JPH09199836A - Method of manufacturing circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To augment the adherence, conductivity and current capacity of a circuit conductor formed on a substrate by flame coating the substrate simultane ously with metallic particles in different mean particle diameters. SOLUTION: A mask 3 undercut in the shape of a large current conductive circuit is bonded onto a substrate 2 so as to cover the whole body 2. Next, in order to augment the adherence of copper foil and flame coating metal comprising a circuit conductor 4, the surface of the circuit conductor 4 to be flame coated is roughened. Furthermore, after bonding the mask 3 in the same shape as that of the mask used for the roughening step onto the board 2, a flame coating unit 6 and the board 2 are relatively moved for the flame coating step so that the flame coating metal may be concentratively sprayed on the parts not covered with the mask 3 At this time, two each of flame coating units 6 are simultaneously actuated in the flame coating step so as to spray the conductor metallic particles in different mean particle diameters on the substrate 2 from respective flame coating units 6. For example, the metallic particles are simultaneously flame coated in the mean particle diameter of 50μm from one flame coating unit 6 while 20μm from the other unit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a circuit board that carries a large current.

[0002]

2. Description of the Related Art As the range of use of electronic circuits is rapidly expanding into the fields of industrial machinery and automobile parts, the inverter circuit, the signal circuit of the power supply device, and the power system circuit are integrated to save labor and save energy. A high-current composite circuit board has been developed as a means for realizing space saving. As a circuit conductor that constitutes such a large-current composite circuit board,
35 μm or 70 μm copper foil has been used, but with the expansion of current capacity, a type of substrate using 175 μm or 210 μm copper foil as a conductor and a type of substrate to which a thick conductor such as a copper bar is attached have already been developed. ing. Further, as disclosed in Japanese Patent Laid-Open No. 51-14140, there is a method of forming a circuit conductor by using a metal spraying technique. A patterning mask is superposed on a substrate and a metal is sprayed on the mask. After that, the mask is separated from the substrate to form the circuit substrate.

[0003]

In the conventional thermal spraying method, the controllable thermal spraying conditions that determine the characteristics of the conductor circuit include the type of thermal sprayed metal, the amount of sprayed metal, and the distance between the substrate and the spray nozzle. Etc. are listed. However, even if these conditions can be controlled sufficiently well, the solidification morphology of the metal deposited on the substrate by thermal spraying is porous, and the contact of individual sprayed metal particles is a point contact structure, so the substrate There is a problem that there is a limit to the improvement of the adhesion, conductivity and current capacity of the circuit conductor formed above.

[0004]

The present invention has been made to solve the above problems, and in a method of manufacturing a circuit board in which a conductor metal is sprayed on the board to form a circuit conductor, the average particle diameter is different. It is characterized in that metal particles are simultaneously sprayed on the substrate.

As described above, when the metal particles having different average particle diameters are simultaneously sprayed onto the substrate, the metal particle having a large particle diameter is sprayed to secure the amount of metal sprayed per unit time, and the metal particles having a small particle diameter are also sprayed. By spraying the metal particles at the same time, the filling rate of the conductive metal of the circuit conductor formed by the spraying can be increased. As a result, the contact area between the sprayed metal particles is increased, so that the adhesion to the substrate is improved and the conductor resistance is reduced, so that the allowable current density is also increased.

The metal particles having different average particle diameters are preferably composed of two kinds of metal particles having a large average particle diameter which is 1.5 to 12 times as large as the small average particle diameter. Here, the reason why the large average particle size is 1.5 times or more the small average particle size is as follows. That is, consider a sphere A having a diameter D _A inscribed in the cube and a sphere B having a diameter D _B in contact with the sphere A with each vertex of the cube as the center. Then D _A /
There is a relationship of D _B ≈1.4. Therefore, if the large average particle size is 1.5 times or more as large as the small average particle size, when the metal particles having the large average particle size are arranged in contact with each other on three axes orthogonal to each other, the metal having the small average particle size is The grains enter into the voids between the metal grains having a large average particle size and fill the voids. Also it has a center at each vertex of the equilateral pyramid, a sphere A of the four diameter D _A which is in contact with each other, densely deployed diameter D _B in the interior of the gap of the equilateral triangle in contact with these spheres A Consider sphere B. Then, there is a relationship of D _A / D _B ≈11.3. Therefore, if the large average particle size is 12 times as large as the small average particle size, when the metal particles having the large average particle size are arranged in contact with the respective vertices of the regular triangular pyramid, the metal particles having the small average particle size have the large average particle size. Enter into the voids between the metal particles of a diameter and fill the voids. In this case, the large average particle size is smaller than the small average particle size 1
When it exceeds 2 times, the number of metal particles having a small average particle size for filling the voids increases and point contact increases, which is not preferable in consideration of electric resistance.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for manufacturing a circuit board according to the present invention will be described in detail below with reference to the drawings. 1A and 1B are a perspective view of a mask used in the manufacturing method of the present embodiment and a perspective view of a circuit board manufactured using the mask, respectively. Further, FIG. 2 is an explanatory diagram of the manufacturing method of the present embodiment.

The steps of the manufacturing method of this embodiment are as follows. That is, 1) First, on the substrate 2, from 18 μm to 21 μm depending on the application.
The circuit conductor 4 is formed of an electrolytic copper foil or a copper plate having a thickness of about 0 μm. The circuit conductor 4 is formed by an ordinary method for manufacturing a circuit board. The substrate 2 is a glass epoxy material,
It is made of insulating material such as composite material, paper phenolic material, paper epoxy material.

2) Next, a mask 3 cut out in the shape of the large current conducting circuit shown in FIG. 1A is brought into close contact with the substrate 2 so as to cover the entire substrate 2. The mask 3 is manufactured by subjecting stainless steel or another material having high impact resistance and heat resistance to NC processing, punching processing, pressure molding and the like.

3) Next, in order to improve the adhesion between the copper foil forming the circuit conductor 4 and the sprayed metal, the surface of the circuit conductor 4 to be sprayed is roughened. The roughening treatment may be, for example, a sandblasting treatment in which fine particles such as ceramics are sprayed, a controlled mechanical polishing treatment by a rotary polishing device, a chemical etching treatment, or an electrochemical treatment. In this roughening process, the average roughness of the surface of the circuit conductor is set to about 5 to 20 μm.

4) Next, the conductor metal is sprayed onto the substrate 2,
A circuit board 1 having a partially thick conductor 5 as shown in FIG. 1B is formed. The arc type thermal sprayer 6 is used for thermal spraying onto the substrate 2.
Is used. The advantages of using the arc type thermal spraying method are that the power consumption is relatively low compared to other methods such as gas type and plasma type, and that the amount of thermal spraying per unit time is larger than other methods. It is advantageous in terms of manufacturing efficiency, that the temperature rise of the substrate during spraying is low and the characteristics of the substrate are not deteriorated, and the adhesion between the sprayed metal and the base is relatively good. In this thermal spraying process, as shown in FIG. 2, after a mask 3 having the same shape as the mask used in the roughening process is brought into close contact with the substrate 2, the sprayed metal is concentrated on a portion not covered by the mask 3. Spraying is performed by relatively moving the spraying machine 6 and the substrate 2 so as to be sprayed. At the time of thermal spraying, two thermal sprayers 6 are simultaneously operated, and conductive metal particles having different average particle diameters are sprayed onto the substrate 2 from the respective thermal sprayers 6. At this time, from one thermal spraying machine 6 to the other of the thermal spraying machines 6 operating at the same time, the particle size of the metal is 1.5 or more,
The metal particles having a particle size 12 times or less are sprayed. For example, one spraying machine 6 simultaneously sprays metal particles having an average particle size of 50 μm and an average particle size of 20 μm from the other. Such control of the particle size is performed by supplying metal wires to the respective thermal spraying machines 6 at different feed rates, or by using metal wires having different wire diameters at the respective thermal spraying machines 6, or at the feed rate and the metal wire. This can be done by controlling both wire diameters at the same time. Therefore, the relationship between the wire diameter and the feed rate and the particle diameter is experimentally obtained in advance.

5) After the formation of the partially thick conductor 5 by thermal spraying, the mask 3 and the substrate 2 are separated, and the mask 3 is repeatedly used at the time of thermal spraying on the substrate 2 to be processed next.

6) Circuit board 1 thus formed
In addition, the following surface deterioration preventing treatment of the partially thick conductor 5 may be performed. That is, the surface of the partially thick conductor 5 is coated with a controlled thickness by solder coating or electrolytic metal plating. Further, if necessary, before or after the above coating treatment, a treatment for mechanically polishing the sprayed surface to adjust the surface roughness and the conductor thickness is also performed. By applying such a coating treatment, it is possible to prevent oxidation of the surface of the partially thick conductor 5 that has been sprayed. The conductivity is, for example, 50 μm on average for a partially thick conductor 5 having an average thickness of 150 μm.
About 15 to 40% when soldered on, average 1
50 to 80 when plated with 50 μm copper
% Improvement. Finally, the circuit board 1 having the circuit pattern of the partially thick conductor 5 is a finished product through the steps of the surface resist treatment and the symbol printing.

The present invention is not limited to the above embodiment. Regarding the thermal spraying method, instead of using the technology of spraying metal particles having different particle diameters with two arc-type thermal sprayers at the same time, an apparatus for spraying particles with a small average particle diameter of the two is used as the feed material. When the powder spraying machine is operated, it is possible to stably control and spray the fine powder. In addition, when using an aluminum substrate having a higher melting point and higher thermal conductivity than the glass epoxy material as the substrate, a plasma spraying machine with a high temperature is used as the spraying machine, and a single plasma spraying machine is used. You may spray mixed powder. In this case, the thick conductor may be formed by directly spraying on the substrate without using the circuit conductor made of the electrolytic copper foil. Further, the mask for forming the thick conductor may be formed by a method such as a dry film on which a pattern shape is printed or resin ink application. When masking with a dry film, the mask used in the roughening treatment is used as it is as a mask for the thermal spraying treatment.

[0015]

As described above, according to the present invention, in a method of manufacturing a circuit board in which a conductor metal is sprayed onto a substrate to form a circuit conductor, metal particles having different average particle diameters are simultaneously sprayed onto the substrate. Therefore, since the filling rate of the conductor metal of the circuit conductor can be increased, there is an excellent effect that the adhesion of the circuit conductor to the substrate is improved and the conductor resistance is reduced.

[Brief description of drawings]

1A and 1B are respectively a perspective view of a mask used in an embodiment of a method of manufacturing a circuit board according to the present invention and a perspective view of a circuit board manufactured using the mask. Is.

FIG. 2 is an explanatory diagram of a manufacturing method according to the above embodiment.

[Explanation of symbols]

 1 circuit board 2 board 3 mask 4 circuit conductor 5 thick conductor 6 thermal sprayer

Claims (2)

[Claims] 1. A method of manufacturing a circuit board in which a conductor metal is sprayed onto a board to form a circuit conductor, wherein metal particles having different average particle sizes are simultaneously sprayed onto the board. . 2. The method of manufacturing a circuit board, wherein the metal particles having different average particle diameters are composed of two kinds of metal particles having a large average particle diameter which is 1.5 to 12 times as large as the small average particle diameter. .