JPH0575240A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To improve adhesion between a solder resist and a road map and to restrain the road map from peeling off by forming the road map on a roughened solder resist. CONSTITUTION:A mask film 14 is manufactured, which is provided with photographic density difference to increase photographic density in the order of a background part 15, a road map pattern 16 and a solder resist pattern 17. The manufactured mask film 14 is vacuum-adhered onto a photosensitive solder resist ink 13a, exposed for ultraviolet hardening and developed. In a part corresponding to the road map pattern 16, photographic density of the road map pattern 16 is lower than that of the resist pattern 17 and higher than that of other exposed parts. Therefore, it is half-exposed and a surface thereof is roughened. An alkali development type photosensitive road map 18 is applied to a roughened part 18 of a solder resist 13b by a method such as screen print, set to touch and heated. Thereby, a printed wiring board wherein the solder resist 13b and the road map 18 are formed can be acquired.

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

[0002]

2. Description of the Related Art In recent years, printed wiring boards, which are widely used in various electronic devices, are remarkably increased in wiring density and surface mounting of electronic components due to downsizing, weight reduction and multifunction of electronic devices. Conductor patterns and lands formed on insulating substrates are becoming narrower in pitch, thinner, and smaller.

Therefore, a solder resist and a road map formed on a printed wiring board are also used for the purpose of preventing solder from adhering to unnecessary portions of the solder, protecting the conductor pattern against oxidation, maintaining insulation and improving solderability. High resolution, high positional accuracy and high quality are required, and the forming method is changing from the screen printing method to the photographic developing method using a mask film.

A conventional method for manufacturing a printed wiring board will be described below. FIG. 2 shows a conventional manufacturing process of forming a solder resist and a road map by a photo-developing method of a printed wiring board. First, in FIG. 2, 1 is an insulating substrate, 2 is a conductor pattern formed on one surface of the insulating substrate 1 with a predetermined wiring pattern, and 3a is a photosensitive layer formed on one entire surface of the insulating substrate 1 so as to cover the conductor pattern. Solder resist ink, 3b is a solder resist formed by exposing and developing a predetermined portion of the photosensitive solder resist ink 3a, 4 is a solder resist forming mask film, and 5a is a photosensitive film formed on the solder resist 3b. Roadmap ink, 5b is a roadmap formed by exposing and developing a predetermined portion of the photosensitive roadmap ink 5a, and 6 is a roadmap forming mask film.

The formation of the solder resist and the road map of the printed wiring board constructed as described above will be described below.

First, an etching resist is formed on a copper clad laminate (not shown) cut into a predetermined size by a screen printing method or a photo-developing method, and then etching is performed using a solution of cupric chloride or the like. , Forming the conductor pattern 2,
After that, the etching resist is removed.

After that, as shown in FIG. 2A, a photosensitive solder resist ink 3a is applied to a printed wiring board having a conductor pattern 2 formed on an insulating substrate 1 and dried by touching with hot air.

Next, as shown in FIG. 2B, the solder resist forming mask film 4 is brought into close contact with the surface of the photosensitive solder resist ink 3a, which has been dried by touch with the finger, and is exposed to ultraviolet rays. As described above, the unexposed portion is developed and removed with a predetermined developing solution to form the solder resist 3b.

Thereafter, as shown in FIG. 2 (d), the photosensitive roadmap ink 5a is applied on the solder resist 3b in an area slightly wider than the area necessary for forming the roadmap 5b, and the touch-sensitive drying is similarly performed. .. After that, as shown in FIG. 2E, the roadmap forming mask film 6 is brought into close contact with the surface of the roadmap ink 5a that has been touch-dried, and after UV exposure, unexposed as shown in FIG. The part is developed and removed with a predetermined developing solution.

After that, the solder resist 3b and the road map 5b are treated again with hot air or the like in order to improve the adhesion and hardness of the solder resist 3b and the road map 5b to the insulating substrate and the conductor pattern. Form.

[0011]

However, in the above-mentioned conventional structure, although the solder resist and the road map have high resolution, there is a risk of undercut occurrence even within the appropriate range of dry-to-touch conditions and development conditions. have.

That is, the cross-sectional shape of the road map formed by the conventional screen printing method is a trapezoid with sharp corners, whereas the cross-sectional shape of the road map formed by the photographic development method is the thickness of the mask film and the exposure. It becomes a rectangle or an inverted trapezoid due to the diffraction phenomenon of light due to the parallelism of the light source. For this reason, the roadmap becomes vulnerable to external force from the lateral direction, and the roadmap peels off during transportation of the printed wiring board or punching of the outer shape with a die, etc., which reduces the yield of the printed wiring board manufacturing process. It was significantly worse.

Further, even if peeling does not occur during the manufacturing process of the printed wiring board, peeling occurs when external force or vibration is applied in the manufacturing process of the electronic device or in the market.
There are problems such as impairing solderability and impairing the function of precision parts.

The present invention solves such conventional problems, and an object of the present invention is to suppress peeling of the road map of a printed wiring board.

[0015]

To achieve this object, a method of manufacturing a printed wiring board according to the present invention comprises a step of forming a conductor pattern on an insulating substrate, and a step of forming the conductor pattern on the insulating substrate so as to cover the conductor pattern. A mask on which a solder resist pattern and a roadmap pattern are formed such that the photosensitive solder resist ink is applied and dried, and the photosensitive solder resist ink has a background portion, a roadmap pattern, and a solder resist pattern in order of increasing photographic density. It comprises a process of exposing and developing with a film and a process of forming a road map on the road map pattern portion on the solder resist roughened in the process.

[0016]

[Function] A portion where a road map of the solder resist is formed by simultaneously exposing the mask film on which the solder resist pattern and the road map pattern are formed so that the photographic density increases in the order of the background portion, the road map pattern, and the solder resist pattern. Surface is roughened.

After that, a road map is formed on the roughened portion of the solder resist surface, whereby the adhesion between the solder resist and the road map can be remarkably improved.

[0018]

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

1 (a), (b), (c) and (d),
3 shows a process of manufacturing a printed wiring board according to an embodiment of the present invention. In FIG. 1, 11 is an insulating substrate, 12
Is a conductor pattern formed by a predetermined wiring pattern on one surface of the insulating substrate 1, 13a is a photosensitive solder resist ink formed on the entire one surface of the insulating substrate 11 so as to cover the conductor pattern 12, and 13b is this photosensitive solder resist. A solder resist formed by exposing and developing a predetermined portion of the ink 13a, 14 is a mask film for forming a solder resist having a photographic density difference, and a background portion 15,
Roadmap pattern 16, solder resist pattern 1
The road map pattern 16 and the solder resist pattern 17 are formed so that the photographic density increases in the order of 7. Reference numeral 18 is a road map, which is formed on the roughened portion 19 formed on the surface of the solder resist 13b.

The formation of the solder resist and the roadmap of the printed wiring board having the above structure will be described.

First, a negative pattern is prepared and prepared as a solder resist and a roadmap forming mask film used for manufacturing a usual printed wiring board.
Next, the negative pattern of the mask film for solder resist formation is first brought into close contact with the unexposed film having the photosensitive layer coated on the polyester film, exposed under normal exposure conditions, and then the negative of the mask film for roadmap formation. Align the pattern at the same position, about 1/3 of the normal exposure amount
Exposure under conditions of ⅕ and development under normal conditions, background portion 15 used in the present invention, roadmap pattern 1
6. A mask film 14 having a photographic density difference is formed so that the photographic density increases in order on the solder resist pattern 17.

Next, as shown in FIG. 1A, an alkali developing type photosensitive solder resist ink 13a is formed on the insulating substrate 11 on which the conductor pattern 12 is formed by a method such as a screen printing method or a curtain coater. Apply, 80 ~
Dry the coating at 85 ° C for 15-20 minutes.

Next, as shown in FIG. 1 (b), the mask film 14 prepared by the above method is vacuum-adhered to the photosensitive solder resist ink 13a and UV-cured at an exposure dose of 400 to 500 mj / m ^2. .. Then, as shown in FIG. 1C, a spray pressure of 1.5 wt.
Develop at -2.0 kg / cm ² for 45-60 seconds. After the development, the portion corresponding to the solder resist pattern 17 becomes an unexposed portion and is completely dissolved and removed. Further, in the portion corresponding to the road map pattern 16, the road map pattern 16 has a lower photographic density than the solder resist pattern 17, Since the density is higher than that of the other exposed portions, it becomes a semi-exposed state and the surface is roughened.

Thereafter, an alkali development type photosensitive road map 18 is applied to the roughened portion 18 of the solder resist 13b by a method such as screen printing and dried by touching with a finger.
By heating at an atmospheric temperature of 0 to 150 ° C. for 40 to 60 minutes, as shown in FIG.
A desired printed wiring board on which the road map 18 is formed can be obtained.

Regarding the printed wiring board according to this embodiment,
When the adhesion of the roadmap 18 to the solder resist 13b was examined, it was 6 to 7H in the pencil hardness test, and it was possible to obtain an improved result as compared with the conventional roadmaps 3 to 4H.

Although the structure of the printed wiring board is a single-sided printed wiring board in this embodiment, it may be a double-sided or multilayer printed wiring board. Further, although the photosensitive solder resist ink 13a is of the alkali development type, it may be of the solvent development type, and the road map 18 is of the photosensitive alkali development type, but may be of the UV curing type or the heat curing type for screen printing. Also has the same effect.

[0027]

As described above, according to the present invention, since the roadmap is formed on the roughened solder resist, the adhesion between the solder resist and the roadmap is remarkably improved, and the peeling of the roadmap is suppressed. This makes it possible to improve the yield of the manufacturing process of the printed wiring board and to realize the printed wiring board that improves the reliability of the electronic device.

[Brief description of drawings]

1A to 1D are cross-sectional views of a main process in a method for manufacturing a printed wiring board according to an embodiment of the present invention.

2 (a) to 2 (f) are cross-sectional views of a main process in a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

 11 Insulating Substrate 12 Conductor Pattern 13a Photosensitive Solder Resist Ink 13b Solder Resist 14 Mask Film 15 Background Part 16 Roadmap Pattern 17 Solder Resist Pattern 18 Roadmap 19 Roughened Part

Claims (1)

[Claims] 1. A step of forming a conductor pattern on an insulating substrate, a step of applying and drying a photosensitive solder resist ink on the insulating substrate so as to cover the conductor pattern, and a background portion of the photosensitive solder resist ink. , A process of exposing and developing with a mask film on which a solder resist pattern and a road map pattern are formed so that the photographic density increases in the order of the road map pattern and the solder resist pattern, and the road map on the solder resist roughened in the process A method for manufacturing a printed wiring board, comprising a step of forming a road map on a pattern portion.