Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1989-05-30
1992-06-23
Ryan, Patrick J.
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
505701, 505702, 505703, 505704, 428209, 428432, 428457, 428461, 428688, 428701, 428901, 428930, 427 62, 156 89, B32B 900
Patent
active
051243113
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
to a superconductive wiring structure incorporated in a thick film integrated circuit and, more particularly, to a protective film for protecting a superconductive wiring strip against influences of the environment so as to cause the superconductive wiring strip to stay in the superconducting state.
BACKGROUND ART
A typical example of the superconductive wiring is reported by Yamanaka et al, in the paper entitled as "Techniques for Formation of Superconductive Wiring on Alumina Substrate", Electronic Parts and Materials , Aug. 1987, Vol. 26, No. 8, pages 89 to 92. According to the paper, the wiring strips are formed by sintering paste lines which are printed on an usual alumina substrate and a fine grained alumina substrate, respectively, and the paste is prepared by mixing a powder of an yttrium-barium-copper oxide into an organic vehicle. The wiring strips are directly printed on the usual alumina substrate and the fine grained alumina substrate, and no protective film is provided on the wiring strips. The usual alumina substrate is lower in purity than the fine grained alumina substrate, so that it is considered that a substantial amount of impurity atoms are contained in the usual alumina substrate.
However, a problem is encountered in the prior-art superconductive wirings in stability. Namely, the wiring strips tend to lose the superconductivity within relatively short time periods, and, for this reason, the propagation paths for electric currents are liable to be blocked in the wiring strips.
Moreover, as reported in the paper, the superconductivity is achieved for the wiring strips formed on the fine grained alumina substrate, but no superconductivity is observed for the wiring strips formed on the usual alumina substrate. Then, another problem is encountered in the wiring strips reported by Yamanaka et al in the substrate used.
It is therefore an important object of the present invention to provide the structure of a superconductive wiring which is fit for use for a prolonged period of time.
It is also an important object of the present invention to provide the structure of a superconductive wiring which allows the wiring strip to stay in the superconductivity regardless of the substrate used.
DISCLOSURE OF INVENTION
It is considered that reactants such as water vapor and carbon dioxides in the atmosphere react with the superconductive ceramic to form a product which causes the wiring strip to lose the superconductivity. One of the reasons why no superconductivity is achieved for the strips on the usual alumina substrate is also supposed to be the difference in purity between the usual alumina substrate and the fine grained alumina substrate. Namely, the usual alumina contains a relatively large amount of silicon dioxide which prohibits the yttrium-barium-copper oxide from the superconductivity through a reaction therebetween.
To accomplish these objects, the present invention proposes to wrap the superconductive strip in a protective film the material of which does not react with the superconductive oxide used for formation of the wiring strip.
In accordance with one aspect of the present invention, there is provided a structure of superconductive wiring fabricated on an insulating substrate, comprising: a) a conductive pattern having at least one wiring strip of a superconductive ceramic formed on the insulating substrate, the superconductive ceramic being of the base; and b) a protective film covering the conductive pattern and formed of a bismuth oxide, the superconductive ceramic material is formed of an oxygen compound containing at least one element selected from the group consisting of scandium, yttrium and lathanides, at least one alkaline earth metal and copper. The basic oxide and the superconductive ceramic may be formed of a bismuth oxide and an oxygen compound containing at least one element selected from the group consisting of scandium, yttrium and lathanides, at least one alkaline earth metal and copper. In one implementation, the oxygen compound may contain
Kanda Yoshio
Mori Satoru
Takeshita Takuo
Yoshida Hideaki
Mitsubishi Kinzoku K.K.
Ryan Patrick J.
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