JPH04326588A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To deal with a SMT printed wiring board having high positional resolution, by selectively removing two layers of etching resist. CONSTITUTION:After a first mask film 4a put on a photosensitive dry film 3a is irradiated by an ultraviolet ray so as to make a specific pattern, a photosensitive dry film 3b is piled up and fixed through thermocompression. For solder resist ink printing, exposure and printing are carried out with a secondary mask film 4c having a circuit pattern of only a through-hole land 1c and a pad part out of an overall one of the mask film 4a. Unexposed parts of dry films 3a and 3b are removed and etching resists 5a and 5b are formed. Then, a bare part of copper is etched so as to form a wiring circuit 1b. Moreover, after only the resist 5a is removed, photosensitive solder ink 6 is applied over all, and the ink 6 on the resist 5a is removed. The ink 6 is hardened by ultraviolet rays and the remaining resist 5a is removed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing printed wiring boards, and more particularly to a method for manufacturing through-hole printed wiring boards having high-density wiring circuits.

0002

[Prior Art] Generally, in the production of through-hole printed wiring boards (hereinafter referred to as T/H PWB),
As shown in (d) and Figures 5 (a) to (d), the tenting method is often used, and according to this method, Figure 4 (
As shown in a), a conductive layer 1 including a copper plating layer and a through hole 1a are formed on an insulating substrate 2, and the insulating substrate 2 shown in FIG.
), a photosensitive dry film 3a is attached, and from above, as shown in FIG.
After burning the predetermined circuit pattern with ultraviolet light through
As shown in FIG. 4(d), unnecessary portions of the photosensitive dry film 3a are removed using a developer.

Next, an etching process using a cupric chloride solution or the like is performed to obtain the conductor circuit 1b shown in FIG. 5(a), and then the etching resist 5a is peeled off. Furthermore, Fig. 5(b)
), the photosensitive solder resist ink 6 is applied to the entire surface, and then exposed and baked using a second mask film 4b having a predetermined solder resist pattern, as shown in FIG. As shown in (d), the photosensitive solder resist ink 6 in the unexposed areas is dissolved and removed by a development process to obtain a T/H PWB.

[0004] In addition, there are other known manufacturing methods to obtain the T/H PWB from which the etching resist 5a is peeled off and removed as shown in FIGS. 5(a) and 5(a).

(1) Hole-filling method (2) Panel-pattern method (3) Pattern plating method (4) Electrodeposition coating method for positive photosensitive resin coating (
5) Electrodeposition coating method for negative photosensitive resin coating (6
) TAF-2 construction method (7) AP-2 construction method (8) Full additive construction method

[Problems to be Solved by the Invention] However, the conventional photo SR printing method has the following problems.

That is, in the photo SR printing method, a mask film is used to selectively leave solder resist ink, and after forming a predetermined circuit pattern on an insulating substrate in a photocuring process, the mask film is aligned. There was a problem in that positional misalignment between the circuit pattern and the solder resist pattern occurred due to variations in the dimensional expansion and contraction of the insulating substrate, and solder resist ink remained on the pad portion for surface mounting, making it impossible to ensure the reliability of component mounting.

Furthermore, in recent years, with the increase in the density of wiring circuits, the use of SMT has progressed, making it difficult to manufacture printed wiring boards with high positional accuracy.

An object of the present invention is to provide a method for manufacturing a printed wiring board that has high component mounting reliability and is compatible with SMT high positional precision printed wiring boards.

[0009]

[Means for Solving the Problems] The present invention provides a printed wiring board having through holes, including the step of drilling holes in a copper-clad insulating substrate, and forming a copper plating layer on the holes in the insulating substrate and on the surface of the insulating substrate. A step of thermocompression bonding a photosensitive dry film on the surface of the copper plating layer, exposing and baking using a first mask film having a predetermined circuit pattern, and then further superimposing a photosensitive dry film and bonding the photosensitive dry film by thermocompression. , a step of exposing and baking using a second mask film having a pattern of only through-hole lands and pad portions of the circuit pattern of the first mask film, and selectively removing the unexposed portions of the photosensitive dry film by developing. a step of removing the exposed copper portion by etching, and a step of selectively removing only the upper layer of the remaining etching resist and etching the lower layer. A step of leaving the resist remaining, a step of applying photosensitive solder resist ink to the entire surface of the substrate and drying it, a step of selectively scraping away the solder resist ink in the portion overlaid on the etching resist, and a step of applying ultraviolet rays. The method includes a step of irradiating and baking the entire surface, and a step of removing the remaining etching resist.

0010

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to (d), FIGS. 2(a) to (d)
3(a) to 3(c) are sectional views showing an embodiment of the present invention in the order of steps.

First, as shown in FIG. 1(a), a conductive layer 1 and through holes 1a are formed on a copper-clad insulating substrate 2 by plating using a known panel plating method, and then a photosensitive layer 1a is formed as shown in FIG. 1(b). Dry film 3a at 1-4 m/min, 80-1
It is thermocompression bonded to the surface of the insulating substrate 2 at 20° C. and 2 to 4 kg/cm 2 .

Next, as shown in FIG. 1(c), a first mask film 4a for wiring circuit printing having a predetermined circuit pattern is brought into contact with the photosensitive dry film 3a, and 50 to 300 millijoules per square centimeter is applied. After irradiating with ultraviolet rays and printing a predetermined circuit pattern, as shown in Figure 1(d), 1~4m/min, 50~80℃, 2~4kg
The photosensitive dry film 3b is overlapped and bonded by thermocompression at a thickness of /cm2.

Furthermore, as shown in FIG. 2(a), a second mask film 4c for printing solder resist ink having a pattern of only through-hole lands and pad portions in the circuit pattern of the first mask film is used. , After exposure and baking, as shown in Figure 2(b), 1-2% at 20-40℃
The unexposed portions of the photosensitive dry films 3a, 3b are removed with a sodium carbonate aqueous solution of
b, and as shown in FIG. 2(c), the exposed copper portion is etched with a cupric chloride solution to obtain a wiring circuit 1b. ℃
Only the upper layer portion of the etching resist 5b is removed using a 1 to 2% aqueous sodium hydroxide solution.

Thereafter, as shown in FIG. 3(a), a photosensitive solder resist ink 6 is applied to the entire surface, and the solder resist ink 6 on the etching resist 5a is removed by squeezing as shown in FIG. 3(b). , the entire surface is irradiated with ultraviolet rays and baked to harden the solder resist ink 6. At this time, the solder resist ink 6 on the etching resist 5a may be removed by curing the solder resist ink 6 and then polishing it with a buffing material. Finally, as shown in FIG. 3(c), the remaining etching resist 5a is removed with a 3-4% sodium hydroxide aqueous solution at 30-50° C. to obtain the printed wiring board of this example.

[0016]

As is clear from the above, according to the present invention, the following effects can be achieved by selectively removing two layers of etching resist.

(1) Since the wiring circuit and the solder resist pattern can be formed while eliminating the influence of dimensional expansion and contraction of the insulating substrate, a printed wiring board with high positional accuracy can be obtained.

(2) An SMT high positional precision printed wiring board is obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing an example of the present invention in the order of steps.

FIG. 3 is a cross-sectional view showing an example of the present invention in the order of steps.

FIG. 4 is a cross-sectional view showing an example of a conventional printed wiring board manufacturing method in order of steps.

FIG. 5 is a cross-sectional view showing an example of a conventional printed wiring board manufacturing method in order of steps.

[Explanation of symbols]

1 Conductor layer 1a Through hole 1b Wiring circuit 1c Through hole land 2 Insulating substrate 3a, 3b Photosensitive dry film 4a, 4c
mask film

Claims (1)

[Claims] 1. In a printed wiring board having through holes, the steps include: drilling a hole in a copper-clad insulating substrate; forming a copper plating layer on the hole in the insulating substrate and on the surface of the insulating substrate; A step of thermocompression bonding a photosensitive dry film on the surface and exposing and baking using a first mask film having a predetermined circuit pattern, and then further stacking and thermocompression bonding a photosensitive dry film, and a circuit of the first mask film. A process of exposing and baking using a second mask film having a pattern of only through-hole lands and pad portions in the pattern, and selectively removing the photosensitive dry film in unexposed areas by development to form an etching resist. a step of removing the exposed copper portion by etching, a step of selectively removing only the upper layer of the etching resist of the remaining etching resist and leaving the lower layer of the etching resist; a step of applying a transparent solder resist ink to the entire surface of the substrate and drying it; a step of selectively scraping off the solder resist ink in the portion overlaid on the etching resist; and a step of irradiating the entire surface with ultraviolet rays and baking it. . A method for manufacturing a printed wiring board, comprising the steps of: removing the remaining etching resist.