JP2003037354A - Method of manufacturing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a printed wiring board which is improved in protection of a through-hole by forming a uniform protective film on the inner wall of the through-hole. SOLUTION: In this printed wiring board manufacturing method, an alkali- soluble resin containing colloidal silica is applied on a copper-plated laminate 1 before a dry film is fixed by application of pressure. By this setup, a protective film 4a can be uniformly formed on the wall surface of a through-hole 3, so that a high-reliability printed wiring board superior in protection of the through-hole 3 can be provided.

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, mobile communication devices, video cameras and the like.

[0002]

2. Description of the Related Art In recent years, printed wiring boards, which are widely used in various electronic devices and the like, are required to have high wiring density and high reliability as the electronic devices become smaller and have more functions. ing. In particular, there is a strong demand for the reliability of the through-hole portion, and various printed wiring board manufacturing methods corresponding to this are proposed.

Generally, a tenting method is widely used as a method for manufacturing a printed wiring board, but a printed wiring board using a hole-filling resin is used as a technique for protecting the through holes from the ingress of a developing solution and an etching solution. The manufacturing method (hereinafter, referred to as a hole filling method) is widely known.

FIG. 3 is a cross-sectional view of a substrate for explaining the manufacturing process sequence of a printed wiring board by this hole filling method. First, as shown in FIG. 3A, a through hole is formed in the copper clad laminate 11, and then copper plating is applied to the entire surface of the substrate to form a conductor layer 12 including a copper plating layer and a through hole 13.

Next, as shown in FIG. 3 (b), a hole filling resin 14 is formed on the conductor layer 12 on the surface of the through hole 13 of the copper clad laminate 11.
After coating the copper-clad laminate 11 with the conductor layer 12 formed thereon
The through hole 13 is filled with the hole filling resin 14 while removing the hole filling resin 14 with a rubber plate or the like. When the hole filling resin 14 is an ultraviolet curing type, the copper clad laminate 11 has 1 to 10 surfaces on both sides.
It is cured by irradiating it with ultraviolet rays of J / cm ² , and in the case of a thermosetting type, it is dried at a temperature of 80 to 140 ° C. for 10 to 30 minutes,
Let it harden.

Next, as shown in FIG. 3C, the excess hole-filling resin 14 applied to the surface of the copper-clad laminate 11 is removed by polishing with a belt, brush, roll, jet scrub, or the like, and then, FIG. As shown in FIG. 3C, the dry film 15 is thermocompression bonded, and as shown in FIG. 3E, the dry film 15 is exposed to ultraviolet rays 17 through the desired mask film 16.

After the exposure, the dry film 15 in the unexposed portion is dissolved and removed with a weak alkaline developer such as sodium carbonate having a pH of 9 to 10, and the etching resist 1 is removed as shown in FIG. 3 (f).
8 is formed. Further, as shown in FIG. 3G, the conductor layer 12 exposed without forming the etching resist 18 is removed by etching.

Finally, as shown in FIG. 3 (h), the etching resist 18 and the filling resin 14 are dissolved and removed with a strong alkaline aqueous solution such as caustic soda having a pH of 12 to 13 to obtain a printed wiring board.

According to this method, after the copper plating, the filling resin 14 is filled inside the through hole 13, so that the filling resin 14 is filled with the developing solution or the etching solution.
There is an advantage that the through hole 13 can be protected by preventing the penetration into the inside.

However, the hole filling method has the following problems in mass productivity.

In FIG. 3 (c), when the excess hole-filling resin 14 applied to the surface of the copper-clad laminate 11 is polished and removed, dimensional variation occurs due to the elongation of the copper-clad laminate 11, and excessive polishing occurs. As a result, the thickness of the conductor layer 12 becomes thin, which may cause disconnection.

When the hardening of the hole filling resin 14 inside the through hole 13 is promoted, it takes a very long time to remove the hole filling resin 14 by peeling. For this reason, productivity may be deteriorated, and discoloration of the copper foil may occur due to the strongly alkaline stripping solution.

As a technique for solving the above problems of the hole filling method, a method of manufacturing a printed wiring board in which an alkali-soluble resin is formed only on the wall surface of a through hole is known. FIG. 4 is a cross-sectional view of a main part of a substrate in a process of manufacturing a printed wiring board for applying an alkali-soluble resin to the substrate.

First, as shown in FIG. 4A, the copper clad laminate 21
A conductor layer 22 including a copper plating layer and a through hole 23 are formed on the top, and dipping is performed in an alkali-soluble resin solution.

Next, the dipping copper clad laminate 21 is slowly pulled up so that no liquid drips on the end face, and the excess resin solution on the surface of the copper clad laminate 21 is removed with a squeegee or the like, and then for 5 minutes. Heat cured at 100 ° C., FIG.
As shown in (b), the through hole protective film 2 is formed on the conductor layer 22.
4a and 24b are formed.

The through-hole protective coating 24b formed on the surface as shown in FIG. 4C is removed by wet polishing of buffs # 400 to # 600 in the dry film pressure bonding pretreatment step. After pretreatment, a dry film 25 is attached as shown in FIG. 4D, and ultraviolet rays 27 are applied to the entire surface from above through a mask film 26 having a desired wiring pattern as shown in FIG. Only the part is exposed.

After the exposure, the dry film 25 in the unexposed portion is dissolved and removed with a weak alkaline developer such as sodium carbonate having a pH of 9 to 10, and the etching resist 2 is removed as shown in FIG. 4 (f).
8 is formed. Further, as shown in FIG. 4G, the etching resist 28 is dissolved and removed, and the exposed conductor layer 22 is removed by etching.

Finally, as shown in FIG. 4 (h), the etching resist 28 and the through-hole protective film 24a are adjusted to pH12.
A printed wiring board is obtained by dissolving and removing with a strong alkaline solution such as caustic soda of -13.

[0019]

However, with the above-mentioned conventional alkali-soluble resin, the wettability and adhesion to the through hole are poor, and it is difficult to apply the resin uniformly to the wall surface of the through hole. In some cases, holes are generated and the through holes cannot be protected from invasion of the etching solution. Further, when the wettability and adhesion of the resin to the through holes are improved, it is difficult to remove the buffs # 400 to # 600 by wet polishing in the dry film pressure bonding pretreatment step.

An object of the present invention is to provide a manufacturing method capable of obtaining a printed wiring board excellent in through hole protection, which solves the problems of the above-mentioned conventional techniques.

[0021]

In order to achieve this object, the invention described in claim 1 of the present invention, in particular, provides through-hole protection before crimping a photosensitive dry film onto a copper clad laminate. A method for producing a printed wiring board, which is characterized in that an alkali-soluble resin containing colloidal silica as a coating is applied to the copper clad laminate, whereby
It is possible to form a uniform protective film on the wall surface of the through hole, and it is possible to manufacture a printed wiring board having excellent through hole protection.

The invention according to claim 2 of the present invention is
The content of colloidal silica in the alkali-soluble resin is 5
10. The method for producing a printed wiring board according to claim 1, wherein the content of colloidal silica is 5 to 10% to form a uniform protective film on the through hole wall surface, and the copper clad laminate. It is possible to easily remove the alkali-soluble resin applied on the surface by buffing, and it is possible to produce a printed wiring board excellent in through-hole protection.

The invention according to claim 3 of the present invention is
The method for manufacturing a printed wiring board according to claim 1, wherein the alkali-soluble resin is applied by a dipping method, and a uniform protective film is formed on the through-hole wall surface by applying the dipping method. This makes it possible to manufacture a printed wiring board excellent in through-hole protection.

The invention according to claim 4 of the present invention is
The method for producing a printed wiring board according to claim 1, wherein the alkali-soluble resin is a resin that is dissolved in a strong alkaline solution having a pH of 11 to 14, whereby the pH is
Since the resin does not dissolve in the sodium carbonate developing solution of 9 to 10, the conductor on the wall surface of the through hole is not exposed,
Therefore, it is possible to prevent the etching solution from entering the wall surface of the through hole. It is possible to obtain the effect that it is possible to manufacture a printed wiring board without breakage of through holes. Also,
Since the pH of the etching resist solution is 12 to 13, the resin is dissolved and removed together with the etching resist.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process cross-sectional view of a main part of a substrate in a manufacturing process of a printed wiring board according to an embodiment of the present invention, and FIG. It is a schematic diagram of the process of apply | coating the through-hole protection film which becomes to a copper clad laminated board.

First, a through hole is formed in a copper clad laminate 1 in which copper foil is formed on both sides of an insulating layer, and the through hole is plated with copper to form a conductor layer 2 as shown in FIG. 1 (a). Through holes 3 are formed. Next, by dipping the copper clad laminate 1, alkali-soluble through-hole protective coatings 4a and 4b containing 5 to 10% of colloidal silica as shown in FIG. 1B are formed. Here, a process of forming the through-hole protective coatings 4a and 4b will be described with reference to FIG.

The copper-clad laminate 1 having through holes is
2 (a) is dipped in an alkali-soluble resin solution containing colloidal silica in an amount of 5-10%, and then the copper-clad laminate 1 is dipped in the alkali-soluble resin 10 as shown in FIG. As in b), pull up slowly so that no liquid drips on the end face, and further remove excess resin solution on the substrate surface with a squeegee 9, etc., and then at 100 ° C. for 5 minutes.
Then, it is heat-cured to form a through-hole protective film as shown in FIG. As a result, the through hole protective coating 4a applied to the wall surface of the through hole 3 is uniformly applied by the contained colloidal silica.

Next, the through-hole protective coating 4b applied to the surface of the copper-clad laminate 1 was wet-polished by the buffs # 400 to # 600 in the dry film pressure bonding pretreatment step as shown in FIG. 1 (c).
As shown in FIG. 1D, the dry films 5 are attached to both surfaces of the copper-clad laminate 1, and the entire surface is irradiated with ultraviolet rays 7 through the mask film 6 having a desired wiring pattern. Then, as shown in FIG. 1E, only the wiring pattern portion is exposed.

After the exposure, the dry film 6 in the unexposed portion is dissolved and removed with a weak alkaline developer such as sodium carbonate having a pH of 9 to 10 to obtain an etching resist 8 as shown in FIG. 1 (f). At this time, the through-hole protective film 4a applied to the wall surface of the through-hole is not dissolved in the developing solution. Further, the conductor layer 2 exposed by dissolving and removing the etching resist 8 on the surface is removed by etching as shown in FIG.

Finally, the etching resist 8 and the through-hole protective film 4a are dissolved and removed with a strong alkaline solution such as caustic soda having a pH of 12 to 13 to obtain a printed wiring board as shown in FIG. 1 (h).

As described above, according to this embodiment, 5 to 10% of colloidal silica is used as the through-hole protective film.
By coating the contained alkali-soluble resin by the dipping method, it can be uniformly formed on the wall surface of the through hole, and the buffs # 400 to # 600 in the dry film pressure pretreatment process can be removed by wet polishing. It has an effect that can be easily performed. Here, if the content of colloidal silica is less than 5%, it is not possible to guarantee the uniformity of formation of the protective film on the wall surface of the through hole,
If it exceeds 10%, the adhesiveness between the cured resin and the conductor layer on the printed wiring board becomes excessive, and it may not be removed by the wet polishing of buffs # 400 to # 600 in the dry film pressure bonding pretreatment step. .

Further, when the resin is dissolved in a strong alkaline solution having a pH of 11 to 14, the protective film on the wall surface of the through hole is not dissolved in the developing step using the weak alkaline solution, and the resin is passed through the etching step while being uniformly held. Therefore, the wall surface of the through hole is not etched, and the printed wiring board requiring high reliability can be dealt with. Here, when the pH is less than 11, it is not suitable because the through-hole protective film dissolves in the developing solution such as sodium carbonate as described above. When the pH of the solution exceeds 14, copper clad laminate is used. Not suitable as it may dissolve the plate itself.

[0033]

As described above, according to the present invention, the alkali-soluble resin used for forming the through-hole protective film contains colloidal silica to form a uniform protective film on the wall surface of the through-hole, and the buff # 400. ~ # 600
Since the film formed on the surface of the copper clad laminate can be easily removed by the wet polishing described above, it becomes possible to efficiently produce a high quality printed wiring board.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a printed wiring board according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an alkali-soluble resin coating step in the embodiment of the present invention.

FIG. 3 is a process sectional view showing a method for manufacturing a printed wiring board by a conventional hole filling method.

FIG. 4 is a process sectional view showing a method for manufacturing a conventional printed wiring board coated with an alkali-soluble resin.

[Explanation of symbols]

1 Copper Clad Laminate 2 Conductor Layer 3 Through Hole 4a Through Hole Protective Coating 4b Applied on Through Hole Wall Surface Through Hole Protective Coating 5 Applied on Substrate Surface 5 Dry Film 6 Mask Film 7 Ultraviolet 8 Etching Resist

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E314 AA25 AA42 BB06 CC04 DD06                       FF05 FF08 FF19 GG14                 5E317 AA24 BB12 CC32 CD21 CD23                       CD25 CD27 CD32 GG09                 5E339 AB02 AC01 AD03 AE01 BC02                       BD06 BD11 BE13 CC01 CD01                       CE11 CE16 CF16 CF17 CG04                       DD04 EE05 GG02

Claims (4)

[Claims] 1. A step of forming a through hole in a copper clad laminate,
Forming through holes in the through holes by plating, pressing a photosensitive dry film onto the copper clad laminate, and forming a conductor pattern on the copper clad laminate by exposing, developing, and etching Characterized in that an alkali-soluble resin containing colloidal silica as a through-hole protective coating is applied to the copper-clad laminate before the photosensitive dry film is pressure-bonded onto the copper-clad laminate. Printed wiring board manufacturing method. 2. The method for producing a printed wiring board according to claim 1, wherein the content of colloidal silica in the alkali-soluble resin is 5 to 10%. 3. The method for producing a printed wiring board according to claim 1, wherein the alkali-soluble resin coating method is a dipping method. 4. The method for producing a printed wiring board according to claim 1, wherein the alkali-soluble resin is a resin that is dissolved in a strong alkaline solution having a pH of 11-14.