JP2551114B2 - Method for manufacturing superconducting circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A method for manufacturing a superconducting multilayer circuit board, which aims to obtain a multilayer board in which circuit connection between layers is surely performed, in order to obtain a ceramic board having a via formation position After printing a paste containing oxide superconducting material as a component, filling and sealing each hole with paste, printing a conductor pattern on this board, drying and firing to form a unit ceramic circuit board And the step of forming a pad pattern by further printing a superconducting paste at the via formation position of this ceramic circuit board, and arranging spacers in the peripheral part of this ceramic circuit board to perform alignment. It includes the steps of stacking ceramic circuit boards and drying them under pressure, and removing the spacers, and then firing and oxidizing them in an oxidizing atmosphere to integrate them. A method of manufacturing a road substrate is configured.

[Industrial applications]

 The present invention relates to a method of manufacturing a superconducting multilayer circuit board.

Elements such as niobium (Nb) and lead (Pb) and niobium tin (Nb ₃ Sn), bismuth, lead, barium, oxygen (Bi-Pb-Ba-
It has been known that substances such as O) show superconductivity, but the superconducting transition temperature (Tc) of metal elements remains at 10 K at the highest, and that of inorganic compounds also includes germanium niobium (Nb ₃ Ge) was highest at 23.5K, and there were only a few materials above 15K.

However, since the high-temperature superconductivity phenomenon of lanthanum-barium-copper-oxygen (La-Ba-Cu-O) oxide ceramics was discovered by Bednorz and Muller in April 1986, yttrium-barium-copper-oxygen Tc of about 90 K for (Y-Ba-Cu-O) system and rare earth element-Ba-Cu-O) system containing Y
We have discovered a superconducting ceramic that exhibits.

After that, the Ba component was replaced with strontium (Sr) or calcium (Ca) component, or the La component was replaced with bismuth (Bi) or thallium (Tl), Bi-Sr-Ca-Cu-O system (Tc ≈ 110K)
And Tl-Ba-Ca-Cu-O system (Tc ≈ 120K) have been announced.

Information processing devices that process large amounts of information at high speed, especially in the computer sector that requires high speed, include high electron mobility transistors (abbreviated as HEMT) and resonant tunneling hot electron transistors (abbreviated as RHET). Although semiconductor devices made of arsenic (GaAs) have been introduced,
Since these semiconductor elements exhibit their characteristics at the temperature of liquid nitrogen (N ₂ ), it is extremely effective to form an electronic circuit mounting such semiconductor elements with superconducting ceramics.

The present invention relates to a method for manufacturing a multilayer circuit board made of these superconducting ceramics.

[Conventional technology]

There are a thin film method and a thick film method as conventional methods for forming an electronic circuit. In both cases, ceramics such as alumina (α-Al ₂ O ₃ ) having excellent heat resistance and a low dielectric constant are used as a wiring board, In the case of the thin film method, a thin film such as gold (Au) or tantalum (Ta) is formed on it by a method such as electron beam evaporation or sputtering, and photo-etching technology (photolithography)
Is used for selective etching to form a conductor line having a fine pattern.

In the case of the thick film method, a pattern made of a conductor paste such as Au paste or silver-palladium (Ag-Pd) paste is formed by screen printing, and the conductor line is formed by firing the pattern.

When the circuit becomes complicated and multiple layers are required, the thick film method is mainly used.After conductor printing is screen-printed on an unfired ceramic green sheet, it is laminated and pressed while positioning. A multilayer circuit board is manufactured by firing and integrating.

However, it has not yet been put to practical use to use a superconducting ceramics instead of the metal vapor deposition film or the conductor paste and use this as a conductor line to form a multilayer circuit board.

[Problems to be Solved by the Invention]

Various compositions have been developed as oxide superconducting materials, but the inventors have been putting them into practical use, and yttrium (Y), barium (Ba), copper (Cu), and oxygen-based ceramics (YBa). ₂ Cu ₃ O _7-d ) It is necessary to adjust the atmosphere during firing in order to obtain superconducting properties. It is difficult to adopt a method of firing and integrating.

Therefore, in multilayering, printing and firing are performed for each ceramic substrate unit, and this is laminated, but in this case, the thickness is increased by the amount of the conductor lines patterned on the substrate. Since there is a warp in the wiring, there is a problem in that in the case of stacking, the wiring connection between the via (Via-hole) formation position and the conductor line of the lower substrate cannot be sufficiently obtained.

[Means for solving the problem]

The above problem is to print a superconducting paste on a ceramic substrate with holes for via formation, fill the holes with paste and seal the conductor, print a conductor line on this substrate, dry it, and then bake it. A step of forming a unit ceramic circuit board, a step of further printing a superconducting paste at the via formation position of this ceramic circuit board to form a pad, and a spacer being arranged at the peripheral portion of this ceramic circuit board. This can be solved by the steps of stacking a plurality of ceramic circuit boards, drying them while applying pressure, and removing the spacers and firing them in an oxidizing atmosphere to integrate them.

[Action]

Rare earth element-Ba-Cu-
A problem in forming an O-based, for example, Y-Ba-Cu-O-based superconducting circuit is that a conductor paste is made using superconducting ceramics, and a substrate formed by patterning by a method such as screen printing is used. When firing to form a conductor line, the organic solvent and binder contained in the paste are decomposed by heating, and at this time the oxides that are the constituent material of the superconducting ceramics are reduced and YBa ₂ Cu ₃ O That is, ceramics having a composition ratio of _7-d cannot be obtained.

For that purpose, it is necessary to fire in an oxidizing atmosphere, but when superconducting paste is screen-printed and stacked, oxygen (O ₂ ) supply is poor and it is difficult to form superconducting ceramics. .

Therefore, in the present invention, a superconducting conductor line is formed in advance for each substrate forming the multilayer wiring substrate.

Next, a pad is provided in a via portion that vertically connects the wiring boards to each other, and the position is raised from the board.

Aligning the Such substrate, is pressurized after stacking, connecting via portion is sufficient, also the pad portion is surrounding a gap, superconducting pad portion for the supply of O ₂ is sufficient It can be made into ceramics.

In this way, the multilayer wiring board has layers connected to each other at beer positions and gaps exist therebetween, but this configuration is advantageous in terms of high frequency characteristics.

That is, when using an alumina substrate, the dielectric constant is about
It is as large as 10, and cross-talk tends to occur between the wirings above and below the alumina substrate, but there is a side effect that this can be prevented by the presence of the air layer.

〔Example〕

After forming a superconducting ceramics having a composition of YBa ₂ Cu ₃ O _{7-d by} a conventional method, it is pulverized by using a disintegrator and a ball mill and sized to obtain fine particles having an average particle diameter of 2 to 3 μm. did.

Then, terpineol, methyl ethyl ketone, and acetone are used as the organic solvent, and polyvinyl butyral (abbreviated as PVB) is used as the binder, and the viscosity is 200
A superconducting paste of 0 poise (Ps) was formed.

Next, prepare an alumina substrate with a size of 10 cm square and a thickness of 0.65 mm, and use a YAG (yttrium-aluminum-garnet) laser in which the via formation part is perforated with a diameter of 0.2 mm. I prepared only the number.

First, a via formation portion of an alumina substrate was filled with a superconducting paste by a screen printing method, and then a wiring pattern having a thickness of 30 μm was formed on this substrate.

And 1000 ℃ in a mixed atmosphere of argon (Ar) and O _2.
After baking for 30 minutes in the same atmosphere at 900 ℃ 1
Annealing was performed over time to form a superconducting line.

Here, the annealing is _{d in} the molecular formula of YBa ₂ Cu ₃ O _7- d.
This is for adjusting the value of.

Next, screen print a superconductor paste on the top and bottom of the via formation position on the baked alumina substrate to a thickness of 20
A μm pad was formed.

Then, spacers made of polyester having a thickness of 50 μm were arranged at the four corners of the substrate, on which no pattern was formed, and the spacers were laminated while being aligned and dried under pressure.

Next, after removing the spacers at the four corners, the same conditions as above, that is, firing in a mixed atmosphere of Ar and O ₂ at 1000 ° C. for 30 minutes, and then in the same atmosphere at 900 ° C. for 1 hour Annealing was performed to form a superconducting pattern.

The multi-layer circuit board having voids between the two boards thus created absorbs the unevenness of each board by the via part and completes the connection, and the pad of the via part is also supplied with sufficient oxidizing gas. Because of this, superconducting ceramics similar to conductor lines could be obtained.

〔The invention's effect〕

By carrying out the present invention, a superconducting multilayer wiring board having a superconducting transition temperature (Tc) of about 80 K can be obtained. By using the thus obtained multilayer circuit board, HEMT, RHET
It has become possible to fully demonstrate the performance of semiconductor devices used at the temperature of liquid N ₂ such as the and Josephson devices.

Claims (1)

(57) [Claims] 1. A ceramic substrate having holes for forming vias is printed with a paste containing an oxide superconducting substance as a component, the holes are filled with the paste, the conductor pattern is printed on the substrate and dried. And then firing to form a unitary ceramic circuit board, and a step of printing a paste containing an oxide superconducting material as a component at a via formation position of the ceramic circuit board to form a pad pattern, Spacers are placed on the periphery of the ceramic circuit board to align the ceramic circuit boards, and a plurality of ceramic circuit boards are stacked and dried while applying pressure. After removing the spacers, firing is performed in an oxidizing atmosphere to integrate them. A method of manufacturing a superconducting circuit board, comprising: