JPH03147311A - Manufacture of aluminum electrode for electrolytic capacitor use - Google Patents

Abstract

PURPOSE:To enhance a close contact property and a dense property of a vapor- deposited film and to increase an electrostatic capacity by a method wherein the vapor-deposited film composed of a lead-titanium oxide layer is formed on the surface of high-purity aluminum by a cathode arc vapor-deposition method in an atmosphere of a specific pressure containing oxygen. CONSTITUTION:A vapor-deposited film composed of a lead-titanium oxide layer is formed on the surface of high-purity aluminum by a cathode arc vapor- deposition method by using an apparatus shown in the figure in an atmosphere whose total chamber pressure containing oxygen is 1X10<-1> to 1X10<-4>Torr. When the cathode arc vapor-deposition method is used, an ionization rate is remarkably large and an ion energy is high. As a result, a dense oxide layer can be formed under an oxygen pressure in a proper range. When an aluminum substrate is used as an anode, the lead-titanium oxide film whose specific permittivity is high can be formed by oxidizing the surface. Consequently, an electrostatic capacity can be increased.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing an aluminum electrode for an electrolytic capacitor, and more specifically, the present invention relates to a method for manufacturing an aluminum electrode for an electrolytic capacitor, and more specifically, a method for manufacturing an aluminum electrode for an electrolytic capacitor, and more specifically, a method for manufacturing aluminum electrodes for electrolytic capacitors, and more specifically, a method for manufacturing an aluminum electrode for an electrolytic capacitor. The present invention also relates to a method for manufacturing an aluminum electrode for an electrolytic capacitor, which comprises forming a vapor deposited film comprising a titanium oxide layer.

[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 recent years, there has been an increasing demand for electrolytic capacitors to be made smaller, and in order to obtain electrolytic capacitors with larger capacitance, the surface area of the aluminum foil is increased by etching at a high magnification. . 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.

Since there is a limit to increasing the surface area of aluminum materials, positive! !
By increasing the dielectric constant of the oxide of the dielectric layer formed on the surface of the side electrode, it is possible to increase the capacitance.

The dielectric constant of aluminum oxide is about 7 to 10,
Other valve metals, tantalum oxide, have a dielectric constant of around 25, and titanium oxide has a high dielectric constant of around 66. Naturally, using such oxides increases capacitance, but general electrolytic Aluminum is used in capacitors because it is universally superior to tantalum and titanium in terms of cost.

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 blating 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. However, in 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, and it is necessary to improve the vapor-deposition technology in order to produce better aluminum electrodes for electrolytic capacitors. There was room left. Further, the method using the above-mentioned vapor deposition technique is insufficient in terms of production efficiency because the processing time is long.

When it is intended to produce a dense oxide thin film with good insulating properties on an aluminum substrate, in addition to improving the vapor deposition technique, it is also possible to improve the metal material used for forming the thin film. Improvements in vapor deposition technology have made it possible to use metals that were not previously used in electrolytic capacitor electrodes, and there is also the possibility that they may provide better properties than ever before.For example, titanium and lead Regarding the thinning of oxides (PbTiOi), as announced in Kakobi on October 7, 1987, the plasma CVD method and sputtering method were simultaneously performed at the Osaka Institute of Technology. It has been reported that the synthesis was successful.

As an example of depositing a lead and titanium oxide/oxide layer on an aluminum substrate, a method is known in which lead and titanium oxides are formed by a sol-gel method. As for physical methods, as in Japanese Patent Application Laid-Open No. 1-175714, there is a technique for forming a thin film of lead titanate on a dielectric film of a film capacitor by physical methods such as vacuum evaporation, sputtering, and plasma CVD. However, there is no known means for forming a titanium or lead oxide vapor deposited film on an aluminum substrate densely and with good adhesion.

On the other hand, electrolytic capacitors generally use aluminum on the cathode side as well, but aluminum has an extremely thin insulating layer formed by a natural oxide film.The capacitance of an electrolytic capacitor is due to this thin insulating layer on the cathode side. It is formed by the combined capacitance of capacitance and anode side capacitance, so in order to obtain a high capacitance value, the cathode side capacitance must be extremely high compared to the anode side capacitance. It is preferable that the capacitor has a capacitance of 100% or no capacitance at all.

[The problem that the invention seeks to solve! ! ] The present invention improves a method for producing an aluminum electrode for an electrolytic capacitor, which comprises depositing lead and titanium on the surface of high-purity aluminum by vapor deposition to form a vapor-deposited film consisting of a lead and titanium alloy oxide layer on the surface. The present invention aims to provide a method for manufacturing an aluminum laminate electrode for an electrolytic capacitor, which can improve the adhesion and density of a deposited film, significantly shorten processing time, and increase capacitance.

[Means for Solving the Problems] According to the present invention, when manufacturing an aluminum electrode for an electrolytic capacitor, buttons and titanium are attached to the surface of high-purity aluminum by vapor deposition, and the surface is made of pins and a titanium oxide layer. forming a vapor-deposited film, and the total chamber pressure including oxygen for the vapor-deposition is I x 10
There is provided a method for manufacturing an aluminum electrode for an electrolytic capacitor, which is carried out by cathodic arc evaporation in an atmosphere of '-' to I x 10-'Torr.

It is preferable to use high-purity aluminum as a high-purity aluminum foil that has been subjected to etching treatment.

Preferably, the anodic 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 in+ is preferred. Note that this evaporation distance varies depending on the equipment used.

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

It is preferable that the thickness of the lead titanium oxide vapor deposited film is 0.05 to 5 μm. For a deposited film of this thickness, the deposition treatment time can be 0.5 to 30 minutes.

The substrate temperature is preferably 200-45Q°C.

Lead and titanium are deposited on the surface of high-purity aluminum by the above-mentioned cathodic arc evaporation, and a vapor-deposited film consisting of a lead and titanium oxide layer is formed on the surface, which is then subjected to normal anodic oxidation to form aluminum for electrolytic capacitors. Manufacture the stems.

Further, aluminum on which a vapor-deposited film consisting of lead and titanium oxide layers is formed according to the present invention can be used as 11% of an electrolytic capacitor.

[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 current concentrated at the arc spot, the target material instantaneously melts and evaporates, 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 dense film.

The present invention applies the principle of cathodic arc evaporation as described above, and uses lead and titanium as metal targets (evaporation sources) and high-purity aluminum as the object to be coated. At this time, by performing cathodic arc deposition under the above-mentioned predetermined oxygen pressure, the inside of the chamber becomes an appropriate oxygen atmosphere, and good adhesion can be achieved.

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 Upper electrode arc ion Sputtering method evaporation method Brating method ion 1
9 (%) 30-50 2-8
2-8 school 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 it is possible to form a dense oxide layer under an appropriate range of oxygen pressure. can be formed. When this aluminum substrate is used as an anode, the capacitance can be increased by oxidizing the surface to form a lead and titanium alloy oxide having a high dielectric constant. In addition, when used as a cathode, if it is used without oxidation treatment, if the bell and titanium are still metals, no capacitance will be generated on the cathode side, and no reduction in capacitance due to the combined capacitance will occur. Even if a natural oxide film is formed, the relative dielectric constant is high, so the reduction in capacitance is small.

Furthermore, in the present invention, since a plurality of cathode units can be installed, cathode arc evaporation can be performed independently for each cathode unit.

[Effects of the Invention] According to the present invention, an aluminum electrode for an electrolytic capacitor is produced by depositing lead and titanium on the surface of high-purity aluminum by vapor deposition to form a vapor deposited film consisting of a lead and titanium oxide layer on the surface. By improving the manufacturing method, there is provided a method for manufacturing an aluminum electrode for an electrolytic capacitor that can improve the adhesion and denseness of the deposited film, significantly shorten the processing time, and increase the capacitance.

Further, according to the present invention, different metals can be simultaneously deposited, the adhesion and density are excellent, and the cathode capacity can be increased by about 4 times.

Furthermore, compared to the capacity of aluminum oxide foil, a capacity 2 to 3 times larger can be obtained, the oxide film has greater adhesion and is denser, and the processing time is significantly shortened.

[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 50x1001111 etched by a conventional method, the total chamber pressure including oxygen pressure was 1X10-'' to 9 x 10-'T.
orr, evaporation distance 200 nra, evaporation rate 0.05μ
/min, and cathodic arc predeposition was performed for 2 minutes to form a lead and titanium deposited film with a thickness of 0.2 μm. The substrate temperature was 400°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) 10a made of lead and a metal target (evaporation source) 10b made of titanium as cathodes, the arc creates an arc spot on the target surface. The energy of the arc current (100
A>, the target material instantaneously melts and evaporates and simultaneously becomes metal ions 12a and 12b, which are released into vacuum. At this time, by applying a bias voltage to the object to be coated 14, which is a high-purity aluminum foil,
These metal ions adhere closely to the surface of the object to be coated 14 together with the accelerated reaction gas particles 16 to form a dense film. In addition, in FIG. 1, 18 and 20 are arc power sources,
22 is a bias power supply, 24 is a rotary table, 26 is a gas inlet, 28 is a gas outlet, and 30 is a vacuum chamber.

Using the aluminum foil having this vapor-deposited film, an aluminum electrode for an electrolytic capacitor is manufactured by performing normal anodic oxidation, and an electrolytic capacitor using this electrode is further manufactured.

An aluminum electrode for an electrolytic capacitor was manufactured by using high-purity aluminum foil that had been etched by a conventional method, and was subjected to 8 chemical formations by a conventional method without forming a vapor deposited film. An electrolytic capacitor using % was manufactured.

The withstand voltage (V) and capacitance (lF/cm2) of the film of the electrolytic capacitor manufactured as described above were as shown in Table 2.

anal presentation Example 1 Comparison! ! 1 Film pressure resistance 88 Capacitance 0.107 0.04,

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an apparatus used for cathodic arc deposition. 10a...Metal target (evaporation source) 10 made of lead
b... Metal target (evaporation source) made of titanium 12a... Metal ion 12b... Metal ion 1
4...Object to be coated with high-purity aluminum

Claims (1)

[Claims] (1) When manufacturing aluminum electrodes for electrolytic capacitors, lead and titanium are deposited on the surface of high-purity aluminum by vapor deposition to form a vapor deposited film consisting of a lead and titanium oxide layer on the surface, and the vapor deposition is Total chamber pressure including oxygen is 1×10^-^1~1×
A method for manufacturing an aluminum electrode for an electrolytic capacitor, characterized in that the method is carried out by cathodic arc evaporation in an atmosphere of 10^-^4 Torr.