JPS63169792A - Manufacture of printed wiring 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 [Industrial Field of Application] The present invention relates to a method for manufacturing a printed wiring board, and particularly to a method for improving printing defects of solder resist.

[Summary of the invention]

The present invention relates to a method of printing solder resist on non-soldered areas, and includes a first printing process for eliminating unevenness due to the thickness of a conductor layer forming a conductor wiring circuit pattern, and a second printing process for covering the non-soldered areas. In the manufacturing method of a printed circuit board including a printing process of the first solder resist, the thickness of the solder resist becomes almost equal to the thickness of the conductor while leaving the etching resist used for forming the conductor wiring circuit pattern in the first printing process of the solder resist. By doing so, the control conditions for the first and second printing steps are relaxed, and the exposure of the non-soldered portions and the bleeding of the resist into the soldered portions are completely prevented.

[Conventional technology]

2. Description of the Related Art Conventionally, printed wiring boards have been widely used in electronic devices such as television receivers and radio receivers. This printed wiring board includes, for example, after forming a wiring pattern using a conductive material on an insulating substrate, an area other than the lands (soldering area), that is, a line connecting between the lands, in order to prevent so-called solder bridges. Manufactured by applying solder resist to non-soldered areas.

Solder resist is generally applied by screen printing. At that time, the printing method that prints solder resist only once on the non-soldered area (single printing method) may cause "bleeding" of the solder resist (print bleeding on the soldered area).
There was a problem with ``no edges'' (exposure of non-soldered areas). Therefore, in order to solve this problem, the first solder resist is printed to completely cover the non-soldered area on the board and to a thickness that is greater than the thickness of the conductor layer, and then the conductor layer is polished. , a two-time printing method (two-time printing method A) has been proposed in which a second solder resist is printed on areas inside and outside the soldering area.

Furthermore, in order to solve the problems of "bleeding" and "no edges" in the one-time printing method, and also to solve the problem of non-solder adhesion during chip component mounting, we created a mask with a pattern opposite to the wiring circuit pattern. After printing the first solder resist on the board using
It has been proposed that a second solder resist is then printed on the conductor layer using a pattern corresponding to the portion of the conductor layer excluding the soldering area (two-time printing method B).

[Problem that the invention seeks to solve]

However, according to the conventional technology, the appropriate range of solder resist printing conditions is narrow and difficult to control, so it is not easy to prevent printing defects such as "bleeding" and "missing edges" during manufacturing.

For example, in the first printing of the two-time printing method, it is necessary to apply sufficient squeegee printing pressure of the screen printer in order to fill the recesses between the conductors with sufficient solder resist.
With normal solder resist printing, sufficient printing pressure could not be applied because "bleeding" appeared on the soldered areas. Alternatively, when the squeegee printing pressure is increased, careful attention must be paid to the surface finish of the soldered area (land) during mechanical polishing.

For example, in the second printing of two-time printing method B, the resist coating cannot be thickened using the squeegee printing pressure that can prevent "bleeding" due to insufficient flatness, so printing conditions that can prevent "edges" must be carefully set. I had to keep an eye on it.

Furthermore, in either the two-time printing method A or B, the second
Before printing, the solder resist on the conductor had to be removed by mechanical polishing.

[Means for solving problems]

In order to solve the above-mentioned problems, the method for manufacturing a printed wiring board according to the present invention is characterized in that the first printing of the conventional two-time printing method A or B is performed using an etching resist that is used for forming a conductor wiring circuit pattern. The method is characterized in that the thickness of the solder resist is made almost equal to the thickness of the conductor while leaving .

[Effect]

According to the present invention, the etching resist is left in the soldering area (land) in the first printing of the two-time printing method A or B, and the squeegee printing pressure is increased to prevent the solder resist from bleeding. The solder resist can be sufficiently filled in the recessed portions. In the second printing, since the non-soldered area is almost flat, the precision of the dimension and shape in the resist thickness direction is increased, and the squeegee printing pressure can be lower than usual, making it possible to print with a printing pressure that does not cause "bleeding". becomes easier. Furthermore, since the solder resist does not bleed into the soldered areas and the non-soldered areas are nearly flat, it is no longer necessary to remove the resist on the conductors by mechanical polishing or the like before the second printing. Ta.

〔Example〕

An embodiment of the method for manufacturing a printed wiring board according to the present invention will be described in order of steps.

As shown in FIG. 1, the etching resist 1 used to form conductor wiring circuit patterns such as lands (soldering areas) 2 and lines 3.4 is left on the insulating substrate 5.

Next, as shown in FIG. 2, a first solder resist printing is performed to fill the pattern gaps (inter-wiring recesses) with solder resist 6 to a thickness that is approximately the same as the conductor thickness.

In conventional solder resist printing, printing bleeds into the soldered area, making it difficult to apply sufficient squeegee printing pressure to make the resist film thickness approximately equal to the conductor thickness.However, in the present invention, etching Because resist 1 remains, there is no need to worry about "bleeding" (the squeegee printing pressure can be increased sufficiently. In this example, the solder resists used were USR-2G (manufactured by Tamura Kaken, UV curing type) and S-22.
2 (manufactured by Taiyo Ink, thermosetting type), etc., and a soft squeegee and a coarse screen were used to apply a squeegee printing pressure of 4 to 5 times the conventional pressure.

Next, as shown in FIG. 3, the etching resist 1 is removed.

As etching resist 1, dry film has a pH of
T-865-AFT (manufactured by Hitachi Chemical, alkaline development type)
, PHT-142F (manufactured by Hitachi Chemical, solvent development type), ER-33-2 (manufactured by Somar, UV curing type),
DA-380B (manufactured by Sunf Chemical Co., Ltd., thermosetting type) and the like can be used, and peeling is performed using a stripping agent compatible with the etching resist used. If necessary, remove the first layer that has smeared onto the etching resist l by surface preparation before peeling.
The solder resist may also be removed. Note that the surface can be leveled by rubbing with a squeegee-like jig or by mechanical polishing using a rotating belt type or the like.

Next, as shown in FIG. 4, a second solder resist is printed so that the solder resist 7 does not cover the soldered area on the board and is included in at least the non-soldered area of the conductor wiring circuit pattern. Cover completely. Furthermore, since printing is performed on a substantially flat surface, the accuracy of the dimension and shape in the resist thickness direction is increased, and it is easy to perform the second solder resist printing with a squeegee printing pressure that does not cause the solder resist thickness to bleed into the soldering area. However, it is also possible to cover the soldering area with cover ink and remove it after printing and curing the solder resist, as disclosed in Japanese Patent Application Laid-Open No. 57-113298.

In this example, regarding FIG. 3, in order to facilitate the removal of the etching resist 1 shown in FIG. 2, the solder resist 1 shown in FIG. It is also possible to print the solder resist on the entire non-soldered area, remove the solder resist on the etching resist 1 by smoothing the surface using the same method as described above, and then peel off the etching resist 1. Even in this case, it is fundamentally different from the first solder resist printing in the conventional two-time printing method in that the solder resist 1 remains.

In the above embodiments, only the steps related to the present invention were described, but the printed wiring board according to the present invention can be a single-sided board, a double-sided board,
Any of the multilayer boards can be used, and the method for manufacturing through-holes in the conductor wiring circuit pattern may be the tenting method or the hole filling method if the method is to form them before the conductor wiring circuit pattern etching shown in Figure 1. , and other generally known methods can all be implemented.

〔Effect of the invention〕

As is clear from the description of the above-mentioned embodiments, after the wiring circuit pattern is formed, the etching resist remains.
The first solder resist printing is done with emphasis on making the solder resist thickness and the conductor thickness almost equal, this makes the surface almost smooth, and finally the second solder resist printing is done with emphasis on finishing only.
By performing solder resist printing, it is possible to print without defects such as exposure of non-soldered areas and printing blur in soldered areas. Therefore, it was possible to eliminate soldering defects such as unattached solder, and to greatly improve the reliability of soldering. Furthermore, compared to the two-time printing method of the prior art, there is no need for a step of removing the solder resist on the conductor by mechanical polishing before applying the second solder resist, and cost reduction can also be achieved by shortening the process.

[Brief explanation of the drawing]

FIGS. 1 to 4 are schematic cross-sectional views showing one embodiment of the method for manufacturing a printed wiring board according to the present invention in the order of steps. Figure 5 is a schematic perspective view (a) showing an example of conventional printed wiring.
and a cross-sectional view (b). 1. Etching resist 5, insulating substrate 6, first solder resist 7, second solder resist 8, exposure of non-soldered parts 9, bleeding (printing of solder resist on land) 10. Solder resist patent applicant Sony Corporation Company etching resist No. 1 Figure 1 Tsuruco resist Registration/Mo←Registration ζ Toko Separation Fig. 3 2nd So 2 Letter Registration Matrice] Fig. 4/ Enching Registration Zetsukan 1-Kara 6 1st solder resist 7 2nd solder resist

Claims (1)

[Claims] In a method for manufacturing a printed wiring board in which a conductor wiring circuit pattern is formed on an insulating substrate, at least the recesses between the conductors in the non-soldered area on the board are completely covered while leaving the etching resist used when forming the wiring circuit pattern. The first solder resist is printed so as to have a thickness almost equal to that of the conductor, and then printed so that it does not cover the soldered area on the board and at least covers the non-soldered area of the conductor wiring circuit pattern. A method for manufacturing a printed wiring board, comprising printing a second solder resist so as to completely cover an area included in the printed wiring board.