JPH0424995A - Method and equipment for plating through hole of circuit board - Google Patents

Abstract

PURPOSE:To obtain a through hole plating method and its equipment capable of completely depositing electroless plating even when the diameter of a through hole is smaller than or equall to 0.4mm, by passing two or more times catalyst process necessary for deposition of electroless plating. CONSTITUTION:Catalyst 5 is a process for imparting catalyst to copper foils on both surfaces of a substratum layer 11 of epoxy resin or the like of a circuit board. When catalyst 13 is imparted in said process, it happens that the catalyst is not completely imparted to the inner side of a through hole 20. This is because, when the diameter of a through hole is smaller than or equal to 0.4mm, the movement of liquid is decreased, the liquid does not circulate, and therefore the efficiency of catalyst impartment is reduced. However, when catalyst is again imparted in catalyst 6 being a second catalyst imparting process, the catalyst 13 is completely imparted to the inner side of the through hole 20. After rinsing, the catalyst is activated by an accelerator 7, and electroless plating is completely deposited in the through hole 20 in virtue of the catalyst in electroless copper plating 8.

Description

[Detailed description of the invention] [Industrial application field] The present invention provides through-hole mechanisms for circuit boards. and related to through-hole repair equipment.

Method for plating [Summary of the invention] The present invention provides a through-hole plating method and apparatus for a circuit board having through-holes, in which through-hole plating is achieved by passing through a catalyst application step, which is a pre-process of electroless plating, twice or more. It is possible to prevent incomplete deposition of electroless plating inside the through-hole and obtain perfect through-hole plating.

[Conventional technology]

Conventionally, as shown in Figure 2, in the method of using general copper plating as through-hole plating, conditioner 1 was used.
This cleans the surface of the circuit board and increases the permeability of the liquid into the through-holes drilled in the circuit board. In soft etching 2, the metal surface of the circuit board is chemically dissolved to remove oxides and the like on the surface. Acid 3 activates the metal surface. The fluid dip 4 prevents the liquid in the catalyst 5 from changing. A catalyst 5 applies a catalyst necessary for electroless plating to the circuit board. The accelerator 7 activates the provided catalyst. Copper plating is deposited using the catalyst applied with electroless copper coating 8 as a nucleus. Sulfuric acid 9 activates the copper surface deposited by electroless copper plating. In copper plating 10, since the copper film obtained by electroless copper plating is thin, the copper film was thickened to the required thickness by electroplating to perform 7-ki in the through holes of the circuit board.

[Problem to be solved by the invention]

However, with conventional through-hole plating equipment, when the diameter of the through-hole becomes smaller than 0.4fi, the electroless plating is completely deposited because the catalyst required for electroless plating is not sufficiently applied inside the through-hole. However, there was a problem in that through-hole plating defects were caused due to failure (Fig. 4).

Therefore, in order to solve these conventional problems, the present invention provides a through-hole plating method and apparatus that allows electroless plating to be completely deposited inside the through-hole even if the diameter of the through-hole is reduced to 0.4 nm or less. The purpose is to obtain.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a through-hole plating method and a structure of a through-hole plating apparatus in which the step of applying a catalyst necessary for electroless plating deposition is performed twice or more. By allowing the catalyst to pass through the through hole, the catalyst is completely applied to the through hole, and electroless plating within the through hole can be prevented from being completely deposited.

[Effect]

When through-hole plating is performed on a circuit board with holes for through-holes using the through-hole plating method and through-hole plating equipment as described above, the catalyst may not be sufficiently applied to the through-holes in the first catalyst application process. Also, by carrying out the catalyst application process two or more times, the catalyst will be sufficiently applied within the through-holes, and the electroless plating will be completely deposited.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of the through-hole plating apparatus of the present invention in the case of copper plating, in which a circuit board (not shown) with holes for through-holes is immersed in conditioner 1 on the left end, washed with hot water, They are washed with water and transported to the tank on the right side in the order of the process using a mobile lift. The circuit board leaving the catalyst tank 5, which is the first catalyst application step, is washed with water and then dried.

By passing through the next catalyst 6 and applying catalyst again on top of the first catalyst, it is possible to achieve a more complete state of catalyst application within the through-hole.

That is, as shown in FIG. 3, even if a catalyst 13 is applied in the catalyst 5, which is a catalyst application step, to a circuit board having copper foils 12 on both sides of a base material layer 11 of epoxy resin, etc., the through holes 20 The catalyst 13 may not be completely applied to the inner side of the container.

This is because when the diameter of the through hole becomes smaller than 0.4 fi, the movement of the liquid within the through hole 20 becomes poor and the liquid does not circulate, resulting in a decrease in the efficiency of catalyst application.

However, in the second catalyst application process, Catalyst 6
When the catalyst is applied again in the step, the catalyst 13 is completely applied inside the through hole 20 as shown in FIG.

After washing with water, the catalyst is activated by the accelerator 7, and the electroless copper plating is completely deposited in the through hole 20 by the action of the catalyst in the electroless copper plating 8, as shown in FIG. Further, through sulfuric acid 9, copper plating 10 completes a functionally sufficient copper conductor in the through hole. As for the chemicals used in this method and apparatus, generally commercially available chemicals can be applied as they are. In addition, if the structure of the device is such that the movement order of the mobile lift etc. that transports the circuit board can be changed by a computer etc., the process of applying the catalyst is provided separately to the catalysts 6 and 7 as shown in FIG. It goes without saying that it is possible to at least unify them into one.

〔Effect of the invention〕

As explained above, the present invention uses a method of passing through the catalyst application process two or more times and a through-hole plating apparatus having a structure that allows the catalyst application process to pass through the process two or more times. This has the effect of preventing the occurrence of through-hole mesokine defects due to insufficient through-hole plating being produced in the through-hole holes of the circuit board.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a through-hole plating apparatus according to the present invention for copper plating, Fig. 2 is a block diagram of a conventional through-hole copper plating apparatus, and Figs. 3 and 4 are through-hole plating by a conventional method. FIGS. 5 and 6 are partial cross-sectional views of circuit boards showing the state of catalyst application and electroless copper plating, and FIGS. FIG. 1 ・ ・ 2 ・ ・ 3 ・ ・ 4 ・ ・ 7 ・ ・ Conditioner, soft etching, acid, pre-dip...Catalyst, accelerator Electroless copper plating Sulfuric acid partial plating Base material layer circuit such as epoxy resin of circuit board Copper film through-hole deposited by catalytic electroless copper plating applied in the copper foil catalyst application process on the substrate Figure 6

Claims (2)

[Claims] (1) A through-hole plating method for a circuit board having through-holes, the method comprising passing through a catalyst application step, which is a pre-electroless plating step, twice or more. (2) A through-hole plating device for a circuit board having through-holes, characterized in that the structure of the through-hole plating device includes a device for passing through a catalyst application step, which is a pre-step of electroless plating, twice or more. Through-hole plating equipment for circuit boards.