JPH05311280A - Reflow tin and solder plated material - Google Patents

Abstract

PURPOSE:To improve the thermal peeling resistance of a plating layer, at the time of applying reflow tin plating or reflow solder plating to parts made of phosphor bronze, by limiting the contents of oxygen, sulfur and phosphorus in the phosphor bronze stock to respective specified values or below CONSTITUTION:At the time of forming a reflow tin plating or reflow solder plating layer by executing reflowing of applying electroplating of Sn or solder to electric parts or the like using phoshor bronze as stock and heating and melting it, the content of oxygen in the phosphor bronze as the stock is regulated to <=20ppm and the content of sulfur to <=40ppm or the content of phosphorus to <=800ppm, by which the thermal peeling resistance of a reflow tin plating layer or a reflow solder plating layer is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a metallic material for a connector contact or a lead of an electronic component and is a phosphor bronze that does not cause peeling of a tin or tin alloy plating layer due to long-term aging, that is, heat peeling Reflow tin,
A solder plated material is provided.

[0002]

2. Description of the Related Art Phosphor bronze is a copper alloy which is excellent in press workability and strength and is therefore widely used as a metal material for electronic parts. In particular, it is a general metal material such as a contactor of a connector or a lead material of parts. When used as a metal material for these parts, tin or tin alloy (solder) plating in which lead is alloyed with tin is applied for the purpose of reducing contact resistance at contacts and improving solderability. .

However, when tin or solder plating material of phosphor bronze is aged for a long time after plating, reaction diffusion between tin of the plating film and copper of the base material proceeds, and along with this reaction diffusion, phosphorus in the mother layer diffuses. The formation of Kirkendall voids in the vicinity of the interface between the base metal and the base material promotes the adhesion of the plating layer to decrease, resulting in peeling. This phenomenon is called thermal exfoliation because it occurs due to a thermal process such as diffusion and segregation due to aging, although the adhesion is good immediately after plating. Since the reaction diffusion of copper and tin proceeds even at room temperature, thermal exfoliation occurs even at room temperature aging, but it is more likely to occur in a temperature rising environment.

On the other hand, electronic parts using phosphor bronze tin and a solder plating material are heated to a temperature higher than room temperature due to high density mounting inside the electronic equipment. Therefore, thermal peeling of the plated material tends to be accelerated. When the heat peeling occurs in the electronic component, the circuit is broken, and thus the heat peeling of the plated material becomes a fatal defect.

Conventionally, as a method for preventing thermal peeling of phosphor bronze tin or solder plating material, nickel is used as an undercoat, copper is used as an undercoat in a thickness of 2 μm or more, and the undercoat is omitted. For example, a method of heat-melting (reflowing) the tin or solder plating film may be used. However, when nickel undercoating is applied, press workability is deteriorated, and when copper undercoating is applied to a thickness of 2 μm or more, there is a problem that productivity of plating is significantly reduced. In addition, the method of reflowing the plating film by omitting the base plating has high productivity of plating and the highest reliability against thermal peeling, so it is currently the most popular heat-resistant peeling material for phosphor bronze tin and solder plating. is doing. However, depending on conditions such as aging temperature and press working, thermal peeling may occur after aging for tens of thousands of hours although it is extremely slight. Therefore, it has been desired to further improve the heat-resistant peeling property of phosphor bronze tin and solder plated materials.

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a reflow tin and a solder-plated material having a heat-resistant peeling property.

[0007]

Under the above circumstances, various experiments were conducted in order to further improve the heat-resistant peeling property of phosphor bronze tin and solder plated materials, and the invention described below was achieved.

1) In a tin or tin alloy plated material obtained by electroplating tin or tin alloy plating of phosphor bronze and heating and melting the plated film, the phosphor bronze base material has oxygen of 20 ppm or less and sulfur of 40 ppm or less. Reflow tin and solder plated material. 2) The reflow tin and solder-plated product according to the above item 1), wherein the phosphorus concentration in phosphor bronze is 800 ppm or less.

Here, phosphor bronze is not limited to those in the range of 3.5 to 9.0% tin and 0.03 to 0.35% phosphorus specified in JIS, and phosphorus is contained in 1.0% or more tin. It also includes tin and tin, which represents a copper alloy that may cause thermal peeling when subjected to solder plating, and tin and phosphorus, as well as those containing other additive elements such as nickel and zinc.

These copper alloys are melted with a predetermined alloy component in consideration of the mixing of sulfur from the furnace material and the molding material, the mixing of sulfur from the raw material, and the like are cast into an ingot. In some cases, the sulfur concentration in the ingot may be adjusted by adjusting the melting flux or adding a trace amount of magnesium or the like. Oxygen in the ingot is adjusted to a desired concentration by controlling the deoxidizing effect of phosphorus and the atmosphere. In addition, it is necessary to be careful so that the oxygen concentration of the product does not rise due to internal oxidation due to the heat treatment in the process of processing the ingot into a plate, strip or wire. In any case, the sulfur concentration and oxygen concentration in the alloy can be appropriately selected depending on the alloy components and the processing method.

Thermal peeling is mainly caused by the formation of Kirkendall voids in the vicinity of the interface between the reaction diffusion layer and the base material, which lowers the adhesion of the plating layer. However, the inner surface of Kirkendall voids contains phosphorus and sulfur. , Oxygen, etc. segregate on the surface to promote thermal exfoliation. Therefore, the present invention is intended to suppress the thermal peeling by controlling the concentrations of these harmful elements in the base material. Adjust phosphorus concentration to 800 with control of sulfur and oxygen concentration.
When the content is controlled to be ppm or less, the heat-resistant peeling property is further improved.

Plating is performed even at the stage of material such as plate, strip, wire,
It is applied even after processing such as pressing. First,
After surface activation such as degreasing and pickling, tin or solder is electroplated. Solder is mainly tin with lead of 5 to 45%
It is generally alloyed to some extent, but bismuth or the like may be alloyed. The heat peeling occurs in the plating film containing tin as a main component, and the present invention also includes the case of containing other plating alloy elements.

Various kinds of electroplating such as tin and solder plating are known such as sulfuric acid bath, organic acid bath, bromide bath, and alkaline bath. The present invention is effective regardless of the plating bath and plating conditions. Is. After electroplating, the plated material is heated above the melting point of the coating and subjected to reflow treatment. Known methods can be applied to the heating method, atmosphere, and rapid solidification (quenching) method of the film in the reflow treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[0015]

EXAMPLE Phosphor bronze (Cu-8.2% S of three compositions)
After n-0.01P) was melted, cold working and heat treatment were repeated to produce a 0.2 mm thick plate. This was degreased and pickled, and tin or solder was electroplated and then reflowed.
The electroplating conditions are shown below.

Tin plating Plating bath: Stannous sulfate 70 g / L Sulfuric acid 70 g / L Organic additive 10 g / L Bath temperature: 25 ° C. Current density: 3 A / dm ² Plating thickness: 1.5 μm 9/1 Solder plating Plating bath : Tin methanesulfonate 60 g / L Methanesulfonic acid 70 g / L Organic additive 10 g / L Bath temperature: 25 ° C. Current density: 3 A / dm ² Plating thickness: 1.5 μm The plating material was cut into a 10 mmW × 50 mmL test piece, Bend 180 degrees (U-bend) with a bending radius of 0.4 mm, age at 85 ° C for a predetermined time, and then bend back to a flat plate.
The heat-resistant peeling property of the plated material was evaluated by visually observing the presence or absence of plating peeling inside the bent portion.

The results are shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, the plated material of the present invention has a high heat-resistant peeling property, and by using this, a highly reliable electric component can be manufactured.

Claims (2)

[Claims] 1. A tin or tin alloy plated material having an electroplated tin or tin alloy layer on the surface of a phosphor bronze base material, wherein the phosphor bronze base material has an oxygen content of 20 ppm or less and a sulfur content of 40 ppm. A reflow tin and a solder plating material characterized by the following: 2. The phosphorus concentration in the phosphor bronze base material is 800 pp.
The reflow tin and the solder plated material according to claim 1, wherein the reflow tin and the solder plated material are m or less.