JP2644885B2 - Multilayer circuit board - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel multilayer circuit board, and more particularly to a multilayer circuit board for mounting electronic components using a ceramic superconductor.

[Conventional technology]

Conventionally, a ceramic circuit board or an integrated circuit using a ceramic such as Al ₂ O ₃ , MgO, ZrO ₂ as an insulating material and a ceramic superconducting material (Y-Ba-Cu-O system or the like) as a wiring conductor has been obtained. In addition, a composite material in which ceramic superconductor powder is combined with an organic substance has been obtained. JP-A-63-26
No. 3745 discloses a wiring member made of a composite material of a superconducting material and a normal conducting material.

[Problems to be solved by the invention]

Conventionally, ceramic superconducting materials are applied as wiring conductors,
The problem of the electronic material using the insulating material as a ceramic is that the ceramic superconductor has a very high reactivity and easily reacts with the ceramic of the insulating material to lose the superconductivity of the ceramic superconductor. In particular, when manufacturing a ceramic multilayer circuit board, since the appropriate firing temperature of the ceramic superconductor is around 1000 ° C., the insulating material also needs to be sintered at around 1000 ° C. for simultaneous sintering. As a ceramic insulating material that can be sintered at around this temperature, many include borosilicate glass. However, this type of glass has a problem in that it reacts with the ceramic superconducting material and easily loses the superconductivity of the ceramic superconductor. In other words, when ceramic is selected as an insulating material for an electronic component to which a ceramic superconductor is applied, the ceramic insulating material is very limited, which is an obstacle to obtaining an electronic component to which a ceramic superconductor is applied.

An object of the present invention is to provide a multilayer circuit board for mounting electronic components to which a ceramic superconductor having low reactivity with an insulating substrate is applied.

[Means for solving the problem]

The present invention resides in a multilayer circuit board on which a superconductor is mounted as a conductor and an electronic component in which an organic substance is applied to an insulator or a holder in contact with the superconductor.

The reason that it is difficult to apply the ceramic superconducting material to an electronic component is that the ceramic superconducting material has high reactivity with the ceramic and reacts to lose the superconductivity. Therefore, an organic substance was applied as an insulating material in contact with the ceramic superconductor for applying the ceramic superconductor.

Organic matter is generally a good insulator and ceramic and organic matter have little reactivity. Further, the organic material and the ceramic can be bonded relatively firmly. The ceramic superconductor has a relatively large coefficient of thermal expansion in ceramics, but in this regard, organic substances generally have a large coefficient of thermal expansion, and have good compatibility with the ceramic superconductor.

It is sufficient that an organic substance is present in a portion in contact with the superconductor, and it is not necessary to constitute the entire electronic material such as an element or a substrate with the organic substance. That is, almost all may be made of ceramics or metal, and the contact portion may be made of an organic substance.

In addition, in addition to applying an organic material to the insulating layer, the Josephson junction is made of a material that causes the superconductivity of the ceramic superconductor to be lost, for example, a glass containing SiO ₂ and B ₂ O ₃ for about several millimeters. And the superconductivity only in the vicinity of the Josephson junction of the ceramic superconductor may be lost.

The LB method (Langmiure-Blodgett method) or the plasma polymerization method is applied as a method of forming an organic thin film as an insulator at the Josephson junction of the Josephson device. The organic thin film of the Josephson junction of the Josephson device is a monomolecular film or a monomolecular film. It is preferable to use a Josephson element in which a plurality of are stacked.

Further, it is preferable that the thickness of the organic thin film at the Josephson junction of the Josephson element is 5 to 100 °.

In general, when a ceramic superconductor and an organic material are joined, the method of using an organic material has a large thermal expansion coefficient. Therefore, when the ceramic superconductor is cooled in liquid nitrogen after joining, a compressive stress acts on the ceramic and a tensile stress acts on the organic material. This means that tension is applied to an organic substance having high tensile strength and compression is applied to a ceramic having high compression strength, which is preferable in terms of reliability. The organic substance used here may be an organic substance alone or an organic composite material containing a filler such as glass cloth or ceramic powder, and the thermal expansion of the organic substance including this organic composite material and the ceramic superconductor is also included. The coefficient difference is preferably suppressed to about 1 × 10 ⁻⁵ / ° C. or less in consideration of reliability in a heat cycle such as adhesiveness.

The perovskite-type superconductor applicable to the present invention includes Y-Ba-Cu-O-based, Bi-Sr-Ca-Cu-O-based, and Tl-Ba-
Although the Ca-Cu-O system a basic composition, a small amount of alkali metal oxide to the extent other than 5 mol% _{(Li 2 O, Na 2 O} , K 2 O),
Alkaline earth metal oxides (BeO, MgO, CaO, BaO, SrO), rare earth element oxides, and other elements such as Si, B, Al may be contained. The critical temperature of the superconducting material is preferably higher than the boiling point of liquid nitrogen or its electric resistivity is lower than 1 μΩcm.

As a method for producing an organic thin film in contact with a ceramic superconductor, there are methods such as thermal evaporation, molecular beam epitaxy, liquid phase epitaxy, melt epitaxy, ion plating, ion implantation, clustering, in addition to the masking or maskless Langmuir-broetet method. Examples include ion beam, laser sputtering, CVD, vapor deposition, and electrolytic polymerization. It is particularly desirable to expand the organic sheet obtained in this way to improve the crystallinity in order to improve the properties of the superconducting material.

The critical current density of the power supply substrate is preferably 10,000 A / cm ² or more.

[Action]

A ceramic-based superconductor or an organic-based superconductor was used as a conductor, and an organic substance was used as an insulator or a holder in contact with the superconductor. The organic substance does not react with the ceramic-based superconductor or the organic-based superconductor to lose superconductivity. Further, since the organic substance and the ceramic superconductor, and the organic substance and the organic superconductor can be bonded relatively firmly, a multilayer circuit board to which the ceramic superconductor or the organic superconductor is applied can be obtained.

EXAMPLES (Example 1) component as _{MgO, CaO, Al 2 O 3} , B 2 O 3, glass cloth made of SiO ₂ or the like is impregnated with a varnish of uncured epoxy resin,
It was dried in a thermostat to obtain a prepreg sheet. A predetermined number of the obtained prepregs were stacked and bonded by pressing under pressure and heating to produce an epoxy-based organic substrate. In this embodiment, glass cloth is used as the filler, but powder or fiber such as Al ₂ O ₃ or SiO ₂ may be used.

Then partially masked on both surfaces of the organic substrate, using a laser spa ivy _{method, Bi 2 Sr 2 CaCu 2 O} x (x ≒ 8) Bi-Sr-CaCu-O -based with a composition of A perovskite-type ceramic superconductor layer was formed. The thickness is about 5 μm. In this example, a Bi-Sr-Ca-Cu-O-based ceramic superconductor was applied, but in addition, a Y-Ba-Cu-O-based or
A Tl-Ba-Ca-Cu-O-based perovskite superconductor is also applicable. FIG. 1 shows an outline of the epoxy-based organic substrate thus produced. Next, the epoxy-based organic substrate prepared above and a prepreg made of an epoxy resin before curing were alternately pressed and laminated. Further, drilling was performed, and copper plating was performed to form through holes. The multilayer substrate manufactured in this manner was used as a power supply substrate used to supply power to the LSI chip. The power supply board is cooled by liquid nitrogen. Ceramic superconductors did not react with organic substances and did not lose their superconducting properties. The superconductor does not generate heat because the electric resistance is zero. The current flowing through the power supply layer was about 1000A.
The power supply to the power supply board from outside the module is performed by the Cu conductor. The joint between the ceramic superconductor and Cu, if directly joined, generates thermal stress due to the difference in thermal expansion coefficient and impairs reliability, so for the purpose of relaxing thermal stress,
Ceramic superconductor powder and Cu powder were mixed at a ratio of 1: 1 and sintered to produce a composite. Furthermore, this composite was used as a stress relieving material and sandwiched between Cu and the ceramic superconductor. Other materials can be used as the thermal stress relieving material, but such a configuration enables highly reliable connection. FIG. 2 shows an outline of the power supply board manufactured in this embodiment.

(Example 2) An epoxy-based organic substrate was produced in the same manner as in Example 1. Next, a part of the Cu plate having the power supply terminal was removed by etching, and a hole for inserting a pin was formed. Then, a perovskite-type ceramic superconductor layer was formed on the Cu plate using the laser spatter method in the same manner as in Example 1.
Then, in the same manner as in Example 1, prepregs were alternately stacked, and through holes were formed in the organic substrate. The power supply substrate thus manufactured and the module were connected with solder. The power supply board is cooled with liquid nitrogen. The ceramic superconductor did not lose its superconducting properties without reacting with organic substances. Further, the current in the power supply layer does not generate heat because it flows through the superconductor portion having zero electrical resistance. The current in the power supply layer is about 1000A. When the ceramic superconducting layer is formed on the Cu plate as described above, mechanical reliability can be improved. FIG. 3 shows an outline of the power supply board manufactured in this embodiment.

(Example 3) An epoxy-based organic substrate was produced in the same manner as in Example 1. Next, a Cu plating with a thickness of about 5 μm was formed on almost the entire surface except for a part of both surfaces of the substrate. Furthermore, C on both sides by CVD method
A Bi-Sr-Ca-Cu-O-based ceramic superconductor was formed on the u film to a thickness of about 10 µm by a CVD method. The structure of the ceramic superconductor is that of Bi ₂ Sr ₂ CaCu ₂ O _x (x ≒ 8) or Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _x (x ≒ 10). Next, a power supply substrate was manufactured in the same manner as in Example 1. Since a ceramic superconductor is a brittle material, when a mechanical tensile stress is applied due to an impact or the like, a problem such as disconnection may occur. However, when Cu is used as the protective film of the ceramic superconductor as in the present embodiment, the reliability against disconnection and stabilization of characteristics is improved.

(Example 4) In the same manner as in Example 1, an organic substrate composed of a fluorine resin containing fluorine and an SiO ₂ glass cloth was produced. Next, the surface of this resin was treated with an alkali metal such as sodium metal to obtain Cu plating. Further, a Cu wiring was formed in a predetermined wiring pattern by etching. Next, masks are applied to both sides of the substrate, and Y-Ba-
A Cu-O-based ceramic superconductor film was formed to a thickness of about 1 μm.
The structure of the ceramic superconductor is YBa ₂ Cu ₃ O _{7_8} (0 <δ <
0.3). After drilling with a drill or laser and treating the inside of the hole with an alkali metal,
I got a hit. Next, the organic substrates thus produced were laminated and pressure-bonded at 380 ° C. to form a multilayer. Further, a hole was drilled, and after the inside of the hole was surface-treated, Cu plating was performed to form a through hole. Then, the organic multilayer substrate was cooled with liquid nitrogen. When the characteristics were measured, the electric resistance of the ceramic superconductor was zero. The electric signal propagated almost without loss because the ceramic superconductor had zero electric resistance.

Similarly, an organic multilayer circuit board was produced using an isomeramine-based resin and a polyimide-based resin as organic substances. When this substrate was further cooled with liquid nitrogen, the ceramic superconductor showed superconductivity in both cases. The electric signal propagated with almost no loss.

(Example 5) A thin-film multilayer circuit board using a polyimide resin as an insulating material and a ceramic superconductor as a wiring conductor was produced.
First, a polyimide layer was applied on the glass ceramic multilayer circuit board which was flattened by glazing, a lift-off layer was applied, a dry etching mask was formed, and then a wiring pattern was formed on the polyimide by dry etching. Furthermore, Bi-
An Sr-Ca-Cu-O-based ceramic superconductor wiring was formed. The structure of the ceramic superconductor is Bi ₂ Sr ₂ CaCu ₂ O _x (x ≒
8) Or Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _x (x ≒ 10).
Further, the lift-off layer was removed. Then, a through hole was formed on this layer using the same method as described above. Next, such an operation was repeated a plurality of times to form a multilayer. The coefficient of thermal expansion of the polyimide insulator was 5.times.10.sup.- ⁶ / .degree. The wiring width is 20 μm, the wiring height is 1 μm, and the wiring pitch is
It was 60 μm. When the substrate thus produced was cooled in liquid nitrogen, the electric resistance of the wiring was zero, indicating superconductivity. Since the electrical resistance was zero, the electrical signal propagated with little loss. FIG. 4 shows an outline of the thin-film multilayer circuit board manufactured in this embodiment.

Example 6 A Josephson junction was formed using a ceramic superconducting material. In this embodiment, the superconducting material is the same as that of Embodiment 2.
In was using Bi-Sr-Ca-Cu- O system used, YBa ₂ Cu
₃ O _{7_8} (0 <δ <0.3) or Tl ₂ Ba ₂ CaCu ₂ O _x (x ≒
8) or Tl-Ba-Ca- such as Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _x (x = 10)
A ceramic superconducting material having a Cu-O-based basic composition is applicable. First, LB is placed on the substrate of ceramic superconducting material.
Tens of meters thick by the method (Langmiure-Blodgett method)
Was formed. As a method for producing an organic thin film, a very thin and uniform film is required, and therefore a thin film forming method by the LB method is preferable. Next, the ceramic superconductor film used above was formed on the organic thin film by a laser sputtering method.
In this embodiment, sodium hadecenylcarboxylate is used as the organic thin film. However, other organic materials having a hydrophilic group and a hydrophobic group such as sodium hadedecynyl phosphate can be applied.

The device thus manufactured was cooled in liquid nitrogen. The ceramic superconductor did not lose its superconducting properties by reacting with organic substances and had an electric resistance of zero. When the current-voltage characteristics were measured, no voltage was generated at both ends of the joined body up to a certain current value, and a voltage was generated at a certain current value or more. That is, a so-called Josephson effect was exhibited. Next, using this element, a magnetic sensor was fabricated from an electromagnetic wave sensor, a minute potential sensor, a Josephson junction, and a ring-shaped wiring. The principle is the same as that of currently available metallic superconductors. That is, it is detected by measuring the electric potential due to the Josephson effect generated at the junction due to magnetism and electromagnetic waves. FIG. 5 shows the principle of the sensor. Electromagnetic waves can be detected from microwaves to optical wavelength bands.

(Example 7) A Josephson junction device including the ceramic superconductor and the organic thin film used in Example 6 was formed in the same manner as in the method manufactured in Example 6. FIG. 6 shows an outline of this element. Further, a logic element using the Josephson junction element was formed. As an organic material for insulating the superconductor, a polyimide resin was used. Next, a tetracyanoquinodimethane-based organic material corresponding to an N-type semiconductor and a tetrathiafulvalene-based organic material corresponding to a P-type semiconductor were joined by vacuum evaporation. Further, a ceramic superconductor was formed on both surfaces of the joined body by a CVD method to produce a diode. In addition, a ceramic superconductor wiring was formed on an organic material, and a storage element utilizing superconducting current was manufactured. Furthermore, an LSI was formed by integrating a large number of the above elements. Furthermore, the operation was confirmed by cooling in liquid nitrogen. When fluorocarbon resin, polyimide, etc. were applied to the organic thin film where the Josephson junction was formed, the relative permittivity of the organic material was changed to that of the conventional inorganic material. Because of the small size, the switching speed is higher than that of the conventional Josephson device.
Further, since the ceramic superconductor is bonded to an organic substance, the characteristics can be stabilized without losing superconductivity due to a reaction or the like. The wiring portions in the LSI other than the elements are formed of the same ceramic superconducting material as that used for the logic elements and the like. Since the insulator that insulates the wiring is an organic material such as polyimide, it has not lost superconductivity. FIG. 7 shows an outline of a wiring portion in the LSI. Since an organic substance has a low dielectric constant, the speed of a signal propagating through a wiring can be increased. The Josephson junction is
In addition to the LB method of this embodiment, it can also be formed by spattering, CVD, vapor deposition or the like of an organic substance such as fluorine resin or polyimide. It is also possible to form a fluorine resin film by plasma polymerization using C ₂ F ₆ gas.

(Example 8) The surface of polyethylene having crystals oriented in one direction by a method such as spreading is treated with an organotitanium compound or the like and CVD is performed.
By the method, a ceramic-based superconducting film was produced. The direction of the crystal of the ceramic-based superconductor forming the ceramic superconducting film on the oriented crystal was uniform, and a ceramic superconductor having a high critical current density was obtained.

Example 9 An organic substrate made of a polyimide resin and SiO ₂ glass cloth was produced in the same manner as in Example 4. Next, tetracyanoquinodimethane (TCNQ) was applied on the substrate, and a wiring pattern was formed using photolithography. Drilling or laser drilling was performed, and the inside of the hole was surface-treated, followed by Pb plating. Next, the organic substrates thus produced were laminated and pressed at 230 ° C. to form a multilayer. After drilling and surface treating the inside of the hole
Pb plating was performed to form through holes. Then, the organic multilayer substrate was cooled with liquid helium. When the properties were measured, tetracyanoquinodimethane showed superconductivity and had zero electrical resistance. Since the electric resistance of tetracyanoquinodimethane, which is an organic superconductor, is zero, the electric signal propagated with almost no loss. Since both the wiring and the insulator are organic substances, the adhesiveness and the reliability against mechanical shock are improved.

〔The invention's effect〕

By using an organic material as an insulating material and applying a ceramic superconductor which exhibits superconductivity at the temperature of liquid nitrogen, a multilayer circuit board for mounting electronic components which is easy to manufacture and which uses the superconductor can be obtained.

In addition, since a superconductor which exhibits superconductivity with liquid nitrogen can be applied, it is not necessary to use liquid helium or the like as in the related art, and it can be used at a higher temperature.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a substrate in which a ceramic superconductor layer is formed on both sides of an organic substrate including a glass cloth. FIGS. 2 and 3 are multilayer circuit boards in which a superconductor is applied to a conductor layer of a power supply substrate. FIG. 4 is a cross-sectional view of a polyimide thin-film multilayer substrate formed by applying a ceramic superconductor as a wiring conductor on a ceramic substrate. FIG. 5 is a circuit diagram showing the principle of the sensor. FIG. 7 is a cross-sectional view of an organic substance applied to a Josephson junction, FIG. 7 is a cross-sectional view of an LSI in which polyimide is used as an insulating material on silicon, and a ceramic superconductor is multilayer-wired, and FIG. FIG. 3 is a cross-sectional view of a module for a large-sized computer to which a multilayer board and a power board are applied. 1 ... ceramic superconductor layer, 2 ... organic material, 3 ... glass cloth, 4 ... ceramic multilayer circuit board, 5 ...
Copper, 6 Stress relief material, 7 Solder, 8 Pin, 9
… Via hole, 10… Glaze layer, 11… Glass ceramics, 12… Copper wiring, 13… Polyimide, 14… Al
N cap, 15… LSI chip, 16… Ceramic superconductor wiring, 17… Al wiring, 18… SiO ₂ insulating film, 19… Silicon semiconductor, 20… Liquid nitrogen, 21… Heat radiator.

Continued on the front page (72) Inventor Hideo Suzuki 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Hironori Kodama 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi Research Laboratory, Hitachi, Ltd. (72 ) Inventor Masahide Okamoto 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-2-113937

Claims (3)

(57) [Claims] 1. A multilayer circuit board comprising an organic insulating substrate and an organic or metal oxide superconducting wiring formed thereon. 2. A fluororesin, phenolic resin, epoxy resin, polyimide resin, isomeramine resin, polyester, polyethylene, polybutadiene, methacrylic resin, acrylic resin, maleimide material, polyvinyl chloride,
Organic crystal or YBa ₂ Cu ₂ O on an organic insulating substrate selected from polypropylene, styrene resin, silicone rubber, diallyl phthalate resin, polyphenylene oxide resin, polysulfone, polyethersulfone, bismaleimide triazine and polyetherimide _{7_8} (0 <δ
<0.3), Bi ₂ Sr ₂ CaCu ₂ O _x , Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _x , Tl ₂ Ba ₂ CaCu
A multilayer circuit board, wherein a superconducting wiring made of a metal oxide selected from ₂ O _x and Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _x is formed. 3. A power supply board, a logic element, a storage element, a diode, an LSI, a magnetic sensor, an electromagnetic wave sensor, a minute potential sensor, a magnet-applied part, an electromagnetic wave generator, and an electromotive force generator used as a module power supply. An electronic device comprising the multilayer circuit board according to claim 1 or 2.