JPH0247894A - Manufacture of superconducting circuit board - Google Patents

Abstract

PURPOSE:To obtain a superconductive multilayer interconnection board having about 80K of superconduction transition temperature by printing superconductive paste on a ceramic board whereon via formation positions are cut out, while being fired to form a unit ceramic circuit board followed by laminating a plurality of ceramic circuit boards and firing in a oxidation atmosphere for being integrated. CONSTITUTION:Every board forming a multilayer interconnection board in advance forms a superconductor line. Next, a pad is provided on a via part circuit-connecting each wiring board in the vertical direction and its position is swollen from the board. The board is positioned, for being heated after lamination to connect the via part. Further, since the pad part has a gap around it being sufficiently supplied with O2, the pad part is make into superconductive ceramics, while each layer of the multilayer interconnection board is connected in the via position. By having a void part between mutual boards, the multilayer circuit board absorbs unevenness of each board at the part to make the connection complete, further, since also the pad of the via part is sufficiently supplied with oxide gas, it is make into the superconducting ceramics equal to the conductive line.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a superconducting multilayer circuit board, the purpose is to obtain a multilayer board in which circuit connections between the eyebrows are reliably made, and a ceramic board with holes formed at via formation positions is used. After printing a paste containing an oxide superconducting material as a component and filling and sealing each hole with the paste, a conductive pattern is printed on this substrate, dried, and then fired to form a unit ceramic circuit board. A step of further printing superconducting paste at the via formation position of this ceramic circuit board to form a pad pattern, and a step of placing spacers around the periphery of this ceramic circuit board and aligning them. The method for manufacturing a superconducting circuit board includes a step of stacking ceramic circuit boards and drying them under pressure, and a +4 step of removing spacers and then baking them in an oxidizing atmosphere to integrate them.

[Industrial application field]

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

It is well known that elements such as niobium 7' (Nb) and lead (Pb) and substances such as niobium stannide (NbxSn) and bismuth-lead-barium-oxygen (Bi-Pb-Ba-0) exhibit superconductivity. However, the superconducting transition temperature ('r
e) is only a high IOK for metal elements, and also for inorganic compounds, niobium germarylamide (Nb:
+Ge) had the highest value of 23.5K, and there were only a few materials with a value of 15 or higher.

However, in April 1986, Bednorz and Muller
Lanthanum, barium, copper, oxygen (La-Ba-
Since the discovery of high-temperature superconductivity in Cu-0)-based oxide ceramics, yttrium, barium, copper,
Superconducting ceramics having a Tc of approximately 90 K have been discovered for oxygen (Y-Ba-Cu-0) and rare earth element containing Y-Ba-Cu-0) systems.

After that, the Ba component is replaced with strontium (Sr) or calcium (Ca) component, and the La component is replaced with bismuth (B
i) or B1-3r-C substituted with thallium (T l )
a-Cu-0 series (Tc #110K) and T l -B
a-Ca-Cu-0 series (T, #120K) and the like 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 11EMT) 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 have become extremely unstable. It is extremely effective if it is made of ring ceramics.

The present invention relates to a method of manufacturing a multilayer circuit board 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-8he 203), which has excellent heat resistance and a low dielectric constant, as wiring substrates. In this case, a thin film of gold (Au), tantalum (Ta), etc. is formed on this using methods such as electron beam evaporation or sputtering, and selective etching is performed using photolithography to create a conductor consisting of a fine pattern. forming a railway line.

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 created by screen printing, and the conductor line is formed by firing the pattern.

When the circuit becomes complex and requires multi-layering, the thick film method is mainly used, in which conductive paste is screen printed on unfired ceramic green sheets, then laminated while positioning and pressurized. A multilayer circuit board is made by firing and integrating the two.

However, it has not yet been put to practical use to form a multilayer circuit board using superconducting ceramics as conductor lines instead of metal vapor deposition films or conductor pastes.

[Problem to be solved by the invention]

Various types of oxide superconducting materials have been developed in terms of composition, including indium (Y), barium (Ba), copper (Cu), and oxygen-based ceramics (which the inventors are currently working on). In order to obtain superconducting properties for Y BazCu+ Oq-'a), it is necessary to adjust the atmosphere during firing, so as in the past, an electronic circuit pattern is printed on a green sheet, dried, and then laminated and fired. death,
It is difficult to adopt an integrated method.

Therefore, when creating multiple layers, each ceramic board is printed and fired and then laminated, but in this case, the thickness increases by the amount of conductor lines patterned on the board. In both cases, the substrates are warped, so when stacking them, there is a problem that the wiring connection between the via-hole formation position and the conductor line on the underlying substrate cannot be sufficiently established.

[Means to solve the problem]

The above problem involves printing superconducting paste on a ceramic substrate with holes drilled at the via formation positions, filling each hole with the paste and sealing it, then printing conductor lines on this substrate, drying it, and then firing it. A step of forming a unit ceramic circuit board, a step of further printing superconducting paste at the via formation position of this ceramic circuit board to form a pad pattern, and a step of placing spacers around the periphery of this ceramic circuit board and determining the position. This problem can be solved by combining a plurality of ceramic circuit boards, stacking them, drying them under pressure, removing the spacers, and then baking them in an oxidizing atmosphere to integrate them.

[Effect]

Rare earth elements -Ba-C, which the inventor is conducting practical research on
The problem with forming a u-0 system, for example, a Y-Ba-Cu-0 system superconducting circuit, is that a conductor paste is made using superconducting ceramics, and a pattern is formed using this by a method such as screen printing. When firing the substrate to form conductor lines, the organic solvent and binder contained in the paste are decomposed by heating, and at this time, the oxides that are the constituent materials of superconducting ceramics are reduced and YBa2Cu
The problem is that ceramics having a composition ratio of 30 t-a cannot be obtained.

To achieve this, firing in an oxidizing atmosphere is necessary, but when superconducting pastes are screen printed and laminated, oxygen (Ot) is poorly supplied, making it difficult to form superconducting ceramics.

Therefore, in the present invention, superconducting conductor lines are formed in advance for each board forming a multilayer wiring board.

Next, a band is provided in the via portion that vertically connects each wiring board to the circuit, and the band is raised above the board.

If you align the substrates and apply pressure after laminating them,
The connection of the via portion is sufficient, and since the pad portion has a gap around it and the supply of 0□ is sufficient, the pad portion can be made of superconducting ceramic.

In this way, each layer of the multilayer wiring board is connected at the via position, and there are gaps between them, but this configuration is advantageous in terms of high frequency characteristics.

That is, when using an alumina substrate, the dielectric constant is approximately 1.
0, and cross-talk tends to occur between wirings located above and below the alumina substrate, but the presence of the air layer has the secondary effect of preventing this.

〔Example〕

A superconducting ceramic having a composition of YBazCuzOt-a was formed by a conventional method, and then pulverized using a disintegrator and a ball mill, and sized to obtain fine particles with an average particle size of 2 to 3 μm.

Terpineol, methyl ethyl ketone, and acetone were used as organic solvents, and polyvinyl butyral (abbreviated as PVB) was used as a binder, and the viscosity was 2.
A superconducting paste with 000 voids (Ps) was formed.

Next, prepare an alumina substrate with a size of 10 cm square and a thickness of 0.65 m, and use a YAG (yttrium aluminum garnet) laser to create a via formation portion with a diameter of 0.65 m.
The required number of sheets with 2 m holes were prepared.

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

Then, in a mixed atmosphere of argon (Ar) and 02
After baking at 00°C for 30 minutes, it was subsequently baked at 9°C in the same atmosphere.
Annealing was performed at 00° C. for 1 hour to form a superconducting line.

Here, the purpose of annealing is to adjust the value of d in the molecular formula of YBa2CuzOy-a.

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

Next, polyester spacers having a thickness of 50 μm were placed on each of the four corners of the substrate where no pattern was formed, and the layers were laminated while being aligned, and dried under pressure.

Next, after removing the spacers at the four corners, the same conditions were used as before, i.e., at 1000°C in a mixed atmosphere of Ar and 02.
After baking for 0 min, it was subsequently baked at 900°C for 1 min in the same atmosphere.
Annealing was performed over a period of time to form a superconducting pattern.

In the multilayer circuit board created in this way, with gaps between the boards, the unevenness of each board is absorbed by the via parts, and the connection is perfect, and the pads in the via parts are also sufficiently supplied with oxidizing gas. This made it possible to obtain superconducting ceramics similar to conductor lines.

〔Effect of the invention〕

By carrying out the present invention, a superconducting multilayer wiring board having a superconducting transition temperature (T) of about 80 can be obtained, and by using the multilayer circuit board thus obtained, HEMT
, it has become possible to fully demonstrate the performance of semiconductor devices used at the temperature of liquid N2, such as RHET and Josephson devices.

Claims (1)

[Claims] Printing a paste containing an oxide superconducting material as a component on a ceramic substrate with a hole formed at a via formation position, filling the hole with the paste and sealing it, and then printing a conductor pattern on the substrate and drying it. and then firing to form a unit ceramic circuit board; further printing a paste containing an oxide superconducting material as a component at the via formation position of the ceramic circuit board to form a pad pattern; A process of arranging spacers around the periphery of the ceramic circuit board, stacking a plurality of ceramic circuit boards while aligning them, and drying them under pressure; and after removing the spacers, firing in an oxidizing atmosphere. A method for manufacturing a superconducting circuit board, comprising: a step of integrating;