Method of manufacturing solid electrolytic capacitors

Details Method of manufacturing solid electrolytic capacitors Method of manufacturing solid electrolytic capacitors

2000-01-28

2001-08-28

Niebling, John F. (Department: 2812)

Metal working

Barrier layer or semiconductor device making

Barrier layer device making

C361S523000, C361S528000

Reexamination Certificate

active

06280483

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of methods of manufacturing solid electrolytic capacitors (hereafter referred to as “solid capacitors”) using conducting polymer as solid electrolyte. In particular, the present invention relates to the field of methods of manufacturing solid electrolytic capacitors to provide an anode foil whose characteristics of the anodized film degrade to a lesser extent during the formation process of the MnO
2
layer which becomes the base of the conducting polymer layer to the following process.
BACKGROUND OF THE INVENTION
A conventional method of manufacturing solid capacitors is described next with reference to drawings.
FIG. 5
shows a perspective, partly in section, illustrating the configuration of a solid capacitor. In
FIG. 5
, after the surface of an aluminum foil
1
, which acts as the anode (positive electrode), is roughened by etching, an anodized film is formed on the surface of the roughened aluminum foil
1
through anodization. An insulative resist
11
separates the aluminum foil
1
into an anode and cathode (negative electrode). The cathode is made by sequentially laminating a MnO
2
layer
12
, polypyrrole layer
13
which becomes the conducting polymer layer, graphite layer
14
, and silver paint layer
15
. A solid capacitor element is configured as described above.
A single or multi-laminated solid capacitor element as configured above is molded with a packaging resin
17
(not illustrated) after terminal members
16
A and
16
B are connected to the anode and cathode. This completes the solid capacitor.
In the conventional method of manufacturing solid capacitors as above, the aluminum foil
1
, the initial material, is generally provided in the form of a strip of predetermined length wound around a reel. The aluminum foil
1
wound around one reel is considered as one lot, and is successively supplied to the above series of processes. Accordingly, if the characteristics of the aluminum foil vary significantly in the processes relatively close to raw materials, the product yield may drop in the conventional manufacturing method.
More specifically, during the process of forming the MnO
2
layer
12
on an anodized film of the aluminum foil
1
in
FIG. 5
, a strip of the aluminum foil
1
is successively immersed in and removed from a solution containing manganese salts. The manganese salt is then thermally decomposed to form the MnO
2
layer
12
on the surface. This process has a marked detrimental effect on the anodized film already formed on the aluminum foil
1
, often resulting in damage to some parts of the anodized film.
Accordingly, another anodization step is implemented after the MnO
2
layer formation process in order to repair the damaged anodized film. However, this repair process is not always sufficient. Considering the degradation in characteristics of the anodized film on an aluminum foil (hereinafter referred as characteristics of the aluminum foil)
1
during the MnO
2
layer formation process, the entire lot of aluminum foil
1
rolled on the reel may not be reliably input to the following MnO
2
layer formation process.
The present invention aims to offer a method of manufacturing solid electrolytic capacitors that allows the reliable input of the entire lot of aluminum foil, on which an anodized film is formed, to the MnO
2
layer formation process, and also to improves the product yield.
SUMMARY OF THE INVENTION
The method of manufacturing solid capacitors comprises the steps of:
sampling a part of aluminum foil, on which an anodization film is formed on its surface, from the lot;
forming the MnO
2
layer on this sample;
inspecting the sampled aluminum foil on which the MnO
2
layer is formed using a predetermined inspection method; and
determining whether to input the lot from which the aluminum foil is sampled to the MnO
2
layer formation process used in solid capacitor formation.
The present invention thus eliminates defective aluminum foil being found after inputting the entire lot of aluminum foil to the MnO
2
layer formation process. This allows to stably and inexpensively to manufacture solid electrolytic capacitors with high reliability without loss in costs and efficiency.


REFERENCES:
patent: 5882719 (1999-03-01), Creasi, Jr.

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