JPH08321677A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE: To provide a method of manufacturing a printed wiring board, wherein a layer of metal other than copper is capable of being formed on a copper circuit through an electroplating method without providing a power feeding lead to the one side of a board. CONSTITUTION: A through-hole 2 is provided to a board 1, and the board 1 is subjected to a copper plating process, whereby all both the sides of the board 1 and the through-hole 2 are coated with copper layers 4a and 4b respectively. A copper circuit 6a is formed on the one side of the board 1 so as to be connected to the copper layer 4b formed on the inner surface of the through-hole 2, and the copper layer 4a is left unremoved on the opposite side of the board 1. The copper circuit 6, the copper layer 4b inside the through-hole 2, the copper layer 4a formed on the opposite side of the board 1 to serve as a power feeder are exposed, and plating resist 9 is applied onto both the sides of the board 1. A layer 12 of metal other than copper is formed on the exposed copper circuit 6a and the copper layer 4b inside the through-hole 2 through an electroplating method. A copper circuit 6 is formed on the copper layer 4a left on the opposite side of the board 1.

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, and more particularly to a method for plating and finishing a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, on the surface of a copper circuit of a printed wiring board, for the purpose of preventing oxidation, improving solder wettability, ensuring bondability of gold wire, imparting hardness to sliding parts and preventing wear. It is common to perform plating with metals other than copper, such as solder, tin, nickel, gold, palladium, and rhodium. Then, plating of these metals is performed by a dipping method in a molten liquid, an electroplating method, or the like. inside that,
The electroplating method is widely used because it is possible to plate only a necessary portion by masking with a plating resist, and it is also possible to stack two or more kinds of metals on top of each other. There is. When the electroplating method is applied, the power supply leads necessary for the electroplating are provided as wiring, though they are not necessary for achieving the functions originally required for the printed wiring board. An example of this power supply lead is shown in FIG. 2. The power supply lead 21 of FIG. 2 has a peripheral frame-shaped power supply part 22 and a copper circuit 23 for electroplating.
It is generally provided for connecting to the power supply unit 22 and is cut off from the frame-shaped power supply unit 22 by a cutting operation when cutting out the final printed wiring board.

The provision of such a power supply lead causes problems such as complicated circuit design and reduced wiring density, and a solution is required. And
The problem of arranging the power supply lead becomes remarkable in a printed wiring board having circuits on both sides of the board.
It is often the case for the circuit on either side. One of the reasons for this is that in a printed wiring board with circuits on both sides, components are often mounted on either side, so plating of a metal other than copper on only the side on which the components are mounted is necessary. This is because the wiring density on the plated surface is often higher than that on the opposite surface. That is, on the opposite surface, there are not many cases where it is necessary to specially arrange the power supply leads and perform plating of a metal other than copper, and even when the power supply leads are arranged, the wiring density is not so high. In many cases, problems such as deterioration do not occur. Therefore, if it is possible to develop a method that enables electroplating of a circuit on either side of a printed wiring board having circuits on both sides without specially arranging the power supply leads, the power supply leads can be arranged. This often solves the problems of complicated circuit design and reduced wiring density, and is useful in the manufacture of printed wiring boards.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and copper is formed on a copper circuit on at least one surface of a printed wiring board having copper circuits on both surfaces of the board. A method for manufacturing a printed wiring board in which a metal layer other than copper is formed by an electroplating method, wherein a metal layer other than copper is electroplated on a copper circuit without disposing a power supply lead on one surface of the substrate. It is an object of the present invention to provide a method for manufacturing a printed wiring board that enables the formation of the printed wiring board.

[0005]

According to a first aspect of the present invention, there is provided a printed wiring board manufacturing method, wherein both surfaces of a substrate are provided with copper circuits, and a metal layer other than copper is electroplated on at least one surface of the copper circuits. A method for manufacturing a printed wiring board formed by a method, characterized by comprising the following steps (A) to (E). (A) A step of forming a through hole in the substrate and then performing copper plating to form a copper layer on the entire surface of both sides of the substrate and in the through hole. (B) A step of forming a copper circuit connected to the copper layer in the through hole on one surface of the substrate and leaving the copper layer on the entire other surface on the opposite surface. (C) The copper circuit at a position where a metal layer other than copper is formed, the copper layer in the through hole and the copper layer at a portion serving as a power feeding portion on the opposite surface are exposed, and both surfaces other than these are plated with a resist. Step of coating with. (D) A step of energizing the power feeding portion to form a metal layer other than copper on the exposed copper circuit and the copper layer in the through hole by electroplating. (E) A step of forming a copper circuit on the copper layer remaining on the opposite surface.

According to a second aspect of the present invention, there is provided a method for producing a printed wiring board according to the first aspect, wherein the metal other than copper formed by electroplating is lead, tin or an alloy thereof. And

The method for manufacturing a printed wiring board according to a third aspect of the present invention is the method according to the first aspect, wherein the metal other than copper formed by electroplating is nickel, gold, palladium, rhodium or an alloy thereof. It is characterized by being.

According to a fourth aspect of the present invention, there is provided a method for producing a printed wiring board according to the first aspect, wherein the substrate before the through holes are formed is a substrate having copper foils on both sides. To do.

The present invention will be described below with reference to the drawings.
In the present invention, as the step (A), as shown in FIG. 1A, the through holes 2 are formed in the substrate 1, and then copper plating is performed to form copper on both surfaces of the substrate 1 and in the through holes 2. Layers 4a, 4
b is formed. As the substrate 1 in the present invention, a copper clad laminate, a multilayer laminate having an inner layer circuit, and the like can be used in addition to a simple insulating substrate. Therefore, the substrate 1
Regarding the formation of the copper layer 4a on the entire surface, when the copper foil 3 or the like is previously formed on both surfaces of the substrate 1 to be used, a copper plating layer is formed on the copper foil 3 or the like to form a copper plating layer. 4a may be used, or a copper layer 4b formed by copper plating may be formed in the through hole 2 and the copper foil 3 formed in advance on both sides of the substrate.
Alternatively, the copper layer 4a can be formed only by itself. In FIG. 1 (a),
The through hole 2 is formed using the substrate 1 provided with the copper foil 3, and copper plating is performed on the copper foil 3 and the like to obtain the copper layer 4a. (The copper foil 3 forms a part of the copper layer 4a.) Next, as a step (B), one surface of the substrate 1 (plating finish surface 5) is connected to the copper layer 4b in the through hole 2. Copper circuit 6
And the copper layer 4a is left on the entire opposite surface 7.
At this time, the copper circuit 6 which is not connected to the copper layer 4b in the through hole 2 can be simultaneously formed. As an example of the method for forming the copper circuit 6, the dry film 8 is attached on both sides, patterned by a photographic method (FIG. 1B), etched, and then the dry film 8 is peeled off to form the copper circuit 6.
Can be formed by the so-called subtractive method (Fig. 1
(C)). Alternatively, a copper circuit may be formed by a so-called semi-additive method in which a plating resist is used as a resist and a circuit is formed after the resist patterning through the steps of copper plating, resist peeling and etching.

Next, in step (C), a metal layer 1 other than copper is used.
2, a copper circuit 6a connected to the copper layer 4b in the through hole 2 (the copper circuit in the portion to be plated is referred to as a copper circuit 6a), a copper layer 4b in the through hole 2 and the opposite Face 7
Then, the copper layer 4a in the portion to be the power feeding portion 11 is exposed, and both surfaces other than these are covered with the plating resist 9 (FIG. 1 (d)). As the plating resist 9, either dry film type or liquid type may be used.

Next, in step (D), the exposed power supply portion 11 is energized to expose a portion other than copper on the copper circuit 6a exposed on the plating finish surface 5 side and on the copper layer 4b in the through hole 2. The metal layer 12 is formed by electroplating (FIG. 1E). The composition of the plating bath used is not particularly limited, but when an alkali development type plating resist is used, it is preferable to use an acidic bath. Examples of the metal forming the metal layer 12 other than copper include lead, tin, solder, nickel, gold, palladium, rhodium, and alloys containing these, and may be selected depending on the purpose of plating finish.

Next, as a step (E), a metal layer 1 other than copper is used.
2 from the substrate formed by the electroplating method to the plating resist 9
Then, the copper circuit 6 is formed on the copper layer 4a remaining on the opposite surface 7 (FIG. 1 (f)). The circuit forming method in this case is not particularly limited, and for example, a method using a dry film as an etching resist can be used.

Further, it is preferable to form a protective film such as a solder resist on the exposed copper circuit 6 of the printed wiring board obtained above so that the copper circuit can be prevented from being oxidized.

[0014]

In the present invention, the copper circuit at the position where the metal layer other than copper is formed on the plated surface side is connected to the power supply section on the opposite surface via the copper layer in the through hole. ,
In the step (D), electricity can be applied to the power supply portion to form a metal layer other than copper on the exposed copper circuit and the copper layer in the through hole by electroplating. Therefore, in the present invention, a metal layer other than copper can be formed by electroplating on the copper circuit on the plating finish surface side without specially disposing the power supply lead on the plating finish surface side. As a result, it is possible to solve the problem that the circuit design is complicated and the wiring density is lowered by disposing the power supply leads.

[0015]

The present invention will now be described based on the present invention, but these examples do not limit the present invention.

(Examples 1 to 5) Step (A): A double-sided copper-clad laminate is drilled to form through holes (through holes), and after desmearing the through holes, electroless copper plating is performed. , Electrolytic copper plating 1μ each
m to 20 μm, to obtain a panel-plated substrate having copper layers formed on the entire surfaces of both sides of the substrate and in the through holes.

Step (B): A dry film (DuPont; trade name: Liston 4620) is used as an etching resist to form a copper circuit connected to the copper layer in the through hole on one surface of the substrate. A copper layer was left on the entire opposite surface. The dry film was peeled off at the end of this step.

Step (C): A copper circuit connected to the copper layer in the through hole at a position where a metal layer other than copper is formed, the copper layer in the through hole and the opposite surface to form a power feeding portion. The copper layer of the part is exposed, and the other part is a dry film which is a plating resist on both sides (manufactured by DuPont; product name Liston 4
620).

Step (D): An electric current was applied to the power feeding portion to form a metal layer other than copper on the exposed copper circuit and the copper layer in the through hole by electroplating. In addition, electroplating for forming a metal layer other than copper was performed using a plating solution having a plating bath composition shown in Table 1. Regarding the gold plating shown in Example 3, the nickel plating of Example 2 was applied, and the gold plating was applied in layers. The dry film was peeled off at the end of this step.

Step (E): A dry film (manufactured by DuPont; trade name: Liston 4620) on the copper layer remaining on the opposite surface.
Was used to form a copper circuit. At this time, the surface plated with a metal other than copper was attached with a dry film to protect it from the etching solution. Finally, the dry film was peeled off to obtain a printed wiring board.

By performing the above steps, a metal layer other than copper is electroplated on the copper circuit on the plated surface side without specially arranging a power supply lead on the plated surface side. Could be formed.

(Examples 6 to 10) Step (A): Drilling for forming through-holes (through holes) is performed on a laminated plate (unclad laminated plate) having no copper foil on its surface, After the desmear treatment in the through holes, electroless copper plating was performed until the film thickness became 1 μm, to obtain a substrate having copper layers formed on the entire surfaces of both sides of the substrate and in the through holes.

Step (B): A dry film (manufactured by DuPont; trade name: Liston 4620) is used as a plating resist, and after patterning the resist, electrolytic copper plating is applied to a thickness of 15 μm, followed by resist stripping and electroless copper. The plating layer is etched to form a copper circuit connected to the copper layer in the through hole on one surface of the substrate, and on the entire surface on the other side and in the through hole, on the electroless copper plating layer. A copper layer on which the electrolytic copper plating layer was formed was formed. The etching after removing the resist was performed using a sodium persulfate-based etching solution.

In the subsequent steps (C) to (E), electroplating for forming a metal layer other than copper was carried out using a plating solution having a plating bath composition shown in Table 1 and using the gold solution shown in Example 8. Regarding plating, a printed wiring board was obtained in the same manner as in Examples 1 to 5 except that the nickel plating of Example 7 was overlaid and the gold plating was performed.

By performing the above steps, a metal layer other than copper is electroplated on the copper circuit on the plated surface side without specially arranging the power supply leads on the plated surface side. Could be formed.

[0026]

[Table 1]

[0027]

According to the present invention, the plating finish surface side,
The copper circuit at the position where a metal layer other than copper is formed is connected to the power supply unit on the opposite surface through the copper layer in the through hole, so this power supply unit is energized to expose the exposed copper. A metal layer other than copper can be formed on the circuit and on the copper layer in the through hole by electroplating. Therefore, according to the present invention, a metal layer other than copper is formed by electroplating on a copper circuit on the plated surface side without specially arranging a power supply lead on the plated surface side. Therefore, it is not necessary to dispose the power supply lead specially, which facilitates the circuit design and solves the problem that the wiring density is reduced due to the disposition of the power supply lead.

[Brief description of drawings]

FIG. 1A to FIG. 1F are cross-sectional views of a main part for explaining a manufacturing process of a manufacturing method of the present invention.

FIG. 2 is a plan view for explaining a power supply lead for electroplating in a conventional manufacturing method. 1 Substrate 2 Through Holes 4a, 4b Copper Layer 5 Plating Finished Surface 6, 6a, 23 Copper Circuit 7 Opposite Surface 9 Resist 11, 22 Power Feeding Part 12 Metal Layer Other Than Copper

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[Procedure amendment]

[Submission date] May 26, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1A to FIG. 1F are cross-sectional views of a main part for explaining a manufacturing process of a manufacturing method of the present invention.

FIG. 2 is a plan view for explaining a power supply lead for electroplating in a conventional manufacturing method.

[Explanation of reference numerals] 1 substrate 2 through holes 4a, 4b copper layer 5 plating finish surface 6, 6a, 23 copper circuit 7 opposite surface 9 resist 11, 22 power supply portion 12 metal layer other than copper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Yoshioka 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Inventor, Eiichiro Saito, 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd. 72) Inventor Hiroaki Fujiwara, 1048 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works Co., Ltd. (72) Inventor, Katsuhiko Ito, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works, Inc. (72) Inventor, Hajime Sugiyama 1048, Kadoma, Kadoma-shi, Matsushita Electric Works Co., Ltd.

Claims (4)

[Claims] 1. A method for producing a printed wiring board, comprising: copper circuits on both sides of a substrate; and a metal layer other than copper formed on at least one side of the copper circuits by electroplating. The manufacturing method of the printed wiring board characterized by having the process of (E). (A) A step of forming a through hole in the substrate and then performing copper plating to form a copper layer on the entire surface of both sides of the substrate and in the through hole. (B) A step of forming a copper circuit connected to the copper layer in the through hole on one surface of the substrate and leaving the copper layer on the entire other surface on the opposite surface. (C) The copper circuit at a position where a metal layer other than copper is formed, the copper layer in the through hole and the copper layer at a portion on the opposite surface to be a power feeding portion are exposed, and plating resist is applied to both surfaces of the substrate. Process of applying. (D) A step of energizing the power feeding portion to form a metal layer other than copper on the exposed copper circuit and the copper layer in the through hole by electroplating. (E) A step of forming a copper circuit on the copper layer remaining on the opposite surface. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the metal other than copper formed by electroplating is lead, tin or an alloy thereof. 3. The method for producing a printed wiring board according to claim 1, wherein the metal other than copper formed by the electroplating method is nickel, gold, palladium, rhodium or an alloy thereof. 4. The method for manufacturing a printed wiring board according to claim 1, wherein the substrate before forming the through holes is a substrate having copper foils on both sides.