JPS5945212B2 - Aluminum electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electrodes for aluminum electrolytic capacitors.

Generally, aluminum electrolytic capacitors use two sheets of aluminum foil, as shown in Figure 1, a dielectric film is formed on the surface of one foil by anodizing, and a separator is sandwiched between it and the other foil. This is then wound to form a capacitor element 1, this capacitor element 1 is impregnated with a driving electrolyte (hereinafter abbreviated as electrolyte), and this is enclosed in a case 2.

In FIG. 1, reference numeral 3 denotes a terminal plate that closes the opening of the case 2, and has an external terminal 4 attached thereto for connection to an external circuit. In addition, FIG. 2 shows an enlarged view of the main parts of the capacitor element 1, in which 5 is an anode foil, 6 is an oxide film,
1 is a cathode foil, and 8 is a separator.

By the way, although this aluminum electrolytic capacitor has the advantage of being small and having a large capacity compared to other capacitors, it also has disadvantages such as the loss value of the capacitor, the impedance value of the capacitor, and the poor frequency characteristics of the impedance. be.

These problems lead to drawbacks such as slow response speed of circuits using electrolytic capacitors and limitations on the range of use.Aluminum electrolytic capacitors are needed to improve the loss value and impedance characteristics of capacitors. This will improve the characteristics of In such aluminum electrolytic capacitors, it is known that the separator has a significant effect on reducing the loss value and impedance value of the capacitor, and improving various characteristics such as loss characteristics at low temperatures, impedance characteristics, and frequency characteristics.

Here, the impedance of the capacitor is Z ■, /
R2+(Lω one hill)2 However, z is the impedance of the capacitor, and ω is the angular velocity, which is expressed as 2πf.

ω■2πf, , f is the measurement frequency, C is the capacitance of the capacitor, L is the inductance of the capacitor, and R is the internal resistance of the capacitor. This internal resistance R is R=RE+R
It can be divided into two parts: RE is the resistance between the two electrode foils, Rs is the resistance of the oxide film dielectric, and the combined resistance of the leads and others. In the above equation, at a constant measurement frequency, L, C, and ω all take constant values. Therefore, in order to improve the characteristics of the impedance z of the capacitor, that is, to reduce the impedance z, the internal resistance R of the capacitor must be reduced. Of this internal resistance, the combined resistance Rs of the oxide film dielectric and the leads has been sufficiently improved at present, and further improvement is difficult; therefore, in order to reduce the impedance z, the interelectrode resistance RE must be reduced. .

This interelectrode resistance RE is expressed by the following equation.

RE=K・σ・1・ρ However, K is a constant, 1 is the distance between the electrodes, ρ is the specific resistance of the electrolyte impregnated in the separator, and σ is the material of the separator.
It shows coefficients depending on shape.

In order to reduce RE under such conditions, the specific resistance ρ of one electrolytic solution is reduced.

Reduce the distance 1 between two electrodes.

However, in order to reduce the specific resistance ρ of the electrolytic solution in No. 1, the composition of the electrolytic solution must be considered.
It is said to be extremely difficult due to problems such as loss change and gas generation.

On the other hand, reducing the distance 1 between the electrodes 2 means making the separator used as thin as possible. For these reasons, materials with a low density of 0.3y/~ or less of resistance and a thickness of 10 to 30 microns are being used for separators of aluminum electrolytic capacitors.

When the separator becomes thinner, when it is sandwiched between the anode aluminum foil and the cathode aluminum foil and wound tightly, the separator will be pierced by the burrs on the cut surface of the aluminum foil, resulting in many shoot defects. It becomes like that. The present invention enables the use of thin separators without causing problems such as shoots.

j- Conventionally, aluminum foil is cut into predetermined dimensions using a steel blade. In this case, mechanical pressing is necessarily required, and the occurrence of burrs on the cut surface is also difficult to avoid. In the present invention, a laser beam is used instead of a steel blade to cut the aluminum foil, and in this case, the cutting is done by heat, so the cross section is rounded and has no burrs, and therefore has a low density. Even when wound together with a thin separator, there is no shot defect between the anode and cathode, and the performance of aluminum electrolytic capacitors can be greatly improved.

Next, specific examples of the present invention will be described. First, in order to confirm whether an aluminum foil with a good cut surface could be obtained using a laser beam, a 100μ thick aluminum foil that had been chemically converted at 50V was heated using a YAG laser (yttrium, aluminum, garnet) manufactured by Nippon Electric Co., Ltd. , Y3Al5Ol2 solid-state laser) was used to cut the foil at an output of 5W while feeding the foil at a rate of 5c7n per second.

As a result, as mentioned above, the cut surface was completely rounded and no burrs were generated at all. Tables 1 and 2 compare the results of investigating various characteristics of electrolytic capacitors manufactured using aluminum foil cut in this way and electrolytic capacitors manufactured using aluminum foil cut with a conventional steel blade. It shows.

In addition, in Table 1, the rating is 25V110000pF.
Table 2 shows the average value of 50 samples each with a rating of 50 V and 6800 μF. In this way, the present invention uses an aluminum electrode foil cut with a laser beam, so even if it is wound together with a thin, low-density separator, shot defects will not occur, making it possible to obtain a high-performance aluminum electrode capacitor with low loss. It has extremely great industrial value as an effective means.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a general aluminum electrolytic capacitor including the present invention, and FIG. 2 is a cross-sectional view showing an enlarged main part of a capacitor element of the same capacitor. 1...Capacitor element, 5 crystals...Anode foil, 7
...Cathode foil.

Claims (1)

[Claims] 1. An aluminum electrolytic capacitor characterized by using an aluminum foil cut by a laser beam as an electrode.