JPS60245193A - Method of forming circuit of circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a circuit on a wiring board, and particularly to a dry circuit forming method in which a circuit is printed with adhesive and metal powder is sprayed.

[Problems with conventional technology]

Conventional methods for forming circuits on wiring boards using etching methods are complicated and have a low sieve value, and because they use cupric chloride and ferric chloride, which are harmful to etching, there are many problems such as wastewater treatment. Printing methods using copper paste or silver paste also have problems such as the gloss paste and silver paste being expensive and the metal particles being covered with a binder, making it impossible to solder the ll'11 path after printing. There was a big problem.

[Purpose of the invention]

The object of the present invention is to provide at low cost a wiring board that is dry in all processes, non-polluting, has good soldering properties, and can obtain satisfactory results in environmental tests such as sulfurization, oxidation, and moisture resistance.

[Structure of the invention]

The circuit is printed with adhesive, metal powder is sprayed onto the printed adhesive, and mechanical pressure is applied to the metal powder and adhesive.
The circuit of the wiring board is formed by heating and curing the adhesive and forming a solder layer on the circuit.

[Embodiments of the invention]

FIG. 1 shows one embodiment of the invention. As shown in Fig. 1a, an insulating resist 2 is applied by screen printing or the like on the parts other than the circuit to be created on the insulating substrate 1 such as paper-based phenol or wood Bf1 substrate, or between the circuits, and then heated and cured. Then, as shown in FIG. 1, a desired circuit is printed with an epoxy thermosetting adhesive 3. Both the insulation resist 2 and the adhesive 3 are printed with a thickness of 20 to 100 um. and,
Spray metal powder 4 such as copper powder with a particle size of 1 to 100 um as shown in Figure 1C, and press the metal powder 4 into the adhesive 3 using a roller 5 or press as shown in Figure 1D. This increases the wisdom 1f of the topmost metal powder and improves its conductivity.

Note that the amount of metal powder can be removed with air or the like and reused. After press-fitting the metal powder 4 into the adhesive 3, the first
As shown in Figure e, the adhesive 3 is cured by heating to 100 to 200[deg.] C. in an oven or the like. And in the worst case, Figure 1 f
As shown in FIG. 3, a solder coat b is applied to the next surface of the adhesive 3, which has good conductivity and the preliminary solder has also been cured. Note that even if the insulation resist 2 shown in FIG. 1a is not printed, oT n
It is Q.

〔Effect of the invention〕

As mentioned above, the uninvented method of forming a circuit on a wiring board is as follows.
It is non-polluting and does not contain any substances, the process is simple and the material cost is low, and since the metal powder is mechanically injected, the outermost layer has good conductivity because the metal powder is only added once. Metal powder is press-fitted to the inside to form a relatively thick metal layer, so
It has high adhesion strength with the adhesive layer, and it also allows solder on the circuit.
, it has remarkable effects such as good soldering properties.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the circuit forming method of a wiring board according to the present invention, in which FIG. 1A shows an insulating material printing process, FIG. 1C shows an adhesive printing process, and FIG. , FIG. 1 d is a cross-sectional side view showing the step of press-fitting the fly powder into the adhesive, FIG. 1 e is the thermosetting step of the adhesive, and FIG. 1 f is a cross-sectional side view showing the solder coating step. 1... Insulating substrate 2... Insulating resist 3... Adhesive 4... Metal powder 5... Roller 6... Solder

Claims (1)

[Claims] The desired circuit is printed on an insulating substrate with adhesive, metal powder is sprayed onto the printed adhesive, mechanical pressure is applied to the metal powder and adhesive, and then the adhesive is heated and cured. 1. A method for forming a circuit on a wiring board, the method comprising: forming a circuit on a wiring board, and then forming a solder layer on the circuit.