JPS60102798A - Method of producing printed 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 Field of Industrial Application This invention relates to a method for manufacturing printed wiring boards used in electronic equipment.

Conventional configurations and their problems In recent years, printed wiring boards with conductive paint on both sides are easy to manufacture, require little capital investment, and can be mass-produced. , radios, tape recorders, toys, and other equipment.

2, ... The manufacturing method for this type of printed wiring board is to form a circuit by etching the copper foil of a copper-clad laminate on one or both sides, then create a through hole in the board, and inject silver paint, etc. into the through hole. It is known that electrical connections are made on both sides of the board by applying conductive paint.

For example, in the copper foil 1 and insulating base material 2 of the double-sided copper-clad laminate shown in FIG. 1 (2L), the copper foil 1
An etching resist 3 is printed in the form of a circuit on the surface of the substrate, and after etching, this resist 3 is removed to form a double-sided circuit as shown in FIG. 1 (01). A through hole 4 is formed by drilling a hole in the insulating base material 2,
As shown in FIG. 1(e), silver paint is applied to fill the through holes 4, and the front and back surfaces are electrically connected through the silver through holes 6. Thereafter, a solder resist 6 is printed on the silver through holes 6 and on necessary circuits, and external processing is performed to manufacture a double-sided printed wiring board.

However, in the above method, since the through holes 6 are formed after etching the copper foil 1, the curing time 3 of the conductive paint for the through holes 6 is long and the high temperature causes dimensional shrinkage of the base material. In recent years, printed wiring boards have been required to have highly accurate dimensions, and it has become difficult to guarantee dimensional accuracy. Furthermore, since the dimensional change is large, the warping behavior during the process is severe, making the work in step 11 after curing extremely difficult. In addition, if you try to form the external shape or component insertion holes by pressing force after the conductive paint has hardened, the base material will deteriorate due to heat curing and become hard and brittle, resulting in poor workability and difficulty in forming the parts between the component insertion holes. Because of the occurrence of cracks, cracking, and chipping of the board, the conditions for press punching and circuit design were extremely limited. In recent years, printed wiring boards have been increasingly equipped with variable insertion of components and small chip components, requiring extremely high precision dimensions, and a solution to the above-mentioned drawbacks has been desired.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a method for manufacturing a fog printed wiring board in which through-holes can be formed using highly accurate conductive paint.

Structure of the Invention In order to achieve this object, the method for manufacturing a printed wiring board of the present invention involves drilling holes in the thickness direction of a copper-clad laminate, filling the through holes with conductive paint, and then heat-treating the board. After forming an etching resist, an etching process is performed to form a copper foil circuit. According to this manufacturing method, when curing conductive paint that requires severe heat treatment,
Since the copper foil remains on the entire surface, the copper foil suppresses dimensional shrinkage of the base material, and the heat dissipation effect of the copper foil prevents heat deterioration inside the base material and reduces warpage5.

DESCRIPTION OF EMBODIMENTS A method of manufacturing a printed wiring board according to an embodiment of the present invention will be described below with reference to the drawings. Figure 2 (a
) to (0 are process diagrams showing a method for manufacturing a printed wiring board in an embodiment of the present invention. Holes are drilled in the thickness direction of the material 2 to form through holes 4 as shown in Figure 2 (tb>).Next, as shown in Figure 2 (C1), silver paint is filled and applied into the through holes 4. This silver paint is cured in a heat oven at 150'C for 1 hour to form through holes 6 and electrically connect the front and back sides.Then, as shown in FIG. 7(d), an etching resist 3 is applied. A circuit pattern was formed by printing and etching the circuit including the top of the through hole 5, and removing the etching resist 3. Thereafter, a solder resist 6 was printed on the top of the through hole 6 and the necessary circuits, and press punching was performed. According to the method of manufacturing the printed wiring board as described above, the copper foil 1 remains on the entire surface of the insulating substrate 2 when the conductive paint is cured. The shrinkage of the dimensions of the insulating substrate 20 is small, and the shrinkage rate is 0.1% compared to the conventional shrinkage of 16 to 0.30% when through holes are formed after etching.
It was 04-0.06%. In addition, the amount of warpage of the insulating substrate 2 during the process is small, and there is no need to rewarp it, making the work easier. In the final process of press punching, paper phenol substrates, which are most often used for this type of printed wiring board,
With conventional manufacturing methods, paper epoxy boards are prone to cracking when the component insertion holes are punched at a pitch of 2.6 cm6.
1. However, in this example, there was little thermal deterioration due to the heat dissipation effect of the copper foil, and there were no cracks. However, a hole pitch of 1.78111 pitches was also possible.

As described above, according to this embodiment, the dimensions are stable and higher density circuit formation is possible.

In this embodiment, a double-sided copper-clad laminate has been described, but the same effect can be obtained with a single-sided copper-clad laminate.

Effects of the Invention As described above, the present invention forms through-holes with conductive paint before etching the copper foil, and since the copper foil remains on the entire surface, dimensional shrinkage of the base material due to heat treatment of the conductive paint can be avoided. It reduces the warpage of the base material during the pressing process, and the heat dissipation effect of the copper foil prevents thermal deterioration inside the base material, improving workability in press punching, etc., resulting in high density and high precision. This method has great practical effects as a substrate manufacturing method.

[Brief explanation of the drawing]

Figures 1 (IL) to (fl are cross-sectional views for explaining the steps of the conventional 7-basis method for manufacturing printed wiring boards, and Figures 2 (a) to (f)
) is a cross-sectional view for explaining the steps of a method for manufacturing a printed wiring board in an embodiment of the present invention. 1...Copper foil, 2...Insulating base material, 3...,...
・Eratinphrecyst, 4... Perforation, 6...
・Silver paint through hole, 6...Fulder resist 0 Name of agent Patent attorney Toshio Nakao and 1 other person Figure 1 Figure 2

Claims (1)

[Claims] After drilling holes in the thickness direction of the copper-clad laminate and filling the holes with conductive paint, heat treatment is performed to form an etching resist, and then etching is performed to form a copper foil circuit. A method for manufacturing a printed wiring board characterized by the following.