JPH02138484A - High phosphorus-content nickel plating method - Google Patents

Abstract

PURPOSE:To laminate an electroplating layer having excellent wettability with solder on the surface of a plating object by subjecting the plating object to plating in a high-phosphorus content nickel electroless plating bath, then passing current thereto under specific conditions while the plating object is held immersed in the bath continuously. CONSTITUTION:A substrate 1 which is the plating object is subjected to the plating in the electroless plating bath which can incorporate phosphorus at a high ratio of 20 to 25% by atom into the plating film of the substrate. While the plating object is then kept immersed continuously in the same plating bath without taking the object out of the plating bath, the current of 1 to 10A/dm<2> current density is passed thereto for 1 to 10 minutes or longer to laminate the electroplating layer 8 on the surface of the plating object. As a result, the plating film 8 which is forcibly lowered in the phosphorus content of only the uppermost part of the film is provided by electroplating on the electroless nickel film 7 having excellent chemical resistance and wear resistance and, therefore, the wettability with solder is greatly improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention relates to a high phosphorus-containing nickel plating method,
It is used for electrical contacts with sliding parts, printed circuit boards, electrical parts with soldering parts, and wiring parts.

(Prior art) As a conventional technology related to the present invention, Japanese Patent Application Laid-Open No. 6024888
There is a 2nd bulletin.

This is an electroless plating bath that can contain phosphorus at a high atomic ratio of 20 to 25% in the nickel film. Contains ~25% phosphorus and has excellent chemical resistance and wear resistance.

(Issues that the invention seeks to solve) However, when the plating film produced by the high phosphorus content nickel plating method is applied to electrical parts such as electrical contacts that have sliding parts, there is always a soldering process, and this solder wettability is There is a problem in that, because of the poor quality, it is not used in products with electrical parts that have electrical contacts.

The technical object of the present invention is to provide an electroless plating method that provides excellent solder wettability in the plating film formed by the high phosphorus-containing nickel plating method.

[Structure of the invention]

(Means for solving the problem) The technical means taken to solve the above technical problem are as follows. That is, after plating with an electroless plating bath capable of containing phosphorus at a high atomic ratio of 20 to 25% in the plating film of the object to be plated, the object to be plated is continuously coated without taking it out of the plating bath. 1 to IOA/dm while immersed in the same plating bath
This is an electroless plating method for high phosphorus-containing nickel plating, in which a current with a current density of 1 to 10 minutes or more is passed for 1 to 10 minutes or more to form a thin electroplating layer on the surface of the object to be plated.

On top of the electroless nickel phosphorus coating, which has chemical resistance 1 and excellent wear resistance, a plating film with a forced reduction in phosphorus content is applied only to the top of the coating by electroplating, resulting in improved solder wettability. This is a significant improvement.

Regarding electroless plating and electrolytic plating, (1) Nt”→
Ni' -2e-, (2) 3PO"→P0+2PO!-
+2e-, the reactions (1) and (2) above occur in both electroless plating and electroplating baths, but in the case of electroplating, the reaction (1) above is dominated by the magnitude of the current density. In comparison, the reaction in (2) is almost constant.

Therefore, it is possible to control the phosphorus content in the coating by changing the current density.

The present invention further improves chemical resistance and abrasion resistance by laminating a nickel film with a controlled phosphorus content within a range of up to 25% in atomic ratio on the top layer of a high phosphorus-containing electroless plated film. It has improved solder wettability.

(Example) Examples will be described below.

Figure 1 shows an electrical contact with a sliding part A, where 1 is an epoxy plate, the sliding part is made of copper foil 2 and a plating film 3, and 4 is 6
It is a Genkin Genkin brush.

Glass Evokin copper clad laminate (CEM3. Copper foil thickness 35
High phosphorus-containing electroless nickel plating (amorphous plating) is applied to the copper foil portion 2 of the substrate 1, on which a predetermined pattern (μm) has been formed by etching.

Pretreatment for plating includes: (1) Degreasing: OPC Clean 91 (Okuno Pharmaceutical);
50cc/l (ion-exchanged water) 30℃, 2 minute immersion, (2) Soft etching...sodium sulfate (Na
z sz ol ) 100g/I! (Ion exchange water 3
The treatment was carried out in three steps: 0°C for 2 minutes, (3) Pickling: immersion in sulfuric acid 100''/j' (ion-exchanged water) at 30°C for 1 minute.

Next, regarding high phosphorous nickel plating, a patent application was filed in 1986-24.
As described in Publication No. 8882, nickel chloride...2
0g/I! , Sodium hypophosphite...100g/l
, Trisodium lienoate...50g/j! , Saccharin sodium...2g IC lithium sulfate...
25g/1. *C3゜H1sNa30. ...3g/L *(N-2 hydroxyethylethylenediamine NN'
N"trisodium acetate)

The plating solution was adjusted to 90° C. and pH 4.6, and the pretreated substrate was immersed in the plating solution, and a current of 1× was applied for 1 minute.

At this time, the substrate is a cathode, and a stainless steel plate or a nickel plate may be used as an anode.

After 1 minute, the current was turned off and electroless plating was performed for 80 minutes.
m plating films are formed.

After that, when the board was taken out from the plating side, it was 2.5A/d.
When a current with a magnitude of 1.5 m is applied (at this time, the substrate is the cathode and the anode is a nickel plate), an electroplated film of about 1.5 μm is formed on the electroless film in 5 minutes. The content is 10% in atomic ratio according to EPMA analysis.

Next, Figures 2 to 4 show the cross-sections of the plated coatings; Figure 3 shows the electroless nickel plating with high phosphorus content and electrolytic low phosphorus content, and the conventional non-electrolytic high phosphorus coating shown in Figure 2. Table 1 shows a comparison of solder wettability, chemical resistance, and abrasion resistance between the electrolytic nickel coating and the electroplated nickel coating shown in Figure 4. Glass Evokin 6 is a copper foil, 7 is an electroless plating film, and 8 is an electrolytic plating film.

Note 1. In the wet area, apply resin-based flux to the test piece, dry it, and immerse it in a eutectic solder bath temperature-controlled at 230 ± 3°C for 5 ± 0.5 seconds. Note 2. Regarding chemical resistance, immersion in ferric chloride 300g/l, 30°C, 1 minute, Note 3. Regarding wear resistance, six element alloys (Pt, Au.

A load of 9g was applied to the test piece using a brush (Pd, other elements), and the test piece was reciprocated 2 million times. From the above results, it was found that the previous excellent properties (chemical resistance, abrasion resistance) were not impaired, and no defects were identified. It was possible to greatly improve the wettability of solder 1, which had been previously used.

Figure 5 shows the phosphorus content in the thickness direction of the electroless plated film + electroplated film in this example, and Figure 6 shows the relationship between current and time in this example. be.

〔Effect of the invention〕

The present invention has the following effects. That is, the solder wettability is better than that of the conventional technology, and it is extremely effective when automating soldering work using a robot or the like.

[Brief explanation of the drawing]

Figure 1 (a) is an explanatory diagram of an electrical contact having a sliding part;
b) is a sectional view of the main part of (a), Figs. 2 to 9 are explanatory cross-sectional views of each plating layer, Fig. 5 is a relationship between the thickness of the plating layer and the phosphorus content, and Fig. 6 is a diagram showing the relationship between current and time in this embodiment. A...Electrical sliding part. ■... Board. 2.6...Copper foil. 3... Plating film. 7... Electroless plating film 8... Electrolytic plating film.

Claims (1)

[Claims] After plating with an electroless plating bath capable of containing phosphorus at a high atomic ratio of 20 to 25% in the plating film of the object to be plated, the object to be plated is continuously coated without taking it out of the plating bath. 1 to 10 A while immersed in the plating bath.
A high phosphorus-containing nickel plating method in which a current with a current density of /dm^2 is passed for 1 to 10 minutes or more to deposit a thin electroplating layer on the surface of the object to be plated.