JPH0265202A - Superconducting ceramic circuit - Google Patents

Abstract

PURPOSE:To prevent breakdown of a circuit element due to the excessive current applied to a ceramic circuit by a method wherein a protective region having the cross-sectional area smaller than that of other conductive line is provided on a part of the conductive line consisting of superconducting ceramic formed on a heat-resisting substrate, and the critical current value of said protective region is set smaller than that of other conductive line. CONSTITUTION:A protective region 2, the cross-sectional area of which is smaller than that of a conductive line 1, is provided on a part of the conductive line 1. If a protective region 2 of small cross-section is provided, the density of critical current, the superconducting state of which is converted into a normal conducting state, is determined by the material to be used in superconducting ceramics, and as a result, the conductive line of the protective region is formed by setting the steady-state current value 3, flowing to the protective region, which is smaller than the critical current value 4. When the current is increased by an abnormal phenomenon or transient phenomena and it exceeds the critical current value 4, the superconducting state is broken, and a current value 5 decreases to the value approximate to zero, because an oxide superconducting body maintains a high resistivity of several OMEGA/cm in a normal conductive state.

Description

[Detailed Description of the Invention] [Summary] Regarding superconducting ceramic circuits, for the purpose of preventing destruction of circuit elements due to excessive current, a part of a conductor line made of superconducting ceramics formed on a heat-resistant substrate is used. The present invention relates to the configuration of a superconducting circuit by providing a protected area having a smaller cross-sectional area than a conductive line and setting the critical current value of this protected area smaller than that of other conductive lines to provide superconductivity.

It was known that 22 elements such as aluminum (All) and titanium (Ti) and multiple inorganic compounds such as lithium titanate (LIT103) and molybdenum carbide (MoC) exhibit superconductivity, but the superconducting transition temperature ( Tc) is at most IOK for metal elements, and for inorganic compounds it is niobium germarylamide (Nb: +Ge).
) was the highest at 23.5K, and there were only a few materials with a temperature of 15K or higher.

However, in April 1986, B.
Since the discovery of high-temperature superconductivity in lanthanum-barium-copper-oxygen (La-Ba-Cu-0) based oxide ceramics by Ednorz and Muller,
Yttrium, barium, copper, oxygen (Y-Ba-CuO
) system and rare earth element-Ba-Cu-0) system containing Y, superconducting ceramics exhibiting Tc of about 90K have been discovered.

After that, Ba is replaced with strontium (Sr) and calcium (
B1-3r-Ca-Cu-0 system (Tc = 105K) in which La is replaced with bismuth (old) or thallium (TA), or Tj! -Ba-Ca-Cu
-0 series (Tc = 118 K) etc. have been announced.

Now, information processing equipment that processes large amounts of information at high speed, especially in the computer sector that requires high speed, uses gallium-based devices such as high electron mobility transistors (abbreviated as HEMT) and resonant tunneling hot electron transistors (abbreviated as RHET). Semiconductor elements made of arsenic (GaAs) are being introduced, but since these semiconductor elements exhibit their characteristics at the temperature of liquid nitrogen (N2), electronic circuits equipped with such semiconductor elements are being manufactured using superconducting ceramics. It is extremely effective if formed with

The present invention relates to the structure of conductor lines made of these superconducting ceramics.

[Conventional technology]

Conventional methods for forming electronic circuits include the thin film method and the thick film method, both of which use ceramics such as alumina (α-Aβ203), which has excellent heat resistance and a low dielectric constant, as the wiring substrate. A thin film of gold (Au) or tankle (Ta) is formed on this by methods such as electron beam evaporation or sputtering, and selective etching is performed using photolithography to form a conductor line consisting of a fine pattern. is forming.

In addition, in the case of the thick film method, a pattern made of a conductor paste such as He〇 paste or palladium (8g-Pd) paste is created using the screen printing method, and the conductor line is formed by firing this. .

Similarly, attempts have been made to form conductor lines using superconducting ceramics as a conductive material.

In other words, an electronic circuit is patterned using a physical method such as electron beam evaporation or sputtering, or a superconductor is formed using a chemical method such as chemical vapor deposition (CVD). Research is also being conducted into forming thin films made of ceramics and patterning electronic circuits using photolithographic techniques.

Research is also being carried out on pulverizing superconducting ceramics, making conductive paste using this as a raw material, and forming electronic circuits using screen printing.

[Problem to be solved by the invention]

Electronic circuits made of superconducting ceramics are being formed on heat-resistant substrates such as alumina substrates using various methods such as thin-film and thick-film methods, but the problem in this case is that they are different from those of general electronic circuits. Similarly, circuit elements may be destroyed by excessive current that occurs when a circuit abnormality such as transient excessive current or resonance occurs when a switch is closed.

As a countermeasure for this, in ordinary electronic circuits, avalanche diodes are added to the circuit, fuses and breakers are
Although protection measures such as external protection have been taken, no suitable protection circuit has been found for superconducting circuits.

Therefore, the challenge is to put this protection circuit into practical use.

[Means to solve the problem]

The above problem is solved by providing a protected area with a smaller cross-sectional area than the conductor line in a part of the conductor line made of superconducting ceramics formed on a heat-resistant substrate, and making the critical current value of this protected area smaller than that of the conductor line. This can be resolved by setting:

[Effect]

The present invention utilizes the phenomenon that when the current flowing through a conductor line exceeds a critical current density, the superconducting state is broken by the magnetic field generated by the current.

That is, as shown in FIG. 1, a protection area 2 having a smaller cross-sectional area than the conductor line 1 is provided in a part of the conductor line 1.

Here, as shown in the figure, the holding area 2 may have a narrow line width or may be formed thinly, but photo-etching may also be used to form a pattern by mask vapor deposition. In this case, the manufacturing process is simpler in the former case.

Now, when the protective region 2 with a small cross-sectional area is provided in this way, in superconducting ceramics, depending on the material used, the superconducting state changes to the normal conducting state FB7. Since the field current density is determined, the cross-sectional area necessary for the protection operation to start can be determined based on this value, and the pattern of the protection region 2 can be designed.

FIG. 2 is a schematic diagram showing the operation of the protected area, in which the horizontal axis shows the elapsed time (1), and the vertical axis shows the current value (1) flowing through the protected area.

Of course, the steady current value 3 flowing through the protected area is set to be less than the critical current value 4 (40% in the case of the figure) to form the conductor line in the protected area.

When the current increases due to abnormal or transient phenomena and exceeds the critical current value of 4, the superconducting state is broken, but since oxide superconductors have a high resistivity of several mΩ cm in the normal conducting state, the current value 5 drops to a value close to 0.

Next, the Joule heat generated in the conductor line in the protected area when it becomes a normal conductive state cools down, and when it becomes a superconducting state again, the current flowing through the protected area returns to the steady current.

As described above, according to the present invention, automatic control is performed even when a large current flows through the conductor line.

〔Example〕

Yttrium (Y), barium (Ba), copper (Cu
)・Oxygen (○)-based superconducting ceramics (YBa2Cu3
Alumina (α
-An zo3) A conductor line 1 including a protective region 2 as shown in FIG. 1 was patterned on the substrate.

Here, the conductor base I is made by making superconducting ceramics having a composition of YBa2Cu3007-d into fine particles with an average particle size of 2 to 3 μm using an inserter and a ball mill, and then kneading them by adding an organic solvent and a binder. Viscosity is 2000 Boise (Ps
) is made into a paste.

Then, in a mixed atmosphere of argon (Ar) and 02
After baking at 00°C for 30 minutes, it was heated to 900°C in the same atmosphere.
A superconducting conductor line was formed by annealing at °C for 1 hour.

Since the current during normal operation is IA, the thickness of the patterned line is 50 μm, and in FIG. 1, the width of the conductor line 1 is 200 μm. The width of region 2 was 50 μm, and the length of protected region 2 was 500 μm.

The reason for this is that a critical current density of 1.8 Appl, Phys.
vol. 26.1987) for thin films obtained by thick film methods, it is approximately I Xl05A/cm2.

Therefore, based on these values, the critical current of the conductor line 1 was determined to be 1OA, and the critical current of the protected area 2 was determined to be 2.5A.

When a current is passed through the conductor line, focusing on protection area 2, as shown in Figure 2, when the current increases from the initial 18 to 2.5A, the protection operation starts, and the current value After reaching 0, the IA returned to its steady value.

〔Effect of the invention〕

By implementing the present invention, which provides a protection area in the superconducting line itself and allows safe operation at LJ, it is possible to provide functions of suppressing excessive current and automatic recovery, and by implementing the present invention, the reliability of the superconducting circuit can be improved. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a protection circuit according to the invention, and FIG. 2 is a schematic diagram showing the operation of a protection area according to the invention. In the figure, 1 is a conductor line, 2 is a protected area, 3 is a steady current value, and 4 is a critical current value.

Claims (1)

[Claims] A protective area having a cross-sectional area smaller than that of the conductor line is provided in a part of a conductor line made of superconducting ceramics formed on a heat-resistant substrate, and the critical current value of the protected area is set to be smaller than that of the conductor line. Features a superconducting ceramic circuit.