JPH0586007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention is characterized in that the Sn content is 1wt% or more and less than 3wt%, and the P content is 0.03wt% or more and 0.35wt%.
Copper alloy-tin-based contacts made of low-tin phosphor bronze, the balance of which is copper and unavoidable impurities, is plated with a tin or tin alloy layer. The present invention relates to a method for manufacturing a contact that does not cause the problem of peeling of the plated layer during use and does not deteriorate during use under severe conditions.

Background of the Invention Contactors for circuit connections such as connectors and switches are made of copper alloys with increased springiness and corrosion resistance, such as phosphor bronze, beryllium copper, and titanium copper, as base materials.
Furthermore, in order to reduce contact resistance, gold or silver plating is often applied as a surface contact metal, but this is not suitable for use in consumer electronic equipment from the viewpoint of cost and mass production. Therefore, in consumer electronic devices, copper alloy-tin contacts plated with inexpensive tin or tin alloy are currently mainly used as surface contact metals.

When a contact is installed inside an electronic device, the temperature inside the device rises to around 100℃ due to the heat generated by electricity, so the contact is exposed to such relatively high temperatures for a long period of time. Become. Additionally, electronic devices are often subject to mechanical vibrations. for example,
A large number of contacts are used in automotive electrical circuits and are subjected to long-term vibrations. Under such usage environments, the creep strength of the base material decreases, and, for example, the male-female contact pressure of the connector decreases, causing the connector to become loosely fitted or come off. Furthermore, conventional copper alloys, especially phosphor bronze base materials, contain more than 3% tin, which makes them difficult to handle electricity (heat).
The extremely poor conductivity has also come to be seen as a problem.

In view of these circumstances, it is necessary to develop a base alloy that can maintain strength under vibration and thermal conditions while ensuring sufficient conductivity.

Furthermore, an important problem associated with conventional contacts is that when the contacts are used under the above conditions, the tin or tin alloy plating layer peels off from the base material.
The drawback of poor contact was recognized. Measures have been taken to overcome the problem of tin plating layer peeling, but with the development of new base metal alloys, it is also necessary to develop an optimal method for preventing tin plating layer peeling.

SUMMARY OF THE INVENTION In view of the current situation, the present inventor conducted intensive research to develop a contact that eliminates the above-mentioned problems, and found that phosphor bronze (with a Sn content of 3 ~10wt%, P content 0.03
The use of low-tin phosphor bronze with a Sn content lower than 0.35wt%) gives good results, and heat-melting (reflow) treatment of the tin-plated layer is effective as a method for preventing peeling of the tin-plated layer. I found out.
Low-tin phosphor bronze with a tin content of 1 wt% or more and less than 3 wt% exhibits improved electrical (thermal) conductivity compared to conventional ones due to its reduced tin content, and at the same time exhibits sufficient electrical (thermal) conductivity under usage conditions such as vibration and heat. Provides a base material that retains strength. The plating of tin or tin alloy onto the base material followed by heating and melting provides a surface contact metal with good adhesion and workability without peeling, and also maintains low cost.

Thus, the present invention provides a copper alloy having a tin content of 1 wt% or more and less than 3 wt%, a phosphorus content of 0.03 wt% or more and less than 0.35 wt%, and the balance consisting of copper and unavoidable impurities. The present invention provides a method for manufacturing a contact, which comprises electroplating tin or a tin alloy onto a base material, followed by heating and melting treatment, or melting and plating tin or a tin alloy.

DETAILED DESCRIPTION OF THE INVENTION In the present invention, it is customary to plate and heat melt a strip, sheet, etc. of the copper alloy and then mold it into a contact. There is no hindrance to applying heat-melting and heat-melting treatments. Here, the explanation will be based on the former.

The copper alloy strip used in the present invention has a Sn content of 1 wt% or more and less than 3 wt%, a P content of 0.03 wt% or more and less than 0.35 wt%, and the balance consists of copper and inevitable impurities. It is a copper alloy. The preferred composition is 1.7~2.3wt%Sn and 0.03~
It contains 0.2wt%P. This is characterized by a lower Sn content than what is commonly referred to as phosphor bronze, and is referred to here as low tin phosphor bronze. Until now, general phosphor bronze had been used as a base material for contacts, especially contacts for automotive electrical equipment, but it had been used as a base material without any deep consideration simply because of its good springiness and corrosion resistance. As such, low-tin phosphor bronze is superior as a contact base material because it has better electrical (thermal) conductivity (IACS value of 30% or more).

This copper alloy strip is subjected to predetermined purification treatments such as alkaline degreasing, electrolytic degreasing, pickling, and water washing in a known manner, and then directly plated with tin or tin alloy without being plated with a copper undercoat. be done. Conventionally, copper underplating has often been used as a measure to prevent peeling of the plating layer, but this is unnecessary in the present invention and is even harmful.

Plating of tin or a tin alloy can be carried out by electrolytic plating, electroless plating or hot-dip plating. The tin alloy includes those containing one or more of lead, bismuth, cadmium, antimony, indium, aluminum, zinc, etc., which are generally known as solder materials.
The plating conditions remain the same as before. Examples of electrolytic plating baths include alkaline baths using potassium stannate, sodium stannate, stannous chloride, etc., oxalate baths, borofusate baths, sulfate baths, and phenolsulfonic acid baths. Can be used. Melt plating is
The typical method is so-called hot-dip plating, in which the product is immersed in a predetermined flux aqueous solution (40°Be aqueous solution of ZnCl ₂ ) for 1 to 2 seconds, then immersed in a hot-dip plating bath for about 10 seconds, and the thickness of the plating layer is adjusted appropriately by air blowing. It is true. Instead of dipping into an aqueous flux solution, the flux may be floated onto the melted layer and immersed through the flux layer into the melted layer.

The copper alloy strip plated with tin or tin alloy is then subjected to a heat melting process. Heat-melting treatment is also called reflow treatment, and involves heating the material at a temperature of 500 to 800 degrees Celsius above the melting point of tin, that is, 231 degrees Celsius, for an appropriate period of 3 to 20 seconds in a heating furnace such as a direct-burner furnace or an Elema furnace. It is done by folding. This treatment causes remelting and fluidization of the tin or tin alloy layer. However, it is not necessary to re-melt the melted material.

Contacts made in accordance with the present invention do not suffer from peeling of the plating layer during use at high temperatures. for example,
After holding at temperature of 105℃, 150℃, 180℃ for 600 hours
Even when a 90° bending peel test is performed, no peeling occurs at all.
Furthermore, even in actual tests where it was incorporated into an automobile electrical circuit as a connector, there was no drop in contact pressure.
It exhibited extremely good conductive performance.

Effects of the Invention The present invention provides a contact which is used under severe conditions such as heat and vibration, and which does not cause long-term failure and which performs an extremely good contact function, and a method for manufacturing the same.

Example 1 A copper alloy strip with a composition of 2 wt% Sn, 0.1 wt% P, and the balance Cu was subjected to alkaline degreasing, electrolytic degreasing, and pickling neutralization, followed by 1.0 μ electrolytic tin plating in a tin sulfate bath without a copper base. I went to

The cresol sulfonic acid bath and plating conditions are as follows.

Cresol sulfonic acid bath: stannous sulfate 55g/sulfuric acid 100g/cresol sulfonic acid
100g/gelatin 2g/beta-naphthol
1 g/Bath Temperature: 25°C Current Density: 3A/dm ² The thus tinned strip was held at 650°C for 5 seconds in a small Matsufuru heating furnace, then cooled to 70°C, washed with hot water, and dried with hot air. This strip was then molded into the shape of a contact. After the contacts thus produced were heated in the atmosphere at 105°C, 150°C, and 180°C for 600 hours, a peel test was performed by bending at 90°, but no peeling of the plating layer was observed.

Comparative Example 1 A contact was produced using the material of Example 1 without subjecting it to heat-melting treatment. When this was held at 105° C. for 360 hours and then subjected to a peel test, the plated layer peeled off.

Reference Example 1 A contact was produced in the same manner as in Example 1 except that the copper undercoat was plated using the sulfuric acid bath described below.

Copper sulfate bath Copper sulfate 210g/sulfuric acid 100g/bath temperature 30°C current density 5A/dm As a result of the ² peel test, the tinned layer peeled off. Copper underplating is detrimental in this invention.

Example 2 The same steel alloy strip as in Example 1 was subjected to alkaline degreasing, electrolytic degreasing, pickling and neutralization, and then solder plating in a phenolsulfonic acid bath. The plating bath composition and conditions were as follows.

Stannous phenolsulfonate 160g/Lead phenolsulfonate 160g/Phenolsulfonic acid 150g/Bath temperature 30°C Current density 3A/ ^dm2Then , the mixture was heated in an Elema furnace at 650°C for 20 seconds and allowed to cool. The obtained mating material is molded into a contact,
90℃ after 600 hours at 105℃, 150℃, 180℃
A bending peel test was conducted, but no peeling of the solder plated layer occurred in any case.

Example 3 The same steel alloy strip as in Example 1 was alkaline degreased, electrolytically degreased, pickled, neutralized, washed with water, coated with a flux of 40°Be zinc chloride aqueous solution, and immersed in molten tin at a bath temperature of 320°C. Tin plating is applied to a thickness of 2μ.

Thereafter, after molding into a contact and holding it at 105°C for 600 hours, a peel test was performed, and no peeling of the plating layer was observed.

Claims (1)

[Claims] 1. The tin content is 1wt% or more and less than 3wt%,
Electroplating tin or a tin alloy on a copper alloy base material with a phosphorus content of 0.03 wt% or more and less than 0.35 wt%, and the balance consisting of copper and unavoidable impurities,
A method for manufacturing a contact, the method comprising subsequently performing a heating and melting process. 2 The tin content is 1wt% or more and less than 3wt%,
A method for producing a contact, characterized by melt-plating tin or a tin alloy onto a copper alloy base material having a phosphorus content of 0.03 wt% or more and less than 0.35 wt%, the remainder consisting of copper and unavoidable impurities. .