JPH069311B2 - 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, the swelling due to the plating layer in the peripheral portion close to the shole (c) is unavoidable, and this swelling occurs. It has been a problem in patterning, and the printing position misalignment with the through hole (c) at the time of resist (d) printing remains 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 above circumstances, and is a new printed wiring board that enables plating only in the through holes and can greatly improve the etching accuracy by suppressing the variation in the thickness of the metal foil. It is intended to provide a manufacturing method.

(Means for Solving the Problems) As a means for solving the above problems, the present invention applies a through hole drilling process after applying a base resist and a peeling resist to the outermost metal foil surface of a laminated plate, and is coated with a catalyst. After this peeling resist is peeled off, the catalyst on the cross section of the metal foil is removed, the through holes are electrolessly plated, further electrolytically plated, and then the underlying resist is peeled off. provide.

(Operation) In the method of the present invention, as described above, through-hole drilling is performed after applying the two-layer resist of the underlayer resist and the peeling resist, the catalyst is covered, and then the peeling resist is peeled off. 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 may rise around the through holes and on the cross section of the metal foil. Instead, only the inside of the through hole can be plated with high precision.

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.

(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 base resist (3) is applied to the surface of the outermost metal foil (2) of the printed wiring board laminate (1). At this time, patterning is not required to apply the base resist (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. The underlying resist (3) has resistance even when immersed in a plating bath at the time of through-hole plating. Specifically, for example, a resist of Eagle negative type manufactured by Shipley Co., Ltd.
It can be applied to a thickness of about m.

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

(b) Next, a stripping resist (4) is applied on the base resist (3) layer.

The peeling resist (4) at this time has an adhesive strength that does not peel off even during the next through-hole drilling process,
Moreover, those which are cured to form a film and which can be easily peeled off are preferably used. The type is not particularly limited, and any appropriate type can be used. And, preferably, it is applied in the order of several tens of μm to 100 μm.

For example, as the stripping resist (4), TC-580SN manufactured by San Nopco Co., Ltd. can be applied in a thickness of 50 to 80 μm.

(c) After forming this peeling resist (4) layer, 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 in which through holes (5) are drilled
In (1), catalyst coating for electroless plating is performed. In this catalyst coating, for example, the laminated plate (1) is dipped in a salt solution having a plating catalytic action to form a through hole.
A catalyst layer (6) for a plating catalytic action is formed on the entire surface of the (5) part 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) Stripping resist after the catalyst layer (6) is formed
(4) Peel off the layer.

By this peeling process, the base resist (3) layer 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 significantly affected, and it is considered as a peripheral part of the through hole. Metal foil (2)
There is no problem that the plating film (7) is thickly attached to the cross section.

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

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.

[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 board 2 ... Metal foil 3 ... Base resist 4 ... Peeling resist 5 ... Through hole 6 ... Catalyst layer 7 ... Plating layer

Continuation of the front page (56) References JP-A-59-149091 (JP, A) JP-B-50-5375 (JP, B1) JP-B-45-4582 (JP, B1)

Claims (1)

[Claims] 1. An outermost metal foil surface of a laminated plate is coated with a base resist and a stripping resist, then through-hole drilling is performed, and after coating with a catalyst, the stripping resist is stripped to remove the catalyst on the cross section of the metal foil. A method for producing a printed wiring board, characterized in that the through holes are electrolessly plated, electrolytic plating is then performed, and then the underlying resist is peeled off.