CS269133B1 - Impregnating electrolyte for electrolytic capacitors with aluminum electrodes - Google Patents

Abstract

The working impregnation electrolyte is intended for electrolytic capacitors with aluminum electrodes, with a wide temperature range of minus 55 °C to plus 125 C, a storage temperature of minus 60 °C and an operating voltage of 6 V to 40 V. The electrolyte contains dimethylformamide, maleic mono-diethylaminate and ammonium ethylene glycol borate. Its advantage is low resistance values at minus temperatures and stability of parameters at a temperature of plus 125 C, which ensures long-term durability of the capacitors.

Description

The invention relates to an impregnating electrolyte for electrolytic capacitors with clinical electrodes, a wide temperature range of minus 55 to plus 125 ° C, for an operating voltage of 6 V to 40 V.

This type of capacitor consists of an AI anode foil with a dielectric oxide layer, a capacitor paper and an AI cathode foil. The capacitor coil is impregnated with a liquid precision electrolyte, inserted into a housing and sealed.

The impregnating electrolyte, which forms the cathode of the capacitors itself, is one of its most important components - it significantly affects all the basic parameters of the electrolytic capacitors. The demands on its properties are constantly increasing, it is required that the capacitors be able to operate in a wide temperature range of minus 55 to plus 125 ° C.

It is known to use an electrolyte based on ethylene glycol, boric acid and ammonia for the impregnation of electrolytic capacitors. However, at temperatures above 70 ° C, this electrolyte acts aggressively on the dielectric oxide layer on the Al anode and at negative temperatures shows an unfavorable course of the temperature dependence of the resistance. Its applicability is therefore only for the temperature range minus 25 to plus 70 ° C.

Furthermore, electrolytes of various compositions based on ethylene glycol, adipic acid and ammonia are known. For the same reasons given for the boron electrolyte, their applicability is only for the temperature range minus 40 to plus 85 ° C.

In order for the electrolytic capacitors to comply with the prescribed parameters at minus 55 ° C, the impregnating electrolyte must have a favorable course of resistance at minus temperatures and at this temperature a very low value of specific resistance. To ensure that the capacitors are suitable for a long time at a temperature of plus 125 ° C. the electrolyte must be sufficiently stable at this temperature and the specified operating voltage of the capacitors and must have a reasonably high sparking voltage.

The properties of the electrolyte at sub-zero temperatures, its stability and the value of the sparking voltage at plus 125 ° C are given by the properties and concentration of the added compounds containing ionogens to a suitable organic solvent.

The disadvantages - narrow temperature range and instability at high temperatures - mentioned for ethylene glycol-based electrolytes with boric acid or adipic acid are eliminated by the dimethylformamide-based impregnating electrolyte according to the invention, which consists of 68 to 93 parts by weight of dimethylformamide, 5 to 25 parts by weight. maleic mono-diethylaminate, 2 to 7 parts by weight of ammonium ethylene glycol borate.

The electrolyte of this composition shows low values of specific resistance at temperatures of plus 30 and minus 55 ° C and is sufficiently stable at temperatures of plus 125 ° C - it does not corrode AI electrodes and does not disrupt the dielectric oxide layer, has good molding ability and reasonably high sparking voltage for capacitors with operating voltage 6 to 40 V.

For a better illustration, the most important parameters of electrolytes and capacitors are given in the following tables.

Electrolytes are labeled:

1. Electrolyte from ethylene glycol and boric acid

2. Electrolyte from ethylene glycol and adipic acid

3. An electrolyte according to the invention

CS 269133 Bl

Addiction spec. resistance of electrolytes at temperature /Ohm.cm/ Electric rolyt + 30 - 25 ·. > 0 temperature / - 40 C/ - 55 1 350 8,000 42 000 450 000 2 72 970 3 BOO 22 900 3 79 227 383 833

The electrolytes show the following increase in specific resistance in the temperature range plus 30 to minus 55 ° C: boric 1,280 times, adipic 318 times, while the electrolyte according to the invention only 10.5 times. Furthermore, the electrolyte according to the invention has a specific resistance value 27 times lower than the adip electrolyte at a temperature of minus 55 ° C.

Durability of capacitors 25 V / 100, uF at + 125 ° C with electrolyte according to the invention

The table shows the changes in capacity, loss factor and residual current during the 5,000 hour test.

time test duration, /throw/ 0 1,000 2,000 5,000 C / ^ iF / 105 106 105 101 tgo /% / 3.5 9.4 10.2 12.2 room /, uA / 1.7 0.9 0.7 0, 5

It can be seen from the table that the electrolyte capacitors according to the invention can operate at a temperature of plus 125 ° C for several thousand hours without significant changes in the parameters of the capacitors.

The composition of the electrolytes according to the invention is described in the following examples: Electrolyte for 6 to 25 V. Mixes by weight of dimethylformamide, 20 parts by weight of maleic mono-diethylaminate and 5 parts by weight of ammonium ethylene glycol borate. The mixture was stabilized by heating to 70 ° C. The specific resistance is 70 to 90 Chm.cm/30 ° C, the sparking voltage is 104 V.

Electrolyte for 40 V 89 parts by weight of dimethylformamide, 7 parts by weight of maleic moro-diethylaminate and 4 parts by weight of ammonium ethylene glycol carbonate are mixed.

The mixture is stabilized by heating to a temperature / U ° C. Spec i (bow resistance Jn 130 15C Ohm.cm/30 ° C, sparking voltage is 140 V.

The impregnating electrolytes according to the invention make it possible to produce electrolytic capacitors with Al electrodes for an operating voltage of 6 to 40 V with a wide temperature range minus 55 to plus 125 ° C, a storage temperature of minus 60 ° C and a shelf life of at least 2 ° C at plus 125 ° C. .

Claims (1)

OBJECT OF THE INVENTION Impregnating electrolyte for electrolytic capacitors with aluminum electrodes, a wide temperature range of minus 55 to plus 125 ° C and an operating voltage of 6 to 40 V, based on dimethylformamide, characterized in that it consists of 68 to 93 parts by weight of dimethylformamide, 5 to 25% by weight. parts of maleic mono-diethylaminate and 2 to 7 parts by weight of ammonium ethylene glycol borate.