JPS5825010A - Glossy plated lead wire for electronic part - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention mainly relates to electronic components such as resistors and capacitors, or lead wires for electronic devices, which have excellent color fastness, solderability, weldability, and flexibility. It concerns shiny electroplated lead wires. Hereinafter, all references to "plating" refer to "electroplating."

Conventionally, the lead wires used especially for aluminum capacitors, aluminum electrolytic capacitors, etc. have a length of about 10 to 10 mm due to their structure.
From the viewpoint of weldability when butt welding with aluminum wire cut to 50 avt, copper wire,
Wires in which tin plating 2 is applied on metal wires such as copper alloy wires, copper-covered wires, and mild steel wires have been used.

However, the above-mentioned tin-plated wire has the following main drawbacks.

■Solderability is poorer than solder-plated wire.

Solderability is the most important characteristic for lead wires for electronic components, but solderability is poorer than, for example, solder-plated wire with a weight composition of 30% tin and 70% lead, and solderability is often poor. A sexual misconduct accident occurred. The reason for this is that the temperature in normal soldering is 280° to 240°C, and in most cases of solder plating, it begins to partially melt at 188°C, whereas in the case of tin plating, the temperature starts to melt at 188°C. It is conceivable that it will not melt until the temperature reaches 282°C.

■Generates whiskers.

Under certain usage conditions, tin plating generates needle-shaped single crystals called whiskers, which can easily cause short circuits between parts.

In order to solve these problems, instead of tin plating,
Lead 2-95 weight 96 (hereinafter abbreviated as %), tin 98-5%
A lead wire with solder plating was considered. Lead is effective in preventing whisker formation, and at the same time, through alloying, it lowers the melting point of the plating layer and improves solderability.

However, this solder-plated wire also has some drawbacks, which can be summarized mainly in the following eight points.

■Causes welding defects.

When manufacturing aluminum electrolytic capacitors, etc., there is a process of welding a lead wire with plating 8 on metal wire 1 to aluminum wire 9, as shown in Figure 2. The temperature will be around 2000℃.

If the plating layer of the lead wire contains lead, the boiling point of tin, copper, iron, aluminum, etc., which is involved in welding, is 2200℃ or higher, but that of lead is 1.
Because the welding temperature is as low as 720° C., lead vaporizes at the moment of welding, often causing a defect called a blowhole 10 in the welded portion, resulting in an undesirable phenomenon in which the strength of the welded portion is reduced.

■Solder plating is usually matte plating, so a process is required to make it glossy.

Solder plating is required by parts manufacturers to be glossy mainly from the viewpoint of commercial value, and soldering is required to be glossy from the viewpoint of properties, so gloss is achieved by felt polishing, wire drawing, or polishing with dies.

Felt polishing produces abrasive powder containing lead, which worsens the working environment. On the other hand, die polishing requires frequent replacement of dies in order to meet strict dimensional accuracy requirements, which increases manufacturing costs, and also requires a slight wire drawing process when the wire passes through the die. This will change the mechanical properties of the

At the same time, it also involves the generation of abrasive powder, and furthermore, it has disadvantages that are unsuitable for mass production, such as the abrasive powder sticking to the die and causing wire breakage.

■Matte solder plating has low color fastness.

A matte plated surface has more irregularities than a bright plated surface and has a larger substantial surface area. Therefore, it becomes easy to adsorb corrosive gases, etc., and is susceptible to corrosion damage such as discoloration.

Among these drawbacks of solder-plated wires, in particular those caused by matte plating, solutions have been attempted by replacing them with bright plating. However, conventional bright plating has been difficult to use for the following eight reasons.

■The bright electroplated layer has more organic substances absorbed in the plating layer than the matte electroplated layer. For example, in the example carried out by the inventors, the carbon occlusion concentration in the matte solder plating layer is about 1 Oppm. In comparison, it was about 100 ppIp in the bright solder plating layer, and therefore, when components using solder plating lead wires are mounted and soldered, the occluded organic matter decomposes and generates gas. This inhibits solder wettability.

This becomes a big problem, especially in short-time soldering operations such as flow soldering.

■The bright solder plating layer has different electrodeposition ratios of lead and tin, and the flexibility of the plating layer differs. For example, when a lead wire is bent or wound around its own wire diameter, the composition range that does not cause cracks in the plating layer depends on the plating thickness, but the composition range that does not cause cracks in the plating layer depends on the typical plated lead wire. At a plating thickness of 10 microns, the lead content is 2096 or more, which cannot meet the requirements depending on the purpose of use.

■Many of the gloss additives for gloss solder plating on the market are multi-component, and managing the plating solution, especially replenishing the additives, requires experience, and it is difficult to maintain a healthy plating state for a long period of time. The life of the liquid is short.

For the above reasons, it has been desired to improve the quality and economy of conventional tin and solder plated wires.

The present invention eliminates the above-mentioned drawbacks, and has a beautiful glossy surface, flexibility that does not cause cracks even when processed by bending, wrapping, etc. The purpose of the present invention is to provide a brightly plated lead wire that has heat resistance and discoloration resistance that do not deteriorate in soldering properties even when soldered, and has good weldability that does not reduce welding strength with aluminum wire.

The present invention is a brightly plated lead wire for electronic components, characterized by comprising a metal wire, a matte electroplated tin layer thereon, and a glossy electroplated solder layer thereon.

8 to 5 are sectional views showing respective embodiments of the present invention. In the figure, numeral 8 denotes a matte electroplated tin layer formed on a metal wire l made of, for example, copper or a copper alloy, and numeral 4 denotes a bright electroplated solder layer further applied thereon.

In the present invention, metal wires refer to copper, copper alloys, for example, copper to which one or more elements such as tin, silver, cadmium, calcium, zinc, lithium, iron, nickel, aluminum, etc. are added. , a mild steel wire or a composite wire, such as a conductive material in which copper or copper alloy is not coated on the steel wire by a cladding method or a plating method. In particular, when using a 6-copper alloy wire containing zinc as the metal wire, as shown in FIG. A base plating layer 5 is provided.

This can prevent the undesirable phenomenon that zinc diffuses from the base material into the plating layer, forms an oxide film on the surface, and impairs solderability.

Figure 5 shows the case where a composite wire is used as the metal wire, 6
7 indicates a steel wire or iron wire, and 7 indicates a copper or copper alloy coating layer.

The matte tin plating layer is formed by a normal borofluoride bath, sulfuric acid bath, sulfamic acid bath, etc., and its thickness varies depending on the purpose of use, and is the sum of the thicknesses of the matte tin plating layer 3 and the bright solder plating layer 4. It is often 5 to 25 microns. Therefore, the thickness of the matte electro-solder plating layer is generally calculated by subtracting the thickness of the glossy electro-solder plating layer 4, which will be described later, from 5 to 25 microns.
It is approximately 8 to 24 microns, but is not limited to this range depending on the application.

On the other hand, the bright electrolytic solder plating layer can be prepared using a normal borofluoride bath.
It is formed from a sulfuric acid bath, a sulfamic acid bath, a phenolsulfonic acid bath, etc., with a brightness additive added thereto.

Most gloss additives are based on organic substances.
For example, commercially available Unicontain Prerite (trade name) manufactured by Ishihara Pharmaceutical Co., Ltd., Stanoster (trade name) manufactured by Blasberg of West Germany, etc. are used.

Its thickness is set to 0.0 mm mainly from the viewpoint of flexibility and solderability.
8-5 microns is preferred and must be strictly controlled. The reason for this is that if the bright electrolytic solder plating layer becomes too thick (more than 5 microns), the bright plating layer becomes brittle due to occluded organic matter, so for example, self-diameter winding may cause a large rack. As a result, color fastness and soldering properties deteriorate. Furthermore, the proportion of organic matter occluded in all the plating layers increases, and the solderability of the plating layer decreases. If the thickness is less than 0.5 microns, the unevenness on the surface of the matte electroplated tin layer cannot be sufficiently smoothed, resulting in insufficient gloss and color fastness. Of course, it is also related to the smoothness of the underlying plating layer, and the smoother it is, the more necessary the thickness of the glossy solder plating layer will be. Therefore, the preferred thickness range of the bright solder plating layer is about 0.5 to 5 microns, and the thickness is selected from this range depending on the purpose and use.

Next, the composition of the bright electro-solder plating layer is related to its plating thickness, and weldability and solderability are determined by its properties. The content of lead is preferably 2 to 80%, because if it is less than 296%, the melting point of the solder plating layer will not be much lower than that of tin, and the soldering properties will not be good, and it will also prevent the formation of whiskers. This is also because it cannot be prevented. When the amount of lead exceeds 8096, the proportion of lead in the entire plating layer becomes high, which is related to the thickness of the inner part of the bright plating layer, and blowholes are generated when welding with aluminum wire, resulting in welding problems. This is not preferable because it reduces the strength of the part and reduces weldability.

The brightly plated lead wire of the present invention configured as described above has the following effects.

■Since the outermost layer in contact with the air is a glossy electroplated solder layer with a smooth, glossy surface, corrosive gases in the air are adsorbed.Therefore, there is no deterioration in soldering properties due to surface discoloration.

3. Since the glossy electrolytic solder plating layer on the surface can be made thinner, there is less occlusion of organic matter, gas generation during soldering is suppressed, and soldering properties are excellent.

Since the glossy electroplated layer on the 0 surface can be made thin, it has flexibility that will not cause cracks even when subjected to severe processing such as bending and wrapping.

■Since the surface is glossy with a glossy electro-solder plating layer, there is no need for polishing with felt or wire drawing dies, improving the working environment.

■ By appropriately selecting the thickness and composition of the surface glossy electrolytic solder plating layer and adjusting the amount of lead in the entire plating layer, blowholes are generated due to the vaporization of a large amount of lead during welding with aluminum wire. This can prevent the phenomenon of deterioration of weldability.

Example 1: A matte electroplated tin layer of 11 μm was applied on a copper-clad steel wire with a wire diameter of 0.5B, and a bright electrolytic solder plating layer of 596 lead and 9596 tin was applied to a thickness of 8 μm on top of that. Created an inventive plating line. As the plating gloss additive, Stanoster manufactured by Blassberg of West Germany was used, and as the plating bath, a normal borofluoride bath was used.

For comparison, a matte solder plated wire with the same composition as the above glossy solder plating layer with a plating thickness of 14 μm, a glossy solder plated wire, and a matte tin plated wire were created, and the characteristics were measured.The results are as follows. As shown in the table. Table 1 shows the occurrence of cracks due to self-diameter winding at 170°C for 2 hours.
Presence of discoloration after heating, 1.2.4 Hr at 170°C
The soldering properties after heating indicate the strength and the number of bends at breakage after welding with the aluminum wire.

Here, the soldering property is expressed as a percentage of the area wetted by solder on the immersed part when a wire sample is immersed in a molten bath having a eutectic solder composition maintained at 280° C. for 2 seconds and then pulled up.

The number of bends to break is determined by bending the aluminum wire alternately to the left and right at 90 degrees after welding the aluminum wire, applying a load of IKF with the lead wire part facing downward, and holding the aluminum wire part in a chuck. The number of times it takes to break is defined as one bending by 90° and then returning to the original position.

From Table 1, it can be seen that the plated lead wire of the present invention is flexible and does not cause cracks when wrapped around its own diameter, and does not discolor when heated.
It can be seen that the soldering properties do not deteriorate, and the bending properties after welding are excellent. On the other hand, glossy solder-plated wire cracks when wrapped around its own diameter and has poor bending properties, while matte solder-plated wire discolors when heated, reduces solderability, has poor bending properties, and has poor bending properties. It can be seen that the bright tin-plated wire changes color when heated, and the soldering properties are significantly reduced.

Table 1 Comparison of characteristics of various lead wires Example 2: Using the same method as in Example 1, test wire samples were made with different compositions and thicknesses of the glossy solder plating layer as shown in Table 2.
The characteristics were compared. However, the total thickness of the matte plating layer and the glossy solder plating layer was set to 14μ. The measurement results of those characteristics are shown in Table 2.

Table 2゜From Table 2, the composition of the bright solder plating layer shows that if the lead content is as low as 2%, the soldering properties are poor, and if the lead content is as high as 90%, the bending properties are markedly reduced, whereas the lead content is 596%. It can be seen that with a thickness of 2.7μ, the solderability after heating and the bending properties after welding are excellent. However, if the thickness of the glossy solder plating layer is as thin as α2μ, the plating surface will not be sufficiently smoothed, resulting in discoloration due to heating and poor solderability, while if it is as thick as 7μ, the self-diameter Wrapping causes cracks, and heating reduces soldering properties, whereas
With a thickness of 2μ, no cracks occur when wrapped around the self-diameter,
It can be seen that it does not discolor when heated, does not lose solderability, and has excellent bending properties.

As described above, the brightly plated lead wire of the present invention has excellent properties, and its cross-sectional shape is not limited to the circular shape shown in the figure, but can be elliptical, square, rectangular, polygonal, or There is no problem even if it is of other unusual shape.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional tin-plated wire. FIG. 2 is a longitudinal sectional view showing a welded portion when the plated wire and aluminum wire are not welded. 8 to 5 are sectional views showing respective embodiments of the lead wire of the present invention. l... Metal wire, 2... Tin plating, 8... Matte electrolytic tin plating layer, 4... Bright electrolytic solder plating layer, 5...
- Base plating layer, 6... Steel or iron wire, 7... Copper or copper alloy coating layer, 8... Plating, 9... Aluminum ml, 10... Blow hole. 1F ] 19 1 do 2 / 1 2 two: ~ 173 figure Σ Sai 4 figure Summer Sai 5 figure ■ ) 9 - 13 1 3 '43 7

Claims (4)

[Claims] (1) A brightly plated lead wire for electronic components comprising a metal wire, a matte electroplated tin layer thereon, and a glossy electrolytic solder plated layer thereon. (2) The brightly plated lead wire for electronic components according to claim (1), wherein the bright electrolytic solder plated layer has a composition of 2 to 80% lead and 98 to 2096% tin. (3) The total thickness of the matte electrotin plating layer and the bright electrosolder plating layer is 5 to 25 microns.
) or (2), the brightly plated lead wire for electronic components. (4) Gloss: The thickness of the electro-solder plating layer is 0.5-5μ
Claims (1), (2), or (3)
) Brightly plated lead wire for electronic components.