JPH0122976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electrolytic capacitor with uniform characteristics and precision.

Conventional electrolytic capacitors are made by electrically or chemically etching anodic oxide film-forming metal foil such as aluminum, tantalum, niobium, titanium, etc. to increase the surface area several tens of times, and then anodic oxidation to generate a dielectric oxide film. Electrolytic capacitors were constructed by winding or laminating these as electrodes. However, the capacitor having the above structure has a drawback that the capacitance varies widely, about ±20%, because the surface area expansion rate during etching varies.

The present invention eliminates the above-mentioned drawbacks and eliminates capacitance, loss,
It is an object of the present invention to provide a method for manufacturing an electrolytic capacitor that has uniform and precise characteristics without variations in leakage current, etc.

The details of the present invention will be explained below. That is, a photoresist such as polyvinyl alcohol-dichromate type or polyvinyl alcohol-cinnamate ester type is applied uniformly to the surface of an anodic oxide film-forming metal foil such as aluminum, tantalum, niobium, or titanium using a spinner or a roller and then dried. .
Next, in order to obtain the required capacitance, a photomask with the necessary pattern, for example, square opaque layers with a side of several μm arranged in a grid pattern at intervals of several μm, is tightly adhered onto the resist film. Ultraviolet light is irradiated using a high-pressure mercury lamp or xenon lamp. Development is carried out by spraying or steaming water or an organic solvent such as trichlorethylene, depending on the type of resist, to dissolve the unexposed portions of the resist, and if necessary, baking to stabilize the resist. Etching of the base metal, that is, the electrode, in the openings where the resist is removed is performed to a predetermined depth by electrolytic etching, chemical etching, electron beam sputtering, or the like. Here, the surface area expansion rate, that is, the etching magnification, depends on the depth of the etching holes and the distribution density of the holes. Further, the length of one side of the holes and the hole spacing can be adjusted as appropriate by adjusting the anodic oxidation voltage. Next, the resist film remaining on the metal foil is peeled off by dipping or spraying it in an organic solvent or stripping solution. Further, the metal foil is washed with water using ultrasonic waves or the like to completely remove dissolved substances in the etching holes. Next, anodic oxidation is performed in an aqueous solution of borate or organic acid salt to a required voltage to form a dielectric oxide film, which is used as an anode. The anode 2 having the etched holes 1 as shown in FIGS. 1 and 2 obtained by the method described above is cut into a certain size, and a heat-resistant material is placed on one end of the anode 2 as shown in FIG. 3. Apply varnish 3 and immerse the part with etching holes 1 in an aqueous solution such as manganese nitrate or manganese sulfate to impregnate it to 200~
It is fired at a temperature of 350°C to form a semiconductor layer such as manganese dioxide. This process of anodic oxidation, impregnation and firing is repeated several times to form a semiconductor layer completely up to the etching hole 1. Next, a carbon graphite layer and a conductive layer such as silver or copper paste are formed on the surface of the semiconductor layer to form a unit element. A plurality of unit elements are stacked according to the required capacitance as shown in FIG.
The electrode on the side to which the varnish 3 is coated, on which no conductive layer is formed, is integrated using ultrasonic waves, a laser, or the like, and an external terminal 4 is connected thereto to form an anode body 5. The conductive layer side is connected in parallel with solder or the like to serve as a cathode, and an external terminal 6 is connected if necessary. This laminate is housed in a container or subjected to resin molding or resin coating to obtain a sheet-like electrolytic capacitor.

The electrolytic capacitor of the present invention obtained by the above method has extremely small variation in surface area expansion rate compared to the etched foil for anode used in conventional electrolytic capacitors, and the variation in capacitance as a finished product is within ±1%. It can be stored in Furthermore, the size, depth, and distribution density of the etching holes are constant, and the resulting dielectric oxide film is homogeneous, so that variations in loss and leakage current can be made small and uniform. Further, by increasing or decreasing the number of laminated layers, an arbitrary capacitance can be obtained. It can also be made into a thin, flat shape by resin molding, etc., and can be applied to ultra-precision electrolytic capacitors and chip-type electrolytic capacitors that are incorporated into integrated circuits.

As detailed above, according to the present invention, a photoresist is coated on the surface of an anodized film-forming metal foil, dried, a photomask is adhered, and ultraviolet light is irradiated, and the unexposed areas are dissolved, and the resist is removed to form an opening. After etching the base metal of the part to expand the surface area and peeling off the residual resist film, a dielectric oxide film is formed and used as an anode.A heat-resistant varnish is applied to one end of the anode, and a semiconductor layer, a carbon graphite layer,
Conductive layers are sequentially formed to form a unit element, and a plurality of unit elements are laminated, and the varnished side is integrated with ultrasonic waves or a laser to form an anode body, and the conductive layer side is connected in parallel with solder or the like to serve as a cathode. As a result, it is possible to provide a method for manufacturing a precise, thin, flat electrolytic capacitor that can reduce variations in capacitance, and can also make variations in loss and leakage current small and uniform.

[Brief explanation of drawings]

The drawings are all related to the present invention; Fig. 1 is a partially cutaway plan view showing the metal foil after etching, and Fig. 2 is a partially cutaway plan view showing the metal foil after etching.
Figure 3 is a cross-sectional view of the metal foil after etching, Figure 3 is a plan view showing an anode that has been cut and coated with varnish, and Figure 4 is a cross-sectional view showing a finished electrolytic capacitor in which unit elements are laminated. 1... Etching hole, 2... Anode, 3... Varnish, 4, 6... External terminal, 5... Anode body.

Claims (1)

[Claims] 1. A method for applying and drying a photoresist on the surface of the metal foil capable of forming an anodic oxide film, a method for applying a photomask to the surface and irradiating it with ultraviolet light, and a method for dissolving the unexposed areas and removing the resist and exposing the underlying metal to the open areas. means for enlarging the surface area by etching; means for peeling off the residual resist film; means for forming a dielectric oxide film to form an anode; means for forming a unit element by sequentially forming a conductive layer, and a means for laminating a plurality of unit elements, and integrating the varnished side with ultrasonic waves or a laser to form an anode body, and connecting the conductive layer side in parallel with solder. 1. A method for manufacturing an electrolytic capacitor, comprising: means for forming a cathode.