JPH0340887B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to lead wires for electronic devices or electronic components that have excellent color fastness and abrasion resistance. Conventionally, lead wires for electronic components, particularly solid-state resistors or diodes, and conductors for electronic devices have been made by coating a core conductor of copper, copper alloy, or copper-coated wire with one or more plating layers of tin or tin-lead alloy. So-called solder-plated conductive wires having two layers are widely used. When such solder-plated wires are used as lead wires for electronic components, they are cut to predetermined dimensions and then assembled with other materials that make up the electronic components using resin molding or printing technology to heat them at 200°C.
undergo heat treatment at before and after temperature. On the other hand, when this solder-plated wire is used for wiring electronic equipment, it is covered with plastic such as vinyl after the wire is twisted.
It undergoes heat treatment at a temperature of around 200℃. Such heat treatment has the drawback that an oxide film is formed on the surface of the solder plated wire, resulting in yellowing. In addition, solder-plated wires undergo natural oxidation during the inventory period after manufacture and are also susceptible to yellowing, and when they yellow, it becomes difficult to solder them during use. On the other hand, electronic components assembled using such solder-plated wires as lead wires are mounted by inserting the lead wires made of solder-plated wires into predetermined holes in printed circuit boards, etc. In the case of a tin-lead alloy plated wire with a melting point, part of the plated layer melts during the heat treatment described above and the surface becomes rough.
Friction between the lead wire and the board creates solder scum, which can cause a short circuit. This can be solved by using, for example, tin-plated wire with a high melting point, but
There are also economic problems with the use of tin, which is more expensive than lead. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a lead wire for electronic components that has high solderability after heat deterioration, color fastness, and abrasion resistance. [Summary of the Invention] According to the present invention, the above object is achieved by plating tin or a tin-lead alloy on a conductor made of copper, copper alloy, or copper-coated steel wire, and plating cellulose esters or cellulose ethers thereon. This is achieved by applying a thin layer of organic material mixed with polyethylene glycol. Moreover, even better results can be obtained by providing a layer made of high fatty acid on top of such an organic substance. The cellulose esters mentioned herein include cellulose nitrate, cellulose acetate, etc., and the cellulose ethers include methyl cellulose, ethyl cellulose, carboxymethyl cellulose, etc. The purpose of mixing polyethylene glycol (PEG) with these celluloses is to increase the lubricity of the celluloses, and the mixing ratio should not exceed 1:1 by weight. That is, as the amount of PEG in cellulose increases, the brittleness of the cellulose film itself increases. Moreover, palmitic acid, stearic acid, etc. are suitable as the higher fatty acids used here. The purpose of this higher grade fatty acid layer is to increase the lubricity of the solder plating wire and at the same time assist in soldering properties. [Embodiment] FIG. 1 shows a cross section of a lead wire according to a first embodiment of the present invention. This is an annealed copper wire with a wire diameter of 0.6 mm as the conductor 1.
After the surface of the conductor 1 was subjected to alkaline electrolytic degreasing and pickling with dilute sulfuric acid, a 35%Sn-65%Pb alloy plating layer 2 with a thickness of about 6μ was provided on the conductor 1 by electroplating. The surface of the plating layer 2 was made glossy with felt, and predetermined solder plating lines were formed in the conventional manner. On top of that, a thin layer of methyl cellulose and PEG dissolved in a mixed solvent of alcohol and water at a concentration of about 1% at a ratio of 1:0.5 was applied to form an organic layer 3, thereby forming a lead wire. As a second example, a solution of stearic acid added to alcohol at a concentration of 0.3% is further applied thinly to the above lead wire to form a higher fatty acid layer 4 (Fig. 2).
was formed to form a lead wire. The performance of the lead wires according to each of the above examples is shown in the table below.

〔Effect of the invention〕

The lead wire of the present invention is extremely superior to conventional lead wires in terms of wear resistance, discoloration resistance, and solderability. It goes without saying that by using the lead wire of the present invention having such characteristics, the reliability of electronic components etc. is significantly improved.In order to obtain the same characteristics, conventionally, tin-plated wire or 95% tin solder was used. However, in the present invention, by using an inexpensive organic material, 35% tin-lead with a low melting point is used.
It is extremely economical because it can use 65% alloy solder-plated wire.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the invention, and FIG. 2 is a sectional view of another embodiment of the invention. 1... Conductor, 2... Plating layer, 3, 4... Organic layer.

Claims (1)

[Claims] 1. An organic material made by plating tin or tin-lead alloy on a conductor made of copper, copper alloy, or copper-coated steel wire, and mixing polyethylene glycol with cellulose ester or cellulose ethers on top of the conductor. A lead wire for electronic components characterized by having layers. 2. The lead wire for electronic components according to claim 1, further comprising a higher fatty acid layer on the organic layer.