JPS6354208B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for manufacturing aluminum electrolytic capacitors (hereinafter referred to as AL electrolytic capacitors), and in particular, a method for manufacturing AL electrolytic capacitors that prevents dry-up during use and improves life characteristics. related to. Generally, in an AL electrolytic capacitor, an element is constructed by interposing a separator such as electrolytic paper between positive and negative electrode foils, and the separator is impregnated with a liquid driving electrolyte (hereinafter referred to as paste). For this reason,
When an electrolytic capacitor is used for a long period of time, the paste gradually evaporates and decreases, resulting in deterioration of characteristics and dry-up, which has the disadvantage that the life span is shorter than that of other capacitors. Especially in recent years,
As miniaturization progresses, electrolytic capacitors can be used in high temperature ranges of 100℃ or higher.
As the demand for AL electrolytic capacitors with long life increases, the above-mentioned drawbacks become more and more problematic. Therefore, although efforts have been made to improve and develop liquid pastes that can be used in the high temperature range of 100°C or higher, as well as various developments in sealing materials and sealing structures, the problem of deterioration of properties due to evaporation of the paste has not yet been adequately resolved. is not given. That is, conventional liquid pastes contain ethylene glycol,
Using N・N-dimethylformamide, methyl cellosolve, ethyl cellosolve, etc., ammonium salicylate, ammonium adipate,
Ammonium benzoate, potassium formate, etc. are used, but since the vapor pressure of the solvent becomes higher than 100℃, evaporation of the paste is unavoidable and AL
Characteristics of the electrolytic capacitor deteriorate. In particular, small rubber-sealed AL electrolytic capacitors with a case diameter of 4 to 8 mm are 16 to 18 mm in diameter.
Compared to the mm type, the disadvantage was that the life characteristics deteriorated significantly due to the above-mentioned reasons. The present invention was invented for the purpose of eliminating the above-mentioned drawbacks.
As a gelling agent, hydroxyethylcellulose,
Hydroxypropyl cellulose, lactalbumin, etc. are added and mixed, and the paste is impregnated into a capacitor element before gelling. By gelling the paste in the capacitor element, evaporation of the paste is suppressed and a good result is obtained. The present invention provides a method for manufacturing an AL electrolytic capacitor that has excellent electrical properties and long life characteristics at high temperatures. The present invention will be explained in detail below. The inventors believed that in order to prevent the paste of AL electrolytic capacitors from evaporating during use, it would be effective to make the paste gel or semi-solid instead of liquid as in the past. We have been considering such pastes. Conventionally, polyvinyl alcohol (PVA), gelatin, agar, and the like have been known as gelling agents for gelling paste (Japanese Patent Application Laid-open No. 66761/1983). Figure 1 shows ethylene glycol, N/N-dimethylformamide, etc. as a solvent, salicylic acid,
A conventional paste with a composition of adipic acid or a salt thereof as a solute is prepared by adding the polyvinyl alcohol as a gelling agent, and the paste before gelling is impregnated into an AL electrolytic capacitor element. , heat the impregnated element at 130°C to 140°C to gel the impregnated paste, use the element to prototype a 6.3V-22000μf AL electrolytic capacitor, and calculate the tanδ and capacitance of the capacitor. Each value,
This figure shows the relationship between the gelling state of the paste and the amount of polyvinyl alcohol as a gelling agent added to the paste. The reason why the above paste is impregnated into the element before gelation and then gelled after impregnation is that by doing this, the paste is impregnated into the element while the viscosity before gelation is low. This is because the paste is sufficiently impregnated into the element and then gelled, so that the impregnated paste gels and is retained within the element. As is clear from Figure 1, in order to gel the paste, it is necessary to add polyvinyl alcohol in an amount of 10 wt% or more of the paste, and as the paste gels, the tan δ of the capacitor rapidly changes. It was found that the capacitance increased significantly and the capacitance changed significantly, making it impractical. Also, when the gelatin, agar, etc. mentioned above were added as a gelling agent, the same results as in the case of polyvinyl alcohol were obtained. However, when the paste gels, when the prototype capacitor element and the capacitor element impregnated with the paste containing no gelling agent are heated under the same conditions, the weight decreases due to the weight loss of the element impregnated with the gelled paste. It was clearly confirmed that the evaporation of the paste was suppressed by gelation.
Therefore, as a result of extensive research on various gelling agents, the inventors found that certain cellulose derivatives and proteins can be used as gelling agents for the above purpose, requiring only a small amount of addition, and making pastes. It has been found that gelling has an excellent effect without impairing its electrical properties. Next, a method for manufacturing an AL electrolytic capacitor according to the present invention will be explained based on a few specific examples. Figure 2 shows that cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose, or lactalbumin, a type of protein, are added to the paste as gelling agents.
The conventional paste described in the figure was prepared by adding each of them, and the same capacitor was prototyped in the same manner as explained in Figure 1, and the capacitor characteristics and the gelling state of the paste, and the addition of the above gelling agent to the paste. The relationship with the amount is shown in the same way as in FIG. 1. From FIG. 2, compared with FIG. 1, the following is clear. (1) As a gelling agent, hydroxyethylcellulose, hydroxypropylcellulose, or
When using lactalbumin, etc., it is necessary to add only a very small amount, i.e., to the paste.
Addition of 0.1wt% or more causes the paste to gel. (2) Even if the paste gels, the initial characteristic values of tan δ and capacitance of the AL electrolytic capacitor impregnated with the paste will be the same as the paste without gelling agent if the amount of gelling agent added is 10wt% or less. It is no different from a capacitor impregnated with That is, conventional gelling agents such as polyvinyl alcohol, gelatin, agar, etc. are added to the paste to make the paste gel-like, and
This increases the specific resistance of the paste, making it unpractical as a driving electrolyte for AL electrolytic capacitors, but cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose,
Alternatively, if lactalbumin, a type of protein, is used as a gelling agent, its concentration is low enough to cause gelation of the paste, and even when gelation occurs, the resistivity does not change suddenly. I understand that. Therefore, a paste to which such a new gelling agent was added was prototyped, and an example of the present invention using this paste will be described below. Table 1 shows an example of the composition of the prototype paste. Composition examples 1 to 6
After impregnating the capacitor element with each paste before gelling, heat the paste at 130 to 140℃ for about 30 minutes to gel, seal it in the case, and apply 6.3V to 22μf (4
x7mm case) prototype AL electrolytic capacitor,
Figures 3 and 4 show the results of a 1000 hour DC load test at an ambient temperature of 105°C.

[Table] As is clear from Figures 3 and 4, the capacitors manufactured according to the present invention performed better in load tests than capacitors using conventional paste (paste without gelling agent) in all composition examples. The gelation of the paste suppresses paste evaporation during capacitor use, and has the excellent effect of greatly improving its life characteristics even under high temperature conditions exceeding 100℃. You can see that Moreover, a further improvement effect appears by combining a cellulose derivative and protein, but this is thought to be related to the properties after gelation. As explained above, according to the present invention, the paste containing the gelling agent is sufficiently impregnated into a capacitor element in a low viscosity state before gelation, and then the impregnated paste is gelled. , the paste is held in a gel state within the element, and gelation suppresses evaporation of the paste during use of the capacitor.This effect is particularly noticeable when used at high temperatures, and does not impair the characteristics of the capacitor. Because of this, the high-temperature life characteristics of electrolytic capacitors can be improved, and a long life can be expected, and a capacitor with stable characteristics and high reliability can be provided.In particular, the small electrolytic capacitor of the present invention has this effect. Yes, small size, high density mounting, long life,
It becomes possible to meet the needs of high-temperature use,
Its practical value is enormous. In addition, by gelling the paste, even if the seal is broken,
Unlike conventional liquid pastes, it does not flow out and contaminate the surrounding area, and the element can be easily handled during the manufacturing process, making it easier to mold the exterior.

[Brief explanation of drawings]

Figure 1 shows the characteristics of a capacitor using a paste containing gelling agents such as polyvinyl alcohol, gelatin, and agar. 2, 3 and 4 are characteristic diagrams of capacitors manufactured according to the present invention.

Claims (1)

[Claims] 1. A method for manufacturing an aluminum electrolytic capacitor, in which an aluminum electrolytic capacitor element wound with electrolytic paper interposed between an anode foil and a cathode foil is impregnated with a driving electrolyte containing a gelling agent,
As the gelling agent, at least 0.1 to 10 wt of any one of hydroxyethyl cellulose, hydroxypropyl cellulose, or lactalbumin is used.
% addition and mixing, and before gelling the driving electrolyte, impregnating the capacitor element, and then gelling the driving electrolyte in the capacitor element. .