JPH0642594B2 - Method for manufacturing printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a printed wiring board. More specifically, the present invention relates to a new method for manufacturing a printed wiring board that can suppress variations in thickness of metal foil after through-hole plating and improve etching accuracy.

(Prior Art) Conventionally, a method of forming a circuit through a through hole drilling process on a laminated plate having a metal foil as the outermost layer, plating the through hole, and then etching the metal foil has been widely adopted as a method for manufacturing a printed wiring board. Has been done.

However, with the increasing demand for high-density mounting of printed wiring boards in recent years, there has been a strong demand for improvement in etching accuracy for circuit fine patterning, and new measures for this have become necessary. There is.

That is, in the conventional method, the plating layer adheres to the surface of the metal foil around the through-holes and the like due to the through-hole plating, so that the variation in the thickness of the metal foil cannot be avoided and there is a limit to the improvement of the accuracy of etching. .

Especially when using electrolytic plating, peripheral effects (creeping effects)
It was unavoidable that a thick adhesion of the plating layer around the through hole was caused by.

As a method for solving such a problem, for example, as shown in FIG. 2, a metal foil for forming a circuit is formed on the outermost layer.
The laminated plate (a) having (a) is drilled by a drill or the like, the resist (d) is printed on the surface of the metal foil except for a slight periphery close to the formed through hole (c), and then the through hole plating layer After forming (e), the resist (d) can be peeled off to minimize the change in the thickness of the metal foil (a) due to through-hole plating, and limit the effect to the surroundings of the limited through-hole (c). It is also considered.

(Problems to be Solved by the Invention) However, even in the case of the measures illustrated in FIG. 2, for example, swelling due to the plating layer in the peripheral portion close to the through hole (c) is unavoidable, and this swelling occurs. It becomes an obstacle in patterning, and resist (D)
The occurrence of misalignment of the printing position with the through hole (c) during printing was also left as a problem.

Therefore, it has been difficult to suppress the thickness variation of the metal foil and improve the etching accuracy by the conventional methods.

The present invention has been made in view of the circumstances as described above, enables plating only inside the through-holes by a simple means, suppresses the variation in the thickness of the metal foil, and greatly improves the etching accuracy. It is an object of the present invention to provide a new method for manufacturing a printed wiring board, which enables simple and accurate processing.

(Means for Solving the Problems) As a solution to the above problems, the present invention provides through-hole drilling after disposing a plating-resistant base resist film and a peeling resist layer on the outermost metal foil surface of a laminate. Characterized by peeling off the peeling resist layer after processing and coating with a catalyst, electroless plating of through holes after removing the catalyst on the cross section of the metal foil, further electrolytic plating, and then peeling the underlying resist film A method for manufacturing a printed wiring board is provided.

(Function) In the method of the present invention, as described above, through-hole drilling is performed after disposing the two-layer resist of the base resist film and the peeling resist layer, the catalyst is coated, and then the peeling resist film is peeled off. In addition, since the through holes are sequentially electroless plated and electroplated after removing the catalyst on the cross section of the metal foil, the plating layer does not adhere to the surface of the outermost metal foil, and the plating layer is formed around the through holes and on the cross section of the metal foil. It is possible to plate only the inside of the through hole with high accuracy without climbing.

Therefore, the variation in the thickness of the metal foil due to the plating process is suppressed, and the etching accuracy for forming the fine pattern is greatly improved.

Moreover, since a method of laminating a resist film is adopted, a uniform film can be formed as compared with the resist coating method, which is labor-saving and simple.

(Example) Hereinafter, the method for manufacturing a printed wiring board of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a process sectional view illustrating the method of the present invention.

(a) First, as shown in FIG. 1, a plating-resistant base resist film (3) is laminated on the surface of the outermost metal foil (2) of the printed wiring board laminate (1). At this time, patterning is not required for laminating the base resist film (3).

Further, as the laminated board (1), it is possible to use an arbitrary structure for a printed wiring board, and also as the metal foil (2),
Appropriate types of foils of copper, aluminum, other metals and alloys are used. And, the underlying resist film (3), even when immersed in a plating bath at the time of through-hole plating, specifically, fluorine resin such as Nittofuron adhesive tape No.903UL manufactured by Nitto Denko, polyimide A film made of resin or the like up to a thickness of about 100 μm can be used.

That is, thermosetting type, photosetting type polyamide-based, polyimide-based, unsaturated polyester-based, and other resin resists are appropriately used.

(b) Next, a peeling resist layer (4) is provided on the underlying resist film (3).

The peeling resist layer (4) at this time may be either a film laminate type or a coating type, has an adhesion strength that does not peel even during the next through-hole drilling process, and facilitates peeling operation. Those are preferably used. The type is not particularly limited,
Appropriate ones can be used. Then, the thickness is preferably about several tens of μm to 100 μm.

For example, the coating type peeling resist film (4) can be formed by coating TC-580SN manufactured by San Nopco Co., Ltd. in a thickness of 50 to 80 μm.

(c) After forming the peeling resist layer (4), the laminated plate
A through hole (5) is drilled in (1) with a drill or the like. As the drilling method, a method known so far may be adopted, and the through hole (5) is formed at a predetermined position.

(d) Next, a laminated plate (1) obtained by punching through holes (5)
Applies catalyst for electroless plating. In this catalyst application, for example, the laminated plate (1) is dipped in a salt solution having a plating catalytic action, and the through hole (5) is applied.
A catalyst layer (6) for plating catalytic action is formed on the entire surface of the portion and the stripping resist (4).

For example, as a typical example, a salt such as palladium is used to form the catalyst layer (6). A conventionally known method can be appropriately adopted as a method for this purpose.

(e) A resist layer for peeling after forming the catalyst layer (6)
Peel off (4).

By this peeling treatment, the base resist film (3) is exposed.

(f) In this state, the catalyst only on the cross section of the metal foil (2) is removed by soft etching, and then electroless plating is performed, followed by electrolytic plating. As a result, the conductive plating layer (7) made of metal is formed only inside the through hole (5). Moreover, since the catalyst on the cross section of the metal foil (2) has been removed in advance, electroless plating is not promoted, and the peripheral effect (creeping effect) during subsequent electrolytic plating is not so much affected and it is considered as a peripheral part of the through hole. There is no problem that the plating layer (7) is thickly attached to the cross section of the metal foil (2).

(g) After the plating treatment, the underlying resist film (3) layer is peeled off to expose the metal foil (2). The metal foil (2) for forming the surface path and the plated layer (7) in the through hole (5) are electrically connected.

For example, by the above steps, the plating layer (7) can be formed in a good condition only in the through hole (5), and the plating variation on the surface of the metal foil (2) around the through hole (5) does not occur.

Of course, the present invention can be modified in various aspects in detail, and is not limited to the above examples. As for the type of resist and the plating conditions, various means including conventionally known ones are appropriately adopted.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to plate only the inside of a through hole of a double-sided printed wiring board, a multi-layer board, etc., and the plating variation on the surface of the metal foil around the through hole does not occur. Patterning by etching becomes possible. The plating process is simplified and its accuracy is improved.

[Brief description of drawings]

FIG. 1 is a process sectional view illustrating the manufacturing method of the present invention. FIG. 2 is a process sectional view showing an example of a conventional method. DESCRIPTION OF SYMBOLS 1 ... Laminated plate 2 ... Metal foil 3 ... Base resist film 4 ... Peeling resist layer 5 ... Through hole 6 ... Catalyst layer 7 ... Plating layer

Continuation of front page (56) Reference JP-A-3-104089 (JP, A) JP-A-59-149091 (JP, A) JP-B-43-16709 (JP, B1)

Claims (1)

[Claims] 1. A metal foil, which is the outermost layer of a laminated plate, is provided with a plating-resistant base resist film and a peeling resist layer, through-hole drilling is performed, and after coating with a catalyst, the peeling resist layer is peeled off to form a metal. A method for manufacturing a printed wiring board, characterized in that after removing the catalyst on the foil cross section, the through holes are electrolessly plated, further electrolytically plated, and then the underlying resist film is peeled off.