JPH03123095A - Formation of conductor pattern of plated through-hole double sided printed board - Google Patents

Abstract

PURPOSE:To enable a conductor pattern to be formed excellently in workability keeping the plating of through-hole in a surely protected state by a method wherein a pattern is exposed to ultraviolet rays, then the conductor pattern covering part of the surface resist layer is left unremoved and a disused part is removed through developing. CONSTITUTION:Specific liquid etching resist is applied onto the surface of a board and the circumferential wall of a plated through-hole 1, which is dried up to form a continuous resist layer 3 on the surface of the board 2 and the circumferential wall of the through-hole 1. Then, a sheet 4 is brought into close contact with the surface of a surface resist layer 3A on the board 2. In this state, a conductor pattern covering part 3a of the surface resist layer 3A and a circumferential wall resist layer 3B are exposed to ultraviolet rays through the intermediary of a pattern mask and then they are set. In succession, the sheet 4 is removed from the surface resist layer 3A together with an uncured disused part 3b, and the set conductor pattern covering part 3a and the circumferential wall resist layer 3B are left through developing. Then, the part of the board 2 where the disused part has been removed is etched, whereby a both sided printed wiring board A where a conductor pattern 5 is formed can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to formation of a conductive pattern on a double-sided printed wiring board with plated through-holes, in which a conductive pattern is formed by etching on a double-sided copper-clad laminate plated with through-holes. Regarding the method.

[Conventional technology]

When forming a conductor pattern by etching on a double-sided copper-clad laminate with plated through holes (hereinafter simply referred to as the board), it is important to prevent the plating on the plated through holes from peeling off or being damaged. The following technology is known as a conventional technology corresponding to this.

One is a plated through hole (1
) with resist ink, etc.) (10)
After filling the conductive pattern of the substrate (2), a pattern resist (11) is printed to cover the conductor pattern of the substrate (2), and after exposing the pattern resist (11), an etching process is performed on the substrate (2). 11)
In this method, the filled etching resist (10) is removed, and the peripheral wall plating surface of the plated through hole (1) is protected by the filled etching resist (10) to form a conductor pattern.

Second, as shown in Figure 8, plated through holes (
1) is filled with an etching resist (10), and then a dry film (12) is closely attached to the surface of the substrate (2).
After exposing the conductive pattern covering part of the dry film (12) in this state, the support film (12A) of the dry film (12) is peeled off, and in that state, the dry film (12) is peeled off.
After developing the resist film (12B) of 12), the substrate (
2) is etched, and then the conductor pattern covering portion and the filled etching resist (10) are etched.
This method attempts to protect the plating by removing it, as in the prior art described above.

Thirdly, as shown in FIGS. 9(a) and (l), in the method using the tri-film (12), the step of filling the plating through hole (1) with the etching resist (10) is omitted, and the plating This method attempts to protect the plated through hole (1) with a conductor pattern covering that closes the opening of the through hole (1).

Fourth, as shown in Figure 1O, a liquid etching resist (13) is applied to the surface of the substrate (2) and the peripheral wall surface of the plated through hole (1), and the resist layer ( Of 13), the conductor pattern covering portion (13A) and the resist layer (13B) on the peripheral wall surface were exposed and developed with a solution, and the substrate (2) was etched, and then both resist layers (13A) were formed.

(13B) and thereby protect the plated through holes (1) with a resist layer (13B) to form a conductor pattern.

[Problem to be solved by the invention]

However, the prior art has the following drawbacks.

When using the first and second hole-filling conventional techniques in which the plated through hole is protected by the etching resist filled in the plated through hole, the filled etching resist shrinks in volume as the solvent evaporates during drying, as shown in Fig. 7. As shown in FIG. 8, poor masking occurs at both ends of the plated through hole, and the plating at both ends of the plated through hole is likely to be removed during etching. Moreover, filling the plated through-holes with etching resist involves filling the plated through-holes with a large amount of etching resist and then scraping off the excess etching resist, which eliminates the need for etching resist on the substrate surface. It will be applied to. As a result, it is necessary to scrape off the etching resist so that it does not remain on the surface of the substrate, making the work complicated.

When using the third conventional technique, if the resist film layer of the dry film is thin or the pattern film is misaligned, the sprayed developer may damage the part blocking the opening of the plated through hole. Defects are likely to occur.

However, when a dry film with a large thickness is used, the resolution of exposure of the conductor pattern is reduced.

In addition, as a dry film, the adhesive strength of the unexposed resist to the support film is increased, and the unexposed portion of the resist film layer is adhered to the support film and removed by peeling off the support film, so that the conductor exposed on the substrate can be removed. An improved idea is to use a so-called dry development type in which only the pattern covering portion can remain.

However, in this case, there is a limit to increasing the film thickness due to the development mechanism, and the desired tenting mask performance is low.

In the case of the fourth conventional technique, although the peripheral wall surface of the plated through hole is covered with a resist layer, since both end openings of the plated through hole are open, the developer hits the peripheral wall surface resist layer during solution development. This may cause deterioration of the peripheral wall resist layer, such as mechanical damage to the peripheral wall resist layer, resulting in poor masking. In particular, when the hole diameter is large compared to the hole diameter, that is, when the plated through hole is long and narrow, poor exposure of the resist layer on the peripheral wall surface is likely to occur, and the uncured portion of the poorly exposed area is washed away by the developer, resulting in the plating through hole. This tends to lead to poor masking of holes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a conductor pattern in a plated double-sided printed wiring board in through-holes, which can eliminate the above-mentioned drawbacks.

[Means to solve the problem]

The method of forming a conductor pattern on a double-sided printed wiring board with plated through-holes according to the present invention is characterized in that the surface of the double-sided copper-clad laminate with plated through-holes and the peripheral wall surface of the plated through-holes are irradiated with ultraviolet rays to form the double-sided copper-clad laminate. applying a liquid etching resist whose adhesive strength to the plate and the adhesive strength to the sheet are reversed, and bringing the sheet into close contact with the surface of the surface resist layer applied to the surface of the double-sided copper-clad laminate;
In this state, the adhesive strength of the conductor pattern covered portion of the surface resist layer to the double-sided copper-clad laminate is greater than the adhesive strength of the sheet, and the adhesive strength of the other unnecessary parts to the double-sided copper-clad laminate is greater than that of the sheet. After exposing the surface resist layer to ultraviolet light through a pattern mask so that the adhesive strength is smaller than the adhesive strength of the sheet, the sheet is peeled off, and the surface resist layer of the double-sided copper-clad laminate is peeled off. After etching is performed on the portion from which unnecessary portions have been removed, the conductive pattern covering portion and the peripheral wall surface resist layer are removed.

[For production]

After exposing the pattern to ultraviolet rays, the conductor pattern covered portion of the surface resist layer is left on the substrate (double-sided copper-clad laminate), and the unnecessary portion is removed from the substrate. A so-called dry development method in which the unnecessary parts are adhered to the sheet more strongly than the substrate, the conductor pattern covering part is adhered to the substrate more strongly than the sheet, and the sheet is peeled off to remove the unnecessary parts from the substrate together with the sheet. Since this method is adopted, no external force is applied to the peripheral wall resist layer during development, and there is no deterioration of the peripheral wall resist layer. In particular, when performing so-called negative type exposure in which the conductor pattern covering portion of the surface resist layer and the peripheral wall surface resist layer are irradiated with ultraviolet rays and cured,
Even if there is an exposure defect in the peripheral wall surface resist layer, the peripheral wall surface resist layer can be completely prevented from being damaged by development. Moreover, by applying a liquid etching resist, the surface resist layer and the peripheral wall resist layer are formed in a continuous state, so the entire surface of the substrate can be covered with the etching resist of a desired thickness by a simple operation such as coating. can.

〔Effect of the invention〕

Therefore, according to the present invention, it has become possible to form a conductive pattern on a plated double-sided printed wiring board in a plated through hole with good operability and in a state where the plating of the plated through hole is reliably protected.

〔Example〕

Next, examples of the present invention will be shown.

To fabricate a through-hole plated double-sided printed wiring board using a double-sided copper-clad laminate (substrate), as shown in Figure 1,
First, a through hole is formed in a substrate, and the entire surface of the through hole including the peripheral wall surface is subjected to electroless copper plating and electrolytic copper plating to produce a substrate (2) with a plated through hole (1).

Next, as shown in FIG. 2, the surface of the substrate (2) and the peripheral wall surface of the plated through hole (1) are cured by ultraviolet irradiation to adhere more strongly to the sheet (4) than to the substrate (2). A liquid etching resist that changes from a state to a state where it adheres more strongly to the substrate (2) than to the sheet (4) is applied, dried, and continuously applied to the surface of the substrate (2) and the peripheral wall surface of the plated through hole (1). A resist layer (3) is formed.

As shown in FIG. 3, the sheet (4) is brought into close contact with the surface of the surface resist layer (3A) of the substrate (2) with the resist layer (3).

As shown in FIG. 4, the conductor pattern covering portion (3) of the surface resist layer (3A) is
a) and the peripheral wall surface resist layer (3B) are exposed to ultraviolet light through a pattern mask and cured.

As shown in FIG. 5, after the resist layer is cured, the sheet (4) is peeled off from the surface resist layer (3A) together with the uncured unnecessary part (3b) of the surface resist layer (3A) that adheres to it. The unnecessary portion (3b) of the resist layer (3A) is removed from the surface of the substrate (2), and the hardened conductor pattern covering portion (3a) and peripheral wall surface resist layer (3B) are removed from the substrate (2).
leave it in In other words, develop it.

As shown in FIG. 6, etching treatment is performed on the portion of the developed substrate (2) from which the unnecessary portion (3b) has been removed;
That is, after removing the copper foil in that area, the conductor pattern covering part (3a) and the peripheral wall surface resist layer (3B) are removed, and the through-hole plated double-sided printed wiring board (A) on which the conductor pattern (5) is formed is removed. ).

As mentioned above, the etching resist and sheet (4) used for so-called peeling development in which the uncured portion (3b) of the surface resist layer (3A) is peeled off and developed together with the sheet (4).
) is shown below.

For etching, polyvinyl alcohol 10 parts by weight Zinc chloride double salt of 4-diazodifninylamine 1 part Glycerin 1 part by weight Water
80 parts by weight, and the sheet (4) may be a polyethylene sheet.

[Another example]

Another embodiment of the invention is shown below.

[1] In the above embodiment, the conductor pattern covering portion (3a) of the surface resist layer (3A) is exposed to ultraviolet rays, and the exposed conductor pattern covering portion (3a) is left on the substrate (2) in a so-called negative type. However, the present invention can also be applied to a so-called positive type in which the unnecessary portion (3b) is exposed to ultraviolet light and the exposed unnecessary portion (3b) is peeled off from the substrate (2). Of course, in the case of this positive type, the etching resist 1 is selected such that the adhesive force to the sheet (4) upon exposure is stronger than the adhesive force to the substrate (2).

[2] Note that although reference numerals are written in the claims section for convenience of comparison with the drawings, the present invention is not limited to the structure of the attached drawings by the entry.

[Brief explanation of drawings]

1 to 6 are cross-sectional views of each process showing an embodiment of the method for forming a conductor pattern on a double-sided printed wiring board plated in through holes according to the present invention, and FIGS. 7, 8, and 1O are 9A and 9B are cross-sectional views showing each process in the conventional example. (1)...Plated through hole, (2)...
...Double-sided copper-clad laminate, (3A)...Surface resist layer, (4)...2 sheet, (3a)...Conductor pattern covering part, (
3B)... Peripheral wall surface resist layer, (3b)...
...Unnecessary part.

Claims (1)

[Claims] Double-sided copper clad laminate (2) with plated through holes (1)
) and the surrounding wall of the plated through hole (1),
A liquid etching resist whose adhesive strength to the double-sided copper-clad laminate (2) and the adhesive strength to the sheet (4) are reversed by ultraviolet irradiation is applied to the surface of the double-sided copper-clad laminate (1). The sheet (4) is brought into close contact with the surface of the surface resist layer (3A), and in this state, the surface resist layer (3A) is
Among A), the adhesive strength of the conductor pattern covering part (3a) to the double-sided copper-clad laminate (2) is greater than the adhesive strength of the sheet (4), and the double-sided copper of the other unnecessary part (3b) After exposing the surface resist layer (3A) to ultraviolet light through a pattern mask so that the adhesive force to the stretched laminate (2) is smaller than that of the sheet (4), the sheet (4) is peeled off. and the sheet (4) of the double-sided copper-clad laminate (2).
Unnecessary parts (3b) of the surface resist layer (3A) are removed due to peeling of
A method for forming a conductor pattern on a through-hole plated double-sided printed wiring board, in which the conductor pattern covering portion (3a) and the peripheral wall surface resist layer (3B) are removed after etching the portion from which the conductor pattern has been removed.