JPH0533109A - Production of hot-dipped material - Google Patents

Abstract

PURPOSE:To prevent the occurrence of surface discoloration due to long-term storage and heating by forming a tin (alloy) plating layer and spraying an aqueous solution of carboxylic acid of specific concentration before the plating layer is solidified. CONSTITUTION:A plating layer of tin (alloy) is formed on a base material composed of copper alloy by a hot dipping method. Subsequently, before the plating layer is solidified, an aqueous solution of carboxylic acid of 1-10wt.% concentration is sprayed on the plating layer and cooled. At this time, the formation of an oxide film on the surface of the plating layer cannot be prevented sufficiently when the concentration is <1%, and, when it is higher than 10%, removal by water washing is made difficult. Because surface discoloration can be prevented even at the time of heating even after long-term storage, deterioration in solderability and increase in contact resistance can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot dip plated material, and more particularly to a method for producing a hot dip plated material which does not cause surface discoloration in the atmosphere.

[0002]

2. Description of the Related Art A plated material made of a copper alloy such as phosphor bronze or brass and plated with tin or tin alloy on its surface is used as a terminal or connector when it is a strip material.
Further, in the case of a wire rod, it is widely used as a lead for electronic parts. As a method for producing this plated material, in addition to the method of electroplating tin or tin alloy on the surface of the base material, it is possible to reduce the cost, and because the diffusivity between the base material and tin or tin alloy is excellent, The hot dipping method is adopted.

In this hot dip plating method, a base material to be plated is introduced into a hot dip bath stored in a plating bath and then pulled up to form a plating layer having a desired thickness on the surface of the base material. Is the way. In this case, since the hot-dip plating bath adhering to the surface of the base material is still in a molten state when the base material is pulled out from the hot-dip plating bath, it is necessary to cool and solidify the hot-dip plating bath.

As the cooling method, cooling is generally performed in the atmosphere, but a method of spraying water forcibly and rapidly cooling is also adopted. In the latter cooling method, the hot-dip galvanizing bath adhering to the surface of the base material rapidly solidifies, so that the growth of coarse crystal grains can be suppressed and the time in the atmosphere at high temperature is shortened. It is more useful than the former case of cooling, in that the oxidation by the atmosphere is suppressed.

[0005]

However, even if the above-mentioned rapid cooling with water spray cannot completely prevent the surface oxidation of the hot dip coating, a slight oxide film is formed on the surface of the formed plating layer. Resulting in. If an oxide film is formed on the surface of the plating layer, if the plating material is stored in the air for a long time or is heated during use (processing into a desired shape), the surface of the plating layer Discoloration is caused.

The plating material having such a surface discoloration is not only inferior in appearance but also inferior in solderability or contact resistance, which is inconvenient in practical use. I have a problem. The present invention is a method for producing a hot-dip plated material that is produced by a hot-dip plating method and that solves the above-mentioned problems in a plated material in which a tin or tin alloy plating layer is formed and that does not cause surface discoloration during storage or processing. For the purpose of providing.

[0007]

In order to achieve the above object, in the present invention, the surface of a base material whose surface is made of copper or copper alloy is plated by tin or tin alloy by a hot dip plating method. A layer is formed, and then, before the plating layer is solidified, the plating layer has a concentration of 1 to 10% by weight.
There is provided a method for producing a hot-dip plated material, which comprises spraying the carboxylic acid aqueous solution.

According to the method of the present invention, when the substrate is pulled up from the hot-dip plating bath made of tin or tin alloy to cool the molten tin or molten tin alloy adhering to the surface of the substrate,
There is no difference from the case of the conventional method except that an aqueous solution containing a carboxylic acid is sprayed and cooled instead of mere water. The carboxylic acid has a carboxyl group,
Any water-soluble substance may be used, and for example, one or two of formic acid, acetic acid, citric acid, propanoic acid, butanoic acid, tartaric acid, oxalic acid, malonic acid, and maleic acid.
You can give more than one seed.

Of these carboxylic acids, citric acid and tartaric acid are preferable because they are easy to handle. The carboxylic acid concentration in the aqueous solution is 1 to 10% by weight. When the concentration is less than 1% by weight, the formation of an oxide film on the surface of the plating layer cannot be sufficiently suppressed, and when the concentration is higher than 10% by weight, the cost is increased and the plating material surface This is because it becomes difficult to wash and remove the carboxylic acid aqueous solution used, which adheres to. A particularly preferred carboxylic acid concentration is 2 to 5% by weight.

After spraying this aqueous solution of carboxylic acid to rapidly cool the hot dip plating bath adhering to the surface of the substrate, the surface of the plating layer may be washed with water or hot water as required.

[0011]

【Example】

Example 1 A strip of 8% phosphor bronze having a thickness of 0.2 mm was subjected to anode electrolytic degreasing in an alkaline bath, water washing, and pickling with 10% sulfuric acid.
Washing with water and further pretreatment with a zinc chloride-based flux were sequentially performed.

This strip is dipped in a molten tin bath having a bath temperature of 270 ° C. and then pulled up. Immediately after that, an aqueous solution having a citric acid concentration of 1% by weight is sprayed and rapidly cooled to obtain a tin-plated strip. did. Example 2 A tin-plated strip was produced in the same manner as in Example 1 except that the aqueous solution of carboxylic acid dissolved tartaric acid in an amount of 8% by weight.

Examples 3 and 4 The aqueous solution of carboxylic acid contained 3% by weight of citric acid, respectively.
Example 1 except that it was 5 wt% soluble
A tin-plated strip was manufactured in the same manner as in. Comparative Example 1 except that water was used instead of the carboxylic acid aqueous solution,
A tin-plated strip was manufactured in the same manner as in Example 1.

Example 5 The same as Example 1 except that the strip was a strip of two kinds of brass, and a 65/35 solder bath having a bath temperature of 260 ° C. was used in place of the molten tin bath. Then, a solder-plated strip was manufactured. Comparative Examples 2 and 3 A tin-plated strip was produced in the same manner as in Example 5 except that the citric acid concentrations were 15% by weight and 0.5% by weight, respectively.

Comparative Example 4 A tin-plated strip was manufactured in the same manner as in Example 5 except that simple water was used instead of the citric acid aqueous solution.
As described above, the surface condition of each of the nine types of tin-plated strips was visually observed immediately after plating.

Each tin-plated strip was allowed to stand for half a year at room temperature and the state of surface discoloration was observed. Furthermore, 15
Leave each tin-plated strip in the atmosphere at 0 ° C for 10 hours,
The state of surface discoloration and solderability at that time were observed. The solderability was evaluated using 25% rosin-IP.
After applying the flux of A to the strip material, use a eutectic solder with a meniscograph solder checker at a temperature of 2
It was measured at 50 ° C.

The above results are collectively shown in Table 1.

[0018]

[Table 1]

[0019]

As is clear from the above description, according to the method of the present invention, surface discoloration does not occur even when it is stored for a long period of time or when it is heated, so that the solderability is lowered and the contact resistance is increased. It is possible to manufacture a plated material that does not cause This effect is obtained by quenching the surface of the plated material with a carboxylic acid aqueous solution after the hot dipping treatment.

Claims (2)

[Claims] 1. A plating layer made of tin or a tin alloy is formed on the surface of a base material having a surface made of copper or a copper alloy by a hot dipping method, and then the plating layer is formed before the plating layer solidifies. A method for producing a hot-dip plated material, which comprises spraying an aqueous carboxylic acid solution having a concentration of 1 to 10% by weight on the layer. 2. The method for producing a hot-dip plated product according to claim 1, wherein the carboxylic acid is citric acid or tartaric acid.