JPS6354784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an aluminum-containing molten solder-plated copper wire having good solderability and oxidation resistance for use in electronic device parts.

Conventional technology Melt-solder plated copper wire has traditionally been used for terminal lead wires in electronic devices because of its good soldering properties, but when exposed to harsh heat treatment conditions in the process of manufacturing circuit components, the subsequent lead The solderability of the wire was significantly reduced, making it difficult to achieve sufficient reliability in circuit connection.

The reason for this is that the solder composition of solder-plated wire is generally a binary alloy of lead and tin, and even if these alloy compositions are changed in various ways, the surface oxidation occurs when subjected to forced external heat treatment. This is so that you cannot escape.

In order to solve these problems,
An aluminum-containing molten solder-plated copper wire shown in Publication No. 1333 has been published. However, unless a method for manufacturing molten solder-plated copper wire that reduces uneven thickness of the solder-plated layer, has a uniform plating composition, and can be plated in long lengths is established and stabilized,
It is not possible to achieve soldering reliability and good finished appearance due to its effective oxidation resistance.

Generally, the method of manufacturing molten solder-plated copper wire is as follows:
The copper wire fed out from the supply roll is first dipped into an acid flux tank for surface treatment, then dipped into a molten solder plating tank, pulled up and passed through a finishing die installed outside the tank, and plated by horizontal drawing. Alternatively, plating may be carried out by vertically pulling up through a finishing die floating or fixed on a molten solder plating tank.

In addition, in order to improve the adhesion of solder to the surface of the copper wire and increase the adhesion amount, a solder plating tank with the same solder composition as the final plating or a different solder composition is installed, and the base solder plating is applied to the copper wire in advance. After applying this, it is passed through a molten solder plating tank for finishing and then subjected to finishing plating.

Here, the method of plating by horizontal pulling through a finishing die set outside the tank is undesirable as it causes uneven thickness in the plating, but it is also possible to perform plating by pulling vertically through a finishing die suspended above the molten solder plating tank. This method is preferable because it reduces uneven thickness of the plating, and also has a good effect on the solderability of the lead wire.

However, even with the above-described manufacturing method, aluminum-containing molten solder-plated copper wire cannot be easily manufactured.

The reason for this is that when a copper wire is immersed in an acid flux bath for surface treatment, and then immersed in a molten solder plating bath containing aluminum for plating, the aluminum in the solder plating bath reacts with the acid flux and rapidly deoxidizes. This is because the aluminum content is reduced and eventually all of the aluminum is consumed.

In order to avoid this problem, a solder plating tank with a desired solder composition that does not contain aluminum is provided, and after base plating is applied on the copper wire in advance, the copper wire is then immersed in a molten solder plating tank containing aluminum.
Finish plating was carried out by vertically pulling it through a finishing die floating on the molten solder surface of the plating tank, but it is possible to reduce the uneven thickness of the plating and perform the plating work over a long length with a uniform plating composition. Moreover, changes in the plating composition caused a significant decrease in solderability, resulting in defects.

In order to solve these problems, the inventors
As a result of studying the case of plating by pulling the material vertically through a finishing die, it was found that the following problems remain unsolved.

When using a molten solder plating tank containing aluminum in a static state by simply heating it with a temperature control device, the specific gravity of aluminum in the molten solder is extremely small compared to that of lead and tin, so it takes a long time. As time passes, aluminum floats onto the surface of the molten solder, and the aluminum content in the solder composition varies between the upper and lower layers of the molten solder.

This tendency becomes particularly strong when the aluminum content is high. When the aluminum content in the upper layer increases, the viscosity of the molten solder increases and the aluminum is oxidized by the air, and the oxidation products (dross) clog the suspended finishing die, resulting in long Plating work becomes impossible.

After applying base solder plating to the copper wire, when it is immersed in an aluminum-containing molten solder plating bath, a small amount of air is brought into the molten solder, so that dross is formed by combining aluminum, lead, and tin. is formed. The formed dross floats from the inside of the molten solder onto the surface due to the difference in specific gravity, and the fine dross with no difference in specific gravity is dispersed in the molten solder. On the other hand, since the wire is continuously fed into the plating tank and immersed,
The dross floating on the molten solder surface is drawn into the molten solder again and the process of bringing it in is repeated.

As a result, some of the dross brought to the bottom of the floating finishing die floats up and accumulates on the bottom surface of the finishing die, causing clogging of the finishing die together with the dross dispersed in the molten solder. This will hinder the plating work.

It was found that the actual plating work involves a slag. Therefore, in order to perform stable long plating work, it is necessary to take measures to keep the viscosity of the aluminum-containing molten solder uniform and to prevent the floating finishing die from being clogged by the formed dross. As a countermeasure, there is a method of stirring the molten solder containing aluminum in the final plating tank using a stirring device, or a method of installing an immersion type jet stirring device in the final plating tank and plating the dross that is formed during stirring. This can be solved by a method that does not interfere with the plating work by catching it outside the process.
However, when the base plating wire is continuously introduced into the finish plating tank and immersed, the aluminum-containing molten solder undergoes air oxidation and dross is formed. ), aluminum is oxidized more selectively than lead and tin, and its content decreases over time during the plating operation, so the solder composition of the final plating layer changes accordingly. It was found that this resulted in a marked decrease in solderability, sometimes resulting in defects.

Purpose of the invention The present invention has been made in view of the above situation, and
The purpose of the present invention is to provide a method for producing a molten solder plated aluminum-containing copper wire that forms a plating layer with a uniform plating composition, enables long plating work with little unevenness in thickness, and has excellent solderability and oxidation resistance. That is.

Structure of the Invention The present invention involves surface-treating a copper wire in an acidic flux tank, applying base plating in a molten solder plating tank that does not contain aluminum, and then passing it through a finish plating tank in which molten solder containing aluminum is stirred.
In the method for producing a plating wire, the molten solder containing aluminum in the final plating tank is passed through a finishing die suspended on the molten solder surface of the final plating tank and vertically pulled up to cool and solidify the final plating layer. In order to replenish the amount of aluminum that decreases with the passage of plating work time, a solder master alloy with a high aluminum content is intermittently or continuously replenished into the final plating tank. , aluminum content
This is a method for producing molten solder-plated copper wire, which is characterized in that the plating is adjusted to a range of 0.007 to 0.025% by weight.

Embodiment of the Invention FIG. 1 is a schematic explanatory diagram of an embodiment of a method for manufacturing molten solder-plated copper wire according to the present invention.
FIG. 2, FIG. 3, and FIG. 4 are a schematic plan view, a schematic front view, and a schematic side view, respectively, of an embodiment of an immersion type jet stirring device, which is an example of a stirring device used in the present invention. FIG. 5 is a schematic enlarged view of the finish plating tank 7 shown in FIG. 1. In describing embodiments of the present invention,
First, the main plating conditions in FIG. 1 will be explained below.

(1) Base plating tank 3: Approximately 400 kg of solder containing 15±1% tin and 85±1% lead was placed in the base plating tank and heated.
Undercoat plating is performed at a temperature of 330±5℃.

(2) Finish plating tank 7: 0.025% aluminum, tin
Approximately 900 kg of aluminum-containing solder with 15 ± 1% lead and the balance was placed in a finishing plating tank and heated to 300 kg.
Finish plating is performed by adjusting the temperature to ±5℃.

(3) Floating finishing die 9: The finishing die floating on the molten solder surface of the finishing plating tank 7 has a square hole and has a diameter of the copper wire used, e.g. 0.50mmφ, 0.65mm.
For mmφ and 0.80mmφ, each side is
Preferably, the holes are square holes with dimensions of 0.56 mm, 0.72 mm, and 0.87 mm.

(4) Metsuki line speed: Constant speed of 50 m/min.

(5) Number of plating lines: 8 lines in parallel and continuous plating work. It goes without saying that neither of these is limited to the above.

Hereinafter, embodiments of the manufacturing method of the present invention will be described based on the drawings.

In FIG. 1, a copper wire 1a fed out from a copper wire supply reel 1 passes through a guide roll 44a and a guide support rod 5, and is immersed in an acidic flux tank 2.
Perform surface treatment before plating. Next, a desired base solder plating is applied in the base plating tank 3 through the guide roll 4b and the guide support rod 5a, and then excess solder is removed with a drawing die 6 to adjust the plating thickness to an appropriate thickness, for example, 2 to 4 μm.

The wire passed through the drawing die 6 is air cooled or forced cooled (not shown) to solidify or semi-solidify the solder plating layer, and then passed through the guide die 8 and guide support rod 5b and immersed in a finish plating tank. Before finishing plating, in order to make the composition of aluminum-containing molten solder uniform, finish plating tank 7 is used.
The immersion type jet stirring device 12 installed inside is activated in advance. The operation and its functions will be described later. The wire rod immersed in the finishing plating tank 7 is passed through a finishing die 9 floating on the aluminum-containing molten solder surface.
The finish plating layer is forcibly cooled and solidified by the cooler 10, and then the guide roll 1 is pulled up vertically through the guide roll 1.
1, the wire rod is wound up by a winding machine 18.

When the finished outer diameter of the plated wire or (and) thermal processing is required, the guide rolls 14, 15, 16 from the guide roll 11 to the water-soluble lubricant tank 13 are
A lubricating liquid is applied to the wire through the wire rod, and after passing through one or more finishing or heat refining dies 17, the wire is wound up by a winder 18. Next, the operation and function of the immersion type jet agitation device 12 will be briefly explained based on FIGS. 2 to 5.

The jet stirring device 12 is installed below the surface of the molten solder, and the pulley of the drive motor (not shown) and the pulley 20 of the jet stirring device are connected by a V-rubber belt. The pulley 20 and the transmission 19 are mechanically interlocked, and the rotation speed of the impeller shaft 25 supported by the heat-resistant bearing 21 can be adjusted appropriately depending on the tension of the V-rubber belt.

As the waterwheel-type impeller 23 rotates, the molten solder enters the suction hole 22 from the suction window 22a, reaches the box body part a from the box body part b, and is jetted radially from the many discharge holes 24. In this way, the aluminum-containing molten solder is continuously stirred and its composition and viscosity are maintained uniform. Jet stirring device 12
As is clear from FIG. 5, the discharge hole 24 is opened upwardly toward the vertically pulled wire rod, and the discharged molten solder is jetted radially near the bottom of the floating finishing die 9. Therefore, when plating a wire using aluminum-containing molten solder, it is possible to simultaneously solve the above-mentioned unresolved problems that could not be solved with the prior art.

That is, the jet stirring device 1 is installed in the finish plating tank 7.
2, the jet stream removes dross that tends to accumulate at the bottom of the finishing die 9 along with the wire rod, thereby preventing clogging of the finishing die 9, and further preventing the finishing die 9 from clogging with the wire rod. Plating tank 7
The fine dross formed and dispersed in the molten solder is naturally trapped in the box parts a and b by the air brought into the molten solder, so plating can be done with a clean and uniform composition. Therefore, long plating work can be performed without clogging the finishing die 9.

Note that the pipe of the discharge hole 24 may be made longer, and a plurality of jet agitators 12 may be used instead of a propeller type agitator, but the jet agitator 12 may be formed in molten solder,
There is no effect of capturing dispersed fine dross. However, in plating work, the aluminum content in the finish plating tank is kept uniform, and a solder master alloy with a high aluminum content is intermittently or continuously added to the finish plating tank according to the manufacturing method of the present invention, and the solder master alloy is melted and stirred. The purpose of making the aluminum content uniform is achieved.

In the method for producing molten solder-plated copper wire according to the embodiment described above, the aluminum content of the aluminum-containing molten solder is reduced by the minute amount of air brought into the finish plating tank with the wire rod, which reduces the plating work time. Fig. 6 shows the results of investigating how it decreases. A, B, and C in FIG. 6 are straight lines of decreasing aluminum content when using copper wires of 0.65 mmφ, 0.80 mmφ, and 0.50 mmφ, respectively. From the slopes of the decreasing lines A, B, and C, the amount of aluminum decreased per hour is 1.7×10 ^-3 on average.
%/hr, 1.9×10 ⁻³ %/hr, and 1.5×10 ⁻³ %/hr. That is, when the wire rod is immersed in a finish plating tank after base plating, dross is formed because a small amount of air is brought into the molten solder. In particular, aluminum is oxidized more selectively than lead and tin, and its content in solder decreases over time.

As is clear from FIG. 6, when the initial aluminum content is maintained at about 0.02% and continuous plating work is performed for 6 to 7 hours, the aluminum content decreases to about 0.01%. The relationship between the decrease in aluminum content and the plating work time depends on the plating conditions: the amount of aluminum-containing molten solder charged into the final plating tank, the blending ratio of lead and tin, the plating temperature,
Although it varies depending on the wire diameter and the number of wires, it was found that there is a linear decreasing relationship. Therefore, if the plating work is continued for a long time, the aluminum content will eventually reach zero, and the solder will lose its oxidation resistance and its solderability will decrease.
When the aluminum content drops to close to 0.01%,
It is necessary to simultaneously replenish the molten solder consumed by plating and correct the aluminum content to return the aluminum content to the initial content.

In order to carry out the corrected formulation, the aluminum content in the molten solder is quickly determined in advance by atomic absorption spectrometry, etc., and based on the quantitative value, lead, lead, and
If adjusted using a master alloy made by adding aluminum to solder with the same composition as the tin content (hereinafter referred to as aluminum/solder master alloy), for example, 70 ± 1% lead, 30 ± 1% tin, and 0.25 to 0.30% aluminum. good.

Atomic absorption spectrometry is performed as follows. First, take a sample of about 1 to 2g from the molten solder containing aluminum, weigh it, put it in a 200ml beaker, and add nitric acid solution (1+1).
Add 40ml and heat to dissolve the sample. This solution
Place in a 100ml volumetric flask and dilute accurately with distilled water. Then, atomic absorption spectrometry of aluminum is performed after passing through the amount necessary for analysis. The time required for analysis is within 1 hour.

Next, Table 1 shows the results of examining the aluminum content in the aluminum-containing molten solder, the workability of plating, and the solderability of the manufactured plating wire after a heating test.

From Table 1, when the aluminum content exceeds 0.025%, even if the molten solder is stirred, there is a tendency for the floating die to become clogged, probably due to an increase in melt viscosity. It becomes difficult to obtain a long thickness (for example, 7 to 15 μm). When the aluminum content is 0.025% or less, the desired plating thickness in the plating line can be obtained over a long length. However, when the aluminum content is less than 0.005%, the resulting plated wire loses its oxidation-resistant effect and its solderability rapidly decreases. Therefore, the aluminum content of the molten solder used in the final plating tank is preferably in the range of 0.005 to 0.025%, but it is preferable to perform the plating operation while keeping the aluminum content in the range of 0.007 to 0.02%. On the other hand, in the main solder composition of lead and tin, if the tin content is increased, the aluminum content can also be increased, but the solderability of the lead wire will not change, and the cost will increase as the tin content increases. The melting temperature also decreases. Therefore, when used as a lead wire to be subjected to high-temperature heat treatment, the lowering of the melting point may be undesirable, so it is preferable that the tin content be 25 to 30%.

However, when using lead wires, high-temperature heat treatment is not performed, but if the surface hardness of the plating layer is improved to prevent wear and oxidation resistance is required for long-term storage, aluminum with increased tin content may be used. It is preferable to use a solder composition.

Next, 900 kg of molten solder consisting of specific gravity 10.22, aluminum 0.02%, tin 30±1%, and the balance lead was put into the finish plating bath, and 0.65 mmφ molten solder plated copper wire was made using the plating conditions of the embodiment described above. In the case of manufacturing, an example will be described below in which the reduction in aluminum content in the molten solder in the finish plating tank is adjusted using an aluminum/solder master alloy.

(Example 1) In the case of 0.65 mmφ copper wire, the average decrease in aluminum content in molten solder is ^1.7 Prepare the solder master alloy wire, and at the start of plating work, remove the master alloy wire.
At a linear speed of 70.63 m/hour, a stainless steel guide tube (not shown) was installed at position C (see Figure 5) near the suction window 22a of the jet agitator immersed in the finish plating tank. The wire is continuously inserted and the plating work is performed while melting. At this time, the feed rate of 3 mmφ aluminum/solder master alloy wire is approximately 5.1 kg per hour.

On the other hand, the amount of aluminum-containing molten solder that adheres to the plating wire and is consumed over time is approximately 5.1 kg per hour because plating is applied to an average thickness of 12 μm.

Therefore, the above-mentioned supply amount and consumption amount are kept in equilibrium, and long plating work is performed while maintaining the aluminum content of the molten solder in the final plating tank at the initial content of 0.02%. Can be done.

(Example 2) In Example 2, 0.3% aluminum/solder mother alloy is
This is an example in which a thin plate weighing approximately 10 kg is cast in a casting mold measuring cm x width 10 cm, and the cast plate is used to adjust the decrease in aluminum content in molten solder in a finish plating tank.

That is, after the beginning of the plating operation, 10
One piece of 0.3% aluminum/solder mother alloy plate weighing 1 kg,
Gently put it into the C position or C position of the final plating tank mentioned in Example 1, and perform the plating work continuously while melting. The result is the same as Example 1, and the amount of molten solder containing aluminum consumed by plating work is reduced by intermittently introducing and melting a 0.3% aluminum/solder mother alloy plate to reduce the amount of molten solder consumed and supplied. It is possible to perform long plating work by maintaining the aluminum content of the molten solder in the final plating tank at the initial content of 0.02%.

(Example 3) In Example 3, after about 6 hours of plating work, when the aluminum content in the molten solder in the final plating tank was reduced to 0.01%, the amount of aluminum reduced was measured using a 10 kg 0.3% aluminum/solder master alloy plate. This is an example of adjusting. In this case, the consumption of aluminum in the molten solder due to oxidation is 0.09Kg, so in order to recover the above aluminum consumption, 3% of 10Kg is required.
It is necessary to supply three aluminum/solder mother alloy plates. Therefore, the sheets are gently placed one by one into the Cd position of the finish plating tank, and the plating work is performed continuously while melting. On the other hand, the amount of aluminum-containing molten solder that adheres to the plating wire and is consumed over time is 30.24
Kg.

Therefore, in the case of Example 3, the consumption of molten solder and 0.3
% aluminum/solder mother alloy plate is kept in equilibrium, the aluminum content of the molten solder in the final plating tank is restored to the initial content of 0.02%, and long plating work can be performed.

(Example 4) In Example 4, after about 8 hours of plating work, when the aluminum content in the molten solder in the final plating tank decreased to 0.0065%, the amount of aluminum reduction was calculated using a 10 kg 0.3% aluminum/solder master alloy plate. This is to adjust the In this case, the consumption of aluminum in the molten solder due to oxidation is 0.122Kg, so in order to recover the above aluminum consumption, 10Kg is required.
Four 3% aluminum/solder mother alloy plates are required. Therefore, it is sufficient to put the sheets one by one into the Cd position of the final plating tank and continue the plating work while melting them.

The amount of aluminum-containing molten solder that adheres to the plating wire and is consumed over time is 40.32 kg. When stopping operations after 8 hours of plating work, the molten solder containing aluminum in the final plating tank is cooled and solidified.
When performing plating work again, use the finish plating tank.
After heating to 300±50°C, four 10 kg 0.3% aluminum/solder master alloy plates are placed one by one into a finish plating tank, melted, and plated.

Next, the method of the present invention will be explained based on examples.

Example 1 This example was carried out using the apparatus shown in FIG.
Eight hard copper wires of 0.640 mmφ were passed through an acid flux bath at room temperature at a wire speed of 50 m/min, and the plating temperature was 330.
The sample was passed through a solder base plating bath consisting of 15±1% tin and 85±1% lead at ±5°C to form a base plating layer with a plating thickness of 2 to 4 μm. After that, the molten solder consisting of 0.023% aluminum, 30±1% tin, and the balance lead at 300±5°C was passed through a finishing plating tank in which a jet stirrer was used to stir the molten solder, and a floating die with a square hole of 0.71 mm on each side was placed. It is passed through and pulled up vertically to form a finishing plating layer, passed through a finishing die of 0.652 mmφ, and wound up on a winder (hereinafter referred to as the plating work conditions of Example 1).

At the start of the plating work, a 3% aluminum/solder master alloy wire of 3 mm diameter was introduced into the finish plating tank at a line speed of 70.63 m/hour, and the plating work was performed while being melted.

Example 2 The solder composition of the finish plating tank is aluminum 0.02
%, tin 30±1%, and the remainder lead, the plating work conditions were the same as in Example 1.

0.3% of 10Kg every 2 hours after the start of plating work
One aluminum/solder mother alloy plate was placed in a final plating tank, and plating was performed while it was being melted.

Example 3 The solder composition of the finish plating tank is aluminum 0.01
%, tin 30±1%, and the remainder lead, the plating work conditions were the same as in Example 1.

Five minutes after the start of the plating work, three 10 kg 0.3% aluminum/solder mother alloy plates were sequentially put into the finish plating tank, and the plating work was performed while melting them.

Example 4 Solder composition of finish plating tank is aluminum 0.0065
%, tin 30±1%, and the remainder lead, the plating work conditions were the same as in Example 1. Start of plating work 5
After a few minutes, four 10 kg 0.3% aluminum/solder mother alloy plates were sequentially put into the finish plating tank, one by one, and the plating work was performed while melting them.

Comparative Examples 1 and 2 The solder composition of the final plating bath was 0.004% aluminum, 30 ± 1% tin, and the balance was lead in Comparative Example 2, and 30 ± 1% tin and 70 ± 1% lead in Comparative Example 2.
The plating work was carried out under the same plating conditions as in Example 1, without supplying aluminum/solder master alloy to the final plating tank. The results of measuring the plating thickness, tensile strength, elongation, flexibility, and solderability after heating at 230°C for 1 hour and at 165°C for 48 hours of the plated wires obtained in the Examples and Comparative Examples are as follows. It is shown in Table 2. In addition, solderability is MIL-STD.
- Determined according to 202M and 208 regulations. In addition, the flexibility was determined according to JISC6402 and JISC6422 standards.

Effects of the invention When plating a wire rod that has been plated with the first layer in a base plating tank in a finish plating tank containing molten solder containing aluminum, dross is formed because a small amount of air is continuously brought into the molten solder. The aluminum content in the molten solder decreases linearly over time, and after long plating work, the aluminum content finally reaches zero, making the solder composition uniform with aluminum, which has an oxidation-resistant effect. It is not possible to obtain a perfect metsuki line. According to the manufacturing method of the present invention, when replenishing the molten solder consumed by plating and correcting the composition to correct the decrease in aluminum content over time using an aluminum/solder master alloy, the finish plating tank An immersion-type jet agitation device is installed inside to constantly stir the molten aluminum solder, so the necessary amount of aluminum/solder master alloy wire or plate material can be continuously or intermittently fed into the molten solder in the finish plating tank. By doing so, it is immediately melted and stirred, and a clean and uniform aluminum-containing molten solder composition is obtained, resulting in a stable finish plating. As a result, there is no clogging of the floating die, and there is less uneven thickness of the matsuki.
Can perform long plating work. Furthermore, when the wire rod is used as a lead wire for electronic device parts,
Since the plating layer is plated with a uniform aluminum-containing solder composition that has an oxidation-resistant effect, the solderability after high-temperature heat treatment is much better than that of conventional products. The degree of contribution to the demand for seed wires is significant.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing one embodiment of the apparatus used in the method of the present invention, and FIGS. 2 to 4 are a schematic plan view and a schematic diagram, respectively, of one embodiment of the immersion type jet stirring apparatus used in the present invention. Front view, schematic side view, fifth
The figure is a schematic enlarged view of the final plating tank shown in FIG. 1, and FIG. 6 is an example of an embodiment showing the relationship between the reduction in aluminum content in the aluminum-containing molten solder of the final plating tank and the plating work time. The main symbols in the drawings are as follows. 1a: Copper wire, 2: Acid flux tank, 3: Base plating tank, 7: Finish plating tank, 9: Floating die,
10: Cooler, 12: Jet stirring device, 17: Finishing die.

【table】

【table】

Claims (1)

[Claims] 1 The surface of the copper wire is treated in an acidic flux bath, the base plating is applied in a molten solder plating bath that does not contain aluminum, and then the wire is passed through a finish plating bath in which molten solder containing aluminum is stirred, and the molten solder in the finish plating bath is In a method for manufacturing a plated wire, in which the plated wire is passed through a finishing die suspended on a surface and vertically pulled up to cool and solidify the plated layer, the plating operation involves reducing the aluminum content of the aluminum-containing molten solder in the finishing plating tank. To replenish the amount of aluminum lost over time,
A solder master alloy with a high aluminum content is intermittently or continuously replenished into the final plating tank to increase the aluminum content to 0.007 to 0.025.
A method for producing molten solder-plated copper wire, which comprises plating the wire by adjusting the weight percentage within the range.