Electrolytic plating method and device for a wiring board

Abstract

A plating bath which accommodates an insoluble node and a printed-circuit board, and a copper dissolved bath which supplies copper ions are arranged. The insoluble anode Is arranged as opposed to the printed-circuit board being a cathode, and a forward / reverse current is applied between both of the electrodes. Iron ions are added to a plating solution.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electrolytic plating method and device filling up a microvia hole formed on a wiring board with metal plating. [0003] 2. Description of the Related Art [0004] For electric appliances such as a cellular phone, a video camera, a notebook computer, etc., it is demanded to mount high-density components. As an implementation of high-density mounting, a buildup board on which a wiring layer and an insulation layer are sequentially formed, a printed-circuit board of an all-layer microvia type to which wiring boards on which microvias are formed are attached with heat and pressure, etc. are proposed. [0005] For a conventional buildup board, micro holes (microvia holes) are formed on an insulation layer, and the inner side and the bottom of the holes are metal-plated, so that wiring layers above and below the insulation layer are electrically connected. [0006] With this method, however, it...

AI Technical Summary

Benefits of technology

[0011] An object of the present invention aims at filling up microvia holes on a printed-circuit board for a short time.

[0013] According to the present invention, electrolytic plating is performed by applying a forward / reverse current with the use of a metal plating solution including iron ions by 0.1 gram / liter or more, whereby microvia holes can be filled up for a time shorter than a conventional method, and a metal film having a smooth surface characteristic can be formed. As a result, microvias which electrically connect wiring layers above and below an insulation layer can be formed for a short time, thereby significantly reducing the manufacturing cost of a multi-layer printed-circuit board.

[0016] With the above described configuration, the deposit speed of metal plating on the surface of a printed-circuit board and that of metal plating within a microvia hole can be suitably controlled. Consequently, a deep microvia hole with a short diameter can be filled up without causing a void, etc. within the hole.

Problems solved by technology

With this method, however, it is difficult to further form one microvia hole on another, and to securely connect the holes in an electric manner.

Therefore, a land cannot be arranged on a microvia hole after microvia holes are stacked.

Due to such a restriction on a pattern design, the whole of a pattern design cannot be made with an automatic wiring tool, and part of the design must be made manually.

As a result, the time period required to design a printed-circuit board becomes long.

However, with the plating method using PR electrolysis disclosed by the above described publication, plating must be performed for a long time (for example, two hours or longer) to fill up microvia holes.

Therefore, the manufacturing cost of a printed-circuit board increases, and it is difficult to use a printed-circuit board on a mass-production level.

However, problems such that a void occurs during plating, or a plated surface becomes rough occur.

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