JPH06188562A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To form a conductor circuit in a stable manner by sufficiently securing the close contact between a board and an electroless copper plated layer in the manufacture of a printed wiring board in which a copper-clad laminated sheet is used. CONSTITUTION:This manufacturing method is composed of a process in which a base copper pattern 12', having the shape corresponding to the prescribed wiring pattern, is formed, a process in which a plated resist layer 15 is formed on the insulative board surface region 13 exposed by etching, a process in which a through hole 14 is formed before conduction of a thick electroless copper plating process, and a process in which a thick electroless copper plated layer 16 in thickness required for the prescribed wiring is formed on the base copper pattern 12' and on the inner wall of the through hole 14.

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 using a copper clad laminate.

[0002]

2. Description of the Related Art Conventional methods for manufacturing printed wiring boards are roughly classified into two methods, that is, a subtractive method which has been widely used and a newly developed additive method, depending on the method of forming a conductor circuit. The subtractive method typically forms a conductor circuit by the procedure shown in FIG.

After using a copper clad laminate 60 in which a copper film 62 is adhered on both sides of an insulating substrate 61 (FIG. 2 (a)), through holes 63 are punched (FIG. 2 (b)). , A thin electroless copper plating 64 as a base plating on the inner wall surface of the through hole 63 and on the copper coatings 62 on both sides ((c) of the same figure).
And thick electrolytic copper plating as main plating on it 65
((D) in the figure). Then, the copper coating 62, the thin electroless copper plating layer 64, and the thick electrolytic copper plating layer 65 are collectively processed by etching to form a conductor wiring 66 (FIG. 8E). After that, the part 67 for soldering the electronic element
The other parts are covered with the overcoat 68 to form the printed wiring board 6
9 is obtained ((f) in the figure).

However, since the subtractive method forms the main part of the conductor wiring by electrolytic copper plating, there is a limit in forming a conductor layer in a fine through hole, and there is a limit in reducing the density and size of a printed wiring board. It was Therefore, an additive method of forming a conductor circuit by electroless copper plating has attracted attention as a method that can cope with high density and downsizing of a printed wiring board instead of the subtractive method.

The additive method is a method of directly forming electroless copper plating on an insulating substrate, and a typical procedure is as shown in FIG. In order to adhere the electroless copper-plated layer to both surfaces of the insulating substrate 50 ((a) in the figure), N
BR-based or epoxy-based adhesive layer 51 (FIG. 2B)
To form. In addition, in order to secure sufficient adhesion, the surface of the adhesive layer is chemically roughened with an oxidizing agent and the anchor effect is used. In the same figure (c), chemical roughening, through hole 5
2 shows a state in which hole 2 and catalyst treatment are performed. Next, after forming a plating resist 53 (FIG. 3D) that masks the area other than the wiring forming portion of the substrate 50, an electroless copper plating layer 54 is formed as a conductor wiring (FIG. 2E). After that, the printed wiring board 57 is obtained by covering the portion other than the portion 55 where the electronic element is soldered with the overcoat 56 (FIG. 7F).

However, in the above-mentioned additive method, since the roughening and the application of the adhesive are likely to be non-uniform, the adhesion between the substrate 50 and the electroless copper plating layer 54 varies, and chromic acid or the like is used in the roughening step. There is also a problem from the viewpoint of environmental protection because it uses toxic substances. As a method for solving the drawbacks of the subtractive method and the additive method, a so-called "partial additive method" has been proposed (Japanese Patent Laid-Open Publication No. Sho 6-96).
1-190797, etc.). This method uses a copper clad laminate as in the subtractive method, forms conductor wiring on the substrate surface by etching, and then forms conductor portions in through holes by electroless copper plating.

However, the partly additive method has the following drawbacks. That is, when performing electroless copper plating in the through holes, it is necessary to cover the parts other than the inner walls of the through holes with a plating resist, and the copper wiring parts already formed by etching on the substrate surface are also covered with this plating resist. Is covered with. Here, the adhesion of the plating resist to the resin of the substrate is relatively large, but the adhesion of the wiring to copper is small, so during the electroless copper plating process in the through hole, the plating resist is not There was a problem of easy peeling.

[0008]

Therefore, the present invention does not require chemical roughening or adhesives, avoids the problem of stripping of the plating resist during the electroless copper plating process, and provides a substrate and an electroless copper plating layer. It is an object of the present invention to provide a method for manufacturing a printed wiring board, which is capable of forming a conductor circuit in a stable manner while ensuring sufficient adhesion.

[0009]

According to the present invention, the above object is to etch a base copper layer containing a copper coating of a copper clad laminate including an insulating substrate and copper coatings on both sides thereof. A step of forming a base copper pattern having a shape corresponding to the predetermined wiring pattern, a step of forming a plating resist layer on the insulating substrate surface region exposed in a shape in which the predetermined wiring pattern is inverted by the etching, the following thickening Prior to the electroless copper plating step, a step of forming a through hole in the copper clad laminate, and a thick electroless copper layer having a thickness necessary for predetermined wiring on the underlying copper pattern and on the inner wall of the through hole. It is achieved by a method for manufacturing a printed wiring board, which includes a step of forming a plating layer.

[0010]

According to the present invention, (1) the thick electroless copper plating necessary for wiring is performed not on the insulating substrate directly but on the underlying copper pattern on the insulating substrate. No adhesive coating or chemical roughening, which was essential in the method, is required, and (2) a plating resist layer for selectively performing this thick electroless copper plating on the underlying copper pattern is formed on an insulating substrate (usually Is formed on the exposed part of resin),
It is possible to perform thick electroless copper plating while the plating resist layer is firmly adhered to the insulating substrate. Since such an interface does not exist, a peeling phenomenon of the plating resist layer does not occur and a conductor circuit can be stably formed.

Even if the peripheral edge portion of the plating resist layer is formed so as to cover the peripheral edge portion of the underlying copper pattern, substantial adhesion is ensured between the resist main portion and the substrate. There is no risk of resist peeling as in the case of the Partial Additive method. In the method of the present invention, even when a double-sided wiring board composed of an insulating substrate and copper films on both surfaces thereof is used as the copper-clad laminate, the insulating substrate and the copper films on both surfaces thereof and the copper wiring inside the substrate are also used. The same effect can be obtained when a multilayer wiring board including layers (copper foil) is used.

The underlying copper layer may be only the copper film of the copper clad laminate, or may include a thin electroless copper plating layer formed as underlying plating thereon. The through holes may be bored after the base copper layer is etched and before the plating resist layer is formed, or before the above etching. In the latter case, it is also possible to perform thin electroless copper plating on the inner wall of the through hole formed by drilling before etching.

In the present invention, generally, after performing thick electroless copper plating which constitutes a predetermined conductor circuit, an overcoat for covering a predetermined region of the thick electroless copper plating layer (conductor circuit) and plating resist is formed. To do. less than,
The present invention will be described in more detail by way of examples.

[0014]

1 to 4 show examples of procedures for manufacturing a printed wiring board according to the present invention. In these figures, the same parts are designated by the same reference numerals. Example 1 A printed wiring board was manufactured according to the present invention by the procedure shown in FIG. (Step 1) Using a copper-clad laminate 10 (FIG. 1A) in which copper foils 12 are adhered on both sides of an insulating substrate 11 made of resin, a copper foil 12 is formed by a method similar to the conventional subtractive method. Is etched to form a base copper pattern 12 'having a predetermined wiring pattern (FIG. 7B). The insulating substrate 11 is exposed in a portion 13 other than the underlying copper pattern 12 '. (Step 2) A through hole 14 is bored at a predetermined portion of the copper clad laminate 10 with an NC drill or the like (FIG. 2 (c)). (Step 3) After the catalyst treatment (not necessary when a copper clad laminate containing a catalyst is used), a plating resist layer 15 is formed on the exposed portion of the substrate 11 by screen printing or application / exposure / development of a photosensitive resist. To be formed ((d) in the figure). The peripheral edge of the resist layer 15 is in a state of being laid over the peripheral edge of the underlying copper pattern 12 ′ (the portion indicated by A in the figure). (Step 4) A thick electroless copper plating layer 16 is formed as a conductor circuit on the underlying copper pattern 12 ′ and on the inner wall of the through hole 14 (FIG. 8E). (Step 5) The printed wiring board 19 is obtained by covering the parts other than the soldering points 17 of the electronic element with the overcoat 18 ((f) of the same figure).

Usually, thereafter, character printing, solder coating, outer shape processing and the like are performed as in the conventional subtractive method. Example 2 A printed wiring board was manufactured according to the present invention by the procedure shown in FIG. The conditions were the same as in Example 1, but the cross-sectional shape of the plating resist 15 was changed to the underlying copper pattern 12 ′.
I changed it so that it would not be a problem. Example 3 A printed wiring board was manufactured according to the present invention by the procedure shown in FIG.

The same procedure as in Example 2 was carried out, but the order of the step of forming the through hole 14 and the etching step for forming the underlying copper pattern 12 'was exchanged. Example 4 A printed wiring board was manufactured according to the present invention by the procedure shown in FIG. (Step 1) Using a copper-clad laminate 10 (FIG. 1A) in which copper foils 12 are adhered on both sides of an insulating substrate 11 made of resin, NC
Through holes 14 are drilled at predetermined locations on the copper-clad laminate 10 with a drill or the like (FIG. 2B). (Step 2) After catalytic treatment, electroless copper plating is applied to form a thickness of several μm on the copper foil 12 and the inner wall of the through hole 14.
The thin copper-plated layer 20 was formed (FIG. 2 (c)). (Step 3) The copper foil 12 and the thin copper plating layer 20 are etched by a method similar to the conventional subtractive method to form a base copper pattern 12 ′ having a predetermined wiring pattern (FIG. 3 (d)). The insulating substrate 11 is exposed in a portion 13 other than the underlying copper pattern 12 '. (Step 4) After the catalyst treatment (not necessary when a copper clad laminate containing a catalyst is used), a plating resist layer 15 is formed on the exposed portion of the substrate 11 by screen printing or application / exposure / development of a photosensitive resist. It is formed ((e) in the figure). The resist layer 15 is in a state of not covering the underlying copper pattern 12 '. (Step 5) A thick electroless copper plating layer 16 is formed as a conductor circuit on the underlying copper pattern 12 ′ and on the inner wall of the through hole 14 (FIG. 5F).

In the subsequent steps, overcoat formation, character printing, solder coating, outer shape processing and the like are performed as in the first embodiment. Each of the printed wiring boards manufactured in Examples 1 to 4 described above can stably form a copper conductor portion even in a small-diameter through hole having a diameter of 0.1 mm (when the thickness of the copper-clad laminate is 1.6 mm). ) Further, since the copper wiring can be formed to the same level as the plating resist by the electroless copper plating, the finished surface has a flat shape, and solder bridges are less likely to occur, and the mountability of SMD components is good.

In addition, the adhesion between the substrate and the copper foil, which has been a problem in the additive method, is sufficiently secured, and since the adhesive layer peculiar to the additive method is not required, the range of material selection is widened, and it can be used in various applications. Can be applied. Further, during the electroless copper plating treatment, since the substantial interface between the copper and the plating resist, which is found in the partly additive method, does not exist, the plating resist does not peel off.
Then, by forming the overcoat, a fine line printed board of the additive method type can be manufactured.

Further, since the electroless copper plating can be performed immediately after the activation treatment by applying the catalyst, the adhesion of the copper conductor in the through hole is good and the activated surface does not touch the resist. There is no contamination by the resist. In addition, since the activator such as the plating catalyst does not remain between the wirings, good insulation between the wirings can be ensured.

Further, since the uniform copper film or the underlying copper layer is etched, a fine circuit can be formed, and the presence of the plating resist enables selective electroless copper plating. Furthermore, the applicant of the present invention has disclosed that
Triethanolamine (T
The treatment can be sped up by using high-speed electroless copper plating using a trialkanol monoamine such as EA) or a salt thereof as a complexing agent and an accelerator.

[0021]

As described above, according to the present invention,
On the one hand, the copper-clad laminate is used as the starting substrate to secure stable adhesion, while on the other hand, the fine line property, which is the original advantage of the additive method, can be utilized, and the adhesive coating process and chemical roughening can be performed. Since no process is required, the advantage of omitting the process is also obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a manufacturing process of a printed wiring board according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a manufacturing process of a printed wiring board according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a manufacturing process of a printed wiring board according to the present invention.

FIG. 4 is a cross-sectional view showing an example of a manufacturing process of a printed wiring board according to the present invention.

FIG. 5 is a cross-sectional view showing a typical printed wiring board manufacturing process by a conventional additive method.

FIG. 6 is a cross-sectional view showing a typical printed wiring board manufacturing process by a conventional subtractive method.

[Explanation of symbols]

10 ... Copper-clad laminate 11 ... Insulating substrate (made of resin) 12 ... Copper film 12 '... Underlying copper pattern 13 ... Surface portion of insulating substrate 11 exposed by etching 14 ... Through hole 15 ... Plating resist 16 ... Thickness Attached electroless copper plating layer

Claims (7)

[Claims] 1. A base copper pattern having a shape corresponding to a predetermined wiring pattern is formed by etching a base copper layer containing a copper coating of a copper clad laminate including an insulating substrate and copper coatings on both sides thereof. The step of forming a plating resist layer on the insulating substrate surface region exposed in a shape in which the predetermined wiring pattern is inverted by the etching, and before the thick electroless copper plating step described below, the copper clad laminate is formed. A printed wiring characterized by including a step of boring a through hole, and a step of forming a thick electroless copper plating layer having a thickness necessary for a predetermined wiring on the underlying copper pattern and on the inner wall of the through hole. Method of manufacturing a plate. 2. The copper clad laminate is a double-sided wiring board comprising the insulating substrate and copper coatings on both sides thereof, or the insulating substrate and the copper coatings on both sides thereof and copper wiring inside the substrate. The method of claim 1 which is a multilayer wiring board comprising layers. 3. The base copper layer comprises the copper coating,
Alternatively, the method according to claim 1 or 2, comprising the copper coating and a thin electroless copper plating layer formed on the copper coating. 4. The method according to claim 1, wherein the through hole is drilled after the etching step. 5. The method according to claim 1, wherein the through hole is drilled before the etching step. 6. The thin electroless copper plating is performed on the underlying copper layer and on the inner wall of the through hole after the through hole drilling step and before the etching step. Method. 7. The overcoat which covers the predetermined area of the thick electroless copper plating layer and the plating resist is formed after the thick electroless copper plating. The method according to item 1.