JPH03202462A - Production of electrode foil for electrolytic capacitor - Google Patents

Abstract

PURPOSE:To stably produce a foil material having large electrostatic capacity by specifying the initial incident angle of a metallic vapor with respect to a base material and turning an inert gas on the incident region of the vapor upon the base material from the downstream side in the traveling direction of the base material. CONSTITUTION:A vapor composed of at least one metal selected from Al, Ti, Zr, Ta, Nb, and Hf or alloy thereof is turned on a base material traveling along a cylindrical drum 1, by which an electrode foil for electrolytic capacitor is formed. At this time, the initial incident angle of the vapor with respect to the base material is set up in the range of 45-90 deg.. It is preferable that the incident region of the vapor upon the base material has a practically hermetically sealed structure, excluding an opening between the lateral end 6 which is positioned on the downstream side in the traveling direction of the base material of a mask 3 and the end 10 which is positioned on the upstream size in the traveling direction of the base material of a mask 4. An inert gas is supplied into the above-mentioned practically hermetically sealed region by means of a nozzle, from the downstream side in the traveling direction of the base material toward the incident region of the vapor upon the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an electrode for an electrolytic capacitor. More specifically, the present invention relates to a method of manufacturing an electrode that contributes to making electrolytic capacitors smaller and larger in capacity.

[Prior Art] As electrodes for electrolytic capacitors, aluminum foil is generally etched to enlarge its surface area. Increasing the surface area of the electrode is essential for increasing the capacitance of a capacitor, and the demand for smaller size and larger capacity demands further expansion of the surface area of the electrode. However, increasing the surface area of aluminum foil by etching is approaching its limit due to factors such as a decrease in the strength of the aluminum foil.

On the other hand, in Japanese Patent Application Laid-Open No. 56-29669, 30
It has been proposed to create an electrolytic capacitor electrode foil with an expanded surface area by creating a porous metal film by injecting the vapor of a valve metal such as aluminum or tantalum onto the substrate at an incident angle of 80 to 85 degrees or more, preferably 80 to 85 degrees. I'm here. Also, JP-A-59-
In Japanese Patent No. 167009, valve metals such as aluminum, tantalum, titanium, niobium, and zirconium are deposited on a substrate such as aluminum foil in an inert gas to form a porous film, which expands the surface area of the electrode and improves dielectric properties. It is proposed to increase the rate.

These techniques have a great effect on increasing the apparent capacitance per unit area of electrolytic capacitors.

[Problems to be Solved by the Invention] However, these techniques still have the following problems.

(1) In order to obtain a sufficient surface area expansion effect, it is necessary to increase the thickness of the valve metal film to 1 to 20 μm, which poses a problem in terms of productivity, and the valve metal other than aluminum must be made of a high melting point material. Therefore, when attempting to form a relatively thick film as described above, the substrate is likely to be thermally damaged during vapor deposition, resulting in loss of flatness.

(2) In the method of vapor-depositing valve metal in an inert gas, increasing the pressure in the vacuum chamber yields a larger surface area, that is, a larger capacitance, even with the same film thickness.On the other hand, increasing the pressure in the vacuum chamber There is a problem that the film deposition rate decreases. Particularly in large production machines that use straight electron beam guns, the evaporation source and the substrate cannot be placed very close to each other, so the film deposition rate decreases significantly as the pressure inside the vacuum chamber increases, resulting in a significant drop in productivity.

The present invention was devised in view of the drawbacks of the prior art as described above, and its purpose is to provide an electrolytic solution that is highly effective in increasing capacitance, has no fear of heat damage during manufacturing, and has excellent productivity. An object of the present invention is to provide an electrode foil material for capacitors.

[Means for solving problems] The object of the present invention is achieved by the following manufacturing method.

Aluminum, titanium, zirconium, tantalum,
directing a vapor consisting of at least one metal selected from the group of niobium and hafnium or an alloy thereof;
A method for manufacturing an electrode foil for an electrolytic capacitor forming a thin film, wherein the initial angle of incidence of the vapor on the substrate is in the range of 45 to 90 degrees, and the direction of the substrate travel with respect to the area of incidence of the vapor on the substrate. A method for manufacturing an electrode foil for an electrolytic capacitor, characterized by directing an inert gas from the downstream side.

The cylindrical drum referred to in the present invention is a part of a traveling system that runs a long substrate, and is a holder that supports and cools the substrate from the back side when forming a thin film on the substrate by vapor deposition. It is. The substrate moves with the cylindrical drum along its circumferential surface. The drum is cooled with a refrigerant during thin film formation.

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of the incident angle of vapor to the substrate in the manufacturing method of the present invention. In the figure, 1 is a cylindrical drum, 2 is an evaporation source, and 3 and 4 are vapor flows from the evaporation source at a predetermined incident angle. This is a mask to limit the incidence to the substrate at the corners.

Further, FIG. 1 schematically shows a cross section parallel to the traveling direction of the substrate and perpendicular to the curved surface of the cylindrical drum. The drum rotates from mask 3 to mask 4 as shown by the arrow.

The center 5 of the evaporation source and the downstream end 6 of the mask 3 in the substrate traveling direction
A normal line 9 is set on the drum surface at a point 8 where a straight line 7 connecting these lines enters the drum (substrate). The angle α between the normal line 8 and the straight line 7 is the initial angle of incidence. The angle has a negative value on the upstream side in the substrate running direction with respect to the normal line, and a positive value on the downstream side in the substrate running direction. It is important that the initial incident angle is in the range of 45 to 90 degrees in order to increase the capacitance of the electrode foil for an electrolytic capacitor of the present invention. If the initial incident angle is too large, the adhesion between the substrate and the thin film will deteriorate, so it is more preferable that the initial incident angle is in the range of 60 to 85 degrees.

The center 5 of the evaporation source and the upstream end 1 of the mask 4 in the substrate traveling direction
A normal line 13 is set on the drum surface at a point 12 where a straight line 11 connecting 0 is incident on the drum. The angle β between the normal line 13 and the straight line 11 is the final angle of incidence. Mask 4, drum 1 and evaporation source 2
Depending on the positional relationship, the final incident angle may be on the upstream side or downstream of the normal to the drum surface in the substrate running direction. That is, there are cases where it is a negative value and cases where it is a positive value. In order to increase the capacitance of the electrode foil for an electrolytic capacitor of the present invention, it is desirable that the final incident angle be a positive value and large. On the other hand, in order to widen the vapor incidence area, increase the film deposition rate, and increase material usage efficiency,
It is desirable that the final incident angle be a positive value and small, or more preferably a negative value and a large absolute value. Therefore, the final angle of incidence is -30
It is preferably in the range of ~30 degrees.

In the present invention, the region of incidence of vapor onto the substrate refers to the area on the drum where the vapor flow from the evaporation source confined by masks 3 and 4 in FIG. 1 is incident on the substrate.

The distance between the masks 3 and 4 and the drum 1 is such that the vapor flow wraps around behind the mask, obscuring the initial and final incident angles, reducing the adhesion between the substrate and the thin film, and obscuring the surface structure of the thin film. The mask ends 6 and 1 are shorter because it is better to be short in order to prevent such problems, and longer in order to retain the inert gas that is directed to the incident area of the vapor base.
The distance between the drum and the drum is preferably 5 m, preferably in the range from m to 100 mm, and more preferably in the range from 10 mm to 60 mm.

In the present invention, it is important to direct the inert gas from the downstream side in the direction of movement of the substrate to the region where the vapor enters the substrate. In order to effectively retain the directed inert gas, the region where the vapor enters the substrate is defined by the downstream end 6 of the mask 3 in the substrate traveling direction and the upstream end 10 of the mask 4 in the substrate traveling direction.
It is preferable that the structure is substantially sealed except for the opening between the two. In other words, the region where the vapor enters the substrate is blocked from below by masks 3 and 4, from above by drum 1, and further from the side by a partition wall (not shown in FIG. 1) that closes between the mask and drum. It is preferable that the The inert gas is supplied to the substantially sealed structure portion through a nozzle from the downstream side in the traveling direction of the substrate toward the region where the vapor enters the substrate.

The length of the nozzle is preferably three times or more the diameter of the nozzle in order to give the ejected inert gas a certain degree of directionality and direct it to the region where the vapor enters the substrate. Further, it is preferable that a plurality of nozzles be provided in the width direction of the drum in order to improve the uniformity of the formed thin film in the width direction.

As the inert gas used in the present invention, in addition to rare gases such as argon, neon, krypton, and helium, nitrogen and hydrogen can also be used.

Among them, argon and nitrogen are preferable because they are easy to handle and inexpensive. Further, it is preferable to add a small amount of oxygen to the inert gas because this has the effect of reducing the particle size of the fine structure of the thin film and increasing the capacitance.

An example of the method for manufacturing the electrode foil for electrolytic capacitors of the present invention is shown below, but the method is not limited thereto.

FIG. 2 is a schematic diagram of a vacuum evaporation apparatus equipped with a long substrate traveling system. A long substrate traveling system consisting of an unwinding shaft 15, a cylindrical cooling drum 16, and a winding shaft 17 is installed in the vacuum chamber 14. An aluminum foil base 18 having a predetermined thickness is installed on the base traveling system.

The vacuum tank 14 includes an upper tank 1 in which an unwinding shaft and a winding shaft are housed.
9 and the lower tank 20 in which the evaporation source 21 is housed, there is a partition wall 22.2.
3 and mask 24.25, and the exhaust port 2
6 and 27, respectively. The mask 24 on the upstream side in the substrate running direction is installed so that the initial angle of incidence of vapor from the evaporation source onto the substrate is a predetermined angle in the range of 45 to 90 degrees. The mask 25 on the upstream side in the traveling direction of the substrate is installed so that the final angle of incidence of vapor from the evaporation source onto the substrate is preferably a predetermined angle in the range of -30 to 30 degrees. The inside of the lower tank is evacuated to 5 x 10-'Torr or less, the pulp 28 is opened, and argon gas is introduced from the downstream side in the direction of substrate travel through the nozzle 29 and into the steam incidence area surrounded by the partition wall 22, 23, the mask 24, 25, and the cooling drum 16. Directly, the pressure in the lower tank should be I x 10-' to I x 10-2.
Adjust to a predetermined pressure in the range of Torr. The evaporation source is an electron beam heater filled with titanium ingots 30.

The substrate is moved to melt and evaporate the titanium ingot, thereby depositing a titanium film of a predetermined thickness on the substrate at a predetermined deposition rate. In this way, an electrode foil for an electrolytic capacitor is obtained.

Although induction oil heaters, resistance heaters, laser heaters, etc. can be used as evaporation sources for aluminum, titanium, zirconium, tantalum, niobium, and hafnium, electron beam heaters are used to evaporate high-melting point metals at high speed. It is preferable to do so.

It is permissible to perform ion blating by emitting high frequency power between these evaporation sources and the substrate as appropriate.

Also, these evaporation sources do not need to be directly below the drum;
A suitable position may be selected as appropriate from the viewpoint of material usage efficiency.

As the substrate used in the present invention, in addition to aluminum foil, aluminum alloy foil, metal foil other than aluminum, plastic film, paper, etc. can also be used.
From the viewpoints of low leakage current and high mechanical strength, it is preferable to use aluminum-saving material, aluminum alloy foil, or plastic film. It is preferable for these metal foils to be roughened by etching or sandblasting to increase the surface area, but to increase productivity by omitting processes, it is preferable to leave them flat in the manufactured state. It is preferable that there be. The thickness of the metal foil is preferably in the range of 10 to 100 μm in view of the relationship between mechanical strength and occupied volume.

Plastics for the plastic film include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, polyethers such as polyphenylene sulfide, aromatic polyamides, polycarbonates, polyether ketones, etc. Polyethylene terephthalate or polypropylene is preferred from the viewpoint of cost. In terms of mechanical stability and strength, these plastics are preferably biaxially stretched to form a film. The thickness of the plastic film is determined from the relationship between mechanical strength and occupied volume.
A range of 50 μm is preferred.

When a thin film consisting of at least one metal selected from the group of aluminum, titanium, zirconium, tantalum, niobium and hafnium or an alloy thereof is formed on only one side of a non-conductive substrate such as a plastic film, The side opposite to that on which the membrane is formed must be metallized. Metallization of plastic films is performed by forming a metal film by vapor deposition or sputtering. The metal film is preferably an aluminum film or a zinc film because it has high conductivity and a small dielectric loss. The thickness of the metal film is 0.00, because the thicker the metal film, the better the conductivity, and the thinner the metal film, the easier it is to self-heal.
A range of 3 to 0.15 μm is preferred. The non-conductive substrate may be subjected to pre-treatment such as adhesion-facilitating treatment prior to metallization. Since titanium, zirconium, tantalum, niobium and hafnium are not highly conductive, if a film of these metals or alloys is to be formed on a non-conductive substrate, the non-conductive substrate must be metallized beforehand. is preferable because dielectric loss can be reduced. aluminum,
The purity of at least one metal or alloy thin film selected from the group of titanium, zirconium, tantalum, niobium and hafnium is 99.8 to reduce leakage current.
% or more, more preferably 99.9% or more. In order to suppress thermal damage to the substrate and to reduce costs, it is better to make these films thinner.On the other hand, in order to increase capacitance, it is better to have a thicker film. It is preferably selected from the range of .03 to 0.4 μm, and more preferably selected from the range of 0.05 to 0.35 μm.

[Effects of the Invention] The present invention not only combines oblique vapor deposition at a specific angle and vapor deposition in gas in the production of valve metal thin films of aluminum, titanium, tantalum, etc., but also provides a method for supplying inert gas from a specific direction. Therefore, it was possible to stably obtain an electrode foil for an electrolytic capacitor that has a large capacitance despite having a thinner film thickness at a low cost. In the present invention, since the amount of inert gas required to be supplied to obtain a predetermined capacitance can be reduced, it is possible to suppress a decrease in the film deposition rate due to an increase in the pressure inside the tank. Due to these, the present invention has a remarkable effect on improving productivity and preventing heat damage to the substrate.

[Method for Measuring and Evaluating Characteristics] (1) Method for Measuring Capacitance Cut a sample into a size of 50 mm x 50 mm and attach it to a holder so that only the surface to be measured is exposed. Using a 10% by weight aqueous ammonium borate solution as an electrolyte, the sample holder and the carbon plate were placed against each other at an interval of 5 Qmm. Using the sample and carbon plate as electrodes, use an LCR meter (Ando Electric ■).
The capacitance at 1 kHz was measured using AG-4311 (manufactured by AG-4311).

The measured value was divided by 25 (cm2) to obtain the capacitance per unit area.

[Examples] The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Example 1 A vacuum evaporation apparatus equipped with a long substrate transport system shown in FIG.
A 0 μm long aluminum foil substrate was attached. Masks 24 and 25 were adjusted so that the initial angle of incidence was 52 degrees and the final angle of incidence was 0 degrees. Further, the distance between the end of the mask opening and the drum was 30 mm. Electron beam heater 2
After filling the titanium ingot 30 into the vacuum chamber 14
The inside of the partition wall 22 is evacuated through the exhaust ports 26 and 27.
23. The pressure inside the lower tank 20, which is separated by the mask 24, 25 and the cooling drum 16, was set to 5×10 −′ Torr or less. Next, argon gas was supplied through the valve 28 and the nozzle 29 toward the region where the vapor was incident on the substrate, and the pressure inside the lower tank was adjusted to 6×10 −′ Torr. While moving the substrate, a titanium ingot was melted and evaporated onto an aluminum foil at a deposition rate of 2.5 μm/min to a thickness of 0.1, 0.5 μm/min.
15. A titanium vapor deposited film of 0.3 μm was formed. When forming the aluminum vapor deposited film and the titanium film, the cooling drum 1
6 was cooled to -20°C.

The electrode foil for an electrolytic capacitor thus obtained had almost no deformation due to heat and had good flatness.

The capacitance of the electrolytic capacitor electrode foil was measured using a 10% aqueous ammonium borate solution as the electrolyte, and the results are shown in FIG. The capacitance increased as the titanium film thickness increased. When the film thickness was 0.3 μm, a very large value of 66 μF/Cm2 was obtained. In the case of only aluminum foil as the base, the capacitance was 3 μF/cm 2 .

Example 2 Electrode foil for an electrolytic capacitor was prepared in the same manner as in Example 1, except that the masks 24 and 25 were adjusted to make the initial angle of incidence 85 degrees and the final angle of incidence 35 degrees in the vacuum evaporation apparatus shown in FIG. It was created.

The electrode foil for an electrolytic capacitor thus obtained had almost no deformation due to heat and had good flatness.

The results of measuring the capacitance of the electrode foil for electrolytic capacitors are shown in FIG. The capacitance increased as the titanium film thickness increased. 45μF/c when the film thickness is 0.1μm
m2, film thickness 0.3. When czm, a very large value of 90 μF/cm2 was obtained.

Comparative Example 1 An electrode foil for an electrolytic capacitor was produced in the same manner as in Example 1, except that argon gas was ejected from the upstream side in the direction of movement of the substrate toward the region where the vapor was incident on the substrate.

The electrode foil for an electrolytic capacitor thus obtained had almost no deformation due to heat and had good flatness.

When the capacitance of the electrode foil for an electrolytic capacitor was measured, as shown in FIG. 3, even if the film thickness was increased, the capacitance did not increase, but on the contrary, the capacitance decreased. Film thickness is 0.
The capacitance was highest when it was 1μm, but it was 34μF/C.
The value remained at m2.

Comparative Example 2 An electrode for an electrolytic capacitor was prepared in the same manner as in Example 1, except that the masks 24 and 25 were adjusted to make the initial incident angle 23 degrees and the final incident angle 123 degrees in the vacuum evaporation apparatus shown in FIG. I made a foil.

As shown in Figure 3, the electrostatic capacitance of the thus obtained electrode foil for electrolytic capacitors increased as the titanium film thickness increased, but even when the film thickness was 0.3 μm, the capacitance remained relatively small at 27 μF/Cm2. Only capacitance was obtained.

Comparative Example 3 An electrode foil for an electrolytic capacitor was produced in the same manner as in Example 1, except that argon gas was not supplied toward the region of incidence of vapor onto the substrate.

As shown in Figure 3, the electrostatic capacitance of the thus obtained electrode foil for electrolytic capacitors does not increase much with increasing titanium film thickness, and is approximately 14 μF/cm even when the film thickness is 0.3 μm.
Only a relatively small value of 2 was obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the initial incident angle and final incident angle in the manufacturing method of the present invention, where α is the initial incident angle, β is the final incident angle, 2 is the evaporation source, and 3 and 4 are the metal vapor sources. It is a mask for shielding. FIG. 2 shows an example of a vacuum evaporation apparatus for manufacturing the electrode foil for an electrolytic capacitor of the present invention, in which 18 is a substrate, 21 is an evaporation source, 28 is a gas supply valve, and 29 is a nozzle. FIG. 3 shows the relationship between the titanium film thickness and capacitance of the electrode foil for an electrolytic capacitor of the present invention and the electrode foil for an electrolytic capacitor of a comparative example.

Claims (2)

[Claims] (1) A vapor made of at least one metal selected from the group of aluminum, titanium, zirconium, tantalum, niobium, and hafnium or an alloy thereof is directed onto at least one side of a substrate running along the surface of a cylindrical drum to form a thin film. A method for manufacturing an electrode foil for an electrolytic capacitor forming an electrode foil for an electrolytic capacitor, the initial angle of incidence of the vapor on the substrate being 45 to
A method for manufacturing an electrode foil for an electrolytic capacitor, the method comprising directing an inert gas from the downstream side in the traveling direction of the substrate to an incident region of the vapor onto the substrate within a range of 90 degrees. (2) The method for manufacturing an electrode foil for an electrolytic capacitor according to claim 1, wherein the final angle of incidence of the vapor onto the substrate is in the range of -30 to 30 degrees.