DE1138479B - Method of manufacturing a cathode for an electrolytic capacitor - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

PATENT DOCUMENT 1138

INTERNAT. KL. H 01 g

REGISTRATION DATE: MARCH 19, 1962

NOTICE
THE REGISTRATION
AND ISSUE OF
EDITORIAL: OCTOBER 25, 1962

ISSUE OF

PATENT DOCUMENT: JULY 8, 1965

DEVIATES FROM EXPLOITATION

(N 21345 VIHc / 21g)

The invention relates to a method for producing a cathode for an electrolytic capacitor, in particular with an anode made of tantalum and / or niobium.

Between the cathode and the electrolyte in an electrolytic capacitor occurs during operation Transition impedance, which adversely affects the nature of the capacitor when the transition resistance high and the junction capacitance is low. This results in a lower capacitance value of the capacitor provided with such a cathode receive.

This phenomenon occurs in particular with electrolytic capacitors of small dimensions, with an anode made of tantalum or niobium. In these types where the anode surface to maintain a high capacity value, usually through special measures at the Manufacturing is enlarged, has the cathode, which is also designed as a container for the electrolyte can be a relatively small surface area, which leads to the occurrence of a disturbing cathode impedance brings with it.

For capacitors with a cathode made of aluminum, it is already known that a considerable Improvement can be achieved in that the Kaihodenfläche is enlarged by etching. However, aluminum is particularly unsuitable for electrolytic condensers with an anode made of tantalum or niobium because of the type of electrolyte used in such a capacitor. The in The cathode metal used in this case, such as silver or nickel, cannot be enlarged sufficiently by etching the surface can be obtained.

According to a known method, a cathode is made for use in a tantalum or niobium capacitor obtained with an enlarged surface that this by electrolytic Deposit is covered with a porous layer of silver.

According to the invention, such a porous silver layer is also applied to the cathode, however without the need for electrolytic machining. The method of the invention exists in that the cathode surface is covered with a paste-like mass, the finely divided Contains silver and / or a compound that is converted to silver when heated, and on a temperature between 400 and 800 ° C is heated.

Such a mass is often used for silvering the surface of ceramic objects. The Silberverbin'düng can z. B. be silver oxide, the process for making a cathode
for an electrolytic capacitor

Patented for:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Claimed priority:
Netherlands of March 22, 1961 (No. 262 704)

Roelof Dirkügel, Zwolle (Netherlands),
has been named as the inventor

already above about 180 ° C in silver metal and oxygen decomposed.

Compared with the known methods of obtaining a porous layer on a cathode surface the method according to the invention has the additional advantage that this coverage can be attached in a simple manner. This is important with regard to the attachment of the Seal; at this point there must be no porous layer on the cathode surface.

example

Silver linings are immersed in:
1. a paste consisting of a suspension of 200 g of silver oxide in 160 ml of acetone or in
2. a suspension of approximately equal parts by weight of silver powder and silver oxide powder in an organic liquid.

The organic liquid is x. B. acetone is used, in which a macromolecular binder is optionally also dissolved. The strips are then heated to various temperatures as indicated in the table below.
This table shows the measured cathode capacity per cm ^{2 of} an untreated strip and of the strips which, according to the invention, are covered with a porous silver layer by means of the suspensions described above. The measurements were carried out in an electrolyte with a specific resistance of 400 Ohm-cm at 20 ° C.

509 603/384

Immersed in Treatment
temperature
⁰ C capacity
_μ ν resistance
ohm Untreated ... Suspension 2 .... \ .— 40.8 331 Immersed in I. 500 66 288 Suspension 1 .... \ 550 81 312 I. 600 65 312 500 81.5 312 550 91 288 600 90.5 276

Claims (1)

PATENT CLAIM: Process for the production of a cathode of an electrolytic capacitor covered with a porous silver layer, which has in particular an anode made of tantalum or niobium, characterized in that the cathode surface is coated with a paste-like mass containing finely divided silver and / or a compound which is converted into silver when heated is covered and then heated to a temperature between 400 and 800 ° C.