JPH04356994A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To provide a printed wiring board where a high resolution road map is made by remarkably improving the yield rate and the productivity in a solder resist and road map formation process, in the printed wiring board used for each kind of electronic equipment. CONSTITUTION:Photosensittve solder resist ink 3a and photosensitive road map ink 5a are developed at the same time, and the omission of a photosensitive solder resist ink developing process becomes possible. Moreover. the exposed part of the photosensitive solder resist ink 3a remains undevolved, so the occurrence of remarkable irregularity between the photosensitive road map ink 5a and the photosensitive solder resist ink 3a and between the insulating board 1 and the conductor pattern 2 surface is suppressed. The close sticking condition with the mask film 6 for road map formation during exposure can be preserved, and for the shape of the road map after exposure and formation, the shape of the mask film can be reproduced accurately.

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 used in various electronic devices such as personal computers and word processors.

0002

[Prior Art] In recent years, printed wiring boards have been widely used in various electronic devices.As electronic devices become smaller, lighter, and more multifunctional, the density of wiring and the surface mounting of electronic components have increased significantly. Conductor patterns formed on insulating substrates and lands on which electronic components are mounted are becoming increasingly narrower in pitch, thinner, and smaller in size, making it necessary to prevent solder from adhering to areas that do not require soldering, protect conductor patterns from oxidation, and maintain insulation. Solder resists and roadmaps formed on printed wiring boards for the purpose of improving solderability and other purposes are now required to have high resolution and high positional accuracy, and the method of forming them has changed from screen printing to mask film photography. It is gradually replacing the developing method.

[0003] A conventional printed wiring board will be explained below. FIG. 2 shows a manufacturing process for forming a solder resist and a roadmap using a conventional photo-development method for a printed wiring board. In FIG. 2, 1 is an insulating substrate, 2 is a conductive pattern, 3a is a photosensitive solder resist ink, and 3b is a photosensitive solder resist ink.
4 is a solder resist, 4 is a mask film for forming a solder resist, 5a is a photosensitive road map ink, 5b is a road map, and 6 is a mask film for forming a road map.

[0004] The formation of the solder resist and roadmap for the printed wiring board constructed as described above will be explained below.

First, an etching resist is formed on a copper-clad laminate (not shown) cut to a predetermined size using a screen printing method or a photo development method, and then etching is performed using a solution such as cupric chloride. A conductor pattern 2 is formed, and the etching resist is peeled off. As shown in FIG. 2(a), a photosensitive solder resist ink 3a is applied to a printed wiring board on which a conductor pattern 2 is formed on an insulating substrate 1, and the ink is dried to the touch using hot air or the like.

Next, as shown in FIG. 2(b), a mask film 4 for forming a solder resist is brought into close contact with the surface of the photosensitive solder resist 3a which has been dried to the touch and exposed to ultraviolet light.
As shown in FIG. 2C, the unexposed areas are developed and removed using a predetermined developer to form a solder resist 3b. After that, Figure 2 (
As shown in d), photosensitive roadmap ink 5a is applied onto the solder resist 3b in an area slightly larger than the area required to form the roadmap 3b, and similarly dried to the touch, as shown in FIG. 2(e). The photosensitive road map ink 5 is prepared by drying the road map forming mask film 6 to the touch.
After bringing it into close contact with the a-side and exposing it to ultraviolet light, the unexposed areas are developed and removed using a prescribed developer, as shown in FIG. 2(f).

[0007] Thereafter, in order to improve the adhesion and hardness to the insulating substrate and conductor pattern, it is treated again with hot air or the like.
A solder resist 3b and a roadmap 5b are formed on a printed wiring board.

[0008]

[Problems to be Solved by the Invention] However, in the above conventional configuration, although the solder resist and roadmap formed on the printed wiring board have high resolution,
Application of photosensitive solder resist ink, drying to the touch, positioning of the mask film for forming the solder resist, exposure, development, and application of photosensitive roadmap ink, drying to the touch, alignment of the mask film for forming the roadmap, exposure. , the development and manufacturing process are complicated and take a long time, making it difficult to mass-produce, and the photosensitive roadmap ink is coated on the solder resist, which has uneven surfaces after development and formation. There is an uneven state between the ink and the surface of the photosensitive solder resist ink 3a, the insulating substrate 1, and the surface of the conductor pattern. For this reason, sufficient adhesion with the roadmap forming mask film during exposure cannot be maintained, leading to the diffraction phenomenon of ultraviolet rays at the mask film shielding part, and the roadmap shape after development and formation is the designed state. The shape of the printed wiring board cannot be reproduced, and in severe cases, the characters and symbols cannot be read, leading to a problem in that the yield rate of printed wiring board manufacturing in the roadmap forming process is deteriorated.

The present invention solves the above-mentioned conventional problems, and significantly improves printed wiring board manufacturing yield and productivity in the solder resist and road map forming process using photosensitive solder resist ink and photosensitive road map ink. , our objective is to provide high-quality printed wiring boards with high-resolution roadmaps.

0010

[Means for Solving the Problems] In order to achieve this object, the present invention includes a process of applying photosensitive solder resist ink to a printed wiring board and drying it to the touch, and applying the photosensitive solder resist ink that has been dried to the touch. A process of exposing with a mask film pattern on which a desired shape has been drawn, and applying a photosensitive roadmap ink whose ingredients such as resin, filler, coloring pigment, additives, etc. are the same as the photosensitive solder resist ink, at least to the photosensitive solder resist. A process of applying the ink to the coated area and drying it to the touch, a process of exposing the dry to the touch photosensitive roadmap ink using a mask film pattern drawn with the desired shape, and a process of applying the photosensitive solder resist ink. It has a structure in which photosensitive roadmap ink is developed at the same time.

[0011]

[Function] With this configuration, it is possible to omit the developing process of the photosensitive solder resist ink, and since the unexposed areas of the photosensitive solder resist ink remain without being developed or removed, The occurrence of significant unevenness between the photosensitive roadmap ink and the photosensitive solder resist ink and the surfaces of the insulating substrate and conductor pattern is suppressed, and the adhesion to the roadmap forming mask film can be maintained during exposure. In this case, the diffraction phenomenon of ultraviolet rays at the mask film shielding portion is almost eliminated, and the road map shape after development and formation can accurately reproduce the shape of the mask film.

0012

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

FIGS. 1(a), (b), (c), (d), (
e) shows the process of forming a solder resist and roadmap for a printed wiring board in one embodiment of the present invention. Note that in FIG. 1, the same parts as in FIG. 2 are given the same numbers, and their explanations will be omitted.

In FIG. 1(a), using the same method as in the conventional example, an alkali-developable photosensitive solder resist ink 3a is screen printed and rolled onto a printed wiring board on which a conductor pattern 2 is formed on an insulating substrate 1. It is coated using a coater, curtain coater, or the like, and dried to the touch in a hot air circulation tank or the like at a temperature of 60 to 80° C. for about 15 to 30 minutes.

Next, as shown in FIG. 1(b), a solder resist forming mask film 4 is brought into close contact and exposed to ultraviolet light at an amount of about 500 to 700 mJ/cm2. Next, as shown in FIG. 1(c), a photosensitive roadmap ink 5a is applied.
is applied onto the exposed photosensitive solder resist ink 3a in the same manner as the photosensitive solder resist 3a, and dried to the touch.

As shown in FIG. 1(d), a mask film 6 for forming a roadmap is brought into close contact with the surface of the photosensitive roadmap ink 5a which has been dried to the touch, and exposed to ultraviolet light under the same conditions as for forming a solder resist. 1(e), the unexposed areas of the photosensitive solder resist ink 3a and the photosensitive roadmap ink 5a are simultaneously developed and removed using a developer containing sodium carbonate as a main component. After that, final drying and curing is performed in a hot air circulation tank or the like at a temperature of 130 to 160°C for about 30 to 60 minutes to ensure the adhesion of the insulating substrate 1 and conductor pattern 2 to the solder resist 3b and the road map 5b. stabilize.

Here, in the embodiment of the present invention, a conventional method of applying a photosensitive roadmap after developing and removing the unexposed area of a photosensitive solder resist is used. Maximum drop between concave and convex parts is 75μ
m, but it can be suppressed to about 20 μm, and the reproduction rate of the roadmap after formation with respect to the mask film is 60 to 10
0% could be improved to 90-100%.

In the embodiments of the present invention, the structure of the printed wiring board is a single-sided printed wiring board, but it may be a double-sided printed wiring board or a multilayer printed wiring board. Although the ink 5a is of an alkali-developable type, it goes without saying that the photosensitive solder resist 3a and the photosensitive roadmap ink 5a may be of a solvent-developable type.

[0019]

As described above, the present invention can shorten the manufacturing process for forming solder resists and roadmaps for printed wiring boards by simultaneously developing photosensitive solder resist ink and photosensitive roadmap ink, thereby improving productivity. This makes it possible to realize an excellent method for manufacturing printed wiring boards, which contributes to the improvement of performance and at the same time provides a high quality printed wiring board on which a high-resolution roadmap is formed.

[Brief explanation of drawings]

[Fig. 1] (a) to (e) are cross-sectional views showing main steps in a method for manufacturing a printed wiring board according to an embodiment of the present invention.

[Fig. 2] (a) to (f) are cross-sectional views showing main steps in a conventional printed wiring board manufacturing method.

[Explanation of symbols]

1 Insulating substrate 2 Conductor pattern 3a Photosensitive solder resist ink 3b Solder resist 4 Mask film for forming solder resist 5a Photosensitive road map ink 5b Road map

Claims (1)

[Claims] 1. A step of applying photosensitive solder resist ink to a printed wiring board and drying it to the touch, and exposing the dry to the touch photosensitive solder resist ink with a mask film pattern in which a desired shape is drawn. Process, resin,
A step of applying a photosensitive roadmap ink having the same components such as fillers, coloring pigments, additives, etc. as the photosensitive solder resist ink to at least the area coated with the photosensitive solder resist ink and drying it to the touch; Printing comprising the steps of: exposing the touch-dried photosensitive roadmap ink with a mask film pattern in which a desired shape is drawn; and developing the photosensitive solder resist ink and the photosensitive roadmap ink at the same time. Method of manufacturing wiring boards.