JPH0318730B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrolytic solution for an electrolytic capacitor, and particularly to an electrolytic solution that is excellent in inhibiting corrosion of an electrolytic capacitor caused by a substrate cleaning agent. [Prior technology] Electrolytic capacitors are manufactured by etching the surface of a film-forming metal such as aluminum to enlarge the surface, and then anodizing the surface to form an oxide film layer that becomes a dielectric. This is used as an anode, a cathode body is placed opposite to this anode body, and a separator paper is interposed between the anode body and the cathode body and they are wound or stacked to form a capacitor element. This capacitor element is impregnated with an electrolyte. This electrolytic solution generally uses polyhydric alcohols such as ethylene glycol, acid amides such as dimethyl formamide, etc. as the main solvent, and various inorganic acids such as boric acid and adipic acid, organic acids, or salts thereof are dissolved therein. is used. This electrolytic solution is held by the separator paper, interposed between the anode body and the cathode body, and serves as a true cathode in contact with the enlarged surface of the anode body. In addition to this function, the electrolyte also has the function of repairing defects in the dielectric oxide film formed on the surface of the anode body, and is an important element that influences the electrical characteristics and life characteristics of electrolytic capacitors. . By the way, recent electrolytic capacitors are very often used by being attached to printed wiring boards, but in order to assemble printed circuit boards, after attaching various electronic components including electrolytic capacitors by soldering, the flux contained in the solder is removed. 1,2,2-trichloro-1,1,2-trifluoroethane, 1,1,
Cleaning is performed using a halogen-based substrate cleaning agent such as 1-trichloroethane. However, electrolytic capacitors are extremely susceptible to these halogens, especially chlorine ions, and if even a small amount of chlorine ions penetrates through the sealing part of the electrolytic capacitor,
The internal aluminum electrodes will corrode, rendering the electrolytic capacitor unusable. Therefore, there is a need to obtain an electrolytic capacitor that can prevent this corrosion and withstand cleaning agents. Conventionally, measures have been taken to prevent corrosion caused by cleaning agents. For example, the sealing part of an electrolytic capacitor is sealed with an elastic sealing body made of various types of synthetic rubber, etc., and a thermosetting resin or the like is applied to the outer surface to form a resin layer to prevent the penetration of cleaning agents ( (Japanese Patent Publication No. 55-52217)
There is. However, such a structure increases the number of manufacturing steps and increases the overall length of the electrolytic capacitor by the resin layer, making it unsuitable for miniaturization. In addition, various silver compounds are added to the electrolytic solution as corrosion inhibitors (Special Publications No. 58-
1538), the addition of several corrosion inhibitors has been proposed. However, conventional corrosion inhibitors show relatively good corrosion inhibition effects on 1,2,2-trichloro-1,1,2-trifluoroethane; For cleaning, 1,1,1-trichloroethane has a high penetration rate from the sealing part of the electrolytic capacitor, causing corrosion in most cases within 250 hours.
At present, sufficient corrosion control has not been carried out. [Problems to be Solved by the Invention] This invention improves the above-mentioned drawbacks of the conventional technology, and uses halogen-based hydrocarbons, especially 1, The object of the present invention is to provide an electrolytic solution for an electrolytic capacitor that can suppress corrosion when washed with 1,1-trichloroethane. [Means for Solving the Problems] The electrolytic solution of the present invention uses an amine salt of salicylic acid as the main solute, and β-butyrolactone, δ-nonalactone, DL-pantoyllactone, δ-valerolactone, and γ-valerolactone as the solvent. It consists of one or a mixture of two or more selected from the group of lactones, or a mixture of one or more selected from the group of solvents and γ-butyrolactone as a solvent. β-butyrolactone, δ-nonalactone, DL
-pantoyllactone, δ-valerolactone, γ
-Valerolactone is a cyclic compound containing -C(=0)-C- in the ring, but
The present invention is characterized in that these lactones are used alone or in a mixed solvent with γ-butyrolactone, which is often used in electrolytes for electrolytic capacitors. The structures of these lactone compounds are shown below. β-butyrolactone δ-nonalactone DL-pantoyllactone δ-valerolactone γ-valerolactone [Operation] This invention uses an amine salt of salicylic acid as the main solute, and uses any of the lactones β-butyrolactone, δ-nonalactone, DL-pantoyllactone, δ-valerolactone, and γ-valerolactone as a solvent. The use of an electrolytic solution makes it possible to withstand corrosion by halogenated hydrocarbons, particularly 1,1,1-trichloroethane, which has a strong corrosive effect, although the reason is not clear. Further, among lactones, corrosion resistance can be improved by mixing these lactones with γ-butyrolactone, which has been conventionally used as a solvent for electrolytes. [Example] Next, the present invention will be described in detail based on Examples. In the experiment, an electrolytic solution according to the present invention and a conventionally used electrolytic solution were prepared, and an electrolytic capacitor element was impregnated with the electrolytic solution, an electrolytic capacitor was manufactured, and a high-temperature load test was conducted after immersing it in 1,1,1-trichloroethane. was carried out to investigate the state of corrosion occurrence. The manufactured electrolytic capacitor has a rated voltage of 50 V and a capacitance of 47 μF. The capacitor element used is the same for all the examples, and is impregnated with the conventional electrolyte and the electrolyte of the present invention. The impregnated capacitor element was housed in an aluminum cylindrical case with a bottom, the opening was sealed with an elastic sealing member, and the sealing part was crimped to complete the electrolytic capacitor. First, in Comparative Example 1, the electrolytic solution used was an ethylene glycol-adipic acid based electrolytic solution, which is often used as an electrolytic solution for ordinary low-voltage electrolytic capacitors. The composition of this electrolyte is as follows. Comparative Example 1 Electrolyte Composition (% by Weight) Ethylene Glycol 84 Ammonium Adipate 12 Water 4 Next, as Comparative Example 2, an electrolyte was used in which salicylate was used as the solute and γ-butyrolactone was used as the solvent. The composition of this electrolyte is as follows. Comparative Example 2 Electrolyte composition (wt%) γ-butyrolactone 82 Triethylamine salicylate 18 As the electrolyte of the present invention, an amine salt of salicylic acid was used as the solute, and β-butyrolactone, δ-nonalactone, and DL-pantoyl were used as the solvent. Electrolytes using lactone, δ-valerolactone, and γ-valerolactone (inventive examples 1 to 5) and mixed solvent examples with γ-butyrolactone (inventive examples 6 and 7) were used. The electrolyte composition of the present invention example is shown in Table 1.

[Table] Then, put these electrolytic capacitors into the cleaning tank of an ultrasonic cleaner (oscillation frequency 29KHz) and
After injecting 1-trichloroethane and performing ultrasonic cleaning for 5 minutes, evaporate the 1,1,1-trichloroethane to dryness in the air, and then apply the rated voltage (50V) in a thermostat at 110°C to determine the lifespan. Tests were conducted to investigate the occurrence of corrosion. For each example, 20 samples were prepared, divided into 10 pieces, each was subjected to a load test for 500 hours and 1000 hours, and after the test was completed, the samples were disassembled to calculate the number of corrosion occurrences. Examined. The results are shown in Table 2.

【table】

〔Effect of the invention〕

As described above, the electrolytic capacitor using the electrolyte of the present invention does not corrode even when the substrate is cleaned using halogenated hydrocarbons, especially 1,1,1-trichloroethane, which has a strong corrosive effect. Almost no occurrence is observed, stable characteristics can be maintained over a long period of time, and the reliability of electronic equipment can be improved.

Claims (1)

[Claims] 1 Using an amine salt of salicylic acid as the main solute and a mixture of one or more selected from the group of β-butyrolactone, δ-nonalactone, DL-pantoyllactone, δ-valerolactone, γ-valerolactone, or An electrolytic solution for an electrolytic capacitor, characterized in that a mixture of one or more selected from the above solvent group and γ-butyrolactone is used as a solvent.