JPH04348590A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To provide a printed circuit board in which halation of photosensitive solder resist is eliminated, yield of manufacturing steps is remarkably improved and reliability of an electronic apparatus is improved in the board used for various electronic apparatuses. CONSTITUTION:After a conductor pattern 2 of a printed circuit board is formed, an insulating layer 1 is colored with an ultraviolet ray absorbing color or shut- off color. Thus, when photosensitive solder resist ink 4a is exposed, after an ultraviolet light incident from the exposed part is transmitted through solder resist, even if it is laterally transmitted on the surface of the layer 1 or arrived at a bottom or a printing frame of an exposure unit, the light is not reflected to arrive at a non-solder resist forming part, and optical polymerization of the ink of the non-solder resist forming part due to the reflection of the light can be prevented.

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.

0002

[Prior Art] In recent years, printed wiring boards have been widely used in various electronic devices, and as electronic devices become smaller and more multifunctional, they are required to have higher wiring densities and higher reliability. It's coming.

[0003] A conventional printed wiring board will be explained below. FIG. 3 shows a manufacturing process for forming a conventional solder resist on a printed wiring board. In Figure 3, 1
2 is an insulating layer, 2 is a conductive pattern, 4 is a photosensitive solder resist, 4a is a photosensitive solder resist ink, and 5 is a mask film.

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

[0005] First, through-hole drilling was performed on the copper-clad laminate.
Copper plating, etc. is applied, and then an etching resist is formed using a screen printing method, a photographic method, etc., and then etching is performed using a solution such as cupric chloride to form a conductor pattern 2, and the etching resist is peeled off. (not shown). Next, as shown in FIG. 3A, a photosensitive solder resist ink 4a is applied to the printed wiring board on which the conductor pattern 2 is formed, and the ink is dried to the touch using hot air or the like.

Next, as shown in FIG. 3(b), a photosensitive solder resist ink 4 is applied to the mask film 5 which is dry to the touch.
After being brought into close contact with the surface a and exposed to ultraviolet light, the unexposed portions are developed with a predetermined developer as shown in FIG. 3(c), and after drying with hot air or the like, a photosensitive solder resist 4 is formed.

[0007]

Problems to be Solved by the Invention In order to form a high-resolution solder resist that corresponds to higher wiring densities, the above-mentioned photographic method is often used in place of the conventional screen printing method. However, in the conventional manufacturing method, when exposing the photosensitive solder resist ink 4a that is dry to the touch, the ultraviolet light incident through the mask film 5 may pass through the photosensitive solder resist ink 4a, or the insulating layer 1 It travels across the surface of the insulating layer 1, or it enters from the surface and is reflected by the opposite surface of the insulating layer 1, reaching areas that should not be exposed, polymerizing the photosensitive solder resist ink in the areas where no solder resist is formed (hereinafter referred to as (referred to as halation), and residual ink was generated in areas where solder resist was not formed after development. This phenomenon is particularly noticeable in the case of solder resist inks with high exposure sensitivity and in printed wiring boards with thin insulating layers where the attenuation of reflected light is relatively low, resulting in a significant deterioration of yield in the printed wiring board manufacturing process.

[0008]Furthermore, when external forces or vibrations are applied during the manufacturing process or market of electronic devices, residual solder resist in the halation area may peel off, impeding solderability or impairing the functionality of precision parts. It had the following problems.

The present invention solves the above conventional problems, and provides printed wiring that eliminates halation in solder resist of printed wiring boards, significantly improves the yield of the manufacturing process, and improves the reliability of electronic equipment. The purpose of this invention is to provide a method for manufacturing plates.

0010

[Means for Solving the Problems] In order to achieve this object, the method for manufacturing a printed wiring board of the present invention includes the steps of forming a conductor pattern on an insulating layer of a printed wiring board, and coloring the insulating layer with an ultraviolet absorbing color. A manufacturing method comprising: a step of coloring the ink, a step of applying and drying a photosensitive solder resist ink on the insulating layer including the conductor pattern, and a step of exposing and developing the photosensitive solder resist ink into a desired shape. This is what I did.

[0011] Furthermore, a step of forming a conductor pattern on the insulating layer of the printed wiring board, a step of applying and drying a photosensitive solder resist ink on the insulating layer including the conductor pattern, and a step of applying the photosensitive solder resist ink In addition to using a mask film of the desired shape, a UV-absorbing sheet is installed on the surface of the printing frame opposite to the exposed surface, or an exposure machine is used to color the printing frame with an ultraviolet-absorbing color. The manufacturing method includes a step of developing solder resist ink.

0012

[Function] With this configuration, when exposing the photosensitive solder resist ink, ultraviolet light incident from the solder resist forming part, that is, the exposed part, passes through the solder resist and then travels across the surface of the insulating layer, or the bottom surface, or the exposure machine. Since the surface of the insulating layer is colored with an ultraviolet absorbing color, even if it reaches the baking frame on the side opposite to the exposed surface, the ultraviolet light will not reflect and reach the areas where solder resist is not formed. Since an ultraviolet absorbing sheet is provided on the surface or the baking frame is colored with an ultraviolet absorbing color, it is possible to prevent photopolymerization of the solder resist ink in areas where no solder resist is formed due to reflected light.

[0013]

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

(Embodiment 1) FIGS. 1(a), 1(b), and 1(c) show the manufacturing process of a printed wiring board in a first embodiment of the present invention. Note that in FIG. 1, the same parts as in FIG. 3 are given the same numbers, and their explanations will be omitted. First, we drilled through-holes in the copper-clad laminate.
Copper plating or the like is applied, and a conductor pattern 2 is formed in the same manner as in the conventional method.

Next, as shown in FIG. 1(a), a colored ink 3 having the same main components as the photosensitive solder resist and a yellow colored pigment is applied to the printed wiring board on which the conductor pattern 2 is formed.
is applied to the surface of the insulating layer 1 including the conductor pattern 2 by a dipping method, dried to the touch and colored, and then alkali-developable photosensitive solder resist ink 4a is screen printed on top of the ink, using a roll coater or curtain coater. Apply at a temperature of 60 to 80℃ using a hot air circulation furnace, etc.
, dry to the touch for about 15 to 30 minutes.

Next, as shown in FIG. 1(b), the mask film 5 is attached tightly, and the amount of ultraviolet light is about 500 to 700 mJ.
/cm2. Then, as shown in FIG. 1(c), the unexposed areas are developed and removed using a developer containing sodium carbonate as a main component. Thereafter, the formed solder resist 3 is dried using hot air or the like, if necessary. After that, it is heated in a hot air circulation furnace at a temperature of 130 to 160℃ for a period of 30 to 60 minutes.
Final curing is performed under conditions of about 10 minutes. After development, it was confirmed that there was no residual ink in the areas where no solder resist was formed, and that not only halation but also back exposure did not occur.

(Embodiment 2) Next, a second embodiment of the present invention will be described below. Figure 2(a), Figure 2(b), Figure 2
(c) shows the manufacturing process of a printed wiring board in the second embodiment of the present invention. In FIG. 2, the same parts as in FIG. 1 are given the same numbers and the explanation is omitted.
The configuration differs from that of FIG. 1 in that colored ink 3 is not used, and an ultraviolet absorbing sheet 6 is placed on the opposite side of the exposure surface, or the printing frame 7 of the exposure machine is colored with an ultraviolet absorbing color.

First, through-hole drilling was performed on the copper-clad laminate.
Copper plating or the like is applied, and a conductor pattern 2 is formed in the same manner as in the conventional method. Next, in FIG. 2(a), an alkali-developable photosensitive solder resist ink 4a is applied to the printed wiring board on which the conductor pattern has been formed using means such as screen printing, a roll coater, a curtain coater, etc., and hot air circulation is applied. Dry to the touch in a furnace or the like at a temperature of 60 to 80°C for about 15 to 30 minutes.

Next, as shown in FIG. 2(b), after the mask film 5 is tightly attached, an ultraviolet absorbing sheet 6 is placed on the opposite side of the exposure surface, or a yellow-colored printing frame 7 is placed on the opposite side of the exposed surface.
The amount of ultraviolet light is approximately 500 to 700 mJ using an exposure machine with
/cm2. Then, as shown in FIG. 1(c), the unexposed areas are developed and removed using a developer containing sodium carbonate as a main component. Exposure and development of the back side is performed in the same manner. Thereafter, the formed solder resist 4 is dried using hot air or the like as needed, and then heated to a temperature of 130 to 100 ml in a hot air circulation oven.
Final curing is performed at 60° C. for about 30 to 60 minutes. After the development, it was confirmed that there was no ink residue in the areas where the solder resist was not formed.

In the examples of the present invention, the photosensitive solder resist ink 4a was of an alkali-developable type, but
The photosensitive solder resist ink 4a may be of a solvent-developed type, and the colored ink is not limited to yellow, but may also include ultraviolet absorbing colors,
It goes without saying that a similar effect can be obtained with a blocking color.

[0021]

Effects of the Invention As described above, the present invention is capable of coloring the substrate surface under a photosensitive solder resist formed on a printed wiring board with an ultraviolet absorbing color or a blocking color, and of coloring a printing frame on the opposite side of the exposed surface. By installing an ultraviolet absorbing sheet on the surface of the board or using an exposure machine with a printing frame colored with an ultraviolet absorbing color, halation and back exposure of the solder resist of printed wiring boards can be eliminated, and the yield of the manufacturing process can be significantly improved. It is possible to create a printed wiring board that improves the reliability of electronic devices.In addition, conventionally, in printed wiring boards with a board thickness of 1.0 mm or less, simultaneous exposure of the front and back sides of the photosensitive solder resist caused halation. Although this was not possible, the structure of the present invention has the effect of making it possible to simultaneously expose the front and back sides.

[Brief explanation of the drawing]

[Fig. 1] (a) to (c) are cross-sectional views showing the manufacturing process of a printed wiring board in a first embodiment of the present invention.

[Figure 2] (a
) to (c) are cross-sectional views showing the manufacturing process of a printed wiring board in the second embodiment of the present invention.

[Figure 3] (a) to (c) are cross-sectional views showing the manufacturing process of conventional printed wiring boards.

[Explanation of symbols]

1 Insulating layer 2 Conductor pattern 3 Colored ink 4a Photosensitive solder resist ink 4 Photosensitive solder resist 5 Mask film 6. Ultraviolet absorption sheet 7. Exposure machine printing frame

Claims (3)

[Claims] 1. A step of forming a conductor pattern on an insulating layer of a printed wiring board, a step of coloring the insulating layer with an ultraviolet absorbing color, and then applying photosensitive solder resist ink on the insulating layer including the conductor pattern. . A method for manufacturing a printed wiring board, comprising a step of drying, and a step of exposing and developing the photosensitive solder resist ink into a desired shape. 2. A step of forming a conductor pattern on an insulating layer of a printed wiring board, a step of applying and drying a photosensitive solder resist ink on the insulating layer including the conductor pattern, and a step of applying the photosensitive solder resist ink to the insulating layer. A printed wiring board comprising the steps of using a mask film of a desired shape, installing an ultraviolet absorbing sheet on the surface of a printing frame opposite to the exposure surface, exposing it to light, and then developing photosensitive solder resist ink. manufacturing method. 3. A step of forming a conductor pattern on an insulating layer of a printed wiring board, a step of applying and drying a photosensitive solder resist ink on the insulating layer including the conductor pattern, and a step of applying the photosensitive solder resist ink to the insulating layer. A method for manufacturing a printed wiring board, which includes using a mask film having a desired shape, exposing the film using an exposure machine with a printing frame colored with an ultraviolet absorbing color, and then developing a photosensitive solder resist ink.