion between the joint surface 40c and the outer edge portion 1a of the stem 1 varies, it flows inside the contact portion. Since there is almost no electric current i, the width of the welded seal portion 53 does not vary in the circumferential direction of the flange portion 40a as in the conventional case.

Example 2. In the first embodiment, after the nickel plating layer 51 is formed on the entire surface of the cap body 40, the gold plating layer 52 is formed on the surface of the cap body 40 excluding the bonding surface 40c to expose the nickel plating layer 51 on the bonding surface 40c. However, in the second embodiment, after the gold plating layer 52 is formed on the entire surface of the cap body 40, the bonding surface 40 is formed.
The nickel plating layer 51 is formed on the surface c and the nickel plating layer 51 is exposed at the joint surface 40c, and the same effect is obtained.

In the first embodiment, nickel is considered as the deposition metal on the cap 4 side, and the nickel plating layer 51 is formed on the entire cap body 40, but the cap body 40 is made of Kovar or the like. If so, this is not necessary. In this case, the cap body 40
The background of Kovar may be exposed only on the joint surface 40c side, and the gold plating layer 52 may be formed on all other portions. Further, also in this case, the gold plating layer 52 may be formed on the entire cap body 40, and then the nickel plating layer 51 may be formed on the bonding surface 40c.

[0019]

As is apparent from the above description, according to the present invention, the nickel plating layer is formed so as to be exposed at the joint surface in the cap body of the cap having the joint surface with the mounting portion. Since the gold plating layer is formed so as to be exposed except the bonding surface, when the electrode is used to weld the cap to the tower mounting part side, heat does not deform the cap and the cap and the tower are not deformed. A uniform welded seal portion is formed between the mounting portion and the mounting portion.

[Brief description of drawings]

FIG. 1 is a sectional view showing an assembled state of a semiconductor device having a hermetic structure according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the periphery of the welded seal portion of the semiconductor device having a hermetic structure according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing an assembled state of a conventional semiconductor device having a hermetic structure.

[Explanation of symbols]

 1 Stem (Tower Mount) 2 Semiconductor Element 4 Cap 40 Cap Body 40c Bonding Surface 51 Nickel Plating Layer 52 Gold Plating Layer

Claims (1)

[Claims] 1. A hermetic semiconductor device in which a semiconductor element mounted on a mounting portion is hermetically sealed by a cap, wherein the cap main body of the cap having a joint surface with the mounting portion is nickel-plated. A hermetic semiconductor device, wherein the layer is formed so as to be exposed at the joint surface, and the gold plating layer is formed so as to be exposed except for the joint surface.