JPH04359591A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To prevent covering of part of a surface of a surface mounting pad with solder resist due to a printing deviation of the resist and to obtain reliability of soldering in a method for manufacturing to form the resist between the pads of an extremely short pitch. CONSTITUTION:An entire printed wiring board formed with a circuit is coated with heat-curable solder resist 1b by a screen printing method, and thermally cured. Then, the resist formed on a circuit layer is removed by polishing using a polishing material such as a buff, sandpaper, etc., and a wiring circuit 2 and a circuit surface of a surface mounting pad 3 are exposed. Then, the entire board is coated with photosensitive liquidlike solder resist 1a by a screen printing method, and dried. Thereafter, after a mask film having a predetermined pattern is aligned with the board, it is exposed with an ultraviolet ray, and the resist on the circuit 2 is selectively cured. Further, uncured resist is dissolved to be removed with developer of 1%-sodium carbonate, etc.

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 a printed wiring board, and more particularly to a method for manufacturing a printed wiring board including a solder resist process.

0002

[Prior Art] Solder resist used for the purpose of preventing solder bridging on printed wiring boards has a high degree of positional accuracy and fine image formation in high-density printed wiring boards that are equipped with fine-pitch surface mount components. to be required,
A photographic method using a photosensitive liquid solder resist is generally used instead of the conventional screen printing method.

FIG. 4 is a perspective view of a high-density printed wiring board produced by a conventional photographic manufacturing method.

[0004] As shown in FIG. 4, the high-density printed wiring board is
In order to prevent solder bridging during soldering, the solder resist 1 covers the wiring circuit 2, and also has a length of 0.5 m.
It is formed between each of the pads 3 for surface mount components with a pitch of m.

[0005] FIGS. 5(a) to (d) and FIGS. 6(a) and (b)
) are cross-sectional views showing the order of steps for explaining a manufacturing method in a solder resist process using a conventional photographic method.

First, as shown in FIG. 5(a), a printed wiring in which a connection circuit 2 and a surface mount component pad 3 are formed using an etching resist 5 having a predetermined pattern by a known dry film tenting method. A board (hereinafter referred to as a printed wiring board) is formed.

Next, as shown in FIG. 5(b), the etching resist 5 on the conductor is eluted and removed with a stripping solution such as a 0.5 to 1.5% aqueous sodium hydroxide solution to form the wiring circuit 2. The surface mount component pad 3 is exposed.

Next, as shown in FIG. 5(c), a photosensitive liquid solder resist is applied to the entire surface of the printed wiring board 4 by a curtain coating method, and heated in a hot air circulation oven at 70 to 100°C for 20 to 40 minutes.
After drying for 0 minutes, a photosensitive solder resist film 6b is formed.

Next, as shown in FIG. 5(d), a mask film 7 having a predetermined pattern is superimposed on the printed wiring board 4, accurately aligned with the printed wiring board 4, and the mask film 7 is passed through the printed wiring board 4. 200-1000mJ/cm2
It is selectively photocured by exposure to ultraviolet 8 rays.

Next, as shown in FIG. 6(a), ultraviolet light 8
The exposed photosensitive liquid solder resist film 6b is selectively photocured to form a photocured photosensitive liquid solder resist film 6c.

Next, as shown in FIG. 6(b), a photosensitive liquid solder resist film 6b which has not been photocured is coated with a film of 0.5 to 1
．． It is eluted and removed with a developer such as a 5% aqueous sodium carbonate solution, leaving only the photocured photosensitive liquid solder resist film 6c.

0012

This conventional manufacturing method has the following problems when forming a solder resist between pads for surface mount components having an extremely fine pitch.

(1) Due to a relative misalignment between the mask film and the printed wiring board, the photocured photosensitive liquid solder resist may cover a portion of the surface of the surface mounting pad. As a result, reliability of soldering between the surface mount component and the printed wiring board cannot be ensured.

(2) Because the width of the photocured photosensitive liquid solder resist film between the pads for surface mount components is extremely narrow, sufficient adhesion to the printed wiring board cannot be obtained, resulting in the photocured photosensitive liquid solder resist film being extremely thin. The liquid resist film may peel off. As a result, solder bridges occur between adjacent surface mount component pads and surface mount components.

[0015] An object of the present invention is to provide a method for manufacturing a printed wiring board with high soldering reliability between a surface mount component, a printed wiring board, and a pad for surface mount components.

[0016]

[Means for Solving the Problems] The method for manufacturing a printed wiring board of the present invention involves applying a solder resist onto a printed wiring board on which a circuit is formed using an etching resist having a predetermined pattern by a known dry film tenting method. , a step of obtaining a solder resist film; a step of curing the solder resist film and then eluting and removing the etching resist on the circuit to expose the circuit; a step of applying and drying a photosensitive liquid solder resist; The method includes a step of exposing the photosensitive solder resist to light through a predetermined mask film, and a step of eluting and removing the unexposed portions of the photosensitive solder resist with a developer.

[0017]

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

FIG. 1 is a perspective view of an example of a printed wiring board according to an embodiment of the present invention.

As shown in FIG. 1, a solder resist 1a formed on a high-density printed wiring board on which surface mount components with a pitch of 0.3 mm are mounted by the manufacturing method of the solder resist process prevents solder bridging during soldering. For this purpose, a solder resist 1b is formed between each of the surface mount component pad 3 and the wiring circuit 2 to cover the wiring circuit 2.

FIGS. 2(a) to (d) and 3(a) to (c)
) are cross-sectional views showing an example of the present invention in the order of steps.

First, as shown in FIG. 2(a), a printed wiring board is prepared, on which wiring circuits 2 and pads 3 for surface mount components are formed using an etching resist 5 having a predetermined pattern by a known dry film tenting method. Prepare 4.

Next, as shown in FIG. 2(b), 1 to 20
PS thermosetting solder resist is applied to the entire surface of the printed wiring board 4 using a curtain coating method, and the temperature is 80 to 150°C.
The solder resist film 6a is dried and cured for 10 to 50 minutes to form a thermosetting solder resist film 6a.

[0023]The following range is optimal for the amount of thermosetting solder resist applied.

[0024]

Next, as shown in FIG. 2(c), the etching resist 5 on which the thermosetting solder resist film 6a is formed is dissolved and removed with a stripping solution such as a 0.5 to 1.5% aqueous sodium hydroxide solution. Connection circuit 2 and surface mounting pad 3
expose the conductor surface.

Next, as shown in FIG. 2(d), a photosensitive liquid solder resist is applied to the entire surface of the printed wiring board 4 by a curtain coating method, and dried for 20 to 40 minutes in a hot air circulating oven at 70 to 100°C. A photosensitive liquid solder resist film 6b is formed.

Next, as shown in FIG. 3(a), a mask film 7 having a predetermined pattern is superimposed on the printed wiring board, and after alignment, a 200-1000 mJ/cm
Expose to ultraviolet light 8 of 2.

Next, as shown in FIG. 3B, the photosensitive liquid solder resist film 6b on the wiring circuit 2 is selectively photocured to form a photocured photosensitive solder resist film 6c.

Furthermore, as shown in FIG. 3(c), a non-photocured photosensitive liquid solder resist film 6b is added to
Elute and remove with a developer such as a 1.5% aqueous sodium carbonate solution.

In FIG. 2(b), an ultraviolet curable solder resist is used to apply the coating at a rate of 0.5 to 2.0 j/cm.
It may be photocured with ultraviolet rays.

In addition, in FIG. 3(a), a method of screen printing using a screen having a predetermined pattern as a mask can be used.

[0032]

As explained above, according to the present invention, the following effects can be achieved by forming solder resists between the connection circuits, between the surface mounting pads, and on the surface of the connection circuits.

(1) Since there is no need for relative alignment between the mask film and the printed wiring board on which the circuit is formed, the solder resist does not cover part of the surface of the surface mounting pads, and the solder resist does not cover part of the surface of the surface mounting pads. It is possible to form a solder resist on the substrate, ensuring reliability of soldering between surface mount components and printed wiring boards.

(2) Since the solder resist is embedded between the pads for surface mount components and has sufficient adhesion to the printed wiring board, it is possible to form a solder resist that does not peel off due to poor adhesion, and prevents solder bridging. It can be done reliably.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example of a printed wiring board according to an embodiment of the present invention.

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 perspective view of a high-density printed wiring board produced by a conventional photographic manufacturing method.

FIG. 5 is a cross-sectional view showing the order of steps for explaining a manufacturing method in a solder resist process using a conventional photographic method.

FIG. 6 is a cross-sectional view showing the order of steps for explaining a manufacturing method in a solder resist process using a conventional photographic method.

[Explanation of symbols]

1, 1a, 1b Solder resist 2 Connection circuit 3 Surface mounting pad 4 Printed wiring board 5 Etching resist 6a Thermosetting solder resist film 6b Photosensitive liquid solder resist film 6c Photocured photosensitive solder resist film 7 Mask film 8 ultraviolet light

Claims (1)

[Claims] 1. Applying a solder resist onto a printed wiring board on which a circuit is formed using an etching resist having a predetermined pattern by a known dry film tenting method,
a step of obtaining a solder resist film; a step of curing the solder resist film and then eluting and removing the etching resist on the circuit to expose the circuit; a step of applying and drying a photosensitive liquid solder resist; A method for manufacturing a printed wiring board, comprising: exposing the photosensitive solder resist to light through a mask film; and removing unexposed areas of the photosensitive solder resist by elution and removal with a developer.