JPH03248494A - Manufacture of printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a printed wiring board by plating small-diameter through holes formed in a board.

[Prior Art] Conventionally, in multilayer printed wiring boards and the like, through holes are formed in the board, and the through holes are plated by electroless plating or the like to connect the layers.

Figure 1 is a model of a plating bath for plating through-holes in a multilayer printed wiring board. The main plating volume 1 is replenished via the filter 7 through the discharge pipe 8, and the plating solution in the main plating volume 1 overflows and is replenished via the filter bag 3 W! 2 and circulated. A heater or a heat exchanger 4 is provided in the replenishment tank 2, and the replenishment tank 2 is also provided with copper.

Raw materials for Metsu II liquid such as alkali and cutting are supplied from a replenishment liquid injection pump 9. Further, an aeration pipe 5 is provided in the plating water tank 1 and the supply tank 2.

In order to plate the through-hole portions of substrates in this plating bath, a large number of substrates 12 are supported in the main plating tank 1, and mechanical vibration is applied to expel the air trapped inside the small-diameter through-holes. While it is plated.

[Problem to be solved by the invention Mi] However, when plating small-diameter through-holes, even if the printed circuit board is vibrated in a plating bath to expel the air trapped in the small-diameter through-holes, the air trapped inside the small-diameter through-holes is not completely removed. This may cause poor plating or reduce the reliability of the printed circuit board.

Further, gases generated during the plating reaction are also a cause. There are other methods for expelling air and gas, such as using submerged spray, but none of them are perfect.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a printed wiring board, which eliminates the drawbacks of the prior art described above and allows complete plating in small-diameter through holes.

[Means for Solving the Problems] The gist of the present invention is to form a small-diameter through hole in a board, and to manufacture a printed wiring board by plating the through hole in a plating bath, in which the inside of the plating bath is vacuumed during plating. The through hole is plated by pulling it out.

[Function] According to the above configuration, the inside of the plating tank is evacuated, so that
Air is no longer trapped in the through hole,
It is possible to eliminate all imperfections.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a plating tank for carrying out the method of the present invention. In the figure, 1 is a main plating tank for accommodating and plating a substrate 12 in which a through hole is formed, 2 is a supply tank, and 3 is a plating tank for carrying out the method of the present invention.
is a filter bag, 4 is a heater or heat exchanger, 5 is an aeration pipe, 6 is a circulation pump, 7 is a filter, 8 is a discharge pipe, and 9 is a replenishment liquid injection pump, which were explained in the conventional example in Fig. 2. That's right.

Now, a sealing lid 1 straddles the top of the plating bath, that is, the top of the main plating tank 1 and the top of the supply tank 2, and seals the tanks 1 and 2.
0, and a vacuum device 11 for evacuating air and debris in the upper space 13 of the tank 1°2.

Next, a method of plating using the above-mentioned plating bath will be explained.

First, a substrate 12 with through holes formed in the main plating layer 1
A large number of sheets are introduced and supported. After that, the sealing lid 10 is attached, and the inside of the tank is evacuated using the vacuum suction device 11. At the same time, the plating solution is supplied to the replenishment tank 2 from the replenishment liquid injection tank 19, and the inside of the main plating volume 1 is plated using the circulation bonder 6. The liquid is poured into grooves and the substrate 12 is plated.

By performing the plating process in a vacuum state using the vacuum evacuation device 11 during plating, the air trapped in the through-holes of the substrate 12 is removed, and the gas generated during the plating process is reduced by nearly 100%. Since it can be removed, good plating processing is possible.

In addition, in the above-mentioned embodiment, an example was explained in which the plating solution is filled in a state where the substrate is evacuated, but the main plating volume 1 and the supply tank 2 are filled with the plating solution, and the substrate 12 is placed in the upper space 13, for example. The structure may be such that the space 13 is evacuated to remove the air in the through holes of the substrate 12 while the substrate 12 is held in the plating solution, and then the substrate 12 is introduced into the plating solution. Alternatively, vibration may be applied as in the conventional method. Even if these methods are used in combination, or if the submerged sagging method and the vacuum evacuation method of the present invention are used together, even more reliable plating can be achieved.

[Effects of the Invention] As described above, according to the present invention, there is no plating failure due to air entrapment in small-diameter through-hole plating of printed wiring boards or plating failure due to gas generated during plating processing, and the reliability of through-holes is greatly improved. to improve. Furthermore, the smaller the diameter of the small-diameter through-hole, the more defects of this type occur, but the present invention can be realized without any problem.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a plating tank for carrying out the method of the present invention, and FIG. 2 is a diagram showing a conventional example. In the figure, ■ is the main plating stack, 11 is a vacuum suction device, and 12 is a substrate.

Claims (1)

[Claims] 1. A method of producing a printed wiring board by forming small-diameter through holes on a board and plating the through holes in a plating bath, the method comprising: plating the through holes by evacuating the inside of the plating bath during plating. Substrate manufacturing method.