JPS63299195A - Manufacture of superconducting printed substrate - Google Patents

Abstract

PURPOSE:To easily obtain a substrate having excellent bondability of a circuit to the substrate and to increase the substrate by flame spraying ceramic superconducting substance powder to a metal plate to form a circuit pattern, placing a prepreg in contact with a ceramic flame sprayed layer formed thereon to be thermally pressure molded, and removing the plate. CONSTITUTION:An aluminum masking plate 2 in which a circuit pattern is scooped out is abutted on the surface of an aluminum plate 1, and yttrium- barium-copper oxide powder is flame sprayed on the plate 1 to form a flame sprayed layer, the plate 2 is removed, alumina is flame sprayed on the whole surface to form an alumina flame sprayed layer 4. Then, it is thermally pressure molded integrally with a glass cloth base epoxy resin prepreg 5 in a laminated structure, the plate 1 is then exfoliated from the molding to be removed. The ceramic superconducting substance powder can also use yttrium-strontiumcopper oxide, and the flame sprayed metal plate can use copper, iron, nickel, aluminum, stainless steel, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a novel printed circuit board in which a circuit is formed using a ceramic superconducting material.

[Conventional technology]

Printed circuit boards include plastic substrates such as paper-based phenolic resin laminates, glass cloth-based epoxy resin laminates, glass cloth-based polyimide resin laminates, alumina, and PEIJ 9.
Mainly used are ceramic substrates such as silicon carbide, aluminum nitride, steatite, and glass ceramics, or metal bases and metal core substrates in which an insulating layer is provided on the surface of a metal plate such as aluminum or iron. Metals or alloys such as copper, nickel, palladium, molybdenum, tungsten, gold, and silver are used for the conductor layers formed on these substrates.

[Problem that the invention seeks to solve]

However, in recent years, there has been significant progress in improving the performance of electronic devices, and in particular, in order to enable high-density mounting of components, it is important to consider how to dissipate the heat generated by components, or how to reduce the heat generated by the resistance of conductor circuits. The big question is how to hold it down. Furthermore, there is a strong demand for faster signal transmission in computers and the like, and in particular, signal delays due to electrical resistance of conductive circuits account for a large proportion.

Therefore, there are great expectations for lowering the resistance of the conductor layer.

Superconducting materials can be considered as materials suitable for such requirements. A superconducting material is a material whose electrical resistance becomes zero below a certain critical temperature, and the development of ceramic-based superconducting materials has been remarkable recently. When oxides etc. reach a critical temperature of 30 to 40, liquid helium (boiling point 4K)
), is known to exhibit superconductivity in liquid hydrogen (boiling point 20K). However, recently, yttrium-barium-copper oxide or yttrium-strontium-
It is known that copper oxide has a critical temperature of 80-90K,
It has attracted much attention because it can be used in liquid nitrogen (boiling point 77K). If these superconducting materials are used as conductor circuits in printed circuit boards, it is possible to solve the current problems of delay in signal transmission due to the electrical resistance of the conductor layer or heat generation due to the resistance.

Generally, the method of forming a conductive circuit on a substrate using such a superconducting material is to print a circuit pattern on the surface of the ceramic substrate before or after firing the ceramic substrate by adding a binder to the superconducting material powder. One possible method is to fire it. However, such methods have various problems. First, since a ceramic substrate is used as the substrate, it is not possible to increase the size. This is because the ceramic substrate is brittle and shrinks greatly during firing. The second problem is the dimensional accuracy of the circuit. That is, the ceramic substrate or circuit portion shrinks during the firing process. Therefore, a circuit pattern must be formed taking this into consideration. Furthermore, the temperature, time, etc. during firing must be accurately controlled, making the process complicated. Furthermore, there is a risk that cracks may occur in the conductor circuit due to shrinkage during firing, and reliability also becomes a problem.

On the other hand, if a plastic substrate is used as the substrate instead of a ceramic substrate, it is possible to increase the size of the substrate. However, since plastic substrates have poor heat resistance, they cannot undergo a firing process at high temperatures like ceramic substrates.

The present invention improves these drawbacks and provides a method for forming a conductor circuit using a superconducting material on a plastic substrate.

[Means for solving problems]

That is, in the present invention, a circuit pattern is formed by thermally spraying ceramic superconducting material powder onto a metal plate, and then electrically insulating ceramic is further thermally sprayed onto the circuit pattern. Next, a prepreg is placed so as to be in contact with the electrically insulating ceramic sprayed layer, and after hot press forming, the metal plate is removed.

As the ceramic superconducting material powder, LiTi1O,
Ba (Pb@Bi) O,, PbMOs8m, LaB
5. , lanthanum-barium-copper oxide, yttrium-
Barium - copper oxide, yttrium - strontium -
Copper oxide, etc. can be used, but currently yttrium-strontium-copper oxide or yttrium-barium-copper oxide has a high critical temperature (80 to 90
K) is suitable because inexpensive liquid nitrogen can be used as a cryogen.

The metal plate to which ceramic superconducting material powder is sprayed is made of copper, iron, nickel, aluminum, stainless steel, or other metals or alloys, and the thickness can be arbitrarily selected from a thin box-like plate to a thick block-shaped plate. can.

Furthermore, in order to form a circuit pattern by thermally spraying ceramic superconducting material powder, it is necessary to mask the parts of the metal plate that is the object to be thermally sprayed, other than the part where the circuit pattern is to be formed. This mask.

A method of thermal spraying is carried out by placing a masking plate with holes in the same shape as the circuit pattern on a metal plate such as aluminum, copper, iron, or stainless steel, and then spraying from above. A method can be used in which a dry film resist or photoresist mask used for copper foil etching of a substrate is formed on a metal plate to be thermally sprayed, thermal spraying is performed thereon, and the resist is removed using a solvent after thermal spraying.

Further, in the present invention, an electrically insulating ceramic is sprayed on the ceramic superconducting material sprayed layer side of the metal plate onto which the ceramic superconducting material has been sprayed. This is to reduce the difference in thermal expansion between the plastic layer and the superconducting material circuit layer to be formed in the next step, improve adhesion, and prevent cracks in the circuit due to thermal shock. As electrically insulating ceramics, zirconia, silica, mullite, spinel, cordetite, etc. are used in addition to the proven alumina, which is most often used as a ceramic substrate. The electrically insulating ceramic sprayed layer may be formed on the entire surface of the metal plate on the side of the superconducting material sprayed layer or only on a necessary portion.

Note that the superconducting effect can be further increased by subjecting the sprayed ceramic superconducting material layer to heating and slow cooling treatment prior to molding with the prepreg. In addition, the thermal spraying methods used for general ceramic thermal spraying, such as gas thermal spraying, plasma thermal spraying, explosive thermal spraying, water plasma thermal spraying, and low-pressure plasma thermal spraying, are applied to thermal spraying of ceramic superconducting materials and electrically insulating ceramics. can.

Prepreg, which is placed in contact with an electrically insulating ceramic sprayed layer and then hot-press molded, is made of paper, thermosetting resin such as epoxy resin, polyimide resin, phenol resin, melamine resin, unsaturated polyester resin, or vinyl ester resin. A B-stage material obtained by impregnating a fiber base material such as glass fiber, Kepler fiber, or quartz fiber is used.

After hot-pressing the prepreg, the plastic substrate, which has a circuit made of a ceramic superconducting material and an electrically insulating ceramic layer on its surface, can be easily peeled off from the metal plate due to the difference in adhesion between the two. That is,
The adhesion between the metal plate and the ceramic superconducting material sprayed layer and the electrically insulating ceramic sprayed layer can be determined by not performing a blast treatment on the metal plate that is the object to be sprayed before thermal spraying, or by performing it very lightly, or by applying a mold release agent. It can be made smaller by coating it in advance.

On the other hand, the adhesion between the ceramic superconducting material layer and the electrically insulating ceramic sprayed layer is affected by the fact that the surface of the ceramic superconducting material layer, which is the object to be sprayed, is rough because it is formed by thermal spraying. When electrically insulating ceramics are thermally sprayed, a large anchoring effect can be obtained. Similarly, the adhesion between the electrically insulating ceramic sprayed layer and the plastic layer is also affected by the fact that the surface of the electrically insulating ceramic sprayed layer is rough and the adhesion area is large, and the resin of the prepreg flows and solidifies during hot press molding. This is good because it acts as an adhesive. Therefore, when the metal plate is peeled off after hot-press molding, the ceramic superconducting material sprayed layer and the electrically insulating ceramic sprayed layer are easily transferred to the plastic layer side. If the metal plate is box-shaped or otherwise thin, an effective method is to remove it with an etching solution used for etching copper foil on printed circuit boards, in addition to the method of peeling it off.

Additionally, the electrically insulating ceramic sprayed layer can be formed on only one side of the plastic substrate, but if warping occurs due to the difference in thermal expansion, it can be prevented by forming it on both sides of the plastic substrate using the same method. .

[Effect]

In forming a circuit using ceramic superconducting material on a plastic substrate as in the present invention, ceramic superconducting material powder is sprayed onto a metal plate to form a circuit pattern, and electrically insulating ceramic is sprayed on top of the circuit pattern to form a prepreg. By the method of removing the metal plate after hot-pressing, it is possible to easily obtain a board with excellent adhesion between the circuit and the board.

When attempting to form a circuit using a ceramic superconducting material on a plastic substrate, it is impossible to use a paste coating method because the plastic cannot withstand the high temperatures of the firing process. Further, in the OVD method and the PVD method, there are restrictions on the types of ceramic superconducting materials that can be used, and there are also restrictions on the size of the substrate on which circuits can be formed due to the size of the device.

In addition, productivity is poor because the film formation rate is slow.

Compared to these methods, thermal spraying has a faster film formation rate and superior productivity. However, when the object to be thermally sprayed is plastic, sufficient adhesion cannot be obtained because it has poor affinity with ceramics. However, instead of spraying directly onto the plastic substrate as in the present invention, the method involves first spraying onto a metal plate, then heat-pressing it so that it comes into contact with the prepreg to integrate it, and then removing the metal plate. It has the following advantages:

The first is that extremely high adhesion can be obtained. This is because the surface of the sprayed layer is rough and has a large adhesion area, making it easy to obtain an anchor effect. This is also because the resin of the prepreg flows due to heat and pressure during hot-press molding, thereby acting as an adhesive to the thermally sprayed layer. The second is the surface of the obtained substrate, i.e.
The surface of the circuit layer and the electrically insulating ceramic layer made of a ceramic-based superconducting material is a transfer of the surface condition of a metal plate, so that a smooth surface can be obtained. Thirdly, by providing an electrically insulating ceramic layer between the circuit layer made of ceramic superconducting material and the plastic layer, defects such as cracks and peeling due to the difference in thermal expansion between the circuit and the plastic layer can be prevented. The point is that it can be done.

In addition to the above-mentioned advantages, if the thermal spraying method is applied, there is no limit to the size of the substrate. Furthermore, since a conventional glass cloth-based epoxy resin laminate or glass cloth-based polyimide resin laminate can be used as the substrate, there is no size restriction as in the case of using a ceramic substrate.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a sectional view showing a state where an aluminum masking plate 2 from which a circuit pattern has been cut out is brought into contact with the surface of an aluminum plate 1.

A powder of yttrium-barium-copper oxide was sprayed onto the aluminum plate 1 with the masking plate 2 in contact using a plasma spraying device to form a sprayed layer. After removing the masking plate 2, alumina is sprayed onto the yttrium-barium-copper oxide sprayed layer 3 and the yttrium-barium-copper oxide sprayed layer 3 side of the aluminum plate 1 using a plasma spraying device to form an alumina sprayed layer 4. A structure shown in FIG. 2 was obtained.

Next, this was heat-press molded and integrated with the glass cloth base epoxy resin prepreg 5 in the laminated structure shown in FIG.

After the molding was completed, the aluminum plate 1 was peeled off and removed from the molded product to obtain a printed circuit board having the configuration shown in FIG.

The thus obtained printed circuit board has a circuit 3 made of yttrium-barium-copper oxide on the surface of a glass cloth base epoxy resin laminate 6 with an alumina sprayed layer 4 interposed therebetween.

When this printed circuit board was placed in liquid nitrogen, the circuit made of yttrium-barium-copper oxide showed superconductivity. Furthermore, the adhesion between the circuit and the alumina sprayed layer, and between the alumina sprayed layer and the glass cloth base epoxy resin layer was good, and no abnormalities such as peeling or cracking were observed even after immersion in liquid nitrogen.

〔Effect of the invention〕

As described above, according to the method of the present invention, formation was conventionally possible only on a ceramic substrate. A circuit made of superconducting material can be formed on a generally widely used plastic substrate, and its adhesion is also good.

Therefore, productivity is better and cheaper than conventional methods, and it is easy to increase the size of the substrate. The printed circuit board obtained in this way has little loss in signal transmission and extremely little heat generated by the circuit due to electrical resistance, so it is extremely useful for applications that require high speed and high density, such as high-speed computers.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the circuit pattern portion (a hollowed-out masking plate is brought into contact with an aluminum plate, and Fig. 2 is a cross-sectional view showing the circuit pattern portion (hollowed out) in contact with the aluminum plate.
FIG. 3 is a cross-sectional view showing a state where the masking plate has been removed and alumina has been thermally sprayed, FIG. 3 is a laminated configuration diagram of thermo-press molding with prepreg, and FIG. 4 is a cross-sectional view of a printed circuit board obtained by the present invention. Explanation of symbols 1... Aluminum plate 2... Masking plate 3.
...Yttrium-barium-copper oxide sprayed layer 4...
Alumina sprayed layer 5...Glass cloth base material Epoxy resin prepreg No. +il Fig. 2 Fig. 4rllJ

Claims (1)

[Claims] 1. A first step of spraying ceramic superconducting material powder onto a metal plate to form a circuit pattern; spraying an electrically insulating ceramic on the ceramic superconducting material sprayed layer side to form a ceramic sprayed layer; The second step is to form a prepreg in contact with the ceramic sprayed layer, and the third step is to heat-press and integrate the prepreg.The metal plate is removed and a ceramic insulating layer and a superconducting material circuit pattern are formed on the plastic substrate. A method for manufacturing a superconducting printed circuit board comprising a fourth step of transferring. 2. The method for manufacturing a superconducting printed circuit board according to claim 1, wherein the ceramic superconducting material is made of yttrium-barium-copper oxide or yttrium-strontium-copper oxide. 3. The method for manufacturing a superconducting printed circuit board according to claim 1, wherein the electrically insulating ceramic is mainly composed of alumina.