JPS58197291A - Plating method with tin or tin alloy - Google Patents

Abstract

PURPOSE:To obtain a tin plating film having excellent adhesion and solderability, by etching the underlying layer for copper plating provided on an electrically conductive surface to roughen the same then plating tin on the outside thereof. CONSTITUTION:An electrically conductive material such as oxygen-free copper or a copper alloy is subjected to cathodic degreasing, anodic degreasing and pickling, whereafter an org. compd. having the effects for brightening, smoothing and dispersing is added to a sulfuric acid bath using copper sulfate or the like and copper plating is applied on said material to form a copper plated underlying layer. The etching treatment for removing the above-mentioned org. compd. and to dissolve the underlying layer of copper by 0.01-1mu thickness to roughen the surface is then applied on said layer by using an etching soln. of H2SO4- H2O2. Tin or a tin alloy is plated on the outside thereof continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for plating tin or a tin alloy (hereinafter referred to as tin) with excellent adhesion and solderability.

In general, a single strip of electrically conductive material with tin plating on its surface is bent, processed, punched, etc., and then molded with resin, etc., and then used as electronic components such as switches and terminal contacts of connectors. It is widely used in

Conventionally, in this plating method, C was applied to the surface of the electrically conductive material.
This is done through a U plating process and a tin plating process, and after copper plating, tin plating is performed by washing with water or activating with water and dilute sulfuric acid, but the adhesion and soldering are I couldn't get enough in terms of sex. That is, the tin-plated product is heat-treated, e.g.
In the close bending test after 1 hour at 100° C., the tin plating film does not peel off, but after 500 hours at 100° C., a close bending peeling phenomenon occurs, and during press punching, the tin plating film peels off on the punched end face.

This peeling phenomenon is thought to be caused by organic substances as impurities contained in the copper plating solution and organic substances as copper plating additives. .

It occurs between copper alloy layers, but rarely occurs between tin and copper alloy layers and pure tin layers.

This peeling phenomenon occurs in electronic parts where tin-plated materials are used.
In particular, peeled-off tin coatings caused poor continuity between high-density leg wires and switch terminals.

In addition, the soldering properties are also affected by the adhesion of a thin film of organic compounds to the surface of the base copper plating layer, which impairs the soldering properties, especially in the case of bright plating that incorporates additives, making it difficult to incorporate into circuits. Soldering often resulted in poor workmanship.

The present invention has been made in view of the current situation and as a result of intensive research, we have discovered a tin plating method with excellent adhesion and soldering properties. That is, in the method of the present invention, after providing a base layer for copper plating on the surface of an electrically conductive material, etching is continuously performed to dissolve 0.01 to 1 μm of the base layer, and tin plating is applied to the outside of the base layer. It is characterized by this.

In the present invention, electrically conductive materials include oxygen-free copper, tough pitch copper, brass, bronze, Cu-Fe alloy, Cu-Be
alloy, Cu-Ti alloy, Cu-Ni alloy, etc.

This electrically conductive material is subjected to cathodic degreasing and anodic degreasing, and examples of the degreasing agent include ENDOX 114 (trade name of Shirtgun Metal Finishing Company).

Next, pickling is performed using an aqueous solution of H2SO4, HCt, HBF4, etc., and copper plating is performed to provide an underlayer. The liquids include a sulfuric acid bath with copper sulfate, a birophosphate bath with copper pyrophosphate, a borosulfide bath with copper borofluoride,
A sulfamic acid bath using copper sulfamate, a curing bath using copper syanide, etc. are used.

The additives include components that have gloss, smoothing, and dispersion effects, and the gloss component is thiocar-7genyl (
'X=S), sulfide, polysulfide [-(
-8-)-X) and other organic S compounds, and smoothing components include dyes (phenazine, triphenylmethane, azine), gelatin, gelatin, dextrin, aromatic sulfonic acids (
naphthalene disulfonic acid, etc.). Dispersion components include ionic activators (polyether), anionic activators (butyl sulfate), and the like.

The method of the invention is particularly suitable for etching solutions such as H2S04.
-H2O2, HBF4-H2O2 or ammonium persulfate-H2SO
4 or the like to remove the organic compound and to the extent that it does not interfere with the appearance of the copper plating, that is, the thickness of the copper base layer is 0.01
An etching process is performed to dissolve ~1μ and roughen the surface.

The thickness of the solution by etching is 0.01 to 1. If the thickness is less than 0.01μ, it will have a great effect on adhesion and soldering properties, and if it exceeds 1μ, it will inhibit the appearance gloss and the plating should be made as thick as the melting thickness. This is because productivity is low and costs are high.

Thereafter, tin plating is performed by a conventional method to obtain the tin-plated product of the present invention.

Next, examples of the present invention will be described.

Example (1) A 7/3 brass strip with a thickness of 0.25 mm and a width of 200 mm was placed in a commercially available aqueous solution of Soyano Metal Finishing Co., Ltd.'s degreaser, Cleaner 160 (trade name), 45 g/l, at a temperature of 65 to 75°C. Cathode degreasing was performed for 920 seconds at a current density (DC) of 3A/dm2, and further at a current density (DC) of 2A7dm.
After performing anodic degreasing for 10 seconds in accordance with No. 2, washing was performed with water.

5- Then with 10% H2SO4 aqueous solution! Pickling was carried out for 1l11o seconds, and a sulfuric acid steel plating bath (Cu50 g/l, H2
SO45011/It, (NI(2)C80,01
g/13, dextrin (C6H2005) no
, o I g/11. HCtO,O], 2.9/A'
) was used to provide a copper plating base layer with a thickness of 1.2 μm at a current density of 5 A/dm 2 . After that, wash continuously with water.
2SO4 2009/l, H2O2 10g/l, alcohol 1ocr.

It was immersed in an etching solution consisting of A for 4 seconds to dissolve about 0.05μ of the underlayer.

Next, tin plating solution (5nSO440Vl, H2SO4
150 νl, 1μ thick with cresol sulphur (110V 1.β naphthol 1.2 g/1. gelatin 2.3 g/l).

Tin plating of 1.5μ and 2μ was performed, washed with water, and dried to obtain a tin-plated brass strip of the present invention.

The thus obtained tin-plated brass strip of the present invention was heated at 100°C x 500°C.
After the heat treatment for hrs, the presence or absence of peeling of the coating was measured by a 18o0 close bending test and a press punching test (clearance ζ2/Zoo), but no peeling phenomenon was observed in either case.

Example (2) 6- Using the same brass strip as in Example (1), degreasing, pickling, copper plating base layer, and etching were performed in the same manner as in Example (1).

Next, the following solder plating solution S n (BF 4 )2 26011
/12Pb (BF'4) 225miq HBF4200g/l Brightener Toho Rayon Co., Ltd. S 60Q/IB
7 cC/1 formalin (37 c)
, using 10g/l of 20Cn/7 boric acid, at a bath temperature of 18°C, with thicknesses of 1μ, 2μ, 3μ and 4μ.
A tin-plated brass strip of the present invention was obtained by tin-plating, washing with water, and drying.

The thus obtained tin-plated brass strip of the present invention was subjected to the same test as in Example (1), but no peeling phenomenon was observed.

Comparative Example (1) Using the same brass strip as in Example (1), only a water washing process was performed without performing an etching process, and all other conditions were the same as in Example (1), with a tin plating layer thickness of 1 μm. ,1
．． Comparative tin-plated copper strips of 5μ and 2μ were obtained.

Comparative Example (2) The same brass strip as in Example (2) was used, but instead of etching, it was treated with a 5% H2SO4 aqueous solution, and everything else was the same as in Example (2), with a tin plating thickness of 1μ,
Comparative tin-plated copper strips of 2μ, 3μ and 4μ were obtained.

Comparative Example (3) Using the same brass strip as in Example (2), using H2H2SO42O0, ■2021g/l and alcohol 2cfJl as the etching treatment liquid, the film thickness of the copper underlayer was reduced to approximately 0.
．． The tin plating thickness was 1μ, 2μ, and 3μ in the same manner as in Example (2) except that 0.005μ was dissolved and the etching treatment was performed.
Comparative tin-plated copper strips of 4μ and 4μ were obtained.

The tin-plated brass strips of Comparative Examples (1) to (3) thus obtained were tested for adhesion and press punchability in the same manner as in Example (1). Admitted.

Furthermore, the soldering characteristics (solder wet area) of the tin-plated brass strip of the present invention and the tin-plated brass strip of the comparative example were measured using the test method shown below. The results are shown in Table 1.

That is, a 25X25X0.25+nm test piece was MiL −
It was carried out according to STD-202D, 208B (vertical dipping method).

First, dipped in acetone for 2 minutes, dried, dipped in 25%-W, W rosin alcohol flux for 5 seconds, dried, 60/40
After being immersed in solder (230±1° C.) for 1±0.1 seconds, it was taken out and immersed in acetone, then immersed in Improvil alcohol, and dried. Note that the immersion area is 25 x 12.5 scale.

9-10- As detailed above, the method of the present invention has remarkable effects such as obtaining tin-plated wires and strips with excellent adhesion and soldering properties.

Applicant's agent: Patent attorney Suzue Takehiko = 11-

Claims (1)

[Claims] After providing a copper plating base layer on the surface of the electrically conductive material, etching is performed to dissolve 0.01 to 1μ of the base layer, and the outside thereof is plated with copper or tin alloy. A method of plating tin or tin alloy.