JPH0269994A - Ceramic superconductive multilayer wiring board and manufacture of the same - Google Patents

Abstract

PURPOSE:To obtain a multilayer wiring board suitable for use in which a ceramic superconductor is used as a conductor of a wiring circuit by joining and laminating boards using the contact of a ceramic superconductor. CONSTITUTION:Ceramic superconductor paste is screen-printed on the surface of a ceramic board 1 and through-holes 2, 3. A plurality of boards 1 are piled one on another and heat-treated in a state in which paste is in contact with other board 1. As a result, a ceramic superconductor is sintered. An in-door wiring 4 and through-hole wirings 5, 6 are formed and the section between the boards 1 is jointed to the wiring 4. The wiring 5 connects the section between layers and the wiring 6 connects all layers. Next, an electrode 7 and a coating layer 8 are provided and the gap caused at sintering time is filled with a filler 9. With this arrangement, since ceramic superconductor paste forms a superconductive wiring having excellent contact by sintering, a multilayer wiring board can be manufactured in which a ceramic superconductor is used as a conductor of a wiring circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is applied to hybrid integrated circuits. In particular, it relates to a multilayer wiring board using ceramic superconductors.

〔overview〕

The present invention provides a multilayer wiring board using a ceramic superconductor, which uses the adhesive properties of the ceramic superconductor to bond and laminate the boards, thereby making the ceramic superconductor suitable for use as a conductor in a wiring circuit. The present invention provides a structure of a multilayer wiring board and a method for manufacturing the same.

[Conventional technology]

BACKGROUND ART With the miniaturization of electronic devices, wiring boards are becoming smaller and more dense, and in addition to increasing the wiring density within the board, multilayer wiring boards in which a large number of wirings are laminated are being developed.

Under these circumstances, in order to further increase the wiring density of the multilayer wiring board, it is necessary to extremely miniaturize the wiring circuit conductors. In this case, a major problem is how to suppress loss and heat generation due to the resistance of the circuit conductor.

In order to solve these problems, multilayer wiring boards using superconducting materials have been considered. A superconducting material is a material whose electrical resistance becomes zero at a specific temperature. The temperature at which electrical resistance becomes zero is called the superconducting critical temperature. In particular, the use of ceramic superconductors that exhibit superconductivity at liquid nitrogen temperatures is expected.

Ceramic superconductors include oxides containing alkaline earth elements, one or both of yttrium and lanthanide elements, and copper; one or both of bismuth and lead, strontium, calcium, and copper as constituents. Oxides containing thallium, barium, calcium and copper as constituents; oxides containing barium, one or both of potassium and lead, and bismuth are known. If these superconductors are used as conductors in multilayer wiring circuits, it will be possible to miniaturize the wiring circuit conductors, which are currently a problem, and it will also be possible to solve various problems caused by signal current loss and heat generation due to electrical resistance. It is expected that

[Problem that the invention seeks to solve]

Conventionally, green sheet lamination methods, printed lamination methods, and thick film multilayer methods have been used as methods for manufacturing multilayer wiring boards.

Green sheet lamination method and printed lamination method involve firing the ceramic substrate and baking the conductor at the same time.
It is necessary to bake at around 1500 to 1600°C. In contrast, ceramic superconducting materials melt at temperatures above 1000°C. Therefore, it is not possible to manufacture a ceramic superconductor multilayer wiring board using these methods.

In addition, in the thick film multilayer method, an insulating layer is formed using dielectric paste, but if ceramic superconductor paste and dielectric paste are fired at the same time, they will react.
The drawback was that superconducting properties were lost. To avoid this reaction, it is also conceivable to print and fire the ceramic superconductor paste and dielectric paste separately.

However, the firing temperature of ceramic superconductors is 850° C. or higher, which is higher than that of dielectrics, and it is difficult to stack them.

An object of the present invention is to provide a structure of a multilayer wiring board suitable for using a ceramic superconductor as a conductor of a wiring circuit, and a method for manufacturing the same.

[Means for solving problems]

The ceramic superconductor multilayer wiring board of the present invention is characterized in that adjacent boards in a laminated structure are bonded using ceramic superconductor wiring as a bonding layer.

It is preferable that the gap between the substrates contains a filling material of an inorganic or organic substance, and it is preferable that the surface is coated with an inorganic or organic substance. This increases the adhesive strength between the substrates, prevents deterioration of the superconductor due to reaction with moisture or carbonated water, and improves stability against the environment. However, it may be desirable to leave a gap between the substrates due to mechanical strength or dielectric constant within the substrate.

To manufacture such a ceramic superconductor multilayer wiring board, a ceramic superconductor paste is screen printed on the surface of the board and through holes, and multiple boards obtained by this process are printed on each surface. The ceramic superconducting paste is stacked in contact with another substrate and heat treated. A sintered ceramic substrate is used as the substrate. A green sheet may be used as the ceramic substrate if it does not react with the ceramic superconductor during firing.

In the heat treatment process, it is desirable to perform the firing and heat treatment in an oxygen cloud atmosphere.

When screen printing, it is desirable to print ceramic superconductor paste in the same pattern on opposite sides of substrates that are stacked adjacent to each other.

Ceramic superconductor pastes are produced by mixing powders of ceramic superconductor materials, powders of metals or their oxides, organic binders, and solvents. The powder of a metal or its oxide includes one or more metals selected from the group consisting of gold, silver, platinum, and palladium, or an oxide thereof, in an amount of 0.1 to 50% by weight based on 100% of the ceramic superconductor material. mixed in the proportion of 50%.

Ceramic superconductor material powders used in the ceramic superconductor paste include: ■ oxides containing alkaline earth elements, one or both of yttrium and lanthanide elements, and copper; ■ oxides containing bismuth and lead. Oxide containing one or both of strontium, calcium and copper; ■ Oxide containing thallium, barium, calcium and copper; ■ Barium, one or both of potassium and lead, and bismuth as constituents. Oxides such as oxides are suitable.

The substrate is preferably one that has low reactivity with the superconductor contained in the ceramic superconductor paste, for example, one whose main component is at least one ceramic material selected from zirconium oxide, magnesium oxide, and strontium titanate. .

In addition, a material that suppresses the reaction with the superconductor, such as a film of the above-mentioned ceramic material, or a film of gold, silver, platinum, or other metal, is formed partially or on the front surface of the alumina or other ceramic substrate or metal substrate. Something is desirable.

Organic binders for producing ceramic superconductor paste include ethyl cellulose, 2) cellulose and other cellulose resins, polymethyl methacrylate and other acrylic resins, alkyd phenol resins, vinyl resins, and epoxy resins. Any other material may be used as long as it undergoes thermal decomposition easily in the firing atmosphere.

As for the solvent used for pasting, one with excellent printability is suitable, and carpitol acetate, terpineol, and others are usually used. However, any solvent may be used as long as it has printability.

Filling substances filling the gaps between the substrates and materials for coating the surfaces include borosilicate glass, crystallized glass and other glass materials, gold, silver, platinum, palladium and other metals and alloys containing these, wax, It has a low reaction with superconducting materials such as polyester resin, phenolic resin, epoxy resin, polyimide resin, fluororesin, and other organic materials, is airtight, and does not crack when the temperature changes between liquid nitrogen temperature and room temperature. Materials that do not cause this are suitable. The suitable thickness of the coating film is approximately 1 to 100 μm, but it may be thicker if no cracks or the like occur.

[For production]

When fired, the ceramic superconductor paste forms superconductor wiring with excellent adhesiveness to the substrate. In particular, a ceramic superconductor paste mixed with metal or its oxide can form superconductor wiring with high adhesive strength. Therefore, superconducting wiring obtained from this ceramic superconductor paste is used as a bonding layer between substrates.

Since each layer is not bonded by the substrate itself,
There is no need to sinter the substrate, and a sintered ceramic substrate can be used as the substrate, and reaction between the superconductor material contained in the ceramic superconductor paste and the substrate can be prevented. Furthermore, since a fired ceramic substrate is used, the margin required for alignment of multilayer wiring patterns can be reduced, and high-density packaging with small wiring intervals is possible.

Furthermore, if ceramic superconductor paste is printed in the same pattern on opposing surfaces of the substrates, the bond between the substrates will be further strengthened.

〔Example〕

The figure is a sectional view of a ceramic superconductor wiring board according to an embodiment of the present invention.

This wiring board includes a plurality of (three in this embodiment) ceramic substrates 1 stacked on each other, ceramic superconductor wiring formed in the surface and through hole 2.3 of each of the plurality of ceramic substrates 1, That is, the ceramic substrates 1 having the intralayer wiring 4 and the through-hole wirings 5 and 6 and adjacent to each other in a laminated structure are bonded using the intralayer wiring 4 as a bonding layer.

The gaps between the ceramic substrates 1 are filled with a filler material 9, and a coating layer 8 is provided on the surface of the ceramic superconductor multilayer wiring board. Furthermore, electrodes 7 are provided on both surfaces.

To manufacture this ceramic superconductor wiring board, a ceramic superconductor paste is screen printed on the surface of the ceramic substrate 1 and the through holes 2.3, and a plurality of ceramic substrates 1 thus obtained are printed on each surface. The printed ceramic superconducting paste is stacked in contact with another ceramic substrate 1 and heat treated.

This manufacturing method will be explained in more detail.

First, a fired ceramic substrate 1 with through holes 2.3 provided at desired positions is prepared, and wiring patterns are printed on both sides of the substrate using ceramic superconductor paste. At this time, the through hole 2.3 is filled with ceramic superconductor paste. Here, the position of the through hole 2 is different for each ceramic substrate l, and the position of the through hole 3 is different for every ceramic substrate l.
is the same for

Next, the ceramic substrates 1 are stacked so that the surfaces with matching wiring patterns face each other, and fired in a furnace with their ceramic superconductor pastes in contact with each other. As a result, the superconductor is sintered, and the intralayer wiring 4 and the through-hole wiring 5 and 6 are formed, and the ceramic substrates 1 are joined by the intralayer wiring 4. Through-hole wiring 5 connects layers, and through-hole wiring 6 connects all layers.

Subsequently, electrodes 7 and coating layers 8 are provided on both surfaces of the ceramic superconductor wiring board, and gaps created during sintering are filled with filler material 9. The coating layer 8 and the filling substance 9 are made of glass or other inorganic material, resin or other organic material, and are made of printing,
Formed by depth molding or other methods. Depending on the material, it is fired at a low temperature. The coating layer 8 and the filling material 9 increase the adhesive strength of the ceramic substrate I, and protect the surface from moisture and carbonated water.

Next, an example of specific manufacturing data will be shown.

(1) Barium carbonate BaCO3 and diythtrium trioxide Y2O as starting materials for ceramic superconductor paste
A ceramic superconductor was obtained by mixing them using No. 3 and cupric oxide Cu, and performing the usual ceramic manufacturing procedures, that is, calcination, pulverization, granulation/molding, and firing. Calcination and firing were performed in the air, and after heating at 925° C. for 20 hours, cooling was performed at a rate of 50° C./hour.

Regarding the ceramic superconductor obtained in this way,
Using zirconia balls, the powder was ground for 10 hours in ethanol under a dry nitrogen gas atmosphere to obtain a ceramic superconductor material powder with an average particle size of 1 μm. To this powder, 30 parts by weight of silver oxide powder (particle size: 0.5 μm) was mixed.

Ethyl cellulose, butylbenzyl phthalate, and terpineol were mixed with this mixed powder, and the mixture was mixed using a crusher.

(2) Ceramic substrate The ceramic substrate 1 is made of zirconia and has a thickness of 0.5
mm was used.

(3) Firing The ceramic substrates 1 on which wiring patterns were printed using the ceramic superconductor paste of (1) were stacked, placed in a furnace, and heated in oxygen at 985° C. for 3 minutes. As a result, the superconductor is sintered, and the intralayer wiring 4 and the through-hole wiring 5.6
was formed, and the ceramic substrates 1 were joined by the intralayer wiring 4.

(4) Electrode, coating layer, and filler material Electrode 7 and coating layer 8 are formed by a printing method using conductor paste and glass paste, and further, the end of the multilayer wiring board is immersed in glass paste and filled with filler material 9. did. This was fired in oxygen at 500°C.

(5) Print a ceramic superconductor paste with bonding strength (1) for intralayer wiring on a zirconia ceramic substrate under the same conditions as (3) and fire it.
When the adhesion strength of the obtained thick film was measured, it was 5 kg・
A high value of f/mm2 or more was obtained. This value is sufficiently larger than the thick film adhesive strength standard of 1.5 kg-f/mm<2>, and the ceramic substrate 1 can be bonded sufficiently firmly. However, such adhesion strength could not be obtained when no metal or its oxide was mixed into the ceramic superconductor paste.

A ceramic superconductor multilayer wiring board was fabricated using the above manufacturing data, and the temperature was repeatedly changed between liquid nitrogen temperature and room temperature, but no changes in the coating condition, cracks, cracks, or other changes on the surface were visually observed. Ta.

〔Effect of the invention〕

As explained above, the present invention has the effect of making it possible to manufacture a multilayer wiring board using a ceramic superconductor.

Further, since the substrates of each layer are bonded to each other by the ceramic superconductor wiring, and the layers are not bonded by the substrate itself, there is no need to bake the substrate. Therefore, there is an advantage that the ceramic superconductor can be manufactured at a relatively low temperature at which it is sintered. Furthermore, since a ceramic substrate after firing can be used, it is possible to prevent a reaction between the superconductor substance contained in the ceramic superconductor paste and the substrate, and it is possible to obtain excellent superconducting properties.

Furthermore, since we use a ceramic substrate after firing,
This has the effect of reducing the margin required for alignment of patterns in multilayer wiring, and enabling high-density packaging with small wiring intervals.

[Brief explanation of the drawing]

The figure is a sectional view of a ceramic superconductor multilayer wiring board according to an embodiment of the present invention. 1... Ceramic substrate, 2.3... Through hole, 4...
・Intralayer wiring, 5.6... Through-hole wiring, 7... Electrode,
9...Covering layer, 9...Filling substance. Patent applicant Mitsubishi Mining Cement Co., Ltd. Representative Patent attorney Naotaka Ide

Claims (7)

[Claims] 1. In a ceramic superconductor multilayer wiring board comprising a plurality of substrates stacked on each other and ceramic superconductor wiring formed in the surfaces and through holes of each of the plurality of substrates, the substrates are adjacent to each other in the stacked structure. A ceramic superconductor multilayer wiring board, characterized in that the above-mentioned ceramic superconductor wiring is bonded as a bonding layer. 2. The ceramic superconductor multilayer wiring board according to claim 1, wherein the surface is coated. 3. A process of screen printing ceramic superconductor paste on the surface of the substrate and through holes, and stacking the multiple substrates obtained through this process in such a way that the ceramic superconductor paste printed on each surface is in contact with the other substrates. A method for manufacturing a ceramic superconductor multilayer wiring board, comprising a step of heat-treating the ceramic superconductor multilayer wiring board. 4. 4. The method of manufacturing a ceramic superconductor multilayer wiring board according to claim 3, wherein the heat treatment step includes a step of firing and heat treatment in an oxygen atmosphere. 5. 4. The method of manufacturing a ceramic superconductor multilayer wiring board according to claim 3, wherein the substrate is a sintered ceramic substrate. 6. 4. The method for manufacturing a ceramic superconductor multilayer wiring board according to claim 3, wherein the ceramic superconductor paste is produced by mixing a powder of a ceramic superconductor substance, a powder of a metal or its oxide, an organic binder, and a solvent. . 7. The metal or its oxide powder contains one or more metals selected from the group consisting of gold, silver, platinum, and palladium or its oxide, and is 0.1 to 50 parts by weight based on 100 parts of the ceramic superconductor material. 7. The method for manufacturing a ceramic superconductor multilayer wiring board according to claim 6, wherein the ceramic superconductor multilayer wiring board is mixed at a ratio of .