JPS58204194A - Nickel electroplating method - Google Patents

Abstract

PURPOSE:To form Ni electroplating films having good adhesion on the surfaces of dissimilar metals, by applying chemical Ni plating on the surfaces of said metals then applying Ni electroplating thereon. CONSTITUTION:A tungsten metallized layer 2 and an Ni chemical plating film 3 are formed beforehand on the surface of a ceramic substrate 1. An Mo plate 4 and a copper bar 6 formed with Ni chemical plating films 5, 7 and metallic leads 11 are brazed to the substrate 1 by Ag solder 10 and are assembled into a structure of one body. Ni electroplating is thereafter applied on the structure to form an Ni electroplating film 8 on the surfaces of the plate 4, the bar 6 and the leads 1. Thereafter, Au electroplating is applied thereon to form an Au electroplating film 9, whereby a ceramic package for a semiconductor element is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention relates to an electrolytic nickel plating method for forming an electrolytic nickel plating film on an interface between dissimilar metals.

BACKGROUND OF THE INVENTION In recent years, from the standpoint of preventing pollution, it has become necessary to perform plating without pretreatment using cyan. With this pretreatment without cyanide, electrical Ni is applied to the metal surface.
When forming a plating film, it is not easy to fully activate and thoroughly clean the metal surface before plating.If the surface to be plated is the surface of a single type of metal, There is a possibility that the surface can be activated and cleaned with pretreatment. However, when applying electrical Ni plating to the surface of dissimilar metals, it is extremely difficult to sufficiently activate and clean all metal surfaces with pretreatment. For this reason, conventionally, when electrical Ni plating was applied to the surface of a dissimilar metal, there was a problem that the adhesion of the plating film was insufficient and the plating film blistered during the heat treatment after the metal Φ treatment.

Object of the Invention The object of the present invention is to provide an improved electrolytic Ni plating film for forming an electrolytic Ni plating film with good adhesion on the surface of dissimilar metals.
The purpose is to provide a plating method.

According to the present invention, before electrolytic Ni plating is applied to a dissimilar metal surface, the dissimilar metal surface (=chemical N1 plating) is applied, and then electrolytic Ni plating is applied.

EMBODIMENTS OF THE INVENTION Although the present invention can be applied to various products having dissimilar metal surfaces, two embodiments of the present invention will be described below, for example, in the case of ceramic packages for semiconductor devices.

FIG. 1 is a sectional view showing an example of a ceramic package for semiconductor devices to which the present invention is applied. In the figure, 1 is a ceramic substrate, 4 is a molybdenum plate, and 6 is a copper rod. Ceramic substrate 10 surface (second is tungsten metallized layer 2
, a chemical Ni plating film 3 is formed in advance.

4 is a molybdenum plate, 6 is a copper rod, 11 is Kovar (peN)
i Co), etc., and these are chemical N
The Ag solder 10 (=therefore is brazed to the ceramic substrate 1 via the i-plated film 3 and the tungsten metallized layer 2).

Prior to brazing, the molybdenum plate 4 and the copper rod 6 are subjected to chemical Ni plating treatment in their single state, and a chemical Ni plating film 5.7 is formed on their surfaces. For example, using a reduction type chemical Ni plating solution, the molybdenum plate 4 is plated for about 2 minutes to form a chemical Ni plating film 5 with a thickness of about 1 μm, and the copper rod 6 is plated for about 6 minutes to form a chemical Ni plating film 5. A chemical Ni plating film 7 having a thickness of about 3 μm is formed. Then this chemical N
i9) for about 10 minutes to increase the adhesion of the chemical Ni plating films 5 and 7.

After that, the molybdenum plate 4, copper rod 6, and gold fi IJ-de 11 on which the chemical Ni plating film 5.7 was formed,
Ag solder 101 = Ceramic substrate 1 (2 soldered) and assembled into an integrated structure.

In this way, the structure (in the assembled state)
An electrolytic Ni plating film 8 is formed on the surfaces of the molybdenum plate 4, copper rod 6, and lead lead 11 by i-plating. Pre-treatment without using cyanide, for example, alkaline cathodic degreasing at 6V, 60°C, 1 minute, hydrochloric acid (1t 1 ) for 3 minutes, H2S 04 Gilt%
jF 5 V, 1 minute, hydrochloric acid (1:1) 30 seconds,
1Ni strike plating 2A/dm2, 1 minute treatment, then electric Ni plating treatment, after that,
+31.

Electric N with good adhesion that can withstand heat treatment of
An i-plated film 8 is obtained.

Thereafter, an electrical Au plating process is performed to form an electrical Au plating film 9. However, this electric Au plating process is the invention! = is not an essential step, but is only a necessary step in the ceramic package of this example.

When the electrolytic Ni plating film 8 is directly formed on the surfaces of the molybdenum plate 4 and the copper rod 6, which are dissimilar metals, after pretreatment without using cyanide, the adhesion of these electrolytic Ni plating films is insufficient. If it is then heat treated at 400 to 500°C, blistering tends to occur.

However, as mentioned above, if the electrolytic Ni plating film 8 is formed on the chemical Ni plating films 5 and 7 after chemical Ni plating treatment, the electrical The adhesion of the Ni plating film can be greatly improved, and blisters are less likely to occur even after subsequent heat treatment. This adhesion improvement effect is due to the chemical Ni plating film 5,
7 thickness, related to (4). This relationship is as shown in FIG.
If an electrolytic Ni plating treatment is performed after forming, an electrolytic Ni plating film 8 with good adhesion and less likely to blister during heat treatment can be obtained.

Figure 2 shows samples that were subjected to electrical Nl plating and electrical Au plating with different thicknesses of the chemical Ni plating film 5.7, and were heated at a heating temperature of 450°C using air as the heating atmosphere.
, electric Ni after heat treatment under the conditions of adding heating time.
- The swelling rate of the Au plating film is plotted.

The present invention has been described above in detail using a ceramic package as an example. However, it goes without saying that the present invention can be widely applied to applications in which electrolytic Ni plating films are formed on surfaces of dissimilar metals, including but not limited to this example.

Effects of the Invention As detailed above, according to the present invention, an electrolytic Ni plating film with good adhesion and excellent heat resistance can be easily formed on a dissimilar metal surface without pretreatment using cyanide. can be done, and the effect is extremely large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing an example of a ceramic package to which the present invention is applied, and Figure 2 is a diagram showing the relationship between the swelling of the electrolytic Ni plating film and the thickness of the chemical Ni plating film formed underneath. 4... Molybdenum plate, 5, 7... Chemical Ni plating film, 6... Copper rod, 8... Electric Ni plating film. -+71° Fig. 1 2 Fig. 2 Hanawa C

Claims (1)

[Claims] (1) An electrolytic nickel plating method for forming an electrolytic nickel plating film on the surface of a dissimilar metal, characterized in that the dissimilar metal surface is subjected to a chemical nickel plating treatment, and then an electrolytic nickel plating treatment is performed. .