JPS5937847B2 - plastic film capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic film capacitor formed by spot welding lead wires at predetermined positions in the length direction of a metal electrode foil. Compared to the above-mentioned capacitors, the quality is improved and the number of man-hours and materials required for manufacturing are greatly reduced.

Conventionally, this type of capacitor is manufactured as follows.

That is, while a pair of dielectric plastic films and a pair of metal electrode foils are overlapped and wound around a winding shaft, a pair of lead wires are connected to each other at predetermined positions in the length direction of the electrode foils. Spot welding is performed on the electrode foil.

After winding the capacitor element in this manner, manufacturing is completed through processes such as pressing and packaging.

Depending on the type of plastic film used, it may be possible to omit the pressing or wrapping process.

The material mainly used as electrode foil in this type of capacitor is aluminum foil, whose thickness is 5 μm.
Many of them have a diameter of 1 to 10 μm, and spot welding lead wires to these requires advanced technology and highly accurate and stable equipment.

The lead wires are often made of soft copper wire plated with tin or solder, or copper coated wires with a steel core plated with tin or solder.

In order to facilitate spot welding to the electrode foil, the tip portion including the part to be welded is flattened as shown in FIGS. 1 and 2.

That is, Fig. 1 is a front view of a conventionally used drawer lead wire, and Fig. 2 is a top view of the same. In both figures, 1 is a lead wire, 2 is a circular cross section, and 3 is a flattened part. This is the part where

Both figures (particularly Figure 2) are enlarged to make it easier to understand the form of the lead wires.

Now, as a result of research on the shape of this lead wire when spot welding it to the electrode foil, the inventor found that the cross-sectional shape of the welded part of the lead wire is parallel to the upper and lower surfaces in the center, and the end surfaces on both sides are arcuate. As shown in the figure, when the ratio of dimensions to a is in the range of 0.55 to 0.8, processing from a lead wire with a circular cross section is relatively easy, and It was also found that weldability was good.

The basis for this will be explained below.

When spot welding a lead wire to a predetermined position on an electrode foil during capacitor manufacturing, at least the part to be welded has a flat shape, and it is necessary to stably place the lead wire on the electrode foil.

Lead breakers are often made of soft copper wire plated with tin or solder, or copper coated wire with a steel core plated with tin or solder. As a result, the tin or solder on the upper and lower surfaces of the cross section moves toward the side end surfaces of the cross section, so that the thickness of the tin or solder plating on the upper and lower surfaces becomes extremely thin, and the side end surfaces tend to become thicker.

This tendency increases as the crushing becomes deeper, and at the same time, cracks occur on the side end faces.

When welding in this state, the tin or solder that is biased toward the side end surface melts and comes into contact with the electrode foil, such as aluminum, but when it recrystallizes, it gives the electrode foil VC cracks and sometimes cuts the electrode foil. .

Furthermore, the tin or plating on the upper and lower surfaces of the lead wires becomes thinner.

Therefore, when welding is performed by placing the welding electrode on the flat surface of the lead wire on the electrode foil, the electric resistance value of the flat surface is different between the center part and the side edge parts of the surface, so the current flow is divided. As a result, the heat generation conditions during welding became unstable, and sufficient welding strength between the lead wire and electrode foil could not be obtained, resulting in unstable welding.
This may cause nδ defects.

In addition, the effects of edges and sharp corners on the side end surfaces can also cause damage to the film during winding, making it easy to end up with a capacitor that has fatal defects overall.

As mentioned above, this tendency becomes more severe as the crushing becomes deeper.

As a result of experimenting with various crushing conditions, the inventor found that a relatively shallow flatness is better.

On the other hand, if the crushing is too shallow, problems will occur.

That is, the width in contact with the electrode foil becomes narrower. In the extreme case, when the lead wire is m-1 without crushing, the lead wire comes into line contact with the electrode foil, and the sitting stability is loose, so the solder plating layer is thick on the top and bottom surfaces, so welding is good. However, overall welding strength becomes weaker.

The same thing can be said when there is slight crushing.

In short, if the crushing is too shallow, the contact width will become narrower,
Welding points can be easily removed due to external force applied to the lead wire,
Furthermore, there is not enough tin or solder on the side end surfaces to compensate for the contact width, resulting in a decrease in welding strength.

However, as mentioned above, the welding has a good fit, so the welding may come off during the rolling process or in subsequent steps, and this tendency is more pronounced as the crushing is too shallow.

As a result of comprehensively experimenting and considering the above points, we found that the cutting edge that is emitted is a dimensional ratio of flatness, and the deep limit of crushing is 0.
．． 55 and 0.55 to 0.8 with a shallow limit of 0.8
It was found that this is the optimal range.

FIG. 4 shows the plating thickness of a lead wire having a circular cross section. For example, for a lead wire with a diameter of 0.5 or 0.6 mvt, the plating thickness is about 5 to 20 μm.

4 is a plated part.

FIG. 5 shows a cross-sectional view when the crushing is deep, and the plating thickness 5 on the side end surfaces becomes thicker, and the plating thickness 6 on the upper and lower surfaces becomes thinner.

Figure 6 is a cross-sectional view of the plating thickness when the crushing is too shallow.
In this case, the width of the contact surface of the flat part of the lead wire with the electrode foil is 7
is narrower, and the range of the connection angle θ cannot be filled with the plating 4 on the side end faces, so the welding strength is likely to be weakened.

Next, two examples of the experiments conducted will be described.

Q, 5 Innφ of solder-plated copper-clad steel wire (CP wire)
Using the lead wire, the dimension of the crushed thickness b is in the range (A) 0.2-0.3 mm (b / a = 0.1 →, 4) (B) 0.35-0 .44mm (
0.55~0.8)〃 (C) 0.45~〈0.5》(〃Q, 9~<1.0
), three types of lead wires were made, and the elements were made by winding and welding them under the same conditions.

Table 1 shows the volume fL of the same number of windings for A, B, and 6 groups.
This shows the results of disassembling a film capacitor element with a value of 0.01 μF and investigating the welding condition.The strong or weak welding of the defective content indicates that the welding is too strong or too weak, which does not meet the specified welding standards. be.

Group A has many weak and unstable welds, while Group 6 shows a tendency to be well welded.

It can be seen that group B is the most stable.

On the wooden surface, the two lead wires of one capacitor element are adjusted.

Of course, as mentioned above, welding is not good if it is too strong or too weak.

Welding residues are those that are so strong that sparks are generated between the welding electrode and the welding electrode, resulting in black spots, welding spots, and cracks or tears in the welded area of the electrode foil.

Welds are defective welds, such as those where there is almost no welding, or where the welding is unstable, or where there is welding, it is very small and does not meet the standards.

From Table 1, the relative defective rate ratio for Group A, Group B, and Group 6 is calculated as A:B:C=4.7:1:2
．． It can be seen that the ratio is 6.

Table 2 shows the electrical screening results during a mass production experiment in which capacitors were made using the same number of elements in each group A, B, and C that were made at the same time as Table 1, and show the number of defective products for each type of defect. .

To explain the details of the defects in the order of symbols, Co indicates an insufficient capacitance defect, SH indicates a short circuit defect, tan δ indicates a dielectric loss tangent value out-of-spec defect, IR indicates an insulation resistance value out-of-spec defect, and TV indicates a breakdown voltage defect.

Broken electrode foil or poor welding (including unstable welding)
is taken as Co, tan δ.

If defective products such as defects caused by Paris or damage to the film due to detached lead wires cannot be captured in front of the TV, please contact T.
It can be captured by V.

From the data in Table 2, it can be seen that the welding condition of Group A is weak and there are many pressure-resistant defects due to Paris.

Group 6 is welded well, but the welded part is narrow and easily comes off, so the weld strength tends to be weak.

On the other hand, the ones in group B are of course defective, but the ones in group A,
The number is smaller than that in Group 6, and it can be said that it is relatively stable.

From the electrical sorting results in Table 2, the relative defective rate ratio is found to be A:B:C=4.7:1:2.0, which is obtained by combining the disassembly results in Table 1 and the electrical sorting results in Table 2. Overall, it was found that Group A had the highest defective rate, followed by Group 6, and Group B showed a stable condition.

The inventor has repeated various experiments in addition to the above two examples, but
I got similar results each time.

FIG. 7 shows the relative failure rate ratio with respect to the crush size ratio -.

Furthermore, in this case, the cross-sectional shape is relatively close to a circle, so if not only the welded part but the entire length of the lead wire is within this range of dimension ratios, the cross-sectional shape will be normal. It was confirmed that these can be handled in the same way as circular ones.

For example, for a lead wire with a diameter of 0.5 mm, the cross-sectional area size is the same = 0.64 myyn, b = 0.35 mm, and to make - = 0.8, a = 0.55 mm,
b=0.44mm.

To do this, a = 0.79 myn, b = 0.44 v
If it is a capacitor that uses an, the lead wire can be inserted into the printed circuit board in the same process as one that uses a lead wire with a circular cross section.
It was found that the lead wire satisfies all the conditions required for a capacitor lead wire, such as mechanical strength and solderability.

As described above, the present invention relates to a plastic film capacitor in which a lead wire is spot welded to a metal electrode foil at a predetermined position in the longitudinal direction of the metal electrode foil. It is used as a measure of flatness, and it has great value as an industrial expert because it allows products with uniform quality and improved performance compared to conventional quality.

[Brief explanation of the drawing]

Figure 1: Front view of a conventionally used lead wire, Figure 2: Also a top view, Figure 3:
...Cross-sectional shape of the welded part of the lead wire used in the present invention, Fig. 4...Cross-sectional view showing the state of the plating thickness of the circular cross section of the lead wire, Fig. 5...Crushed Figure 6 is a cross-sectional view showing the state of plating thickness when it is deep.
...A cross-sectional view showing the state of plating thickness when crushing is too shallow, illustrating No. 7.

Claims (1)

[Claims] 1. A plastic film made by spot welding a copper wire, copper wire, etc. lead wire with a solder plating, tin plating, etc. plating layer on the outside at a predetermined position in the length direction of a metal electrode foil such as aluminum. In a capacitor, the above-mentioned lead wire with a circular cross section has a flat cross section at least at the welded part, the upper and lower surfaces of the cross section are parallel, and both end surfaces are arcuate, and the distance between the upper and lower surfaces is small. That is, the maximum length a of both end surfaces for the thickness b)
A plastic film capacitor having a dimensional ratio b/a of 0.55 to 0.8.