JPH07162136A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To provide a highly reliable printed wiring board having no faulty soldering after mounting of a part by a method wherein the generation of saggings by heat when a photosolder resist is exposed and the prescribed front and back side continuity holes are completely blocked up. CONSTITUTION:A photo-cured part 6 is formed by coating photosolder resist 4 on one surface of an insulating substrate 1 with a front-back continuity hole 2, the internal photosolder resist 4 is exposed by passing light through the prescribed front-back continuity hole 2 only from the other surface, and a photo- cured part 6 is formed. Then, the non-exposed part of the photosolder resist 4 is developed and removed by exposing from the coated surface. Pertaining to the other surface, photosolder resist 4 is applied, exposed and developed using the ordinary method, the photosolder resist 4 on both sides of the insulating film 1 is completely hardened, and a printed wiring board, having the completely blocked front-back continuity hole 2, is obtained.

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 having a structure in which front and back conduction holes are closed with a photo solder resist.

[0002]

2. Description of the Related Art As a conventional method of manufacturing a printed wiring board, a method of closing front and back conduction holes with a photo solder resist is disclosed in Japanese Patent Application Laid-Open No. 2-67786. As shown in FIG. 2 (a), first, as shown in FIG. 2 (a), this printed wiring board is manufactured on one surface (one surface) of the insulating substrate 1 having front and back conduction holes 2 and 3 having a diameter of 0.6 mm or less and a conductor pattern. After applying the photo solder resist 4 by the screen printing method, preliminary drying (normal temperature of 100 ° C. or less) is performed to form a semi-cured photosensitive layer. Next, as shown in FIG. 2B, the photo solder resist 4 is exposed to ultraviolet rays through a mask film 7 having a predetermined pattern (usually 500 to 1,000 mJ / c).
m ² ), and the photo-cured portion 6 is formed. At this time, the temperature of the insulating substrate 1 rises to 50 ° C. or higher, and the photo solder resist 4 slightly melts. Next, as shown in FIG. 2C, development is performed with an aqueous solution of sodium carbonate or the like to remove the photosolder resist 4 in the unexposed portion.

Next, as shown in FIG. 2D, the uncoated surface (the other surface) of the photo solder resist 4 is 1.1 to 1.3 times as thick as the photo solder resist 4 previously coated. The photo solder resist 4 is applied by screen printing and pre-dried to form a semi-cured photosensitive layer. Next, FIG.
As shown in (e), the photo solder resist 4 is covered with the mask film 8 having a predetermined pattern from the previous 1
Ultraviolet exposure is performed with 1.5 times the energy to form the photo-cured portion 6. Next, as shown in FIG. 2 (f), after developing with an aqueous solution of sodium carbonate or the like to remove the photosolder resist 4 in the unexposed portion, main heat treatment (normal temperature 100 ° C. or higher)
Then, the photo solder resists 4 on both sides are completely cured to obtain a printed wiring board in which the front and back conduction holes 2 are closed.

[0004]

In this conventional method for manufacturing a printed wiring board, since the photo solder resist is not cured when the photo solder resist is exposed, the photo solder resist is remelted by the heat during the exposure. Fig. 2
As shown in (f), there is a problem that front and back conduction holes 3 that are not closed are generated.

An object of the present invention is to provide a method of manufacturing a printed wiring board which prevents the occurrence of front and back conduction holes that do not close and does not cause soldering defects after component mounting and has high reliability.

[0006]

A method of manufacturing a printed wiring board according to the present invention comprises a step of applying a photo solder resist on one surface of an insulating substrate having front and back conduction holes and a conductor pattern, and predrying the insulating substrate. Light-curing by exposing the photo solder resist inside the front and back conduction holes from the other surface side of the substrate only through the light through the front and back conduction holes, and through the mask film from the one surface of the insulating substrate. A step of exposing and photo-curing the photo solder resist, a step of developing the photo solder resist to remove an unexposed portion, and a step of applying a photo solder resist on the other surface of the insulating substrate and preliminary drying. A step of exposing the photo solder resist through a mask film to photo-cure it, a step of developing the photo solder resist to remove an unexposed portion, Or comprising the ultraviolet irradiation treatment and the step of closing the sides introducing hole completely cured both sides of the photo solder resist.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1A to 1G are sectional views showing a first embodiment of the present invention in the order of steps. In the first embodiment of the present invention, as shown in FIG. 1A, first, screen printing is performed on one surface (one surface) of an insulating substrate 1 having front and back conduction holes 2 having a diameter of 0.6 mm and a conductor pattern. Method, the photo solder resist 4 is applied to a thickness of about 5 μm or more, and then pre-dried at a temperature of 80 ° C. for 30 minutes to form a semi-cured photosensitive layer. At this time, the front and back conduction holes 2 are closed by the photo solder resist 4. Next, as shown in FIG. 1B, front and back conduction is performed through the first mask film 5 that transmits light only to the front and back conduction holes 2 that are blocked from the uncoated surface (the other surface) of the photo solder resist 4. Hole 2
100mJ / cm ² of photo solder resist 4 inside the
And is exposed to ultraviolet light to form the photo-cured portion 6. At this time, the temperature of the photo solder resist 4 rises only about 20 to 30 ° C., so that no dripping occurs without remelting. next,
As shown in FIG. 1C, 500 mJ / cm ² of UV light is exposed from the coated surface of the photo solder resist 4 through the second mask film 7 having a predetermined pattern to expose the photo solder resist 4 to the photo-cured portion 6. To form. This time,
The temperature of the photo solder resist 4 becomes 50 ° C. or higher, but since the photo solder resist 4 in the front and back conduction holes 2 is photo-cured to form the photo-cured portion 6, no sagging occurs. Next, as shown in FIG. 1D, development is performed with a sodium carbonate aqueous solution having a concentration of about 1% by weight to remove the photosolder resist 4 in the unexposed portion.

Next, as shown in FIG. 1 (e), a photosolder resist 4 is applied to the other surface by a screen printing method so that the thickness is about 5 μm or more, and then pre-dried at a temperature of 80 ° C. for 30 minutes. A photosensitive layer in a semi-cured state is formed. Next, as shown in FIG. 1 (f), UV exposure of 500 mJ / cm ² is performed through the third mask film 8 having a predetermined pattern, and the photo solder resist 4 is exposed to the photo-cured portion 6.
To form. Next, as shown in FIG. 1 (g), after developing with an aqueous solution of sodium carbonate having a concentration of about 1% by weight to remove the unexposed portion of the photo solder resist 4, a temperature of 150 ° C.
Then, the main heat treatment is performed for 60 minutes to completely cure the photo solder resists 4 on both sides to obtain the printed wiring board according to the first embodiment in which the front and back conduction holes 2 are closed.

The second embodiment of the present invention is different only in the photo solder resist coating method and the curing method, and the constitution of each step is as shown in FIGS. 1 (a) to 1 (g). Is the same as. First, as shown in FIG. 1A, the diameter is 0.6 m.
Insulating substrate 1 having m front and back conduction holes 2 and conductor pattern
After applying the photo solder resist 4 to one side (one side) by the curtain coating method so that the thickness is 5 μm or more, it is pre-dried at a temperature of 80 ° C. for 30 minutes to form a semi-cured photosensitive layer. At this time, the front and back conduction holes 2 are closed by the photo solder resist 4. Next, as shown in FIG. 1B, the first solder layer 4 transmits light only to the front and back conduction holes 2 that are closed from the non-coated surface (the other surface) of the photo solder resist 4.
The photo-solder resist 4 inside the front and back conduction holes 2 is exposed to ultraviolet rays at 100 mJ / cm ² through the mask film 5 of (1) to form a photo-cured portion 6. At this time, the temperature of the photo solder resist 4 rises only about 20 to 30 ° C., so that the photo solder resist 4 does not melt again and no drool occurs. Next, FIG. 1 (c)
As shown in FIG. 3, the photocured portion 6 is formed on the photosolder resist 4 by exposing the coated surface of the photosolder resist 4 to ultraviolet rays of 500 mJ / cm ² through the second mask film 7 having a predetermined pattern. At this time, the temperature of the photo solder resist 4 becomes 50 ° C. or higher, but the front and back conduction holes 2
Since the photo solder resist 4 therein is photo-cured to form the photo-cured portion 6, no sagging occurs. Next, as shown in FIG. 1D, development is performed with a sodium carbonate aqueous solution having a concentration of about 1% by weight to remove the photosolder resist 4 in the unexposed portion.

Next, as shown in FIG. 1 (e), a photo solder resist 4 is applied to the other surface by a curtain coating method so that the thickness is about 5 μm or more, and then the temperature is 180 ° C.
And pre-dried for 30 minutes to form a semi-cured photosensitive layer.
Next, as shown in FIG. 1 (f), 500 mJ / cm ² is applied through the third mask film 8 having a predetermined pattern.
Then, the photo-cured portion 6 is formed on the photo solder resist 4. Next, as shown in FIG. 1 (g), after developing with an aqueous solution of sodium carbonate having a concentration of about 1% by weight to remove the unexposed portion of the photo solder resist 4, 2,000
By irradiating with ultraviolet rays of mJ / cm ² , the photo solder resist 4 on both sides was completely cured and the front and back conduction holes 2 were closed.
A printed wiring board according to the example is obtained. In the second embodiment,
Since the photo solder resist is applied by the curtain coating method, the production efficiency can be improved.

[0012]

As described above, according to the present invention, a photo solder resist is applied on one surface of an insulating substrate having front and back conduction holes and a conductor pattern and pre-dried, and then the front and back conduction holes are formed from the other surface of the insulating substrate. The internal photosolder resist is exposed to light and is photo-cured, so that it is possible to prevent dripping due to heat during exposure of the photosolder resist and completely close the specified front and back conduction holes. It is possible to obtain a highly reliable printed wiring board without soldering defects.

[Brief description of drawings]

1A to 1G are cross-sectional views showing a process sequence of a first embodiment of the present invention.

2A to 2F are cross-sectional views showing the order of steps for explaining an example of a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 and 3 Front and back conduction hole 4 Photo solder resist 5 1st mask film 6 Photocuring part 7 2nd mask film 8 3rd mask film

Claims (3)

[Claims] 1. A step of applying a photo solder resist on one surface of an insulating substrate having front and back conduction holes and a conductor pattern and pre-drying, and passing light from the other surface side of the insulating substrate to only the front and back conduction holes. A step of exposing and photo-curing the photo solder resist inside the front and back conduction holes; a step of exposing and photo-curing the photo solder resist from the one surface of the insulating substrate through a mask film; The step of developing the solder resist to remove the unexposed portion, the step of applying the photo solder resist on the other surface of the insulating substrate and pre-drying, and the photo-curing by exposing the photo solder resist through the mask film. And a step of developing the photo solder resist to remove the unexposed portion, and a photo-cured photo solder resist on both surfaces of the insulating substrate. Completely curing and closing the front and back conduction holes. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the step of completely curing the photo-cured photo solder resist on both surfaces of the insulating substrate includes a step of curing by heat treatment. 3. The method of manufacturing a printed wiring board according to claim 1, wherein the step of completely curing the photo-cured photo solder resist on both surfaces of the insulating substrate includes a step of curing by ultraviolet irradiation treatment.