JPH03108793A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To enable plating only in a through-hole part and to improve etching accuracy by restraining dispersion in thickness of metal foil by boring a through- hole after laminating anti-plating resist film on a surface of metallic foil and thereafter by carrying out through-hole plating. CONSTITUTION:An anti-plating resist film 3 is laminated on a surface of an outermost layer metallic foil 2 of a printed wiring board lamination board 1. After a layer of peeling resist 4 is formed as required, a through-hole 5 is bored. Then, it is immersed in salt solution having plating catalysis; a catalyst layer 6 is formed in a part of the through-hole 5; the layer of the peeling resist 4 is peeled to allow the catalyst layer 6 to remain only inside the through-hole 5; catalyst in only a cross section part of the metallic foil 2 is removed by soft etching; and electrolytic plating is carried out to form a plating layer 7 inside the through-hole 5 alone. After plating treatment, the layer of the antiplating resist film 3 is peeled to expose the metallic foil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a printed wiring board. More specifically, the present invention relates to a new method for manufacturing printed wiring boards that can suppress variations in the thickness of metal foil after Sulpol plating and improve etching accuracy.

(Prior technology) Conventionally, a method has been widely adopted as a manufacturing method for printed wiring boards, in which a laminate with metal foil arranged on the outermost layer is drilled with through holes, and after the through holes are plated, a circuit is formed by etching the metal foil. It has been done.

However, as the demand for high-density mounting of printed wiring boards has increased in recent years, there has been a strong demand for improved etching accuracy for fine-patterning circuits, and new measures have become necessary for this purpose. There is.

In other words, in the conventional method, a plating layer is formed on the surface of the metal foil due to Sulpol plating, and this unavoidable variation in the thickness of the metal foil has a limit on the etching accuracy. Ta.

As a solution to this problem, for example, as shown in Figure 2, a metal 2^ for circuit formation is added to the outermost layer.
After drilling holes in the laminate (B) having (A) using a drill etc., printing resist (1) on the surface of the metal foil except around the through holes (X), and then forming a through hole plating layer (E). It has also been considered to limit the change in the thickness of the metal foil (A) due to through-hole plating to the area around the through-holes by peeling off the resist (1).

(Problem to be Solved by the Invention) However, even with the method shown in FIG. 2, the build-up of the plating layer around the through-holes cannot be avoided, which hinders patterning and also causes problems during resist printing. The occurrence of printing position misalignment with the through-holes also remained a problem.

The reality is that, depending on the methods used so far, it has been difficult to suppress variations in the thickness of metal foil and improve etching accuracy in any case.

This invention was made in view of the above-mentioned circumstances, and it is possible to plate only the through-hole portions, suppress variations in the thickness of the metal foil, and improve the etching accuracy of the wiring board. The aim is to provide a new manufacturing method.

(Means for Solving the Problems) This invention solves the above-mentioned problems by laminating a plating-resistant resist film on the surface of the metal foil of the outermost layer of a laminate, followed by Sulpol drilling, and then Sulpol plating. A method for manufacturing a printed wiring board is provided.

Further, more specifically, the present invention provides the following method: 1. After laminating the metal foil surface with a scratch-resistant resist film 1, it is subjected to through-hole drilling, and after being coated with a scratch-resistant resist film, through-hole plating is performed, and then a scratch-resistant resist film is applied. A method comprising peeling is provided.

(Function) In the method of the present invention, after the plating resistance film 1 to laminate 1 is formed, Sulpol drilling is performed, and then Sulpol plating is performed. It is possible to plate only the through-hole portions without having to worry about over-filling the peeled layer.

Therefore, variations in the thickness of the metal foil are suppressed, and the etching accuracy for forming fine patterns 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 attached drawings.

FIG. 1 is a cross-sectional view showing the steps of the method of the present invention.

(a) As shown in FIG. 1, a plating-resistant 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 plating-resistant resist film.

As the laminate (1), any structure for printed wiring boards can be used, and as the metal foil (2), any appropriate type of metal foil such as copper, aluminum, other metals, or alloys can be used. be done. The plating-resistant resist film (3) has resistance even when immersed in a plating bath during through-hole plating. Specifically, an example is Nitto Denko Corporation's 21-Freon adhesive tape No. 903 U I-
A film up to a thickness of about 100 μm made of fluororesin, polyimide resin, etc. can be used.

A thermosetting resist film or a photocuring resist film is used as appropriate.

(b) Then, if necessary, peeling resists 1 to 4 are provided on the plating-resistant resist film (3) layer.

The resist (4) at this time may be either a film type or a coating type.

Both should have adhesion strength to the extent that they will not peel off during the next drilling process, and should be coated to a thickness of several tens of micrometers to about 100 micrometers.

For example, as a coating type of this peeling resist (4), TC-5803N manufactured by Sannopco Co., Ltd.
It is possible to apply approximately 0 μm.

Note that this step (b) is omitted and the peeling resist (4)
It is not necessary to use .

(c) After forming this peeling resist (4) layer as required, through-holes (5) are drilled in the laminate (1) using a drill or the like. As this drilling method, a method known up to now is used, and a through hole (5) is formed at a predetermined position.

(d,) Next, the laminate (1) with Sulpol (5) holes drilled therein was soaked in a salt solution having a plating catalytic action to apply a catalyst for plating treatment, and a catalyst was applied to the through holes (5). Form layer (6).

For example, in the case of electroless plating, layers 1 to 6 (layers 6) made of a salt such as palladium are formed. Conventional methods can also be adopted as appropriate for this purpose.

(e) After forming the catalyst layer (6), the peeling resist (4) layer is peeled off so that the catalyst layer (6) remains only inside the Surpol (5).

This treatment exposes the plating-resistant resist film (3) layer.

(f) In this state, only the cross section of the metal foil (2) is removed by soft etching and then electrolytically plated, or electroless plated and then electrolytically plated as shown in FIG. As described above, the plating layer (7) is formed only within the through hole (5).

Depending on which method you use, Characteris 1~
The structure of the layer (6) and the processing conditions may be selected as appropriate.

(g) After the plating process, the plating-resistant resist film (3) layer is peeled off to expose the metal foil (2). The metal foil (2) and the plating layer (7) in the Surpol (5) are electrically connected.

For example, through the above steps, it is possible to form the plating layer (7) only within the Surpol (5th layer), and no variation in thickness will occur due to the plating process on the surface of the metal foil (2).

FIG. 2 shows the case where step (b) is omitted. If necessary, apply Charalis 1 to layer (
6) is formed and plated.

Of course, this invention can be modified in various ways in terms of details, and is not limited to the above-mentioned examples.

(Effects of the invention) As explained in detail above, this invention makes it possible to plate only through-holes in double-sided printed wiring boards, multilayer boards, etc., eliminates variations in the thickness of metal foil due to plating processing, and allows patterning by high-precision etching. It becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are process cross-sectional views showing the manufacturing method of the present invention, respectively. FIG. 3 is a process sectional view showing an example of a conventional method. 1... Laminated plate 2... Metal foil 3... Resist film 4... Peeling resist 5... Through hole 6... Catalyst layer 7... Plating layer

Claims (2)

[Claims] (1) After laminating a plating-resistant resist film on the metal foil surface of the outermost layer of the laminate, through-hole drilling is performed,
A method for manufacturing a printed wiring board, which comprises subsequently performing through-hole plating. (2) The method for manufacturing a printed wiring board according to claim (1), which comprises the steps of: coating the catalyst after through-hole drilling, and peeling off the plating-resistant resist film after through-hole plating.