JPH03228396A - Manufacture of multilayer printed circuit board - Google Patents

Abstract

PURPOSE:To easily obtain a multilayer printed circuit board sufficiently and effectively having a predetermined through hole conducting function by bringing a cathode electrode into opposite contact with an inner layer circuit pattern electrically connected to the conduction hole of the board to be electrically plated. CONSTITUTION:Inner layer circuit board materials having predetermined outer and inner layer circuit patterns 8a, 8b are laminated through a prepreg layer disposed therebetween, and drilled to obtain a multilayer printed circuit board 1 having a predetermined blind hole 2. Thereafter, the board 1 is coated at a predetermined area with a plated resist layer, chemically copper-plated, and covered on the wall in the hole 2 with a chemical copper-plated layer 3. Then, a cathode electrode is brought into opposite contact with the region 8b' in which the pattern 8b in contact with the layer 3 is exposed, electrically copper- plated, and covered with a plated layer 5 having a conducting function.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a multilayer printed wiring board, and particularly to a multilayer printed wiring board having conductive holes such as through-hole connections and blind-hole connections. Relating to a manufacturing method.

(Prior Art) In response to the miniaturization and higher functionality of electronic devices, multilayer printed wiring boards have been put into practical use for the purpose of increasing the density of circuit configurations or miniaturizing circuit parts. In other words, there are multilayer printed wiring boards in which inner layer circuit patterns are arranged and integrated in multiple stages via insulating layers, and outer surface circuit patterns are integrated to form a complex circuit, and a wide variety of electronic devices are used. used in equipment.

By the way, in this kind of multilayer printed wiring board, outer layer circuit patterns are connected to each other, certain inner layer circuit patterns are connected to each other,
Alternatively, there are often cases where a certain inner layer circuit pattern and an outer layer circuit pattern are electrically connected. Electrical connections between the circuit patterns are made as follows.

That is, after the required inner layer circuit board and outer layer circuit board are stacked together with a prepreg layer in between and pressure-molded to obtain a multilayer printed wiring board, the required through holes are formed in predetermined areas by bottom drilling or laser processing. Through-holes and blind holes are drilled, and chemical plating and electroplating are sequentially applied to the inner walls of these through-holes to connect conductors between the circuit batten layers.

(Problems to be Solved by the Invention) However, the method for manufacturing a multilayer printed wiring board having through-hole connections or blind-hole connections as the conductive holes has the following disadvantages. That is, after multilayer molding,
For example, by drilling the required through holes using trill processing,
When a required connection layer is formed by successively applying chemical copper plating and electrolytic copper plating to the inner wall surface of the drilled through hole, it is often impossible to maintain a sufficient electrical connection.

In other words, the thickness of the copper layer (film) deposited on the inner wall surface of the through hole during chemical copper plating is usually as thin as a few microns.
The cathode potential applied via the outer layer circuit pattern (outer layer copper foil layer) causes a voltage drop within the through hole, and as a result, the required current density cannot be obtained in the middle of the through hole. Therefore, as shown in the cross section in FIG.
-There is a problem that the electrical conduction function is not sufficiently performed. In addition, Fig. 2 shows the case of a blind hole in a multilayer printed wiring board, where 1 is the multilayer printed wiring board main body, 2 is the blind hole, 3 is the chemical copper plating layer, 4 is the inner circuit pattern layer, and 5 is the Each electrolytic copper plating layer is shown.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention aims to provide a manufacturing method that can easily obtain a multilayer printed wiring board that is sufficiently and reliably provided with the required sulfol conduction function.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for manufacturing a multilayer printed wiring board, which includes a step of depositing a conductive layer on the inner wall surface of a conductive hole of the multilayer printed wiring board by electroplating. The electroplating process is performed by placing a cathode electrode in contact with an inner layer circuit pattern that is electrically connected to a conductive hole of a multilayer printed wiring board.

(Function) According to the method of the present invention, the chemical plating layer formed on the inner wall surface of the conductive hole such as a through hole or a blind hole is provided with a required electroplating potential via the inner layer circuit pattern. In other words, the cathode electrode is connected to the middle of the chemical plating layer on the inner wall surface of the conductive hole, and potential drop is avoided or prevented, so that electroplating is always possible without any non-adhesion of the electroplating layer. An adhesion layer will be formed.

(Example) The following is a diagram schematically showing embodiments of the present invention.
An example will be described with reference to (d).

First, as shown in cross section in Figure 1(a), the thickness is 1.2 mm.
A circuit board material 6 was prepared by laminating a copper foil 7 with a thickness of 18 μm on at least one surface of an insulating layer 6a. Next, each of the seven copper foil layers of the circuit board material 6 was photoetched to obtain a circuit board having the required outer layer circuit pattern and inner layer circuit pattern.

The inner layer circuit board having the required outer layer circuit pattern 8a or the inner layer circuit board having the required inner layer circuit pattern 8b configured as described above is laminated with a prepreg layer interposed therebetween, and pressure molding is performed. A multilayer printed wiring board was obtained. In the above-described lamination and pressure molding, a part of the externally processed side of the inner layer circuit pattern 8b that is connected to the blind hole 2 to be formed is exposed to the extent that the cathode electrode can be brought into contact with the inner layer circuit pattern 8b. This partial exposure of the inner layer circuit pattern 8b may be achieved by using holes formed in the counterbore process (detection of marks for layer order and alignment) during the lamination and pressure molding.

Next, using a carbide drill 8 with a tip angle of 165 to 170' and a diameter of 0.41, a required blind hole 2 is formed in a required area of the multilayer printed wiring board formed as described above. A multilayer printed wiring board 1 having blind holes as shown in cross section in Figure (b) was obtained.

After that, a plating resist layer is applied to the desired area of the multilayer printed wiring board having the blind holes 2 obtained above, and a chemical copper plating process is performed to form the blind holes 2.
A chemical copper plating layer 3 was deposited on the inner wall surface. Next, the blind hole 2 formed by the chemical copper plating process is
The exposed region 8b' of the inner layer circuit pattern 8b, which is connected to the chemical copper plating layer 3 on the inner wall surface, is brought into contact with the cathode electrode and subjected to the required electrolytic copper plating treatment. In this electroplating process, since a required plating voltage is applied to the chemical copper plating layer 3 via the inner layer circuit pattern 8b, Cu ions are easily electrically induced into the blind hole 2 and the required electrical As copper plating progresses,
A plating layer 5 having a sufficient conductive function is formed (
Figure 1C).

Although the example of the method for manufacturing a multilayer printed wiring board having blind holes has been described above, it can also be applied to a method for manufacturing a multilayer printed wiring board having a so-called through-hole connection. Even when a connection layer was formed on the inner wall surface of the through hole by chemical copper plating and electrolytic copper plating, a plating layer having a -like and sufficient conductive function was similarly deposited. Further, in the above description, a chemical copper plating method was used as the chemical plating method, and an electrolytic copper plating method was used as the electroplating method, but it goes without saying that the method is not limited to these.

[Effects of the Invention] According to the present invention, a multilayer printed wiring board having small-diameter through holes, high aspect ratio through holes, or interstitial higher holes and forming a conductive layer (connection layer) on the inner wall surface of these can be produced with high yield. , and can be easily manufactured. Furthermore, the through-hole connection layer formed by the plating method maintains an excellent conductive function and contributes to improving the reliability of the printed wiring board itself.

[Brief explanation of drawings]

1(a) to 1(c) schematically show an embodiment of the manufacturing method according to the present invention, and FIG. 1(a) is a sectional view of the main part of the circuit board material, b) is a cross-sectional view of the main part of a multilayer printed wiring board with blind holes, Figure 1 (C)
2 is a cross-sectional view of a main part of a multilayer printed wiring board in which a required conductive layer is formed on the inner wall surface of a blind hole, and FIG. It is. 1...Multilayer printed wiring board 2...Blind hole 3...Chemical plating layer 5...Electroplating layer 6... ...Circuit material 7...Copper foil 8a...Outer layer circuit pattern 8b...Inner layer circuit pattern gb'...Inner layer circuit pattern (continuity hole) 1 person with exposed area

Claims (1)

[Scope of Claim] A method for manufacturing a multilayer printed wiring board, which includes a step of depositing a conductive layer on the inner wall surface of a conductive hole of a multilayer printed wiring board by chemical plating treatment and electroplating treatment, wherein the electroplating treatment is performed by multilayer printing. A method for manufacturing a multilayer printed wiring board, characterized in that the manufacturing method is carried out by bringing a cathode electrode into contact with an inner layer circuit pattern that is electrically connected to a conductive hole of the wiring board.