JPH0217662A - Corrosion-resistant hermetic seal cover and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a seal cover suitable for a hermetic seal of a semiconductor device.

[Conventional technology]

One type of puff casing for semiconductor devices is a ceramic package as shown in FIG. In FIG. 2, the ceramic substrate 1 includes a lower plate having a metallized layer for bonding semiconductor elements in the center, an intermediate plate on which a lead pattern is formed and an opening in the center, and an inner edge of the lead pattern exposed. 3 of the upper plate with an even larger opening
It has a structure in which the layers are integrated, and a plurality of metal leads 2 are joined to the long sides so as to be electrically connected to the outer tips of the lead patterns, and a cover is not attached around the opening of the upper layer plate. A metallized layer 3 is formed. The metallized layer and the lead pattern are usually formed of Mo--Mn based conductive paste, and these leads 2 are plated with gold. In a package using such a substrate 1, the semiconductor element 4 is first bonded to the central recess of the substrate 1, and the electrodes on the element 4 and the inner tips of the lead patterns are connected to thin connector wires (
After connecting the wires (not shown), a seal ring 5 and a metal cover as shown in FIG.
It consists of various processes for attaching. The process of attaching the cover 6 is generally called a hermetic seal, and the seal ring 5 is made of an Au-3n alloy solder, which has a lower melting point than the Au-3i alloy solder used for bonding the semiconductor elements 4, and a Pb-3 alloy solder.
n-alloy brazing or the like is used, and at least the peripheral edge of the metal (usually Kovar type) cover 6 where the sealing 5 comes into contact is coated with a coating of gold, nickel plating, etc. that has good brazing properties. is normal.

Conventional hermetic seal covers are known to simply have nickel plates coated on both sides of an iron alloy plate, or those in which the iron alloy plate is directly nickel plated and then gold plated. The former type, which is simply coated with a nickel plate, has the disadvantage that corrosion tends to progress from the sheared surface.
In addition, the latter method, which only uses plating, has the disadvantage that local electrodes of gold and nickel are formed due to pinholes created during plating, which tends to cause corrosion of the iron-based alloy. If corrosion of the iron-based alloy progresses and penetrates the hermetic seal cover from the upper surface to the lower surface, airtightness will be lost.

If the airtightness and sealing properties are lost, corrosive gases, humidity, temperature differences, pressure differences, etc. present in the usage environment will have adverse effects such as condensation on the semiconductor elements.

Furthermore, if the iron-based alloy is missing from the cover into the package due to the above-mentioned corrosion and adheres to the surface of the semiconductor element, a short circuit will occur and the reliability of the semiconductor device will be reduced, which is a fatal defect.

[Problem to be solved by the invention]

An object of the present invention is to provide a highly reliable hermetic seal cover that eliminates the above-mentioned drawbacks and has improved corrosion resistance.

[Means to solve the problem]

In order to achieve the above object, the present inventors deposited pinhole-free nickel on both sides of an iron-based alloy plate, and then applied nickel plating and then gold plating to the entire surface, thereby achieving good corrosion resistance. The present invention was achieved by discovering that it is possible to obtain a hermetic seal cover.

That is, the present invention provides a corrosion-resistant steel alloy sheet in which a rolled nickel layer with a thickness of 3 microns or more is deposited on both sides of an iron-based alloy plate, and a nickel plating layer and a gold plating layer are sequentially provided on the outside of the nickel layer. This is a hermetic seal cover, and the manufacturing method for this hermetic seal cover is to apply a nickel layer on both sides of an iron-based alloy plate, then roll it, and then first apply nickel plating to the outside of the nickel layer, and then apply gold plating to the entire surface. It is distinctive in the way it is applied.

[For production]

Conventional iron-based alloys in which nickel plating and then gold plating are applied to the entire surface have pinholes as defects in the plating, and the pinholes create local electrodes that easily corrode the iron-based alloy. However, if there is a rolled nickel layer of 3 μm or more between the plating and the iron-based alloy plate, even if local electrodes occur due to the nickel plating and gold plating, the effect of pinholes will be reduced because the rolled nickel layer is denser than the nickel plating. Corrosion of iron-based alloys can be reduced. If the rolled nickel layer is less than 3 μm, it is a denser layer than nickel plating, so corrosion of the iron alloy will occur compared to a conventional iron alloy with nickel plating and then gold plating on the entire surface. Although it is possible to recognize the effect of reducing the nickel layer, the effect is small compared to the case where the rolled nickel layer is 3 μm or more.

In addition, a rolled nickel layer is applied to both sides of the iron-based alloy, and the iron-based alloy is punched into the shape of a hermetic seal cover.There are nickel layers on the top and bottom surfaces, but the iron-based alloy is exposed on the sheared surface. Corrosion progresses from this part. However, by applying nickel plating and then gold plating to the entire surface, exposure of the iron-based alloy on the sheared surface is prevented and corrosion is suppressed.

〔Example〕

Next, the present invention will be explained by examples.

0゜mm thick Kovar plate sample (1), 0
．． Sample (2) in which a 101 m square Kovar plate with a thickness of 1 haze was directly plated with nickel (4 μm thick) and then gold plated (2 μm thick).
Sample (3) was prepared by simply applying a 1-thick nickel plate and punching out 10 dragon angles, and a 0.01-mm-thick nickel plate was applied to both sides of a 0.1-mm-thick Kovar plate and rolled. Sample (4) of the present invention, which was punched out into 10 mm squares, was barrel-plated with nickel plating (4 μm thick), and then gold plating (2 μm thick) on the entire surface, was tested at 5% using a salt spray tester.
A 24 hour test was conducted in NaCl at room temperature. Table 1 shows the results of observing the corrosion state using a stereoscopic microscope (30x magnification) after the salt spray test.

As shown in Table 1, the Kovar plate sample (1
) is completely corroded. Sample (2), in which the Kovar plate was directly nickel-plated and then gold-plated, had considerable corrosion on the top and bottom surfaces of the sample, and corrosion was also observed on the sides. In addition, sample (3), which was simply a nickel plate adhered to a Kovar plate, showed considerable corrosion from the punched sheared surface. No corrosion was observed on the top and bottom surfaces of sample (4) of the present invention, but slight corrosion was observed on the side surface (sheared surface).

As a result of this test, it was confirmed that corrosion resistance was significantly improved by rolling the nickel layer deposited on both sides of the Kovar plate, and then applying nickel plating to the entire surface and then gold plating the entire surface.

〔Effect of the invention〕

The present invention reduces corrosion of the hermetic seal cover, greatly improving the reliability of semiconductor devices, and is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hermetic seal cover according to the present invention, and FIG. 2 is a structural view of a ceramic package. 1...Ceramic substrate, 2...Metal lead, 3...
- Metallized layer, 4... Semiconductor element, 5... Seal ring, 6... Hermetic seal cover 7...
Gold plating layer, 8... Nickel plating layer, 9... Nickel adhesion layer, 10... Kovar material. Patent applicant Sumitomo Metal Mining Co., Ltd.

Claims (2)

[Claims] (1) A corrosion-resistant hermetic seal cover in which a rolled nickel layer with a thickness of 3 microns or more is applied to both sides of an iron-based alloy plate, and a nickel plating layer and a gold plating layer are sequentially provided on the outside of the nickel layer. (2) A corrosion-resistant hermetic seal characterized by applying a nickel layer to both sides of an iron-based alloy plate, rolling it, and first applying nickel plating to the outside of the nickel layer, and then applying gold plating to the entire surface. How to manufacture the cover.