Process for preparing a Nb capacitor

Details Process for preparing a Nb capacitor Process for preparing a Nb capacitor

1999-09-03

2001-06-05

Dinkins, Anthony (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Solid electrolytic capacitor

C361S524000

Reexamination Certificate

active

06243255

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a capacitor (condenser) using Nb and a process for preparing same, more particularly, to a process for preparing a solid electrolytic Nb capacitor.
BACKGROUND OF THE INVENTION
There has been hitherto known a Nb capacitor, more particularly, solid electrolytic Nb capacitor in which Nb (niobium) is used for an anode body. An outline of a typical process for preparing the solid electrolytic Nb capacitor will be explained below step by step.
1) Powder-preparing step
Nb powders are admixed with a liquid binder to granulate secondary Nb particles of coagulated Nb powders. These granulated secondary Nb particles are then sieved to eliminate enormously large mass of coagulated secondary Nb particles, thereby, to obtain secondary Nb particles having a uniform particle size.
2) Compression molding & sintering step
By using the secondary Nb particles having a uniform particle size which was prepared in the above powder-preparing step, an anode body for a capacitor is made. Explaining it more in detail, lead of Nb wire is embedded into the secondary Nb particles. Then, a compression-molded article (-compact) of the secondary Nb particles is prepared. Thereafter, the prepared compression-molded article is sintered in a vacuum of not more than 10
−5
Torr at high temperatures of 1200 to 1300° C. to prepare an anode body for a capacitor.
3) Formation step
On the surface of the anode body for a capacitor prepared in the above compression molding & sintering step, a dielectric of a Nb-oxide layer is formed by an anodic oxidation process. The anodic oxidation process is a process for forming an oxide layer on the surface of an anode body by immersing anode body and its counter electrode in an electrolytic solution and maintaining the anode body at an electrostatic potential higher than that of a counter electrode. Using, for example, an aqueous solution containing 0.6% by volume of phosphoric acid as an electrolytic solution, the anodic oxidation is carried out with keeping its liquid temperature at 60° C.
4) Solid-electrolyte-layer-forming step
On the dielectric, i.e., the oxide layer of Nb, a solid electrolyte layer is formed. The solid electrolyte layer is formed by polymerizing a conductive polymer such as polypyrrole or the like.
4) Steps of forming graphite and Ag layers to mold-application After forming the solid electrolyte layer, graphite and Ag layers are formed on the thus formed solid electrolyte layer in this order. Then, the thus obtained laminate is subjected to mold-application.
SUMMARY OF THE DISCLOSURE
In the course of investigations toward the present invention the following problems have been encountered.
It was found that the solid electrolytic Nb capacitor prepared by the above conventional process has such drawbacks that abnormal behavior is observed on the frequency response of its dielectric loss (tan &dgr;). For example, it is shown in FIG.
2
(
a
).
Accordingly, it is an object of the present invention to provide a solid electrolytic Nb capacitor whose abnormal dielectric loss (tan &dgr;) behavior is restrained which has been observed previously dependent on the amplitude of frequency, and a process for preparing same.
According to an aspect of the present invention, there is provided a process for preparing a solid electrolytic Nb capacitor that the solid electrolytic Nb capacitor is obtained by forming a laminating film or laminating films on a first laminate comprising a Nb anode body, a Nb-oxide layer and a solid electrolyte layer formed on the Nb-oxide layer. The process of the present invention further comprises the step of removing absorbed water remained between the Nb-oxide layer and the sol id electrolyte layer existing in the first laminate or a second laminate which includes the aforementioned first laminate and one or more layer of the laminating film.
According to a second aspect of the present invention, there is provided a solid electrolytic Nb capacitor prepared by the process of the present invention. In the solid electrolytic Nb capacitor of the present invention, absorbed water is removed which remained between the Nb-oxide layer and the solid electrolyte layer. In a further aspect of the present invention, a solid electrolytic Nb capacitor comprises a Nb anode body, a Nb-oxide layer and a solid electrolyte layer formed on the Nb-oxide layer, and is substantially freed from any water absorbed on the Nb-oxide layer between the Nb-oxide layer and the solid electrolyte layer.


REFERENCES:
patent: 3597664 (1971-08-01), Vallani
patent: 5471365 (1995-11-01), Nakamura et al.
patent: 11-329902 (1999-11-01), None

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