JPH0653634A - Circuit forming method for wiring board - Google Patents

Abstract

PURPOSE:To prevent scattering or fog and to make it easy to obtain a necessary amount of printing required to forming a circuit, by charging circuit-forming particles containing conductive metal particles and a charging control agent, developing circuit-forming patterns, and fixing the circuit-forming particles and forming circuit patterns. CONSTITUTION:A circuit forming pattern 2a is formed on a wiring board 1 with resin particles not containing conductive metallic particles. Next, the circuit-forming pattern 2a is charged by a corona charger 3. And the charged circuit-forming pattern 2b obtained in this way is developed with circuit-forming particles 4. The circuit-forming particles printed are fixed by a flash lamp 5, and a circuit pattern 6 is formed. Since the surface potential of the circuit- forming pattern to be developed is high, it becomes possible to obtain an enough amount of printing. In addition, it is difficult for fog to be produced since only the circuit-forming pattern is selectively charged. Consequently, printability increases, and it becomes possible to meet the request for the formation of narrow-pitched circuit patterns.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a circuit on a wiring board.

[0002]

2. Description of the Related Art As a method of printing a circuit pattern on a wiring board, a method of forming a circuit pattern on the wiring board by a screen printing method using a printing paste containing conductive metal particles has been widely used. It is in practical use. However, in this method, it is necessary to make a printing screen for each circuit pattern, and especially in the case of a multi-layer substrate which tends to be produced in a large variety of small quantities, the number of types of printing screen increases and the production period becomes long. At the same time, the product price rises. Further, even if the circuit pattern is partially changed, the printing screen has to be reprinted, which makes it impossible to deal flexibly.

In order to solve the above drawbacks of the screen printing method, in recent years, a method of printing a circuit pattern on a wiring substrate by an electrophotographic method is being developed.

In the circuit pattern printing by the above-mentioned electrophotography, the circuit printing particles are attached to the electrostatic latent image formed on the photosensitive drum by electrostatic force to develop the circuit pattern, and then the wiring pattern is printed. Transfer to the substrate. Conventional circuit printing particles are prepared by mixing conductive metal particles, a thermoplastic resin, a charge control agent and the like by the same manufacturing method as a general electrophotographic toner, melting and kneading them, and roughly crushing and It is produced by pulverizing and classifying.

[0005]

In the above-mentioned conventional circuit pattern printing method by electrophotography, the circuit printing particles contain conductive metal particles. Since the conductive metal particles are included, the insulating properties of the particles are low, and the chargeability is poor as compared with general toner. Due to the deterioration of the charging property, scattering and fog are likely to occur, and there is a problem in that it is difficult to obtain a print amount necessary for forming a circuit.

[0006]

A circuit forming method for a wiring board according to the present invention comprises a first step of forming a circuit forming pattern on a wiring board by resin particles containing a charge control agent, and a circuit forming pattern. A second step of charging the pattern, a third step of charging the circuit-forming particles containing at least conductive metal particles and a charge control agent to develop the circuit-forming pattern, and a circuit for fixing the circuit-forming particles. And a fourth step of forming a pattern.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1A to 1D are process sectional views showing an embodiment of the present invention.

First, the circuit forming pattern 2a is formed on the wiring substrate 1 with resin particles containing no conductive metal particles (FIG. 1 (a)). Next, the circuit forming pattern 2a is charged by the corona charger 3 (FIG. 1 (b)). The charged circuit-forming pattern 2b thus obtained is developed with the circuit-forming particles 4 (FIG. 1C). The printed circuit-forming particles are fixed by the flash lamp 5 to form the circuit pattern 6 (FIG. 1D).

The present embodiment will be described in more detail below.

The resin particles were obtained by mixing the styrene-acrylic copolymer as the binder resin, the low molecular weight polypropylene as the wax, and the azo metal-containing dye as the charge control agent in the weight ratios shown in Table 1, respectively, and melt-kneading them. After coarse pulverization with a cutter mill and fine pulverization with a jet mill, air-flow classification was performed to obtain particles having an average particle size of about 12 μm.

[0012]

[Table 1]

Using the resin particles, a circuit-forming pattern was formed on a green sheet of an alumina glass-based ceramic material, which is a wiring substrate, by a dry electrophotographic laser printer.

Next, the circuit forming pattern formed on the green sheet is charged by a corona charger. At this time, a voltage of 7 kV was applied to the corona charger to charge the wiring board with a gap of 5 mm, and the surface potential of the charged wiring pattern was about 1 kV, which was larger than about 700 V of a normal photoconductor. Became.

The circuit-forming particles have a weight ratio of 85:15 of styrene-acrylic copolymer as a binder resin, low-molecular weight polypropylene as a wax, azo-based metal as a charge control agent, and silver and palladium as conductive metal particles. The powders mixed in the respective ratios were mixed in the weight ratios shown in Table 2, and were melt-kneaded, coarsely pulverized by a cutter mill, finely pulverized by a jet mill, and then classified by air flow to obtain an average particle diameter of about 20 μm. .

[0016]

[Table 2]

The circuit-forming particles have an average particle size of about 100.
After mixing with ferrite powder of μm, the charged circuit-forming pattern is developed by using the two-component magnetic brush developing method of dry electrophotography, and the circuit-forming particles are fixed on the green sheet by radiant heat from a flash lamp. A pattern was formed. The printed circuit-forming particles have poor chargeability, but the surface potential of the circuit-forming pattern to be developed is high, so a sufficient amount of printing can be obtained, and only the circuit-forming pattern is selectively charged. Since the fogging is less likely to occur, the printability is improved and it is possible to cope with the formation of a circuit pattern with a ridge pitch. Further, particularly when printing is performed a large number of times in order to increase the film thickness of the circuit pattern, only the circuit pattern is selectively charged, so that alignment is unnecessary.

The green sheet printed with the wiring pattern obtained as described above is cut into a predetermined size, laminated and subjected to hot pressing. Next, after heating at a temperature higher than the decomposition point of the resin, a firing process is performed so that the ceramic material is sintered. By this baking treatment, the resin components of the green sheet and the circuit-forming particles are decomposed and scattered to form a circuit made of a conductive metal. The sheet resistance of this circuit was 10 to 20 mΩ / □.

[0019]

As described above, according to the present invention, unlike the conventional screen printing method, a printing screen is not required, which is advantageous in terms of shortening lead time and cost, and also enables high-mix low-volume production. It also has the effect of being able to respond quickly and flexibly to design changes.

[Brief description of drawings]

1A to 1D are process sectional views showing an embodiment of the present invention.

[Explanation of symbols]

 1 Wiring Substrate 2a, 2b Circuit Forming Pattern 3 Corona Charger 4 Circuit Forming Particle 5 Flash Lamp 6 Circuit Pattern

Claims (10)

[Claims] 1. A first step of forming a circuit forming pattern on a wiring substrate with resin particles containing a charge control agent, a second step of charging the circuit forming pattern, and at least conductive metal particles. And a charge control agent, the third step of charging the circuit-forming particles by charging to form the pattern, and the fourth step of fixing the circuit-forming particles to form a circuit pattern. Circuit forming method for wiring substrate. 2. The method for forming a circuit on a wiring board according to claim 1, wherein the wiring board is a green sheet of a ceramic material. 3. The circuit forming method for a wiring board according to claim 1, wherein the wiring board is a sintered body of a ceramic material. 4. The circuit forming method for a wiring board according to claim 1, wherein in the first step, the circuit forming pattern is formed on the wiring board by a dry electrophotographic method. 5. The method for forming a circuit on a wiring board according to claim 1, wherein in the first step, the circuit forming pattern is formed on the wiring board by a wet electrophotography method. 6. The circuit forming pattern is charged by a corona charger in the second step.
A method for forming a circuit on a wiring substrate as described above. 7. The circuit forming method for a wiring board according to claim 1, wherein in the third step, the circuit forming pattern is developed with the circuit printing particles by dry electrophotography. 8. The method for forming a circuit on a wiring board according to claim 1, wherein, in the third step, the circuit-forming pattern is developed with the circuit-printing particles by a wet electrophotography method. 9. The circuit forming method for a wiring substrate according to claim 1, wherein fixing is performed by a flash lamp in the fourth step. 10. After the first to fourth steps,
The circuit forming method for a wiring board according to claim 1, wherein the second to fourth steps are repeated.