JP3155750B2 - Method for producing aluminum electrode for electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum electrode for an electrolytic capacitor, and more specifically, to deposit a specific metal on the surface of high-purity aluminum by a cathodic arc vapor deposition method, The present invention relates to an aluminum electrode for an electrolytic capacitor having an oxide layer formed thereon.

[Prior art] Electrolytic capacitors are small, large-capacity, inexpensive, and have excellent characteristics such as smoothing of rectified output, and are one of the important components of various electric and electronic devices. An aluminum foil converted to an oxide film is used as an anode, the oxide film is used as a dielectric, and an electrolytic solution is interposed between the current collector and the collector.

In addition to aluminum, so-called valve metal such as tantalum or titanium can be used as an electrode of the electrolytic capacitor similarly to aluminum. Among the metals of this type, when the relative dielectric constant of an oxide film closely related to the capacitance of a product electrolytic capacitor is used as an index, the relative dielectric constant of aluminum oxide is 7 to 10, and the relative dielectric constant of tantalum oxide is Compared to the dielectric constant of 25.2 and the relative dielectric constant of titanium oxide of 66.1, it is not a large value. Aluminum is generally used for electrolytic capacitors instead of tantalum or titanium, mainly because aluminum is superior to these in terms of cost.

Using aluminum, which is a material having a certain relative permittivity defined as physical properties, to increase the surface area by performing high-magnification etching on the surface of the aluminum foil to obtain an electrolytic capacitor with a larger capacitance Is planned. This technique of increasing surface area by providing complex irregularities on the surface of the material is now highly sophisticated, but it is becoming increasingly difficult to increase the capacitance of electrolytic capacitors solely by this technique. It is becoming.

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

In order to solve this problem, a thin film is formed by adhering or welding another valve metal having a higher relative dielectric constant to the surface of the aluminum material, thereby increasing the relative dielectric constant without increasing the cost. There is. For example, by depositing a desired metal on an aluminum substrate by a physical method such as a vacuum deposition method, an ion plating method or a sputtering method, and forming a deposited film as a mixed composite film of aluminum and a deposited metal on the surface. A large capacity is obtained. This kind of technology originated in the thinning of PbTiO ₃ , and this synthesis was carried out by simultaneously performing a plasma CVD method and a sputtering method in a carpentry trial published on October 7, 1987 (Kako). Successful implementation.

However, in the method described above, the adhesion and denseness of a deposited film of a metal such as titanium on an aluminum substrate are not always sufficient, and in particular, by improving the deposition technique,
There remains room for producing better aluminum electrodes for electrolytic capacitors. Further, the method using the above-described vapor deposition technique requires a long processing time, and is insufficient in terms of production efficiency.

For example, JP-A-63-306614 discloses a method in which an aluminum-titanium metal layer is formed by an ion plating method and then anodized to form a mixed oxide dielectric. No. 59-167009 discloses a method of forming a porous metal film by evaporating a conductive metal by an evaporation method, but such a conventional method has problems in adhesion and denseness, In particular, a titanium anode film formed using titanium has unstable film characteristics.

The applicant of the present invention previously disclosed, as Japanese Patent Application No. 1-165388, when manufacturing aluminum electrode foil for electrolytic capacitors, deposited tantalum on the surface of high-purity aluminum by vapor deposition to form a vapor-deposited film consisting of a tantalum layer on the surface. Then, anodizing is performed, and the above-mentioned vapor deposition is performed by a cathodic arc vapor deposition method. This proposal focuses on the cathodic arc vapor deposition method as a method for performing vapor deposition, but as a result of further studies, as a metal to be adhered to the surface of high-purity aluminum, in addition to the valve metal, the metal other than the valve metal is used. It has been ascertained that mixing a metal can provide a more excellent aluminum electrode for electrolytic capacitors.

[Problems to be Solved by the Invention] The present invention is to improve an aluminum electrode for an electrolytic capacitor in which titanium is attached to the surface of high-purity aluminum by a cathodic arc evaporation method to form an evaporation film composed of a titanium layer on the surface, By mixing a specific metal other than a valve metal in addition to titanium as a metal to be adhered to the surface of high-purity aluminum, a dense oxide layer is formed by a cathodic arc vapor deposition method. An object of the present invention is to provide an aluminum electrode for an electrolytic capacitor that can provide double the capacitance.

[Means for Solving the Problems] According to the present invention, barium and titanium are used as individual evaporation sources, and a cathodic arc vapor deposition method is performed under a predetermined oxygen pressure to convert ionized barium and titanium together with oxygen into high-purity aluminum. A method for producing an aluminum electrode for an electrolytic capacitor, characterized by forming a dense layer in which barium, titanium and oxygen are mixed by adhering to a surface of an aluminum electrode.

In order to deposit two metals, barium and titanium, on the surface of high-purity aluminum, when performing cathodic arc deposition, a plurality of cathode units serving as metal targets (evaporation sources) are installed, and at least one of them is made of barium. By using one of them as titanium, two metals can be deposited simultaneously.

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

The preferred conditions for producing barium / titanium oxide, that is, a mixture of barium, titanium and oxygen, by cathodic arc evaporation are as follows.

The total chamber pressure range including oxygen pressure is 1
× 10 ^-1 to 1 × 10 ^-4 Torr.

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

It is preferred to carry out cathodic arc deposition at an evaporation distance of 50 to 400 mm. In addition, since the evaporation distance depends on the performance of the device to be used and the like, the evaporation distance is not always suitable for some devices and needs to be determined appropriately.

Preferably, cathodic arc deposition is performed at an evaporation rate of 0.01 to 0.5 μ / min.

It is preferable that the thickness of the deposited film of barium / titanium oxide, that is, the deposited film of a mixture of barium, titanium and oxygen is 0.05 to 5 μm.

 The substrate temperature is preferably 200 to 450 ° C.

Barium and titanium are deposited on the surface of high-purity aluminum by the above-described cathodic arc deposition, and a barium-titanium oxide layer, that is, a mixed layer of barium, titanium and oxygen, is formed on the surface, and an electrolytic capacitor is formed by using this in a usual manner. Can be manufactured.

[Operation] When an arc discharge is generated under a substantial vacuum using a metal target (evaporation source) as a cathode, the arc forms an arc spot on the target surface and randomly runs around on the target surface. Due to the energy of the arc current concentrated on the arc spot, the target material instantaneously melts and evaporates, and at the same time, becomes a metal ion and is released into a vacuum. At this time, by applying a bias voltage to the object to be coated, the metal ions adhere to the surface of the object to be coated together with the accelerated reaction gas particles to form a dense film.

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

Table 1 compares the ionization rate and particle energy on the substrate between the cathodic arc deposition method of the present invention and the conventional ion plating method and sputtering method. In addition, the ionization rate is, of the atoms that have reached the unit area of the substrate,
It is the number of ionized substances expressed as a percentage.

According to such a cathodic arc vapor deposition method, the ionization rate is remarkably large and the ion energy is high, so that the reaction efficiency is improved and the adhesion between the aluminum substrate and barium and titanium can be remarkably improved.

In particular, by using the cathodic arc evaporation method,
A plurality of cathode units can be installed, each of which can perform its own cathodic arc deposition. Furthermore, since the ionization rate is extremely high and the ion energy is high, a dense oxide layer can be formed under an appropriate range of oxygen pressure. Can be formed.

[Effects of the Invention] According to the present invention, an aluminum electrode for an electrolytic capacitor in which titanium is deposited on the surface of high-purity aluminum by a cathodic arc deposition method to form a vapor-deposited film composed of a titanium layer on the surface is improved. By mixing barium, which is a metal other than the valve metal, in addition to titanium as a metal to be adhered to the surface of aluminum, a dense oxide layer is formed by cathodic arc evaporation and tripled compared to aluminum oxide. The present invention provides an aluminum electrode for an electrolytic capacitor capable of providing a capacity of:

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited only to the following examples.

Example 1 Using a high-purity aluminum foil 50 × 100 mm etched in a usual manner, a total chamber pressure including oxygen pressure of 2 to 10 × 10 ⁻² Torr, an evaporation distance of 200 mm, an evaporation rate of 0.05 μ / min, The thickness of the barium / titanium oxide film, that is, the mixed film thickness of barium, titanium, and oxygen was 0.2 μm, and the substrate temperature was 400 ° C., and cathodic arc deposition was performed using barium / titanium oxide, a mixed material of barium, titanium, and oxygen.

FIG. 1 shows an outline of an apparatus used for cathodic arc deposition. Using this apparatus, an arc discharge is generated in a substantial vacuum using a metal target (evaporation source) 10 made of barium and a metal target (evaporation source) 11 made of titanium as a cathode, and the arc forms an arc spot on the target surface. Forming and running around the target surface randomly,
The energy of the arc current concentrated on the arc spot (100
According to A), the target material instantaneously melts and evaporates and becomes metal ions 12 and 13 at the same time, and is released into a vacuum.
By applying a bias voltage to these, these metal ions adhere to the surface of the object to be coated 14 together with the accelerated reaction gas particles 16 to form a dense film. In FIG. 1, reference numerals 18 and 20 denote arc power supplies, 22 denotes a bias power supply, 24 denotes a rotary table, 26 denotes a gas inlet, 28 denotes a gas outlet, and 30 denotes a vacuum chamber.

Using the aluminum foil having the vapor-deposited film as an aluminum electrode for an electrolytic capacitor, an electrolytic capacitor was manufactured by a conventional method. Table 2 shows the withstand voltage and electrostatic capacity of the electrolytic capacitor obtained from the obtained film.

Comparative Example 1 Using a high-purity aluminum foil 50 × 100 mm that had been subjected to an etching treatment by a conventional method, 8 V formation was performed by a conventional method, and this aluminum foil was used as an aluminum electrode for an electrolytic capacitor, and an electrolytic capacitor was manufactured by a conventional method. . Table 2 shows the withstand voltage and electrostatic capacity of the electrolytic capacitor obtained from the obtained film. Table 2 Example 1 Comparative Example 1 Withstand voltage (V) 8 8 Capacitance (mF / cm ² ) 0.121 0.043

[Brief description of the drawings]

FIG. 1 is a view 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) 12 Metal ion, 13 Metal ion 14 Coating object made of high-purity aluminum 16 Reaction Gas particle, 18 Arc power supply 20 Arc power supply, 22 Bias power supply 24 Rotary table, 26 Gas inlet 28 Gas outlet, 30 Vacuum chamber

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/055 C23C 14/08 C23C 14/24

Claims (1)

(57) [Claims] A cathodic arc vapor deposition method is performed under a predetermined oxygen pressure using barium and titanium as separate evaporation sources to deposit ionized barium and titanium together with oxygen on the surface of high-purity aluminum to obtain barium, titanium. A method for producing an aluminum electrode for an electrolytic capacitor, comprising forming a dense layer in which titanium and oxygen are mixed.