JPH05179455A - Method for plating cu and cu alloy with ni - Google Patents

Abstract

PURPOSE:To subject Cu or Cu alloy stock to Ni-P alloy plating and to improve corrosion resistance at a low cost when a connector made of the stock is plated. CONSTITUTION:Cu or Cu alloy stock is plated with an Ni-P alloy in a 1st process and the plated stock is heated at 700 deg.C to a temp. below the m.p. of the Ni-P alloy in a 2nd process to increase the P content of the surface part by diffusion. By this method, the corrosion resistance of an Ni plating film as the underplating of a connector is improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is applicable to Cu and Cu alloys with Ni.
Regarding the plating method, the corrosion resistance of the Ni plating film is improved at low cost.

[0002]

2. Description of the Related Art Cu and Cu alloys (hereinafter simply referred to as Cu)
Since is excellent in electrical conductivity and thermal conductivity, is widely used as an electronic material / part. The method of Ni plating on Cu is relatively easy. After degreasing the Cu surface, it is activated with an acid to perform electroplating or electroless plating. The present invention also relates to a connector plating method using Cu as a raw material.

Ni plating is often used as a base plating for Sn or Au as a connector material. The surface function of the connector is low contact resistance, and the underlying Ni plating plays a role in maintaining the initial performance of the top surface plating of Sn or Au selected to have low contact resistance. If the corrosion resistance of the underlying Ni plating is insufficient, the surface function of the outermost surface plating of Sn or Au deteriorates due to the progress of corrosion from the pinhole. Therefore, as a simple means of improving the corrosion resistance, from the meaning of suppressing the pinhole, which is the corrosion base point, as much as possible,
It is to design the plating layer thick.

Recently, Ni-
Attention has been paid to P alloy plating. Ni-P alloy plating is a typical example of electroless plating, in which sodium hypophosphite is used as a reducing material and Ni is deposited by its reducing power without using an external power source. At this time, from the reducing material to P
Eutectoid in the Ni plating film.

When P is contained in the Ni plating film, P is 5
It is a supersaturated solid solution of Ni up to about Wt% (hereinafter, simply expressed as%), but when the P content further increases from 5%, the structure gradually changes to an amorphous-like structure. And in the high P Ni plating film with a P content of 10% or more,
It has been shown that the corrosion resistance is significantly improved. This is P
It is explained that the electrons of the 3s and 3p bands fill the vacancies of the d band of Ni and reduce the surface activity of the Ni-P alloy.

[0006]

The problem to be solved by the present invention is to improve the corrosion resistance of the Ni plating film which is the undercoat of the connector. To simply increase the thickness of the plating film leads to high cost, especially when Au is used for surface plating,
Plating thickness becomes a significant cost control factor. Further, when a high-P plating film of about 15% is produced, the cost of the plating solution is high and the deposition rate of this plating is slow, which also leads to high cost.

[0007]

Therefore, in the present invention, after Ni-P alloy plating which is stable in cost, Ni and Cu of the raw material are mutually diffused by heat treatment, and as a result, the P content of the plating surface portion is reduced. Tried to increase. That is, the gist of the present invention is that the first step of plating Cu and Cu alloy with Ni-P alloy and the material plated with Ni-P alloy at 700 ° C. or higher and of Ni-P alloy Ni to Cu and Cu alloys consisting of a second step of heating at a temperature below the melting point
It is a plating method.

The Ni-P alloy plating in the first step has a P content of 5% or more, which has an amorphous-like crystal structure, and is basically abundant in the market and has a stable cost of 8 to 12%.
Is selected. It also includes electroplated Ni-P alloys. In order to maintain the surface cleanliness of the Ni-P alloy plating, the second heating step is performed in a non-oxidizing atmosphere such as nitrogen, argon, or vacuum, or in a reducing atmosphere in hydrogen or a hydrogen / nitrogen mixed gas stream to improve productivity. Considering the above, the temperature shall be 700 ℃ or higher. In addition, the melting point of Ni-P alloy differs depending on the P content.
(The higher the P, the lower the melting point). Therefore, the upper limit of the heating temperature was set below the melting point.

[0009]

FUNCTION AND EFFECT The Ni—P alloy plating film obtained by the present invention has a P concentration gradually increasing from the material / plating interface to the surface, and the plating surface becomes a high P plating film. Therefore, it is not necessary to improve the corrosion resistance of the Ni-P alloy plated film at a relatively low cost, and as a result, it is not necessary to apply Sn or Au plating thickly thereon.

[0010]

[Example] A commercially available electroless Ni plating solution (Nihon Kanigen S
It was immersed in −753) for 20 minutes. The thus obtained electroless plated film on Cu is subjected to a fluorescent X-ray film thickness meter (Seiko-Electronic Industries S
FT-8000), a plating thickness of 5 mm and a P content of 8% were obtained. Furthermore, electroless Ni plating
Cu was vacuum heat-treated at 750 ° C for 10 minutes and electroless Ni was similarly applied.
When the plating film was measured by a fluorescent X-ray film thickness meter, it was confirmed that the P content in the surface layer increased to 12%.

Also, electroless Ni-plated Cu after heat treatment
When the cross section was cut obliquely and the cross section was analyzed by EPMA, it was found that Ni and Cu diffused into each other and the P content in the surface layer increased. Figure 1 shows the EP measured in this example.
The analysis result of MA is shown. Furthermore, it produced in the same way.
A sample with heat treatment at 50 ° C. and a sample with no heat treatment but without electroless plating were immersed in 1N HNO ₃ to measure the corrosion weight loss. As a result, while those with heat treatment have a corrosion weight loss per unit area of 40 mg / (m ² min),
The number of non-heat-treated products was 60 mg / (m ² min).

[0012]

[Brief description of drawings]

FIG. 1 is an EPMA analysis result of a cross section of electroless plated Cu according to the present invention.

Claims (1)

[Claims] 1. A first step of subjecting a material made of Cu and a Cu alloy to Ni—P alloy plating, and the material subjected to the Ni—P alloy plating at 700 ° C. or higher and below the melting point of the Ni—P alloy. Cu characterized by comprising a second step of heating at a temperature
And Ni plating method on Cu alloy gold.