JPS586298B2 - Electrolyte for driving aluminum electrolytic capacitors - Google Patents

Description

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

Conventionally, as this kind of electrolytic solution, one in which an ammonium salt of an organic carboxylic acid is dissolved in ethylene glycol as a main solvent is known.

Such an electrolyte has excellent effects on the low-temperature characteristics of the capacitor, but on the other hand, it has the disadvantage of causing corrosion during high-temperature load tests of the capacitor.

That is, to explain this corrosion using the typical aluminum electrolytic capacitor shown in the figure, the capacitor consists of a wound element 1, a case 2 that houses the element, a sealed opening of the case, a synthetic resin plate 4, and a rubber plate. It is composed of a sealing plate 3 made up of a combination of plates 50, external terminals 6, and internal terminals 8 that connect the external terminals and lead foils 7. However, during the high temperature load test, the lead foils 7 and internal terminals 8 in particular were corroded. can be seen.

Corrosion is noticeable when the synthetic resin plate 4 is made of phenolic resin, and is accelerated by charging and discharging or by passing a ripple current, and eventually the lead foil 7 and the like are corroded and cut.

Therefore, the object of the present invention is to provide an electrolytic solution that is a combination of ethylene glycol and an ammonium salt of an organic carboxylic acid.
It is an object of the present invention to provide an improved electrolytic solution for driving an aluminum electrolytic capacitor that can prevent the above-mentioned corrosion without impairing its excellent properties.

That is, the electrolytic solution of the present invention is prepared by dissolving an ammonium salt of an organic carboxylic acid as an ionogen in ethylene glycol as a main solvent, and adding 2.0 to 10% boron oxide (B203) to the electrolytic solution.
It is characterized by the fact that it is added in an amount of % by weight, thereby effectively achieving the intended purpose.

In the electrolytic solution of the present invention, if the amount of boron oxide added is less than 2.0% by weight, no corrosion suppression or prevention effect may be observed, whereas if it exceeds 10% by weight, the corrosion prevention effect may not be sufficient. As a side effect, the viscosity of the electrolytic solution increases and the conductivity decreases, which is undesirable because it causes a decrease in capacity and an increase in loss in the low-temperature characteristics of the capacitor.

Therefore, these addition amount ranges are excluded from the present invention.

In the electrolytic solution of the present invention, ammonium salts of organic carboxylic acids such as adipic acid, suberic acid, and sebacic acid are suitable.

Further, in the electrolytic solution of the present invention, the content ratio of ethylene glycol as a solvent and ammonium salt of an organic carboxylic acid as a solute is arbitrary, and the solute is usually used within the solubility limit.

Examples of the present invention will be described below.

In the examples of the present invention, boron oxide, which is an additive, dissolves well in a solvent at around 100°C.
The solute and additives were mixed to form an electrolyte, which was then used to form a capacitor of the form described and illustrated.

The following tests were conducted with such a capacitor.

The capacitor rating is 160V, 680μF,
The ripple load test was conducted at a temperature of 85°C and a ripple current of 6
The test was carried out under the conditions of 0 Hz, 2 A, and a current application time of 500 hours.

In Table 1, Z/Zo is 120Hz at -25℃
impedance at (2 and 120Hz at +20°C)
The smaller this value is, the better the low-temperature properties are.

Furthermore, the synthetic resin plate 4 (see drawing) constituting the sealing plate 3 of the capacitor subjected to the tests shown in Table 1 is made of phenol resin.

As is clear from Table 1, when boron oxide is added to the basic electrolyte consisting of the ammonium salt of ethylene glycol organic carboxylic acid, effective corrosion prevention can be achieved without substantially impairing the excellent low-temperature properties of the basic electrolyte. It can be done.

The effect of adding boron oxide depends on the amount added.

Table 2 shows the additive amount effect as a typical example when ethylene glycol and ammonium adipate are selected as the basic electrolyte.

In Table 2, Z/ZQ has the same meaning as in Table 1, and A
and B indicate cases where the synthetic resin plate 4 constituting the sealing plate 3 of the capacitor subjected to the tests in Table 2 is made of phenol resin and polypropylene resin, respectively.

As is clear from Table 2, the amount of boron oxide added is 0.5
It is effective in the range of ~10% by weight, and even when the most corrosive phenolic resin board is used as the sealing board, it is effective in the range of 2 to 10% by weight.
Valid within a range of % by weight.

Furthermore, in the present invention, it has been confirmed that even if a hydrogen absorbent is further added to prevent an increase in the internal pressure of the capacitor due to the generation of hydrogen gas, the respective effects of the hydrogen absorbent and boron oxide are effectively produced. .

For example, in a basic electrolyte solution consisting of 100 cc of ethylene glycol and 5 g of ammonium adipate, 2% by weight of boron oxide and 0.5 g of dinitrophenol as a hydrogen absorbent.
When the same type of test as shown in Table 1 was carried out using an electrolytic solution to which .

As is clear from the above description, according to the present invention, by adding boron oxide to an electrolytic solution in which an ammonium salt of an organic carboxylic acid as an ionogen is dissolved in ethyne glycol as a main solvent, corrosion inside a capacitor is prevented and reliability is achieved. It is possible to obtain an aluminum electrolytic capacitor with high performance.

[Brief explanation of drawings]

The figure shows a cross-sectional view of a typical aluminum electrolytic capacitor, where 1 is a wound element, 2 is a case, and 3 is a sealing plate.

Claims (1)

[Claims] 1. An electrolytic solution for driving an aluminum electrolytic capacitor, characterized in that 2.0 to 10% by weight of boron oxide is added to an electrolytic solution prepared by dissolving an ammonium salt of suberic acid, adipic acid, or sebacic acid as an ionogen in ethylene glycol as a main solvent.