JPH0362787B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a method for manufacturing a discoloration-resistant molten solder-plated wire such as copper or copper alloy, copper-clad steel wire, etc. used as a lead wire for electronic components. (Prior Art) In solder-plated wires used as lead wires for electronic devices, electronic components, etc., the quality of solderability is an important issue. In particular, it is important that the solderability does not deteriorate even if the solder-plated wire is stored for a long period of time after manufacturing or is subjected to heat treatment or the like during processing. Typically, molten solder-plated copper wire or copper-clad steel wire is used.
If it is kept at a high temperature of 170 degrees Celsius or higher for a long time, or if it is kept in salt water spray, the surface may turn blue, making it almost impossible to solder. It is thought that one of the causes of such discoloration is residual chloride used as a flux or chlorine ions dissolved in the molten solder, but no solution has been found to this problem. Fluxes that have been commonly used are mainly inorganic oxygen fluxes such as hydrochloric acid, ammonium chloride, and zinc chloride, and in addition to these, there are organic fluxes and rosin fluxes. All of these fluxes are attached to the wires and directly enter the molten solder bath, so chlorine ions and organic substances accumulate in the molten solder, and these chlorine ions and organic substances are mixed into the solder layer. This will adversely affect the solderability of the solder-plated wire. (Purpose of the Invention) The present invention was made to solve such conventional problems, and it is an object of the present invention to prevent chlorine ions and other impurities from being mixed into the solder plating layer.
This provides a method for manufacturing a discoloration-resistant fused solder-plated wire in which the solderability does not deteriorate even after long-term storage or heat treatment. (Structure of the Invention) In continuous melt soldering of copper-based metal wires, after performing electrolytic pickling in an inorganic acid or an inorganic acid solution that does not contain chlorine ions, It is activated by immersing it in an inorganic acid solution, and then, after washing with water, it is immersed in a molten solder plating bath. The above-mentioned metal means a metal wire such as copper, copper alloy, or copper-clad steel wire. Further, for the electrolytic cleaning, it is preferable to use a solution of an inorganic acid that does not contain chlorine ions, such as sulfuric acid, phosphoric acid, hydrofluoric acid, nitric acid, etc., or a mixed acid solution of these inorganic acids, and to use the following working conditions. Concentration range: 5% to 40% by weight Temperature: Room temperature Processing time: 2 seconds or more Current density: 20 to 200A/dm ² If the concentration is as high as 40% or more, fumes will become intense during electrolytic cleaning, which is an environmental problem. . If it is less than 5%, the electrical resistance of the liquid increases and the effectiveness decreases.
Processing time is related to current density, and if the current density is low, it takes a long time. When the current density is high and the processing time is long, the wire diameter becomes thinner. After the electrolytic cleaning treatment described above, it may be washed with water and then immersed in a molten solder bath for plating. However, if smut occurs on the surface of the metal wire, that part will not be plated. It is preferable to remove the smut in an inorganic mixed acid solution, wash with water, and then immerse in a solder bath. The concentration of pickling solution is 10
If the amount is less than 10% by weight, the effect will be low, so it is preferably 10% by weight or more. In addition, if the metal wire dries after washing with water, or if it takes a long time to immerse it in the solder bath, the solderability after plating will deteriorate. must be held within 10 seconds. Generally, as a pretreatment method for hot-melting metal, after removing scale, dust, and oil, flux treatment is performed. If only this descaling or degreasing treatment is performed, the metal surface of the plated object may be covered with a very thin oxide film. That is, since the active metal surface is not exposed, a plated layer with good adhesion cannot be obtained even if it is immersed in molten metal as it is. Therefore, the plated object is immersed in a flux containing chlorine ions, etc. to activate the metal surface and at the same time maintain that state, and when immersed in the molten metal, the plated object and the molten metal are separated. The conventional method is to perform flux treatment to facilitate reaction. When performing molten solder plating on copper or copper alloy, selective diffusion occurs between the tin in the solder and the copper material, and the intermetallic compounds generated at the interface are more concentrated than on the pure copper side.
It is said that there are two types: Cu ₃ Sn and Cu ₆ Sn ₅ .
The generation of these intermetallic compounds is important for forming a solder plating layer with good adhesion and solderability, but for this purpose, rather than flux treatment, it is necessary to use copper that retains its active surface. Alternatively, it is important to be able to immerse the copper alloy into molten solder. For this purpose, electrolytic cleaning treatment as described above is optimal. It is also desirable to immerse the device in molten solder within 10 seconds after cleaning to prevent the oxide film from being regenerated. Next, the results of a solderability test performed on the solder-plated wires plated in this manner will be explained. (Example) After performing anodic electrolytic cleaning on a copper wire with a diameter of 0.6 mm in a 15% sulfuric acid aqueous solution at a current density of 20 A/dm ² for 5 seconds,
It was immersed in a 20% sulfuric acid aqueous solution at room temperature for 3 seconds and then washed with water. Solder 3 seconds after washing with water (Sn: 63%, Pb: 37%)
We produced solder-plated copper wire that was melt-plated. For comparison, a solder-plated copper wire was produced using a commercially available inorganic acid flux mixed with HCl and subjected to similar solder plating. The solder adhesion rates determined by the soldering test are shown in Table 1. Please note that the soldering test was conducted in air at 170±5℃.
After heating and holding for 24 hours, measurement was performed using the method specified in JIS-C5033. In addition, the solderability after salt water spray was determined based on the salt water spray test method specified in JIS-Z-2371, after holding for 48 hours, JIS-C-
Measured using the method specified in 5033. In addition, in the same table, the samples are those obtained by the method of this invention;
The sample shown is that of the above comparative example.

[Table] In the same table, "untreated" refers to the state as it is removed from the plating bath. As shown in the table above, the solderability of the comparative example deteriorated, whereas the present invention activates the surface by electrolytic cleaning with sulfuric acid and enables solder plating without flux treatment. It is recognized that the solder-plated copper wire has the effect that the solderability hardly deteriorates even after heat treatment or salt water spray treatment. In addition, as a corrosion resistance test, we compared the time until discoloration occurs when 0.6 mm diameter solder-plated copper wires were exposed to salt water spray according to JIS-Z-2371 for a long time, using the method according to the present invention and the method according to the conventional method. As a result,
The results are as shown in Table 2.

[Table] In the above table, discoloration indicates discoloration to the edge color. From this table, it can be seen that the products of this invention are also excellent in corrosion resistance. (Effect of the invention) As described above, in the conventional flux treatment, the chlorine ions in the flux remain in the plating layer after plating, causing discoloration during long-term storage and making the solderability difficult. There was a tendency to deteriorate the
When the electrolytic cleaning treatment according to the present invention is performed as described above, the solderability does not deteriorate even after heat treatment or long-term storage, and the corrosion resistance is also excellent. This has the advantage that it becomes unnecessary.

Claims (1)

[Claims] 1 In continuous molten soldering of copper-based metal wires,
After electrolytic pickling in an inorganic acid or inorganic mixed acid solution that does not contain chlorine ions, activation treatment is performed by immersing it in an inorganic acid or inorganic mixed acid solution that does not contain chlorine ions, followed by molten solder plating after washing with water. A method for producing a discoloration-resistant molten solder plated wire, the method comprising immersing the wire in a bath.