JPH0334527A - Manufacture of anode foil for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain an electrode foil, for electrolytic capacitor use, whose corrosion-resistant property is excellent by a method wherein a chemically formed foil after a chemical formation operation is immersed in a liquid in which a silane coupling agent has been dissolved in a solvent and it is then heat-treated. CONSTITUTION:An aluminum foil which has been etched is immersed in an aqueous solution of oxalic acid, sulfuric acid, boric acid or the like; a voltage is applied to execute a chemical formation treatment. Then, the chemically formed foil is immersed, for several minutes to several tens of minutes, in a liquid in which a silane coupling agent such as gamma-aminopropyl triethoxysilane, vinyl trimethoxysilane or the like has been dissolved in a solvent composed of at least one out of water, methanol, ethanol, methyl acetate, ethyl acetate, benzene, toluene and xylene. After this immersion, the chemically formed foil is taken out and is heat-treated in the air.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a JM method for anode foil for electrolytic capacitors.

(Prior Art) Electrolytic capacitors such as aluminum electrolytic capacitors are used, for example, by being soldered to a printed wiring board. During soldering, solder flux adheres to capacitors and circuit boards, and to remove this, a cleaning process is performed using an organic solvent.

Conventional organic solvents include halogen-based organic solvents with excellent cleaning ability, such as trichloroethane and Freon 113.

(Problems to be Solved by the Invention) However, when cleaning is performed, the cleaning solution may enter the inside of the capacitor through the capacitor's sealing part or the gaps between the terminals, and especially if a cleaning solution containing a halogenated organic solvent is used, moisture in the electrolyte solution may leak. As a result, chlorine ions are liberated.When voltage is applied to the capacitor in this state, the liberated chlorine ions easily react with aluminum, etc. in the oxide film, causing corrosion on the electrode surface, which shortens the life of the capacitor. The disadvantage is that it deteriorates significantly.

In order to improve this drawback, methods are known in which various corrosion inhibitors are added to the defroster solution. For example, an invention in which a nitro compound is added as a stabilizer for a halogenated organic solvent (JP-A-61-100918), an invention in which a silver compound is added as a chloride ion precipitant (JP-A-58-1538),
An invention in which hydrotalcite is added as a chloride ion adsorbent (Japanese Unexamined Patent Publication No. 58-60527@) is known.

However, these conventional inventions have the disadvantage that they are not very effective when used for high temperature/high voltage electrolytic capacitors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an anode foil for a vertical electrolytic capacitor, which improves the above-mentioned drawbacks and improves the deterioration of capacitor life due to corrosion.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for producing PJtf7A foil for defroster capacitors, which is formed by chemically forming a metal having a valve action to form an anodized film. , the chemically formed foil after chemical conversion is immersed in a solution in which a silane coupling agent is dissolved in a solvent, and then heat-treated. The present invention provides a method for manufacturing an anode foil for an electrolytic capacitor having the following characteristics.

(Function) A silane coupling agent is a compound in which an organic functional group and an alkoxy group are bonded to a silicon atom, as shown in the following general formula.

(n=o, 1 or 2; R is a methyl group or ethyl group; X is an aliphatic hydrocarbon group, an alicyclic dihydrogen group,
aromatic hydrocarbon group, vinyl group, amino group, epoxy group,
The alkoxy group is easily hydrolyzed in a small amount of water and reacts with the water i1 group to form a strong oxane bond (Aj-0
-5i).

Furthermore, it is known that aluminum hydroxide exists on the surface of the anodic oxide film.

For this purpose, if an electrode foil made of aluminum or the like is immersed in a solution containing a silane coupling agent dissolved in a solvent after chemical formation,
A silane coupling agent film is formed on the surface of the anodic oxide film, forming oxane bonds. This oxane bond prevents the electrode foil from being corroded by free chlorine ions dissolved in the electrolyte.

Note that when heat treatment is performed after immersion in the liquid, the film of the silane coupling agent adheres more firmly to the surface of the anodic oxide film.

(Example) Hereinafter, the present invention will be explained based on examples.

First, etched aluminum foil is immersed in an aqueous solution of oxalic acid, sulfuric acid, boric acid, etc., and a voltage is applied to perform chemical conversion treatment.

Next, this chemically formed foil is subjected to silane coupling such as γ-aminopropyltriethoxysilane or vinyltrimethoxysilane in a solvent consisting of at least one of water, methanol, ethanol, methyl acetate, ethyl acetate, benzene, toluene, and xylene. immerse it in a solution containing the agent for several minutes to several tens of minutes.

After dipping, the chemically formed foil is taken out and heat treated in the atmosphere.

The corrosion resistance of the above examples was measured below.

The conditions for making the anode foil are as follows.

Formation conditions: Formation '/& temperature 80''C, (7)*'7M 10wt% aqueous solution Current density 0.5A/d Formation voltage 500■ Formation time Constant current formation until 500V, constant frost pressure for 30 minutes after reaching 500V to chemically form.

Immersion conditions Nisilane coupling agent was dissolved at 1Qvt%, temperature 20
Immerse in the solution at ℃ for 10 minutes.

Heat treatment conditions: Heat in the air at a temperature of 85°C to 200°C for 3 to 120 minutes.

This anode foil is laminated and wound together with a separator and a cathode foil, and an element is used.
．． Impregnated with an electrolytic solution containing ammonium decanedicarboxylate dissolved in 1Qwt% or ammonium borate 3Qwt%, rated at 400mm, 220μF, length 50rmz diameter 2
It is assumed to be a 5s electrolytic capacitor.

Corrosion resistance testing was carried out by immersing this electrolytic capacitor in trichloroethane for 10 minutes, then taking it out and exposing it to 400 VDC.
After being left in an atmosphere at a temperature of 110° C. with the Honjo applied, it was decomposed and the anode foil was visually inspected to see if corrosion had occurred. For comparison, the same test was also conducted on the conventional example. The conventional example was manufactured under the same conditions as the example of the present invention, except that the anode foil was not subjected to immersion treatment with a solution containing a silane coupling agent and heat treatment.

The number of each sample is 20. The results are shown in the table.

Margin below.

In the table above, each symbol represents the following substance.

A-γ-aminopropyltriethoxysilane B-vinyltrimethoxysilane (,-3aminopropyltriethoxysilane D-3glycidoxybrobyltrimethoxysilane E-3chloropropyltrimethoxysilane “-3mercaptopropyltrimethoxy Silane G - Aminopropyltriethoxysilane P - 1.6% ammonium dicarboxylate 10wt%
Q-Ammonium borate 3Qwt% As is clear from the table, according to the present invention, corrosion did not occur even after being left for 1000 hours, whereas conventional example 1
Corrosion occurred in all 20 cases after exposure, and in conventional example 2, corrosion occurred for 200 hours.
18 corrosion occurred after being left standing.

Also, heat treatment 3 after immersion treatment! l! When we investigated the relationship between temperature and corrosion occurrence, we obtained the results shown in Figure 1. As the anode foil, a chemically formed foil is immersed in a solution of γ-azinopropyltriethoxysilane dissolved in water at a temperature of 20° C., and then heat-treated for 3 minutes. The rating of the electrolytic capacitor is 400V, 220μ.The electrolyte is 1 part ethylene glycol.

It is assumed that 10 wt% of ammonium dicarboxylate is dissolved and 3 Qwt% of ammonium borate is dissolved. Further, the corrosion test was carried out by leaving the electrolytic capacitor in an atmosphere at a temperature of 110° C. for 1000 hours, then disassembling the electrolytic capacitor and visually checking whether or not corrosion had occurred in the anode foil.

The number of samples shall be 20 for each. As is clear from Figure 1,
The electrolytic capacitor a using the former electrolytic solution has zero corrosion when the heat treatment temperature is 110° C. or higher, and the electrolytic capacitor b using the latter electrolytic solution has zero corrosion at 85° C. or higher.

Furthermore, when the relationship between heat treatment time and corrosion occurrence was investigated, the results shown in FIG. 2 were obtained. The anode foil was heat-treated at a temperature of 85° C. under the same chemical formation conditions and subsequent immersion conditions as those used in FIG. 1.

Foils tested at four different temperatures: 105°C, 150°C, and 200°C are used. The electrolyte, electrolytic capacitor ratings, and corrosion tests shall be the same as in Figure 1. In addition, in FIG. 2, the electrolytic solution contains ammonium 1.6 decanedicarboxylate,
Heat treatment temperature is 85°C.

Electrolytic capacitors with temperatures of 105°C, 150°C, and 200°C are designated as 1, 2, and 2, respectively, and the electrolyte contains ammonium borate and the heat treatment temperature is 85°C.

The electrolytic capacitors at 105°C, 150°C and 200°C are designated as O', bar and 2', respectively.

The number of samples shall be 20 for each. As is clear from Figure 2,
The time required for the occurrence of corrosion to be zero is 3 minutes and 30 seconds and 3 minutes for electrolytic capacitors 1 and 2, 2 minutes for both electrolytic capacitors 1 and 2, 1 minute for both electrolytic capacitors Both condensation knee and knee were 30 seconds, and it can be seen that the higher the heat treatment temperature, the shorter the treatment time.

(Effects of the Invention) As described above, according to the manufacturing method of the present invention, the foil after chemical formation is immersed in a liquid containing a silane coupling agent and then heat-treated. electrode foil is obtained.

[Brief explanation of drawings]

Figure 1 shows heating area 3! li! A graph of the relationship between temperature and the number of corrosion occurrences. Figure 2 shows a graph of the relationship between heat treatment time and the number of corrosion occurrences.

Claims (1)

[Claims] (1) In a method for manufacturing an anode foil for an electrolytic capacitor in which an anodized film is formed by chemically converting a metal having a valve action, the chemically formed foil after chemical conversion is immersed in a solution in which a silane coupling agent is dissolved in a solvent, and then A method for producing an anode foil for an electrolytic capacitor, the method comprising heat treatment.