JP2001155548A - Lead wire for electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead wire superior in adhesion, the solder wetting and discoloration-proof of a plated film layer without environmental contamination, and capable of keeping these superior properties even in extruding and thinning the lead wire. SOLUTION: (1) In this lead wire for electronic parts, having a plated film layer of tin alloy on a lead wire, the plated film layer of tin alloy is a single tin alloy film layer formed by heating two layers composed of a relatively thick tin plated-layer formed directly on the conductor and a relatively thin film layer of metal excluding tin, formed on the tin plated-film layer. (2) In a lead wire for electronic parts having a plated film layer of tin alloy on a conductor, the tin alloy plated-film layer is a single tin-silver alloy film layer formed by heating two layers of a relatively thick tin plated-film layer formed directly on the conductor and a relatively thin silver film layer formed on the tin plated-film layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead wire for electronic parts. More specifically, the present invention relates to a lead wire that can be used as a conductor for electronic equipment wiring or a lead material for electronic components.

[0002]

2. Description of the Related Art In recent years, various and various electronic components have been mass-produced.

[0003] To connect these electronic components, lead wires for electronic components are used.

[0004] Diodes, transistors, capacitors,
As a lead wire used for a resistor or the like, a solder plated wire formed by plating tin or tin-lead solder on a conductive wire is often used.

Here, a copper wire or a copper alloy wire is used as the conductive wire.

[0006] The plating of tin or tin-lead solder here is for the purpose of preventing heat oxidation and improving the solder wettability during the soldering operation of the lead wire.

[0007] Electronic components using the conventional lead wires for electronic components as well as home appliances and industrial products mounted with the electronic components include plating layers of the used electronic component lead wires and the electronic components. The lead used for connecting the lead wires contains solder that is harmful to the environment.

For this reason, when a large amount of household electric appliances and industrial products incorporating these electronic components and lead wires are disposed of in a waste storage site or the like as household oversized garbage or factory waste, they are included in them. Lead elutes due to acid rain, etc.
There is a concern that the wastewater containing the eluted lead ions will cause environmental pollution in groundwater.

Therefore, in recent years, lead-free solder containing no lead has been actively studied for such reasons.

However, the conventional solder-joining process using a tin-lead solder plating film has been cultivated for many years as a highly reliable bonding method for electronic equipment parts, and an equivalent high-reliability lead instead of this is used. It is not easy to develop lead-free solder plating.

[0011]

A first example of a lead-free solder plating film having the same high reliability as a conventional tin-lead solder plating film is a tin-plated wire. This tin-plated wire has good wettability with a lead-free tin alloy and has a high bonding strength. However, the tin-plated wire has a disadvantage that whiskers are easily generated in the tin-plated film layer.

Accordingly, tin alloy plated wires have been developed as an improvement over the disadvantages of the tin plated wires. This tin alloy plated wire has the advantages of good wettability with a lead-free tin alloy, high bonding strength, and no generation of whiskers. However, tin alloy plating can be performed only in a binary system, and there is a disadvantage that the stability of the plating solution is poor.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned drawbacks of the prior art, to have no environmental pollution, to have good adhesion of a plating film layer, and to have solder wetting. An object of the present invention is to provide a lead wire for an electronic component which has excellent properties and discoloration resistance, and which can maintain those excellent properties even when being drawn to a small diameter.

[0014]

The gist of the present invention lies in the following two points.

(1) In a lead wire for an electronic component having a tin alloy plating film layer provided on a conducting wire, the tin alloy plating film layer is a relatively thick tin plating film provided immediately above the conducting wire. An electronic component characterized in that two layers comprising a layer and a relatively thin metal film layer other than tin provided on the tin plating film layer are formed into a single tin alloy film layer by heat treatment. Lead wire.

(2) In a lead wire for an electronic part comprising a tin alloy plating film layer provided on a conducting wire, the tin alloy plating film layer is a relatively thick tin plating film provided immediately above the conducting wire. Characterized in that two layers comprising a layer and a relatively thin silver film layer provided on the tin plating film layer are heat-treated to form a single tin-silver alloy film layer. Lead.

In the present invention, the metal film layer other than tin is provided by one or more metals selected from silver, copper, gold, palladium, nickel, bismuth, antimony, indium and zinc. It is preferred that

In the present invention, the metal film layer other than tin is formed by electrolytic plating, electroless plating, vapor deposition, sputtering,
It is preferably provided by one method selected from a melting method and a displacement precipitation method.

That is, in the lead wire for electronic parts of the present invention, after a tin plating film is formed on a conductive wire such as a copper wire or a copper alloy wire, at least one kind of metal other than tin is formed on the tin plating film. The composite plating wire is heat-treated.

After the tin-plated film is formed on the conductive wire as described above, at least one kind of metal other than tin is formed on the tin-plated film, and then the composite plated wire is heat-treated. The plating film layer may be a single-layer tin alloy.

The tin alloy plating film layer thus obtained has solderability equivalent to that of a conventional tin-lead solder plating film, has good wettability with a lead-free tin alloy, and has good bonding properties. High strength, no whisker failure, and excellent solderability and heat resistance after heat treatment.

Further, the tin alloy plated wire obtained in this manner is used as a base wire, which is drawn through a wire drawing die into a thin diameter tin alloy plated wire. It also has excellent wire drawing workability that the tin alloy plating film layer can be maintained as it is.

Further, the tin alloy plated wire thus obtained has a low melting point because the plating film layer is made of a tin alloy, so that the joining operation can be performed at a low melting point.

[0024]

Next, an embodiment of a lead wire for an electronic component of the present invention and a conventional comparative example will be described.

Example 1 First, a copper alloy wire having an outer diameter of φ0.6 mm was prepared.

Next, the prepared copper alloy wire was degreased, pickled, and washed with water.

Next, the degreased, pickled, and water-washed copper alloy wire is led to an electrolytic tin plating apparatus containing an organic tin sulfonate plating solution, and electrolytic tin plating is performed on the copper alloy wire to a thickness of 6 μm. Did.

Next, the tin-plated copper alloy wire was led to an electrolytic silver plating apparatus containing a silver cyanide plating solution, and electrolytic tin plating was performed on the tin plating to a thickness of 0.5 μm. The current density of this silver plating is 4 A / dm ² .

FIG. 2 is a cross-sectional view of the tin-plated / silver-plated copper alloy wire thus obtained.

In FIG. 2, 1 is a copper alloy wire, 2 is a tin plating layer, and 3 is a silver plating layer.

Next, the tin-plated / silver-plated copper alloy wire thus obtained was heat-treated at 250 ° C. for 10 minutes. By this heat treatment, the tin plating / silver plating film layer became a tin-silver alloy plating film layer.

FIG. 1 is a sectional view of the tin-silver alloy-plated copper alloy wire thus obtained.

In FIG. 1, 1 is a copper alloy wire, and 4 is a tin-silver alloy plating film layer.

Next, the tin-silver alloy-plated copper alloy wire thus obtained was used as a base wire, which was drawn to a small diameter through a drawing die, then annealed, and finally subjected to skin pass. Was obtained.

Example 2 First, a copper alloy wire having an outer diameter of φ0.6 mm was prepared.

Next, the prepared copper alloy wire was degreased, pickled, and washed with water.

Next, the degreased, pickled, and water-washed copper alloy wire is led to an electrolytic tin plating apparatus containing an organic tin sulfonate plating solution, and electrolytic tin plating is performed on the copper alloy wire to a thickness of 6 μm. Did.

Next, the tin-plated copper alloy wire was led to an electrolytic zinc plating apparatus containing a zinc sulfate solution, and electrolytic zinc plating was performed on the tin plating to a thickness of 0.5 μm. The current density of the zinc plating is 20 A / dm ² .

Next, the tin-plated / zinc-plated copper alloy wire thus obtained was heat-treated at 250 ° C. for 10 minutes. By this heat treatment, the tin plating / zinc plating film layer became a tin-zinc alloy plating film layer.

Next, the tin-zinc alloy-plated copper alloy wire thus obtained was used as a base wire, which was drawn to a small diameter through a drawing die, then annealed, and finally subjected to skin pass. Was obtained.

Comparative Example 1 First, a copper alloy wire having an outer diameter of φ0.6 mm was prepared.

Next, the prepared copper alloy wire was degreased, pickled, and washed with water.

Next, the degreased, pickled, and water-washed copper alloy wire is led to an electrolytic tin-lead solder plating apparatus containing a tin-lead solder plating solution so that the copper alloy wire has a thickness of 6 μm. Electrolytic tin-lead solder plating was performed.

Next, the tin-lead solder-plated copper alloy wire obtained here was used as a base wire, which was drawn to a small diameter through a drawing die, then annealed, and finally subjected to a skin pass to obtain a comparative example. Thus, No. 1 lead wire for an electronic component was obtained.

Comparative Example 2 First, a copper alloy wire having an outer diameter of φ0.6 mm was prepared.

Next, the prepared copper alloy wire was degreased, pickled, and washed with water.

Next, the degreased, pickled, and water-washed copper alloy wire was led to an electrolytic tin plating apparatus containing a tin plating solution, and electrolytic copper plating was performed on the copper alloy wire to a thickness of 4 μm.

Next, the tin-plated copper alloy wire is led to an electrolytic tin-bismuth alloy plating apparatus containing a tin-bismuth plating solution, and the tin-bismuth alloy plating is performed on the copper alloy wire so as to have a thickness of 2 μm. Did.

Next, the tin-plated / tin-bismuth alloy-plated copper alloy wire thus obtained was used as a base wire, which was drawn to a small diameter through a drawing die, then annealed, and finally subjected to a skin pass. Thus, a lead wire for an electronic component of Comparative Example 2 was obtained.

(Characteristic test method) Next, a characteristic test was performed on the lead wires for electronic parts of Examples 1, 2 and Comparative Examples 1 and 2 thus obtained.

A. Adhesion test after heat aging First, the electronic component lead wires of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were each heat-aged at 175 ° C for 4 hours.

Next, the heat-aged lead wires for the electronic components of Examples 1, 2, Comparative Example 1, and Comparative Example 2 were each wound to the same outer diameter as the conductor diameter, that is, the self-diameter. ,
Whether peeling occurs in the plating film layer due to the winding,
I looked at it.

The term "twist winding" as used herein means that one end of a lead wire for an electronic component to be tested is gripped by a vise, the other end is bent at an angle of 90 degrees, and then bent. This is a method of twisting about several tens of times using the bent portion as a fulcrum and winding it around its own diameter.

The test results were evaluated as follows.

Evaluation 1: no peeling Evaluation 2: slight peeling evaluation 3: peeling b. Solderability test Solderability was evaluated by the meniscograph method specified in JIS-C0053.

The flux used was 25% ww rosin, and 1
Heating was performed at 75 ° C. for up to 20 hours, and the solder wetting time was measured.

C. Discoloration Resistance The discoloration resistance was maintained for 10 days in an atmosphere of constant temperature and humidity of 40 ° C. and 95% RH, and the color resistance of each test line was visually determined.

The criteria are as follows.

Evaluation 1: no discoloration Evaluation 2: slight discoloration Evaluation 3: discoloration d. Whisker generation frequency The whisker generation frequency was maintained for 7 days in a 50 ° C constant temperature bath, and the occurrence of whiskers was visually determined.

The criteria are as follows.

Evaluation 1: no occurrence Evaluation 2: slight occurrence Evaluation 3: occurrence (Characteristic test results) Table 1 shows these characteristic test results.

[0062]

[Table 1]

As can be seen from Table 1, all the lead wires for electronic parts of Comparative Example 1 plated with the conventional tin-lead solder are good. However, although not shown, since the tin-lead solder plating film layer contains lead, there is a problem of environmental pollution.

The lead wire for an electronic component of Comparative Example 2, which is a tin-plated / tin-bismuth alloy-plated copper alloy wire, has a disadvantage that whiskers are frequently generated.

Further, in the lead wire for an electronic component of Comparative Example 2, since the outermost plating film layer is made of a tin-bismuth alloy plating film layer, when the wire is drawn to a small diameter through a wire drawing die, the wire becomes the most. There is a disadvantage that the tin-bismuth alloy plating film layer is scraped off from the outer plating film layer.

On the other hand, the lead wires for the electronic parts of Examples 1 and 2 have good characteristics as well as the lead wires for the electronic parts of Comparative Example 1 which are plated with the conventional tin-lead solder. Although not performed, the plating film layer does not contain lead, and thus has an excellent feature that there is no environmental pollution. Furthermore, even when the outermost plating film layer is cut off when the lead wire for electronic components of Example 1 and Example 2 is drawn to a small diameter through a drawing die, the entire plating film layer is removed. Since it is an alloy, its solderability does not decrease.

Although not exemplified, copper, gold, palladium, nickel, bismuth, antimony, indium and the like were used as a metal layer to be applied to the outermost surface, and these were subjected to electrolytic plating, electroless plating, vapor deposition, and the like. Sputtering method,
Even when provided by one method selected from a melting method, a displacement precipitation method and the like, excellent results similar to those of Examples 1 and 2 were obtained.

[0068]

The lead wire for electronic parts of the present invention has no environmental pollution, has excellent adhesion of the plating film layer, excellent solder wettability and resistance to discoloration, and has excellent properties even when drawn to a small diameter. And can be used industrially as lead wires for electronic components.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electronic component lead wire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a tin-plated / silver-plated copper alloy wire, which is an intermediate product of the lead wire for an electronic component according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper alloy wire 2 Tin plating layer 3 Silver plating layer 4 Tin-silver alloy plating film layer

Claims (4)

[Claims] 1. A lead wire for an electronic component comprising a conductive wire and a tin alloy plating film layer provided thereon, wherein the tin alloy plating film layer is a relatively thick tin plating film layer provided immediately above the conductive wire. And a two-layered relatively thin metal film layer other than tin provided on the tin-plated film layer to form a single tin alloy film layer by heat treatment. Lead. 2. A metal film layer other than tin is made of silver, copper, gold, palladium, nickel, bismuth, antimony, indium,
2. The lead wire for an electronic component according to claim 1, wherein the lead wire is a metal film layer composed of one or more metals selected from zinc. 3. A method in which a metal film layer other than tin is provided by one method selected from an electrolytic plating method, an electroless plating method, a vapor deposition method, a sputtering method, a melting method, and a substitution deposition method. 2. The lead wire for an electronic component according to claim 1, wherein: 4. A lead wire for an electronic component comprising a tin alloy plating film layer provided on a conducting wire, wherein the tin alloy plating film layer is a relatively thick tin plating film layer provided immediately above the conducting wire. A lead layer for an electronic component, wherein a single layer of a tin-silver alloy film layer is formed by heat treatment of two layers consisting of a tin film layer and a relatively thin silver film layer provided on the tin plating film layer. line.