JPH0645734A - Printed-wiring board and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To enable a resin to be filled up without fail by a method wherein a printed-wiring board having a via hole and a through hole is immersed in a sensitive insulating resin solution and after filling up these holes with the insulating resin, the insulating resin inside the through hole is removed during the exposure/development steps but leaving the insulating resin inside the via hole only. CONSTITUTION:An insulating substrate 1 whereon a through hole 4, a via hole 3 and a circuit pattern 2 are formed is immersed in a sensitive insulating solution so as to fill up the through hole 4 and the via hole 3 with an insulating resin 6. Next, the whole surface is coated with a solder resist for exposure and development step. At this time, if the through hole 4 side is masked to be shielded from ultraviolet rays but the via hole 3 side is not masked to be exposed to the ultraviolet rays, the solder resist inside and on the periphery of the through hole 4 is removed together with the insulating resin 6 on the through hole 4 sidewall during the development step. On the other hand, a solder resist pattern 5 is formed on the via hole 3 while the inside thereof is filled up with the insulating resin 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a method for manufacturing the same, and more particularly to a printed wiring board having via holes filled with a photosensitive insulating resin and a method for manufacturing the same.

[0002]

2. Description of the Related Art A printed wiring board basically has an insulating substrate 1, a circuit pattern 2 formed on the front and back surfaces of the insulating substrate 1, and a front and back surface as shown in FIG. It is composed of a conductive through hole for connecting the upper circuit pattern 2. There are two types of through holes. One is only for electrically connecting the front and back circuit patterns 2, and is called a via hole 3. The other is to connect the circuit patterns 2 on the two surfaces and to insert and solder the lead terminals of this component when mounting an electronic component or the like, which is called a through hole 4. is there. Focusing on the hole diameters of the through hole and the via hole, the hole diameter of the through hole is generally larger than the hole diameter of the via hole due to the above-mentioned difference in application. The target of the present invention is the via hole 3 described above. Here, regarding the positional relationship between the pad on which the surface mount component is mounted and the via hole, the via hole is usually
The wiring is pulled out from the pad and provided at a position avoiding the pad. In recent years, as the mounting density of electronic devices has increased, the wiring pattern of the printed wiring board has been densified. As a result, the number of via holes placed directly on the pad is increasing.

It is desirable that the via hole of such a printed wiring board is closed at the time of mounting components, for the reasons described below. (A) When a printed wiring board on which a component is mounted is conveyed by vacuum suction, if the via hole 3 is not closed, air leaks from the via hole 3 and vacuum suction is not reliably performed. (B) When soldering by flow soldering is performed in the step of assembling components on the printed wiring board, flux is spouted from the back surface (solder surface) of the printed wiring board to the front surface (component surface) through the via hole 3. (C) In the case of the mounting method of soldering the surface mount component to the printed wiring board with cream solder, if the surface mount component connecting pad has a via hole, the melted cream solder is sucked into the via hole during reflow soldering. The solder joint between the surface mount component and the printed wiring board becomes insufficient.

A method of closing a via hole in a conventional printed wiring board will be described below. FIG. 4A shows a solder resist pattern 5 formed by exposing and developing using a dry film-like photosensitive solder resist. In this case, the via hole 3 is not filled with resin, and the via hole 3 has a shape in which the front and back surfaces of the via hole 3 are tented by the film-shaped solder resist pattern 5 having a film thickness of about 50 to 150 μm.

FIG. 4B shows a solder resist pattern 5 which is formed by coating a liquid solder resist by a screen coating method and exposing and developing it. In this case, it is difficult to reliably tent the via hole 3 with the solder resist pattern 5, and a part of the opening of the via hole 3 as shown in FIG. 4B is often discontinuous.

Further, FIG. 4C shows a solder resist pattern 5 which is formed by coating a liquid solder resist by a spray coating method and exposing and developing it. In this case, the solder resist layer is hardly formed in the via hole 3.

In addition to this, a liquid solder resist is flown downward from above like a curtain, and the printed wiring board is passed across the curtain-shaped solder resist,
Although there is a curtain coating method of applying a solder resist, it is difficult to surely close the via hole 3 due to the viscosity or the like by the method using the liquid solder resist in any of the methods, as described above. The method of closing the via hole was mainly a method of closing the opening of the via hole 3, and there was no printed wiring board in which the inside of the via hole 3 was reliably filled with resin.

[0008]

The above-mentioned conventional printed wiring board has the following drawbacks. In the case where the dry film solder resist as shown in FIG. 4A is used, the via holes 3 are covered with the solder resist pattern 5 to close the openings on the front and back surfaces. However, the inside of the via hole 3 is hollow. This can damage the tenting.
On the other hand, in order to prevent breakage of the tenting, it is necessary to increase the thickness of the dry film solder resist to about 100 μm to obtain tenting strength. In this case, the resolution of the solder resist pattern deteriorates because the thick solder resist is exposed and developed. In the method shown in FIGS. 4B and 4C, the curtain coating method, or the like, since the liquid solder resist is used, the resin (solder resist) cannot be reliably filled in the via hole 3.

An object of the present invention is to solve the above-mentioned conventional drawbacks and to provide a printed wiring board in which not only the opening of the via hole is closed but also the insulating resin is surely filled inside.

[0010]

The printed wiring board of the present invention comprises:
In a printed wiring board including a via hole that conducts a circuit pattern formed on one surface of an insulating substrate and a circuit pattern formed on the other surface of the edge substrate, the via hole is filled with a photosensitive insulating resin. It is characterized by

In such a printed wiring board, a step of dipping the photosensitive insulating resin in the via hole and the through hole of the printed wiring board including the through hole and the via hole by dipping and filling the surface of the printed wiring board. Removing the excess photosensitive insulating resin, forming a layer of photosensitive solder resist on the surface of this printed wiring board, and exposing a predetermined portion of this solder resist layer to development to form a solder resist pattern. At the same time as the formation, the step of removing the photosensitive insulating resin in the through hole described above is removed by the developing process at this time, and the method is manufactured by a method for manufacturing a printed wiring board.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an optimum embodiment of the present invention will be described with reference to the drawings. 1A to 1E are cross-sectional views for explaining a first embodiment of the present invention in process order.

First, as shown in FIG. 1A, the insulating substrate 1 having the through holes 4, the via holes 3 and the circuit pattern 2 is dipped in a photosensitive insulating liquid adjusted to about 1 poise, As shown in FIG. 1B, the through hole 4 and the via hole 3 are filled with the insulating resin 6. In this case, since the hole diameter of the through hole 4 is larger than the hole diameter of the via hole 3 as described above, the insulating resin 6 is packed in the via hole 3 while the inner wall of the through hole 4 is filled. An insulating resin layer is formed on.

Next, as shown in FIG. 1C, the excess insulating resin 6 attached to the front and back surfaces of the insulating substrate 1 is removed by passing the insulating substrate 1 between two rubber rollers facing each other. . After that, as shown in FIG. 1D, a solder resist adjusted to about 3 poise is applied by a spray coating method, and further exposed to ultraviolet rays. And about 1%
Development is carried out using a sodium carbonate solution having a concentration of. At this time, if the through holes 4 are masked so that they are not exposed to the ultraviolet rays and the via holes 3 are exposed to the ultraviolet rays, the solder resist inside or around the through holes 4 may be developed at the time of development. It is removed together with the insulating resin on the side wall of the through hole 4. On the other hand, the solder resist pattern 5 is formed on the via hole 3, and the insulating resin 6 remains filled inside, so that the via hole 3 is filled with the insulating resin as shown in FIG. Get the printed wiring board.

Next, a second embodiment of the present invention will be described. 2A to 2E are sectional views for explaining the second embodiment of the present invention in the order of steps. First, FIG.
As shown in (a), the insulating substrate 1 on which the through holes 4, the via holes 3 and the circuit pattern 2 are formed is approximately 1
The insulating resin 6 is filled in the through hole 4 and the via hole 3 as shown in FIG. Next, the insulating substrate 1 is passed between two rubber rollers facing each other, and
As shown in (c), the excess insulating resin 6 adhering to the front and back surfaces of the insulating substrate 1 is removed, and further at about 80 ° C. for about 1
Dry for about 0 minutes to eliminate the stickiness of the insulating resin 6. After that, as shown in FIG. 2D, a solder resist adjusted to about 200 poise is applied by a screen coating method, and exposure is performed using ultraviolet rays. Then, development is performed using a sodium carbonate solution having a concentration of about 1%, and
As shown in (e), a printed wiring board having insulating resin filled in the via holes 3 is obtained.

According to this embodiment, since the insulating resin 6 is dried before applying the solder resist, it is possible to prevent the insulating resin filled in the via hole from flowing out during the manufacturing process, which is more reliable. The beer hole can be closed. This has a particularly remarkable effect when the printed wiring board is multi-layered and becomes thicker or the diameter of the via hole is increased, so that the amount of the insulating resin packed in the inside is increased.

Next, a third embodiment of the present invention will be described. The present embodiment differs from the first and second embodiments in the method of removing excess insulating resin. In this embodiment, a squeegee is used to remove excess insulating resin. The manufacturing method of this embodiment will be described below with reference to FIGS. 3A to 3C are schematic views of the configuration of the apparatus for explaining the insulating resin immersion hole filling step and the insulating resin removing step in the present embodiment.

In this embodiment, masking tape is attached to the two opposite sides of the front and back surfaces of the insulating substrate 1 (shown in FIG. 1A) whose via hole is to be filled with the insulating resin. As shown in FIG. 3A, this is the tape reel 7 on the sending side and the tape reel 8 on the winding side.
An insulating substrate 1 is indicated by an arrow in the drawing between an upper masking tape 9 stretched between the upper and the lower masking tape and a lower masking tape 10 similarly stretched across the masking tape 9. It is performed by transporting in the direction shown. This masking tape is for facilitating handling of the insulating substrate in a later step and for protecting the peripheral portion of the insulating substrate.

Next, in this state, as shown in FIG. 3 (b), the insulating substrate 1 is conveyed to the dipping device 11 and dipped in the liquid of the insulating resin, as shown in FIG. 1 (b). The via hole 3 is filled with the insulating resin 6.

After that, as shown in FIG. 3C, the insulating substrate 1 is conveyed to the take-up reel 8 side and passed between the upper and lower squeegees 12, so that as shown in FIG. Excess insulating resin on the front and back surfaces of the insulating substrate 1 is removed.

After that, through the same steps as those of the first or second embodiment, a printed wiring board having the insulating resin 6 filled in the via hole 3 as shown in FIG. 1E is obtained.

As described above, an appropriate method can be selected as a method for removing the excess insulating resin on the insulating substrate.

[0023]

As described above, according to the present invention, after the printed wiring board having the via holes and the through holes is dipped in the liquid of the photosensitive insulating resin and the insulating resin is filled in these holes. The insulating resin inside the through hole is removed together with the solder resist when the photosensitive solder resist on the through hole is exposed and developed. On the other hand, the insulating resin in the via hole is cured by exposure so that it remains in the via hole even after development. As a result, according to the present invention, the resin can be reliably filled in the via hole.

Therefore, when the printed wiring board is transported by vacuum suction, the vacuum suction cannot be performed and the printed wiring board cannot be transported. Further, there are no problems such as flux blown out from the via hole and suction of cream solder during assembly.

Further, in the conventional manufacturing method using a dry film, the thickness of the solder resist pattern is 100 μm.
According to the present invention, a liquid solder resist is used, but the film thickness can be 30 to 40 μm. Therefore, the via holes can be filled while maintaining a good pattern state without sacrificing the resolution of the solder resist pattern.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention in process order.

FIG. 2 is a diagram for explaining a second embodiment of the present invention in process order.

FIG. 3 is a diagram showing a schematic configuration of an apparatus for explaining an insulating resin immersion hole filling step and an insulating resin removing step in a third example of the present invention.

FIG. 4 is a diagram for explaining a method of closing a via hole in a conventional printed wiring board.

[Explanation of symbols]

 1 Insulating Substrate 2 Circuit Pattern 3 Via Hole 4 Through Hole 5 Solder Resist Pattern 6 Insulating Resin 7,8 Tape Reel 9,10 Masking Tape 11 Immersion Device 12 Squeegee

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[Procedure amendment]

[Submission date] March 23, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Next, as shown in FIG. 1C, the excess insulating resin 6 attached to the front and back surfaces of the insulating substrate 1 is removed by passing the insulating substrate 1 between two rubber rollers facing each other. . Thereafter, as shown in FIG. 1D, a solder resist adjusted to about 3 poise is applied by a spray coating method, dried at 80 to 90 ° C. for 10 to 30 minutes, and then exposed to ultraviolet rays. . Then, development is performed using a sodium carbonate solution having a concentration of about 1%. At this time, if the through holes 4 are masked so that they are not exposed to the ultraviolet rays and the via holes 3 are exposed to the ultraviolet rays, the solder resist inside or around the through holes 4 may be developed at the time of development. It is removed together with the insulating resin on the side wall of the through hole 4. On the other hand, the solder resist pattern 5 is formed on the via hole 3, and the insulating resin 6 remains filled inside, so that the via hole 3 is filled with the insulating resin as shown in FIG. Get the printed wiring board.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Next, a second embodiment of the present invention will be described. 2A to 2E are sectional views for explaining the second embodiment of the present invention in the order of steps. First, FIG.
As shown in (a), the insulating substrate 1 on which the through holes 4, the via holes 3 and the circuit pattern 2 are formed is approximately 1
The insulating resin 6 is filled in the through hole 4 and the via hole 3 as shown in FIG. Next, the insulating substrate 1 is passed between two rubber rollers facing each other, and
As shown in (c), the excess insulating resin 6 adhering to the front and back surfaces of the insulating substrate 1 is removed, and further at about 80 ° C. for about 1
Dry for about 0 minutes to eliminate the stickiness of the insulating resin 6. Then, as shown in FIG. 2D, a solder resist adjusted to about 200 poises is applied by a screen coating method, or a solder resist of about 1 to 6 poises is applied by a spray coating method or a curtain coating method, and ultraviolet rays are applied. Is used to perform exposure. Then, development is performed using a sodium carbonate solution having a concentration of about 1%, and as shown in FIG.
A printed wiring board having insulating resin filled in the via holes 3 is obtained.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

[0023]

As described above, according to the present invention, after the printed wiring board having the via holes and the through holes is dipped in the liquid of the photosensitive insulating resin and the insulating resin is filled in these holes. The insulating resin inside the through hole is removed together with the solder resist when the photosensitive solder resist on the through hole is exposed and developed. On the other hand, the insulating resin in the via hole is cured by exposure so that it remains in the via hole even after development. As a result, according to the present invention, the resin can be reliably filled in the via hole.

Claims (2)

[Claims] 1. A printed wiring board including a via hole for electrically connecting a circuit pattern formed on one surface of an insulating substrate to a circuit pattern formed on the other surface of the insulating substrate, wherein a photosensitive insulation is provided in the via hole. A printed wiring board characterized by being filled with resin. 2. A step of filling a photosensitive insulating resin in the via hole and in the through hole of a printed wiring board including a through hole and a via hole by immersing a hole in the printed wiring board, and an excess of the excess adhesive adhering to the surface of the printed wiring board. Removing the photosensitive insulating resin; forming a layer of a photosensitive solder resist on the surface of the printed wiring board; exposing a predetermined portion of the solder resist layer to development to form a solder resist pattern; And a step of removing the photosensitive insulating resin in the through holes by the developing process.