JPH0770446B2 - Method for manufacturing electrode foil for electrolytic capacitor and method for manufacturing electrolytic capacitor - Google Patents

Description

The present invention relates to a method for manufacturing an electrode foil for an electrolytic capacitor and a method for manufacturing an electrolytic capacitor.

(Prior Art) An electrode foil for an electrolytic capacitor is composed of an anode foil and a cathode foil.

In general, as the anode foil, one obtained by electrochemically or chemically roughening the surface of an aluminum foil, immersing it in an electrolytic solution and anodizing it, and forming aluminum oxide serving as a dielectric on the foil surface is used.

The cathode foil is formed by electrochemically or chemically roughening the surface of the aluminum foil and then subjecting the surface to hydration prevention treatment.

The electrolytic capacitor is constructed by winding the anode foil and the cathode foil with a separator sandwiched between them, impregnating them with an electrolytic solution, and then sealing them in a metal case such as aluminum.

(Problems to be Solved by the Invention) One of the main characteristics of electrolytic capacitors is the rate of change in capacitance in a life test at high temperatures. This is 85 degrees Celsius
It is a characteristic that shows a capacity change before and after a life test such as a load test or a no-load test in a high temperature atmosphere of 105 ° C.

In recent years, with the downsizing of electrolytic capacitors, the electrode foils used are also becoming higher in etching magnification.
When the etching magnification of the electrode foil becomes high, the etching structure on the foil surface becomes fine and the effective surface area increases, so that the electrode foil is easily oxidized in the environment such as air or a driving electrolyte.

In particular, since the cathode foil only has a thin film such as a natural oxide film on the surface, it was easy to cause a capacity decrease when left standing.

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a method for manufacturing an electrode foil for an electrolytic capacitor and a method for manufacturing an electrolytic capacitor, which can suppress the capacity decrease of the electrolytic capacitor and stabilize the high temperature life characteristics.

(Means for Solving the Problems) In the present invention according to the above object, a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween is used for an electrolytic capacitor which is impregnated with an electrolytic solution and is hermetically sealed in a case. When manufacturing an electrode foil for an electrolytic capacitor, after immersing the electrode foil material forming the electrode foil in an aqueous solution in which 1 wt% to 5 wt% of a silane coupling agent is dissolved in pure water,
It is characterized by heat treatment.

Further, the present invention relates to an electrode foil material for forming a cathode foil and / or an anode foil used in an electrolytic capacitor, after immersing the silane coupling agent in an aqueous solution in which 1 wt% to 5 wt% of pure water is dissolved. After the heat treatment, the obtained anode foil and cathode foil are wound with a separator in between, and the capacitor element is impregnated with an electrolytic solution and sealed in a case. The heat treatment temperature is preferably 100 ° C or higher.

Examples of silane coupling agents that can be used in the present invention include vinyltris (β-methoxyethoxy) silane (KBC-1003, Shin-Etsu Chemical Co., Ltd.), vinyltriethoxysilane (KBF-1003), vinyltrimethoxysilane (KBM). −
1003), γ-methacryloxypropyltrimethoxysilane (KBM-503), β- (3,4epoxycyclohexyl) ethyltrimethoxysilane (KBM-303), γ-glycidoxypropyltrimethoxycinlan (KBM-303). −40
3), γ-glycidoxypropylmethyldiethoxysilane (the same KBM-402), N-β (aminoethyl) γ-aminopropyltrimethoxysilane (the same KBM-603), N-β
(Aminoethyl) γ-aminopropylmethyldimethoxysilane (KBM-602), γ-aminopropyltriethoxysilane (KBE-903), N-phenyl-γ-aminopropyltrimethoxysilane (KBM-573), γ-methylcaptopropyltrimethoxysilane (KBM-803) and the like. Among them, γ-glycidoxypropyltrimethoxysilane and N-β (aminoethyl) γ-aminopropyltrimethoxysilane are particularly preferable in consideration of solubility in water and storage stability of an aqueous solution.

(Function) Generally, the silane coupling agent is represented by R-Si (OR ') ₃ , but when dissolved in water, it causes hydrolysis to generate R-Si (O').
H) Change to ₃ . On the other hand, on the surface of the electrode foil, a natural oxide film is formed even on the cathode foil which is not anodized, and the aluminum oxide is represented by Al ₂ O ₃ .nH ₂ O. When the electrode foil is treated with a silane coupling agent, the coupling agent --OH reacts with the aluminum oxide --OH to dehydrate. And by further heat treating it Instead, a thin film is formed on the foil surface.

It is considered that this silicon compound film suppresses the hydration reaction on the foil surface and thus suppresses the capacity decrease.

(Examples) Hereinafter, the present invention will be described in detail based on Examples.

[Example 1] Using a commercially available etched foil for a cathode having a thickness of 50 µm, a 25 wt% aqueous solution of γ-glycidoxypropyltrimethoxysilane was used.
After soaking at 1 ° C for 1 minute, heat treatment was performed at 400 ° C for 30 seconds.
Next, this cathode foil was wound with a commercially available 90 μm-thick 6.3 WV anode foil with a separator interposed between the foil and ethylene glycol-
Impregnate with pure water-ammonium adipate electrolyte 6.
A 3V3300 μF capacitor was produced.

Example 2 Using a commercially available etched foil for a thick cathode of 50 μm, it was immersed in a 3 wt% aqueous solution of N-beta (aminoethyl) γ-aminopropyltrimethoxysilane at 50 ° C. for 1 minute, and then 250 ° C.
Heat treatment was performed for 1 minute. Then, as in Example 1, 6.
A 3V3300 μF capacitor was produced.

[Conventional example]

A commercially available etched foil for a thick cathode of 50 μm was used as it was, and a 6.3V3300 μF capacitor was manufactured in the same manner as in Examples 1 and 2.

About the manufactured 6.3V 3300μF capacitor 105 ℃ 1000
The results of the time load and no load tests are shown in Table 1. Further, FIG. 1 shows the progress of the capacity change during the test. Embodiments 1 and 2 according to the present invention as compared with a conventional example
Showed a remarkable effect with less capacity reduction.

FIG. 2 is a diagram showing changes in the capacitance of the capacitors when the concentration of the aqueous silane coupling agent solution to be treated in Examples 1 and 2 was changed. As is clear from FIG. 2, it was found that the effect appears when the concentration is 1% or more.

Further, as is clear from FIG. 2, the effect is saturated when the concentration of the silane coupling agent is 5% by weight or more. Generally, since the silane coupling agent is expensive, the addition amount of the silane coupling agent is set to 5% by weight or less in terms of cost.

The treatment temperature with the aqueous solution of the silane coupling agent can be obtained at room temperature as shown in Example 1, but the higher treatment temperature is more effective for promoting the hydrolysis. Therefore, the treatment temperature up to the boiling point of the aqueous solution can be used, but in consideration of the efficiency of continuous treatment, 90 ° C
The following are particularly preferred.

Further, the heat treatment is necessary for the molecules of the silane coupling agent to bond with each other, and the temperature therefor is preferably 100 ° C. or higher.

Further, in the examples of the present invention, only the treatment of the cathode foil was described, but the capacity reduction of the anode foil may be a problem depending on the system of the electrolytic solution used, and in that case, the anode foil is treated. Can also obtain the same effect.

(Effect) As described above, according to the present invention, it is possible to obtain an electrolytic capacitor with a small decrease in capacitance, which can greatly contribute to a longer life and higher reliability.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in capacitance in a capacitor test for an example of the present invention and a conventional example, and FIG. 2 is a diagram showing an effect when a concentration of a treatment liquid of the example of the present invention is changed.

Claims (2)

[Claims] 1. When manufacturing an electrode foil for an electrolytic capacitor, which is used for an electrolytic capacitor in which a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween is impregnated with an electrolytic solution and is hermetically sealed in a case. The electrode foil material for forming the electrode foil is immersed in an aqueous solution in which a silane coupling agent is dissolved in pure water in an amount of 1% by weight to 5% by weight, and then heat-treated, to produce an electrode foil for an electrolytic capacitor. Method. 2. An electrode foil material for forming a cathode foil and / or an anode foil used for an electrolytic capacitor is immersed in an aqueous solution in which pure water contains 1% by weight to 5% by weight of a silane coupling agent, and then heat treated. After that, the obtained anode foil and cathode foil are wound with a separator sandwiched between them, and the capacitor element is impregnated with an electrolytic solution and hermetically sealed in a case.