JPS622514A - Electrolytic capacitor - 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] [Industrial Application Field] The present invention relates to aluminum electrolytic capacitors, and in particular uses an electrolytic solution that prevents corrosion of the anode foil and pull-out lead tabs caused by cleaning with halogen-based ITR solvents. This is related to electrolytic capacitors.

[Prior art and problems to be solved by the invention] In general, an electrolytic converter is made by etching a high-purity aluminum foil and using an anode foil whose surface is anodized, and an etched aluminum foil facing the anode foil. .

The device is constructed by impregnating an element with an electrolytic solution in a wound structure with a separator paper interposed between the aluminum cathode foil, housing the device in an aluminum case, and sealing it with an elastic sealing member.

In recent years, this electrolytic capacitor is mounted on a printed circuit board, and after soldering U, half [1] is removed due to flux removal.
．． Substrate cleaning is performed using halogen-based organic solvents such as 1-1-lichloroethane and trichloro-1-lifluoroethane.

However, halogen-based organic solvents diffuse through the sealing body of electrolytic condenser 1) and enter the capacitor. Dissociation of chloride ions occurs in the tf solution. These dissociated chlorine ions cause corrosion of the anode foil and lead-out tab portion of the electrolytic capacitor during use, resulting in defects in the electrolytic capacitor.

Therefore, it is necessary to apply resin on the surface of the conventional model, L, and the elastic sealing body II.
A method of imparting corrosion resistance has been implemented. However, this method does not meet the demands for miniaturization and cost reduction.

In addition, P-nitrophenol or P-nitrobenz 6 is added to the electrolyte.
It is known to add corrosion inhibitors such as acids to improve corrosion resistance against halogen-based solvents, but it cannot be said that the corrosion resistance is sufficient, and cleaning with 1.1.1-trichloroethane is recommended. Corrosion resistance has not been achieved in most cases.

In general, the corrosion of aluminum by chlorine ions is expressed by the following formula: %, and the corrosion growth process can be divided into two stages. First, in the first step, chlorine ions react with the metal surface of aluminum in contact with Ti to generate Aj2cLa. Since this first step is a competitive reaction with the formation of aluminum into a non-fJJ state, the reaction rate is slow.

The next second stage is 9. Δff1c
J: As f3 increases by 1 degree, Aucf23 acts as a catalyst, activates the metal surface of aluminum, and easily elutes Δ13+ from the metal surface of aluminum, making it easier to react with chlorine ions. Corrosion progresses rapidly. The reaction rate of this second stage is much faster than that of the first stage.

Therefore, the present inventors discovered that ethylenediaminetetraacetic acid, nitrilotriacetic acid, or their salts, which are used as metal ion sequestering agents, are effective in the second stage of corrosion.
It has been found that it has the effect of suppressing the elution of 8p3+ and can prevent corrosion.

[Objective of the Invention 1 The present invention has been made in view of these circumstances, and includes the following:
1.1-1-It gives sufficient corrosion resistance to the electrolytic solution for cleaning the plate of electrolytic capacitors with halogen-based multi-layer solvents such as 10-ethane and trifluoroethane. An object of the present invention is to provide an electrolytic capacitor I which can prevent corrosion of a lead tab portion.

[Means for Solving the Problems and Their Effects] In order to achieve the above object, the electrolytic condenser according to the present invention contains ethylene glycol as the main solvent and adipic acid or a salt thereof as the main electrolyte in an electrolytic solution containing: Ethylenediaminetetraacetic acid or a salt thereof and di-1-lilotriacetic acid or a salt thereof are added and dissolved.

In this electrolytic condenser, the second stage of corrosion can be suppressed, and the elution of aluminum from the surface of the aluminum metal can be suppressed, thereby preventing corrosion of the cathode foil and the lead-out tab.

[Practical IM Examples of the Invention] Examples of the electrolytic capacitor according to the present invention will be described below. The embodiment is described with respect to an aluminum electrolytic capacitor with a general wound structure.

The electrolytic capacitor used in the example is made by electrochemically etching aluminum foil, anodizing it in an aqueous phosphate solution to form an oxide film on the surface, and then attaching the lead tab for electrode extraction to the aluminum anode. Create foil.

On the other hand, after etching the aluminum foil, remove the lead tab for drawing out the electrode (=J) to create an aluminum cathode foil, overlap the separator paper between the positive +4i foil and the cathode foil, and wind it. Then, this capacitor element is impregnated with electrolyte and housed in, for example, a bottomed aluminum case.
The case opening is sealed with an elastic sealing member.

Table 1 shows the composition of conventional examples in which ethylene glycol was used as the main solvent and ammonium adipate was dissolved as the main electrolyte, and the weight ratio of ethylenediaminetetraacetic acid and nitrilotriWI acid for these conventional examples was 0.1. 3. Owt
An example of the present invention using an electrolyte containing % added and dissolved is shown below.

The electrolytic condensers υ of the embodiments of the present invention and the conventional examples are not shown in the margin table-1 below.
50W V -10μ using the electrolyte used in
I made a prototype of an F electrolytic capacitor.

This sample capacitor was subjected to 28K I-IZ ultrasonic cleaning for 5 minutes using two solvents: 1,1.1-1-lichloroethane and trichlorotrifluoroethane.

Thereafter, a high-temperature load test was conducted at 105° C. by applying a rated voltage, and after 500 hours and 1,000 hours, it was dismantled and the corrosion occurrence rate (number of B corrosion occurrences/number of tests) was investigated.

The results are shown in Table-2.

From the results shown in Margin Table 2 below, the electrolytic capacitor of the present invention:
L+ 1. Shows excellent corrosion resistance when washed with 1-1-lichloroethane, and also has excellent corrosion resistance against trichlorotrifluoroethane.

Incidentally, salts of ethylenediaminetetraacetic acid and nitrilotriacetic acid also have similar effects.

The amount of ethylenediaminetetraacetic acid or its salt and nitrilotriacetic acid or its salt of the present invention is o, iwt by weight.
It has been found that even a small amount of % is effective for corrosion resistance, and as the amount added increases, corrosion resistance is improved. In other words,
The amount added is 0.01 to 10 wt% for seedling formation.

However, even if the addition amount is 10 wt% or more in terms of ff1ffi ratio, no commensurate effect can be obtained, a supersaturated state occurs, precipitation occurs in the electrolyte, and good characteristics cannot be obtained! , :.

[Effects of the Invention] As explained below, according to the present invention, 1. L 1-
It is possible to provide sufficient corrosion resistance to the 'Fi solution for substrate cleaning using halogen-based organic solvents such as trichloroethane or ]. Prevents corrosion of lead tabs 1. It has a significant effect.

Memo t'? r11. tlE'ii! (White R) Showa 60
9J13, 1985 Special GFF Application No. 141989
Representative Hideo Noboriuchi of the patent applicant 5, Notice of reasons for refusal 1 A. 1 Voluntary submission 1, the formula on the 14th line of the 3rd page of the specification is r [Au3+3ce-+Aid3] J is r [
/13++3cff-→AAd2all and corrected Shimazu.

that's all procedure? [11th official book (spontaneous) September 18, 1986

Claims (2)

[Claims] (1) In an aluminum electrolytic capacitor, ethylenediaminetetraacetic acid or a salt thereof, and nitrilotriacetic acid or a salt thereof are added to an electrolytic solution containing ethylene glycol as the main solvent and adipic acid or a salt thereof as the main electrolyte. An electrolytic capacitor characterized by additive-dissolved. (2) the ethylenediaminetetraacetic acid or a salt thereof;
The amount of nitrilotriacetic acid or its salt added is 0.0 by weight.
The electrolytic capacitor according to claim 1, wherein the content is 1 to 10 wt%.