JP2002176245A - Method for sealing through hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sealing a through hole in which reliability of the product and flatness of the upper layer are enhanced without causing any problem of contamination by preventing formation of significant recesses on and under a filler. SOLUTION: At the time of sealing a through hole in a substrate, liquid photosolder resist SR is supplied to the part 20 of a through hole thus filling the through hole. Subsequently, it is dried touching a finger and then developed without being exposed. According to the method, the photosolder resist is not left as a contaminant on the surface of the substrate after being developed and vertical recess of the photosolder resist SR in the through hole is reduced after development.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for closing a through hole in a plate-like body. For example, the present invention relates to a method suitable for filling through holes in a printed wiring board manufacturing process.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of printed wiring boards, through holes may be formed in a substrate to form an interlayer conductive structure. Such a through-hole does not need to be penetrated after the interlayer conductive structure is formed. Rather, if it is kept penetrating, it may cause problems such as the inability to fix by suction when mounting components later. For this reason, the through holes are generally closed after the interlayer conductive structure is formed.

A conventional general method for this will be described with reference to FIG. In the conventional method, first, a liquid photo solder resist SR is supplied to a portion 20 of a through hole by printing. Thus, the liquid photo solder resist SR
Slightly protrudes to the supply side (upper side in FIG. 3), and the opposite side (lower side in FIG. 3) is depressed. In this state, after touch drying, exposure is performed from the lower side in FIG. This gives
A photosensitive layer 21 is formed near the lower surface in FIG. 3 of the liquid photo solder resist SR. Then, this is developed.
Then, although the lower photosensitive layer 21 in FIG. 3 of the liquid photo solder resist SR does not melt, the vicinity of the upper surface melts, so that the upper surface is also depressed like the lower surface. In this state, some unexposed portions remain on the upper surface side of the liquid photo solder resist SR, so that both-side exposure curing and thermal curing are performed thereafter.

[0004]

However, the above-mentioned conventional method has the following problems. That is, the upper and lower dents are large as the closed shape,
There are also about m. For this reason, the dent may become a liquid pool or remain as a void in a later process. As a result, the reliability of the product has been reduced, and the flatness of the upper layer has been impaired. Further, if the lower surface in FIG. 3 is contaminated with a liquid photo-solder resist during printing or the like, it is hardened by exposure as it is, causing a defect.

The present invention has been made to solve the above-mentioned problems of the conventional closing method. In other words, the challenge is to prevent the formation of large dents above and below the filler, to improve the reliability of the product and the flatness of the upper layer, and to close the through-hole so that there is no contamination problem. It is to provide a method.

[0006]

According to the method for closing a through-hole according to the present invention, which has been made to solve this problem, a liquid photo-solder resist is supplied to a plate-like body having a through-hole at the position of the through-hole. And fill the through holes with liquid photo solder resist (Step 1)
By exposing the liquid photo-solder resist to the developing solution without exposing the liquid photo-solder resist to remove the protruding portion from the through-hole (step 2),
Close the through hole of the plate.

Here, in the step 1, the liquid photo solder resist is allowed to reach the surface on the side opposite to the supply side,
It is desirable that the liquid photo solder resist is touch-dried before being subjected to the step 2. The touch drying at that time is preferably performed under conditions that are stronger than normal touch drying conditions. Further, it is desirable that step 2 is performed under weaker conditions than normal development conditions.

According to this method, the through hole is closed by the liquid photo solder resist in the step 1. Even if extra liquid photo solder resist adheres to the plate surface at this time, since it is subjected to the development in step 2 without performing exposure, it remains as it is and does not cause a defect.
Further, since most of the inside of the through hole is filled with the liquid photo solder resist in the step 1, the development in the step 2 is sufficient under the condition that the protruding portion is removed. As a result, the shape after closure has a small upper and lower dent. Therefore, the reliability of the product and the flatness of the upper layer are not impaired.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
This embodiment embodies the present invention as a method of closing a through hole formed in a substrate with an insulating material in the manufacture of a printed wiring board. Here, a photosensitive solder resist is used as the insulating material.
In addition, for the through holes, it is assumed that an interlayer conductive layer has already been formed by plating.

In this embodiment, as shown in FIG. 1A, first, a liquid photo solder resist SR is supplied to a through hole portion 20 by printing from above in FIG. At this time, unlike the case of the prior art shown in FIG. 3, the supply amount is adjusted so that the liquid photo solder resist SR reaches the lower opening end of the through hole in FIG. In this work, it is ideal that the liquid photo solder resist SR reaches the same position as the lower surface,
It may be a little protruding downward. The liquid photo solder resist at this time was DSR2200C manufactured by Tamura Seisakusho.
A relatively high viscosity grade such as -6G-2MT may be used. The supply of the liquid photo solder resist SR at this time is intended only to close the through holes, and is not intended to form a solder resist. The formation of the solder resist is performed in a later step.

In this state, touch drying of the liquid photo solder resist SR is performed. The conditions shall be stronger than the normal touch drying conditions. That is, the touch drying condition recommended by the manufacturer of the above-mentioned liquid photo solder resist is 80 ° C.2
When the time is 0 minutes, the temperature is set to 80 ° C. for about 30 to 50 minutes. In the state after touch drying, the amount of protrusion of the photo solder resist SR from the through hole is about 50 μm on the upper side in FIG. 1 and about 5 to 10 μm on the lower side in FIG.

This is subjected to development without exposure. The developing conditions at this time are weaker than the normal developing conditions. That is, by making the conveyor speed faster than usual, the time during which the photo solder resist SR comes into contact with the developing solution is made shorter than usual. Thereby, the photo solder resist SR elutes a little. Therefore, FIG.
As shown in (b), the protruding portions above and below are removed, and the upper and lower portions are slightly recessed. The depth of the dent in this state is about 50 to 150 μm for both the upper and lower sides.
It is smaller than the case of the prior art shown in FIG. For this reason, there are few problems such as liquid accumulation in the dents, voids, and flatness of the upper layer in a later step. Further, even if the liquid photo solder resist adheres to the plate surface at the printing stage, it is removed during development. For this reason, the adhered photo solder resist does not remain as contamination and does not cause defects. Here, the photo solder resist SR to be developed is not exposed at all and does not include a cured pattern. Thus, the term "development" may not be strictly appropriate, but please forgive me.

After that, the state shown in FIG.
After the V cure and the main drying are performed, it becomes possible to supply to a subsequent process. UV cure is 6 on each side.
The irradiation is performed by irradiating UV of about 00 mJ / cm ^{2 for} about 4 to 5 seconds. As a result, the substrate temperature rises to about 80 to 90 ° C., and the main drying is directly performed. The main drying is performed at a temperature of 15
It is performed so that the time of 0 ° C. or more is secured for about 30 minutes. Then, in the ordinary equipment, it takes about one hour as the total main drying time including the preceding and subsequent heating and cooling times.

If only the main drying without UV curing is performed, the photo solder resist SR in the through hole shrinks at the time of the main drying, thereby increasing the amount of dents and generating cracks. This is a photo solder resist SR
Is heated without cross-linking. On the other hand, if only UV curing without main drying is performed, peeling may occur rarely with the original solder resist formed in a later step. However, UV curing and main drying may cause contamination if performed under very strong conditions, and thus the above-described conditions may be used. Then, in the original formation of the solder resist, the development may be performed under stronger conditions.

The thickness of the photo solder resist SR in the through hole in the state after the main drying was measured and compared with that of the present embodiment and the conventional one. The results are shown in the graph of FIG. In this test, the total thickness of the substrate was 1
000 μm, and in the case of this embodiment, the touch drying time was set to 30 minutes, 40 minutes, and 50 minutes. The number n was set to 10. In the graph of FIG. 2, the vertical axis represents the thickness of the photo solder resist SR in the through hole. Therefore, when this value is subtracted from the total thickness of the substrate and divided by 2, the value is a rough value of the depth of the upper and lower dents. As can be seen from this graph, all of the embodiments have an average of 740 to 8
The thickness is about 00 μm. The variation is not so large, and the standard deviation is about 32 μm for 30 minutes dry, about 40 μm for 40 minutes dry, and about 38 μm for 50 minutes dry. And the maximum value). Therefore, the depth of the upper and lower dents is generally about 50 to 150 μm.

On the other hand, according to the conventional method,
Regardless of the maximum value, the minimum value is extremely small and greatly varies (standard deviation: about 178 μm). Therefore, the average value also remains at about 218 μm. Therefore, the process lacks stability. The depth of the upper and lower dents is 400 on average
It is close to μm and the variation is large.

As described above in detail, in the present embodiment, when closing the through hole of the substrate in the manufacturing process of the printed wiring board, the liquid photo solder resist SR is used.
Is supplied into the through-hole and filled, and after touch drying,
It is developed without exposure. For this reason,
The photo solder resist does not remain as a contaminant on the plate surface after the development, and the upper and lower dents of the photo solder resist SR in the through holes after the development are small. In this way, a through hole closing method has been realized which improves the reliability of the product and the flatness of the upper layer, and prevents the problem of contamination.

Here, the photo solder resist SR
Developing without exposing is as follows:
In particular, it contributes to reducing the recess on the lower side in FIG. That is, since the lower surface of the photo solder resist SR elutes during development, the liquid photo solder resist S
When supplying R, the through holes can be filled all the way down. If exposure is performed as in the prior art, the lower surface of the photo solder resist SR does not elute, so it is necessary to prevent the photo solder resist SR from projecting from below the through hole. For this reason, at the stage of supplying the liquid photo solder resist SR, it is necessary to leave a large gap below in consideration of safety. This is not the case with the method of the present embodiment.

The present embodiment is merely an example, and does not limit the present invention. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof. For example, the target substrate is not limited to the one not including the inner layer pattern as shown in FIG.
It may include an inner layer pattern. Further, the present invention can be applied both in the initial stage of lamination and after the final lamination. Further, the conductor patterns on the front and back sides when the present method is applied may be patterned as shown in FIG. 1, or may be solid before patterning. In the state before patterning,
Before the development, the solder resist SR protruding from the through hole and the solder resist adhering to the plate surface can be scraped off by a scraper.

[0020]

As is apparent from the above description, according to the present invention, it is possible to improve the reliability of the product and the flatness of the upper layer by preventing the formation of a large dent above and below the filler.
Also provided is a method of closing through-holes without causing contamination problems.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic procedure of a through hole closing method according to an embodiment.

FIG. 2 is a graph showing a thickness of a solder resist in a through hole.

FIG. 3 is a diagram showing a schematic procedure of a conventional method of closing a through hole.

[Explanation of symbols]

 20 Through-hole SR Photo solder resist

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E314 AA27 CC01 DD05 DD06 FF08 GG26 5E317 AA24 BB01 BB11 CC25 CD23 CD27 GG14 GG20

Claims (3)

[Claims] 1. A liquid photo solder resist is supplied to a plate-like body having a through hole at a location of the through hole, and the through hole is filled with the liquid photo solder resist (step 1). A developer is brought into contact with the liquid photo-solder resist without performing the process to remove a portion protruding from the through hole (step 2).
A method for closing a through hole, characterized in that: 2. The method for closing a through hole according to claim 1, wherein the liquid photo solder resist reaches the surface opposite to the supply-side surface in the step 1, and the liquid photo solder resist is supplied before the step 2 A method for closing a through-hole, comprising drying a photo solder resist under a condition stronger than a normal condition for drying a touch. 3. The method for closing a through hole according to claim 1, wherein the step 2 is performed under a condition weaker than a normal developing condition.