JPS59191321A - Method of producing electrolytic condenser - 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 relates to a method of manufacturing an electrolytic capacitor.

Traditionally, anode body materials for electrolytic capacitors include tantalum, niobium, zirconium, vanadium, hafnium,
So-called valve action metals such as titanium and aluminum are known, and in the past many researchers have investigated the basic characteristics of these metals alone or in their alloys as electrolytic capacitors.
We have been considering practical application.

However, in order to be put to practical use as a capacitor, the electrical characteristics such as leakage current and dielectric loss of the oxide film unique to the anode material must reach a certain level. Only those using tantalum and aluminum as anode bodies.

Capacitors using tantalum as anode material have excellent electrical properties such as leakage current and dielectric loss, are stable and extremely reliable, and are characterized by being compact and having large capacity.

However, the supply of tantalum has not been able to keep up with the increasing demand over the past few years, and due in part to resource shortages, the price of the material has skyrocketed, leading to an increase in product prices. on the other hand,
Capacitors using aluminum as the anode material are characterized by being inexpensive, but in addition to being more difficult to miniaturize and increase capacity, they are inferior to capacitors using tantalum as the anode material in terms of electrical characteristics and stability. There is.

Under these circumstances, electrolytic capacitors whose anodes are made of materials that have excellent electrical characteristics such as leakage current and dielectric loss and stability, can be made smaller and larger in capacity, and can be inexpensively and stably supplied are being developed. Development was strongly desired.

As a result of various studies, the present inventors used titanium hydride and aluminum powder as raw materials, mixed, pressed, and sintered these powders to create an aluminum-titanium alloy porous sintered body as an anode body. In some cases, we have discovered that it is possible to obtain a porous material for electrolytic capacitors that meets these needs, and we have already proposed it.

We have also already proposed that when this aluminum-titanium alloy is used as an anode body, the most suitable chemical solution for anodizing is a phosphoric acid aqueous solution.

However, the present inventors discovered that AJ-T using phosphoric acid aqueous solution
As a result of further detailed study of the anodic oxidation of porous alloy bodies, we discovered one problem. it is,
If a resin coating is applied after solidification (after Ag paste), the capacitance decreases. This capacity reduction may exceed a maximum rate of 10 times. This phenomenon is caused by MnO,
This is thought to occur because the cathode does not completely adhere to the surface of the chemical conversion coating.

After the silver paste treatment, the inside of the porous body is open to the outside air, so there is adsorbed water inside the pellet due to external moisture, which acts as an electrode force, and the MnO2 is completely adhered and coated. The capacitance of the unconverted chemical coating area (referred to as the non-solidified area) is also detected. On the other hand, those coated with resin are isolated from the outside air compared to when Ag paste is applied, and the adsorbed water inside the pellets disappears when the resin is thermally cured (over 100°C), resulting in complete adhesion due to MnO. , only the volume of the covered portion (referred to as the solidified region) will be detected. Therefore, the ratio of the capacitance after resin coating to the capacitance after Ag paste is almost MnO.
It is thought that this corresponds to the coverage rate of .

A decrease in capacity during resin packaging, that is, a decrease in MnO coverage, leads to a decrease in CV value, which is not substantially desirable. The influence is particularly large when the capacity reduction rate exceeds 10%.

An object of the present invention is to provide a manufacturing method that can prevent such loss of capacitance and make effective use of powder C.

According to the manufacturing method of the present invention, a porous anode body made of an Al-Ti alloy is anodized in a phosphoric acid aqueous solution up to a constant voltage lower than the final formation voltage, and then the porous anode body made of an Al-Ti alloy is anodized with ammonium lactate or (conducted in an aqueous solution of ammonium borate), and then anodized again to the final formation voltage in a phosphoric acid aqueous solution or one of the above two types of ammonium-based aqueous solutions. It becomes possible to make it smaller.

Hereinafter, the present invention will be explained in detail according to examples.

Example Al powder with an average particle size of 3 μm and titanium hydride powder with an average particle size of 3 μm were mixed so that the atomic ratio of AI and Ti was 54 = 46, and after compression molding into a cylinder shape, it was heated to 1070 mm in a vacuum. A porous Al-Ti alloy body was produced by holding at a temperature of 2 hours and sintering, and used as an anode body.

Next, these anode bodies were anodized to 60 V in 0.5 volume of phosphoric acid aqueous solution (anodization 1-■),
Thereafter, anodization was performed separately with two types of aqueous solutions containing 1 volume of ammonium lactate or 1% by weight of ammonium succinate up to SOV. (Anodization 1-■) Furthermore, each of the two types of anodized products with different chemical solutions used in the above-mentioned anodization 1-■ was anodized again to 80V in a 0.005 volume H phosphoric acid aqueous solution. I did it.

(Anodization 2) For comparison, as a conventional method, anodization 1 was performed in a phosphoric acid aqueous solution of 0.5 volume H to the final formation voltage of 80 V. A sample was prepared by performing anodic oxidation again.

Impregnation with manganese nitrate and thermal decomposition were repeated 6 times for the 80Vf chemical products obtained by the above three types of chemical conversion methods.

After that, graphite and Ag paste were baked.

The capacitance after baking the Ag paste was approximately 6.5 fiF (120H2) for all three types of chemical formation levels. (3゜p each
(average value) Next, after solder dipping, resin dipping was performed to finish the exterior. The resin used was a thermosetting two-component epoxy resin. The table shows the capacitance at 120H2 after resin packaging and the rate of change (reduction rate) with respect to the capacitance after Ag paste. Also, 17i + current (LC) 20.8 V (16Vw x 1.3)
The values (median values) after aging at 85° C. for 16 hours at an applied voltage of 1 are shown in the table. (16 ■Evaluation - 5 minute value) (As can be seen from the table below, according to the anodizing treatment method of the present invention, the capacity reduction rate after resin coating with respect to the capacitance after Ag paste is Compared to the conventional chemical conversion method using only an aqueous phosphoric acid solution, the capacitance is significantly smaller (reduction rate % or less), and a large capacitance value is finally obtained.Furthermore, the leakage current value is also reduced by the anodizing treatment of the present invention. The reason why the anodic oxidation 2 is performed is that the leakage current value can be made smaller.

In addition, in this example, a phosphoric acid aqueous solution (
Although the case where 0°005 VO,E%) was used was shown, it was confirmed that similar effects could be obtained using an aqueous solution of ammonium lactate or ammonium borate.

As explained above, it is clear that the manufacturing method of the present invention is highly effective in the sense that it can prevent substantial loss of capacitance and effectively utilize the Cv value of the raw material powder.

Claims (1)

[Claims] In an electrolytic capacitor manufacturing method in which an alloy consisting of aluminum and titanium is used as the anode metal and is anodized, an electrolyte solution or a solid cathode semiconductor layer and an external cathode are sequentially formed. is carried out in an aqueous phosphoric acid solution, followed by a final chemical reaction in an aqueous solution of ammonium lactate or ammonium borate, and then again in an aqueous phosphoric acid solution or one of the two ammonium-based solutions. 1. A method for manufacturing an electrolytic capacitor, comprising an anodizing step of performing anodic oxidation up to a voltage.