JPH02113588A - Formation of electric circuit - Google Patents

Abstract

PURPOSE:To form an electric circuit having a good accuracy without using a masking plate by a method wherein a metal having a good conductivity is subjected to plasma spray coating on a ceramic substrate formed with grooves to correspond to a wiring pattern in a reduced pressure and the metal having a good conductivity adhered on parts other than the grooves is removed. CONSTITUTION:Grooves 2 to correspond to a wiring pattern are formed in advance on a ceramic substrate 1. Then, after a metal having a good conductivity is subjected to plasma spray coating on the substrate 1 by a plasma spray coating gun 3 in a reduced pressure, the metal having a good conductivity adhered on parts other than the grooves is removed by a grinding wheel to form an electric circuit. As the flame spraying is executed in a reduced pressure in such a way, the adhesion of the substrate with the metal having a good conductivity is improved more significantly than that, which is performed by an atmospheric flame spraying method, and moreover, the generation of oxidation during the flame spraying can be prevented and a solderability is also improved in a degree identical with that with a normal metal. Thereby, the wiring pattern of a good accuracy is formed without using a mask.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for forming an electric circuit in an electric component.

[Prior Art] Conventionally, as a method for forming an electric circuit, an etching method using a copper-clad laminate or a plating method on a substrate has been used. However, since these conventional electric circuit forming methods are wet processes, the steps are complicated and the management of highly toxic processing liquids is time-consuming.

In order to avoid these problems, a method of directly forming wiring patterns on a board using thermal spraying was proposed in Japanese Patent Laid-Open No. 61-919.
It is disclosed in Publication No. 95. According to this method, a printed wiring board is manufactured by placing a mask with holes corresponding to the wiring pattern on the board and spraying a highly conductive metal onto the board from above the mask. be.

[Problem to be solved by the invention]

However, the conventional method of manufacturing a printed wiring board using a mask has a problem in that the manufacturing cost of the mask increases. That is, in order to form highly accurate wiring patterns on a substrate, it is necessary to prevent deformation of the mask as much as possible. When a thin mask is used, thermal deformation of the mask during thermal spraying is unavoidable, making it difficult to form highly accurate wiring patterns, and making it impossible to use the mask repeatedly, increasing costs.

Additionally, if the mask is made thicker to prevent thermal deformation, the process of drilling holes corresponding to the wiring diagram becomes complicated.
Mask manufacturing costs increase. Further, in the method of manufacturing a wiring board using a mask, there is a problem in that the thermal sprayed coating corresponding to the wiring pattern peels off when the mask is removed from the substrate after thermal spraying.

Therefore, an object of the present invention is to form a highly accurate electric circuit on a ceramic substrate without using a mask plate.

(Means for Solving the Problems) According to the present invention, when forming an electric circuit, a groove corresponding to a wiring pattern is formed in advance on a ceramic plate in the process of manufacturing a ceramic plate serving as a substrate. The grooves may be formed either before or after the ceramic plate is fired, but the easiest method is to form the grooves before the final firing.

In this way, the present invention comprises a first step of plasma spraying a highly conductive metal under reduced pressure onto a ceramic substrate on which grooves corresponding to the wiring pattern have been formed in advance, and a highly conductive metal adhered to areas other than the grooves. An electric circuit is formed by the second step of removing.

[For production] Regarding the present invention, first, the first step will be explained.

In the first step, as mentioned above, thermal spraying is performed on a ceramic substrate on which grooves corresponding to the wiring pattern have been formed in advance, and the thermal spraying improves the electrical characteristics, solderability, and adhesion of the resulting electrical circuit. This is done by plasma spraying under reduced pressure to maintain the temperature. In atmospheric plasma spraying, oxidation during spraying reduces the resistance of the metal sprayed into the grooves to 1Ω/C (!
1 or more, it is too thick (and cannot be used as an electrical circuit).

Moreover, the solderability is also poor.

According to the method of the present invention in which thermal spraying is carried out under reduced pressure, the adhesion between the substrate and the conductive metal is dramatically improved compared to atmospheric thermal spraying. Furthermore, since oxidation during thermal spraying can be prevented, the solderability is as good as that of ordinary metals.

The reduced pressure plasma spraying method used in carrying out the present invention is carried out at a pressure of 150 mmHg or less, preferably 50 mml'g or less. The particle size of the raw material powder used for thermal spraying is 75-5.
microns, preferably 25-5 microns.

In the present invention, the sprayed layer that ultimately becomes the electric circuit matches the shape of the groove formed on the ceramic substrate, so when forming the groove on the ceramic substrate, the width, depth, and
Form into a cross-sectional shape. The cross-sectional shape of the groove is rectangular, rectangular,
It can be of any shape such as a triangle or a semicircle.

The ceramic substrate used in the present invention can be made of glass, alumina, silica, partially stabilized zirconia, or other ceramics.

Further, the highly conductive metal used in the present invention may be gold, silver, copper, or other metals, but copper is advantageous in terms of cost.

Next, the second step will be explained. This step consists of removing the highly conductive metal adhering to areas other than the grooves after the first step, but the simplest method is to remove it mechanically by polishing with a grindstone or sandpaper. .

The present invention forms an electric circuit on a substrate through the two steps described above.

According to the method of the present invention, the uniformity of the film thickness of the conductive portion can be ensured by polishing after thermal spraying, compared to the conventional circuit forming method using a mask. Furthermore, for example, if the groove is triangular,
The wire diameter and thickness of the conductive portion can be changed arbitrarily by selecting the cross-sectional shape of the groove and combining the polishing process, such as increasing the amount of polishing to reduce the wire diameter.

Note that the present invention is not limited to circuit formation on a flat plate such as a printed wiring board, but can also be formed on a ceramic board, such as a rotary transformer manufactured by embedding and bonding copper wire into a circular grooved ferrite core. Applicable to electrical circuit components.

[Example] In FIGS. 1 and 2, copper powder of 30 mm and 1 g was thermally sprayed in a vacuum chamber 4 onto an alumina substrate 1 in which a groove 2 corresponding to a wiring pattern was formed in advance. The groove 2 had a right-angled cross section with a width of 0.8 mm and a depth of 0.15 mm, and the particle size of the copper powder used for thermal spraying was 5 to 25 microns. After a thermal spray coating 5 having a thickness of 200 microns was uniformly sprayed onto the alumina substrate l, the copper coating adhering to areas other than the grooves was removed by grinding with a grindstone 6 to obtain a printed wiring board 7.

The sprayed copper coating in the grooves of the printed wiring board 7 thus obtained is very dense and free of oxidation, and the electrical resistance measurement results are excellent at 0.01Ω/cm, with good solderability. there were.

〔Effect of the invention〕

As explained above (according to the present invention, there is no need for complicated steps like the conventional wet process circuit forming method,
The manufacturing process and equipment can be greatly simplified, and the time required for circuit formation can also be shortened. Furthermore, compared to the thermal spraying method that uses a mask plate, the process of manufacturing a mask plate can be omitted. Further, the electric circuit formed by the method of the present invention has excellent electrical resistance and solderability comparable to that of ordinary metals, and has other excellent effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the method of the present invention. FIGS. 2(a) to 2(d) are explanatory diagrams showing the steps of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Groove, 3... Plasma spray gun, 4... Decompression chamber, 5... Thermal spray coating, 6...
Grinding wheel, 7...Printed wiring board.

Claims (1)

[Claims] A first step of plasma spraying a highly conductive metal under reduced pressure onto a ceramic substrate with grooves corresponding to the wiring pattern;
A method for forming an electric circuit, comprising a second step of removing highly conductive metal adhering to areas other than the grooves.