JPH0444204A - Aluminum electrode for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain an aluminum electrode for electrolytic capacitors having a capacitance which is twice or more as large as that of the conventional one by forming a barium-titanium oxide layer by anodic oxidation after a barium- titanium layer is formed on the surface of high-purity aluminum by permitting barium and titanium to adhere to the surface by a cathode arc vapor deposition method. CONSTITUTION:When cathode arc vapor deposition with barium and titanium is performed an etched high-purity aluminum foil of 50 X 100 mm in size under a condition of 5 X 10<-4> Torr in chamber pressure, 200 nm in vaporizing dis tance, 0.05 mum/min in vaporizing speed, 0.2 mum in barium-titanium film thickness, and 300 deg.C in substrate temperature, the targets materials melt and vaporize into metallic ions 12 and 13 in a moment. The metallic ions are evolved into a vacuum space and stick to the surface of an object 14 to be coated together with accelerated reactive gas particles, forming a compact film. When anodic oxidization is performed under a condition of 85 deg.C and 70V in aluminum dihydrogen phosphate aqueous solution (1.3 g/l) by using the aluminum foil coated with the vapor-deposited film, an oxide having a high specific dielectric constant is obtained. Therefore, the capacitance can be increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum electrode for an electrolytic capacitor,
More specifically, the present invention relates to an aluminum electrode for an electrolytic capacitor in which a specific metal is deposited on the surface of high-purity aluminum by cathodic arc evaporation, and then anodized to form a dense oxide layer on the surface.

[Prior art] Electrolytic capacitors are small, large-capacity, inexpensive, and have excellent properties such as smoothing rectified output, and are one of the important components of various electrical and electronic devices. It is created by using an aluminum foil that has been changed into an oxide film as an anode, using this oxide film as a dielectric, and interposing an electrolyte between it and a current collecting cathode.

In addition to aluminum, metals such as tantalum and titanium, which are so-called valve metals, can be used as electrodes of electrolytic capacitors in the same way as aluminum. Among these types of metals, when looking at the dielectric constant of the oxide film, which is closely related to the Wpt capacity of a product electrolytic capacitor, as an index, the dielectric constant of aluminum oxide is 7 to 10, and the dielectric constant of tantalum oxide is 7 to 10. The ratio is 25.2 and the specific permittivity of titanium oxide is 6.
The reason why aluminum is generally used instead of tantalum or titanium is mainly because aluminum is superior in terms of cost.

In order to obtain an electrolytic capacitor with a larger capacitance using aluminum, which is a material with a certain dielectric constant defined as a physical property, the surface area is increased by applying a high-magnification etching treatment to the surface of the aluminum foil. is planned. This technique of increasing the surface area by creating complex irregularities on the surface of a material is now highly sophisticated, but it is becoming increasingly difficult to increase the capacitance of electrolytic capacitors solely by increasing the surface area using this technique. It is becoming.

There is a limit to increasing the surface area of an aluminum material having a constant dielectric constant, and there is a problem mainly in terms of cost when using other valve metals having a higher dielectric constant for the electrode.

As a means to solve this problem, a thin film is formed by attaching or welding another valve metal with a higher relative permittivity to the surface of the aluminum material, thereby increasing the relative permittivity without increasing cost. For example, a desired metal is evaporated onto an aluminum substrate by a physical method such as a vacuum evaporation method, an ion blasting method, or a sputtering method, and a evaporated film, which is a mixed composite film of aluminum and the evaporated metal, is formed on the surface. By doing so, large capacity can be obtained. This type of technology originated from the thinning of PbTiOs, and this synthesis began in October 1987.
Plasma CVD
It was successfully realized by performing the method and sputtering method simultaneously.

However, with the above-mentioned method, the adhesion and density of the vapor-deposited film of metal such as titanium on the aluminum substrate are not necessarily sufficient.In particular, we need to improve the vapor-deposition technique to create a better aluminum electrode for electrolytic capacitors! ! ! There was still room to build. Further, the method using the above-mentioned vapor deposition technique is insufficient in terms of production efficiency because the processing time is long.

For example, JP-A-63-306614 discloses a method in which a mixed oxide dielectric is formed by forming an aluminum-titanium metal layer by an ion blating method and then performing an anodizing treatment. Kaisho 59-167009
No. 1 discloses a method of forming a porous metal film by depositing a conductive metal using a vapor deposition method, but such conventional methods have problems with adhesion and density, and in particular, Titanium anode films made using titanium have unstable film properties.

In manufacturing aluminum electrode foil for electrolytic capacitors, the mainland V people previously filed a patent application No. 1-165388.
An electrolytic capacitor characterized in that tantalum is deposited on the surface of high-purity aluminum by vapor deposition to form a vapor deposited film consisting of a tantalum layer on the surface, and then anodization is performed, and the vapor deposition is performed by a cathodic arc vapor deposition method. We proposed a method for producing aluminum Th% foil for aluminum. This proposal focused on the cathodic arc evaporation method as a method for vapor deposition, but after further study, we found that in addition to valve metals, other metals than valve metals could be used as the metal to be deposited on the surface of high-purity aluminum. We have now discovered that it is possible to provide an even better aluminum electrode for electrolytic capacitors by performing cathodic arc evaporation with a mixture of metals, followed by anodic oxidation.

[Problems to be Solved by the Invention] The present invention improves an aluminum electrode for an electrolytic capacitor in which titanium is deposited on the surface of high-purity aluminum by cathodic arc evaporation to form a deposited film consisting of a titanium layer on the surface. In addition to titanium, a specific metal other than the valve metal is mixed as a metal to be attached to the surface of high-purity aluminum, and cathodic arc evaporation is performed, followed by anodic oxidation. The purpose of the present invention is to provide an aluminum electrode for an electrolytic capacitor that can provide an electrostatic capacitance more than twice that of aluminum oxide formed into a lIi electrode by forming a mixed oxide layer with a metal. do.

[Means for Solving the Problems] According to the present invention, barium and titanium are deposited on the surface of high-purity aluminum by cathodic arc evaporation to form a barium/titanium layer on the surface, and then barium/titanium is deposited by anodizing. Aluminum TFI for electrolytic capacitors characterized by forming a titanium oxide layer! is provided.

Barium and titanium on the surface of high-purity aluminum
When performing cathodic arc evaporation, a plurality of cathode units are installed as metal targets (evaporation sources), and at least one of them is barium and at least one of them is titanium. Two metals can be deposited simultaneously.

It is preferable that the high-purity aluminum be a high-purity aluminum foil that has been subjected to an etching treatment.

Suitable conditions for producing barium titanium oxide by cathodic arc evaporation are as follows.

The chamber pressure range is lX1G-'' to lX10-'T
orr.

Preferably, cathodic arc deposition is carried out in an inert gas atmosphere selected from the group consisting of argon, helium, and nitrogen.

Cathodic arc deposition with an evaporation distance of 50 to 400 am is preferred. Note that since the evaporation distance depends on the performance of the device used, this evaporation distance is not necessarily suitable depending on the device, and needs to be determined as appropriate.

Cathodic arc deposition is preferably carried out at an evaporation rate of 0.01 to 0.5 μ/min.

The thickness of the barium/titanium oxide vapor deposited film is 0.05 to 5μ.
It is suitable if

The substrate temperature is preferably 200 to 450°C.

Barium and titanium are deposited on the surface of high-purity aluminum by cathodic arc evaporation as described above, a barium-titanium layer is formed on the surface, and further anodic f! Oxidation is performed to form a barium titanium oxide layer, which can be used to manufacture electrolytic capacitors by conventional methods.

[Operation] When an arc discharge is caused under a substantial vacuum using a metal target (evaporation source) as a cathode, the arc forms an arc spot on the target surface and runs around randomly on the target surface.

Due to the energy of the arc concentrated at the arc spot, the target material is instantaneously melted and vaporized, simultaneously turning into metal ions and being emitted into the vacuum. At this time, by applying a bias voltage to the object to be coated, the metal ions, together with the accelerated reaction gas particles, adhere to the surface of the object to be coated, forming a borderline film.

The present invention applies the principle of such cathodic arc evaporation, and uses barium and titanium as metal targets (evaporation sources) and high-purity aluminum as the object to be coated.

Table 1 shows a comparison of the ionization rate and particle energy on the substrate between the cathodic arc evaporation method of the present invention and the conventional ion blating method and sputtering method. The number of ionized substances expressed as a percentage.

1 Tsuchigami II Arc Ion Sputtering Veterinary Control Routing Injection Ionization Rate (%) 30-50 2-8
2~81 child X energy (eV) 10~100
0.1-1 0.2-10 According to this cathodic arc evaporation method, the ionization rate is extremely high and the ion energy is high, so the reaction efficiency is improved and the adhesion between the aluminum substrate and barium and titanium is improved. can be significantly improved.

In addition, by using the cathodic arc evaporation method in particular, it is possible to install multiple cathode units, each of which can perform cathodic arc evaporation independently. A metal layer can be formed.

When an aluminum substrate on which barium and titanium are vapor-deposited is used as an anode, the capacitance can be increased by oxidizing the surface by anodic oxidation to form an oxide with a high dielectric constant. .

[Effects of the Invention According to the present invention, 1! ! Aluminum for electrolytic capacitors is made of aluminum for electrolytic capacitors, which is made by adhering titanium using the polar arc vapor deposition method to form a vapor-deposited film consisting of a titanium layer on the surface. Barium, which is a metal other than the working metal, is mixed and cathodic arc evaporation is performed, and then positive fi! By performing the oxidation, a mixed oxide layer of barium and titanium is formed, which results in the formation of a positive I7
f! Provided is an aluminum electrode for an electrolytic capacitor that can provide a capacitance twice or more as compared to oxidized aluminum oxide.

EXAMPLES] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited only to the following Examples.

Using high-purity aluminum foil 50 x ioo + i + i etched using a conventional method, the chamber pressure was 5 x 10-' TOrr, and the evaporation FIEM200111 was used.
1. Cathode arc evaporation of barium/titanium was performed at an i firing rate of 0.05 μ/min, a barium/titanium film thickness of 0.2 μ, and a substrate temperature of 300° C.

The outline of the equipment used for cathodic arc evaporation is shown in Figure 1.
When this device is used to generate an arc discharge under a substantial vacuum using a metal target (evaporation source) 10 made of barium and a metal target (evaporation R) 11 made of titanium as cathodes, the arc creates an arc spot on the target surface. As a result, they form and run randomly over the target surface.
The energy of the arc current concentrated at the arc spot (10
0A), the target material instantaneously melts and evaporates into metal ions 12 and 13, which are released into vacuum. The metal ions are accelerated t′LfS reaction gas particles 1
Together with G, it adheres closely to the surface of the object to be coated 14 to form a dense film. In FIG. 1, 18 and 2o are arc sources, 22 is a bias power source, 24 is a rotary table, 2
6 is a gas inlet, 28 is a gas outlet, and 3o is a vacuum chamber.

Using the aluminum foil having this vapor-deposited film, 85%
C. and 70 V, and using this as an aluminum electrode for an electrolytic capacitor, an electrolytic capacitor was manufactured by a conventional method. Table 2 shows the capacitance of the obtained electrolytic capacitor.

Using high-purity aluminum foil 50x IOO 111 that has been etched using a conventional method, dihydrogen phosphate-
85°C in ammonium water bath (1,3g/#)
, 70 V anodic oxidation conditions, and using this aluminum foil as aluminum %ffi for an electrolytic capacitor, an electrolytic capacitor was manufactured by a conventional method. Table 2 shows the capacitance of the obtained electrolytic capacitor.

Capacitance (+F/c12) IL4 4.7

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an apparatus used for cathodic arc deposition. 10... Metal target made of barium (evaporation source) 11... Metal target made of titanium (evaporation source) 1
2...Metal ion 13...Metal ion 14.
...Object to be coated made of high-purity aluminum 16...Reactive gas particles 18... Arc power source 20
... Arc @ source 22 ... bias power supply 24 ...
Rotary table 26...Gas inlet 28...Gas outlet 30...Vacuum chamber FIG.

Claims (1)

[Claims] (1) Barium and titanium are deposited on the surface of high-purity aluminum by cathodic arc evaporation to form a barium-titanium layer on the surface, and then barium and titanium are deposited on the surface of high-purity aluminum by anodic oxidation.
An aluminum electrode for an electrolytic capacitor characterized by forming a titanium oxide layer.