JPH05311279A - Hot dip tin or solder plated material - Google Patents

Abstract

PURPOSE:To improve the thermal peeling resistance of an Sn or solder plating layer, at the time of applying hot dip plating of Sn or solder 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 applying hot dip plating of Sn or solder to electric parts or the like using phosphor bronze as stock, phosphor bronze in which the content of oxygen as impurities in the phosphor bronze is limited to <=20ppm and the content of sulfur to <=40ppm or the content of phosphorus to <=800ppm 15 used. This parts made of phosphor bronze are subjected to degreasing, pickling and flux treatment and are thereafter immersed into hot dip Sn or hot dip solder, by which a phosphor bronze member having an Sn plating layer or a solder plating layer excellent in thermal peeling resistance can be manufactured.

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 It provides a molten tin and a solder plating material.

[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. Examples of the method include a method of heat-melting (reflowing) tin or a solder-plated film, or a method of performing hot-dip plating without applying base plating. 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 the highest productivity of plating and the highest reliability against thermal peeling, so it is currently the most widely used heat-resistant peeling material for phosphor bronze tin and solder plating. ing. Also, hot dip plating has the same level of heat-resistant peelability as reflow plating without the underlying layer, but depending on the conditions such as aging temperature and press working, thermal peeling can occur with aging for tens of thousands of hours, although it is extremely slight. is there. And, unlike electroplating, hot dipping does not require a plating bath or electricity, and thus has an advantage of high productivity. Therefore, it has been desired to further improve the heat-resistant peelability of the hot-dip plated material.

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a hot-peeling molten tin and a solder plating material.

[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) Hot-dip tin or solder-plated material in which tin or tin alloy hot-dip plated phosphor bronze has a phosphor bronze base material having an oxygen content of 20 ppm or less and a sulfur content of 40 ppm or less.

2) The phosphorus concentration in phosphor bronze is 800 ppm.
The molten tin according to the above item 1), characterized in that:
Solder plating material.

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 by 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 and the mixing of sulfur from the raw material, and are cast into the 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 the Kirkendall voids contains phosphorus. , 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 possible 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 hot-plated. Solder is mainly tin with lead of 5 to 45%
It is generally alloyed to some extent, but bismuth, zinc, etc. 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.

As the phosphor bronze having a desired shape, known ones such as degreasing with an alkaline solution, wet pretreatment such as activation by pickling, or pretreatment with a non-oxidizing furnace can be used. The hot-dip plating of tin or solder plating is carried out by inserting phosphor bronze into a hot-dip metal having a desired plating composition. Prior to this, there is no particular problem in applying zinc chloride flux after pretreatment. The plating thickness of the plated material pulled up from the molten metal is controlled while the coating remains in a molten state. A known method such as a mechanical wiper or an air knife can be applied to control the plating thickness.

The phosphor bronze tin and the solder plating material thus produced have extremely high heat-resistant peeling property.

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

[0017]

Example After phosphor bronze (Table 1) having three compositions was melted, cold working and heat treatment were repeated to manufacture a 0.2 mm thick plate. This was degreased, pickled, and further immersed in GX-5 (Asahi Chemical Laboratory) for flux treatment. Immediately after this 3
Molten tin or molten 9/1 (90% Sn-10%
Pb) Immersed in solder. After soaking for 3 seconds, it was pulled up and air-cooled.

The plated material was cut into a test piece of 10 mmW × 50 mmL, bent 180 degrees (U-bend) with a bending radius of 0.4 mm, aged at 85 ° C. for a predetermined time, and then bent back to a flat plate, By visually observing the presence or absence of peeling of the plating, the heat-resistant peeling property of the plated material was evaluated.

The results are shown in Table 1.

[0020]

[Table 1]

[0021]

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 plated material having a tin or tin alloy hot-dip plated 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 4 or less.
Molten tin, a solder plating material characterized by being 0 ppm or less. 2. The phosphorus concentration in the phosphor bronze base material is 800 pp.
2. The molten tin according to claim 1, wherein the molten tin is less than or equal to m.
Solder plating material.