JPS5937759B2 - Mixing tank for plating bath replenisher - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixing tank that supplies and replenishes a replenishing solution while a plating bath is being circulated through a circulation pipe in order to control and adjust the liquid composition within the plating processing tank.

Printed wiring boards are plated to provide electrical continuity to circuit pattern portions and through hole portions. In this case, if the concentration of the liquid composition of the plating bath is not controlled within a predetermined range, the adhesion of the metal to be deposited on the printed wiring board may be weak, or spots or uneven plating may be formed. In order to obtain a good plating layer, the concentration of each solution in the plating bath used must be strictly controlled. By the way, printed wiring boards are immersed in a plating bath for a long time, and copper plating is deposited on the board in an almost proportional relationship, so the solution in the plating bath is consumed and the liquid composition changes. The situation is centrally managed on a control panel based on signals from sensors placed in the plating bath, which sends signals to replenish any insufficient solution and automatically supplies replenishing solution.

FIG. 1 is a diagram showing a conventional apparatus, in which numeral 1 is a plating tank, in which printed wiring boards 2 to be plated are packed in a rack and immersed. A solution 3 of the plating bath is circulated from inside the tank 1 through a circulation pipe 4. The temperature of the circulating liquid 5 in this plating bath is adjusted by a heat exchanger 6, and the circulating liquid 5 is pressurized by a pump 7.
It has been brought back inside. A replenisher 8 is stored in a tank 9.

The replenisher 8 includes, for example, a water-soluble copper salt, a copper complexing salt for complexing the copper salt, an alkali metal hydroxide for adjusting the pH of the bath,
and water are used. 10 is an automatic control device in which a sensor 13 actually measures the concentration of each solution in the plating bath 3;
The concentration is automatically controlled to be maintained within a set range.

If a shortage of a certain solution occurs, a signal is issued, and when the solenoid valve 11 provided below the replenisher tank 9 is actuated, the replenisher 8 is refilled through the replenisher supply pipe 12 to the circulation pipe 4. Ru. Conventionally, the circulation pipe 4 and the replenisher supply pipe 12 were connected as shown in FIG. By the way, since the fluid flowing inside the pipe has a large resistance on the pipe wall and a slow flow rate, it takes time for the replenisher fluid 8 to mix with the circulating fluid 5, which is the main flow, and the plating tank is filled without being completely mixed. 1
In some cases, they were brought back inside. In this case, the liquid composition of the plating bath 3 became non-uniform, resulting in variations in plating. The present invention is an attempt to solve such a problem, and the present invention provides a mixing tank in the middle of the circulation pipe in which the plating bath replenisher can be uniformly mixed.

An embodiment of the present invention will be described based on the drawings. The mixing tank 19 of the present invention has a vertical outer tube 20 and an inner tube 23 arranged concentrically. The outer tube 20 has upper and lower ends 21 and 22 sealed to form a closed container. Note that the end portion may be provided with a flange portion and made into a sealed structure with a joint via packing. The middle of the circulation pipe 4 is connected to the lower side of the outer pipe 20 as an inlet pipe 26 to the mixing tank 19, and the discharge pipe 30 for replenishing liquid 8 from the replenisher tank 9 to the mixing tank 19 is connected to the upper part of the outer pipe 20. Connected to the side part. The inner tube 23 is welded to the lower end plate 22 of the outer tube, its upper end 24 opens into the outer tube 20, and its lower end is connected to an outlet pipe 25 of a circulation pipe fed back into the plating tank 1. Next, the operation of the present invention will be described. The circulating liquid 5 of the plating bath discharged from the plating treatment tank 1 is sent into the mixing tank 19 from the inlet pipe 26 of the circulation pipe.

Since the inlet pipe 26 is connected to the lower side wall of the outer pipe 20, the circulating fluid 5 spirally ascends through the solution passage 27 formed by the outer pipe 20 and the inner pipe 23, and reaches the upper end of the inner pipe 23. It enters the inner pipe 23 through the opening 24 and is discharged from the outlet pipe 25 and returned to the plating tank 1. The replenisher 8 has a replenisher discharge pipe 30 connected to the upper side surface of the outer tube 20, and the distal end 31 of the discharge pipe protrudes to the center of the solution passage 27, with a nozzle 32 shown in FIG. If the replenisher 8 is provided on the back side in the flow direction of the circulating fluid 5, the replenisher 8 will be discharged to a place where an excess flow is formed while the circulating fluid 5 is flowing in a spiral manner, so that the replenishing fluid 8 can be quickly mixed. By using the mixing tank of the above configuration, the present invention allows the replenisher to be mixed extremely quickly and uniformly with the plating bath solution, so that the plating bath can be made uniform within the plating tank. Therefore, uniform plating can be obtained on any part of the printed wiring board immersed in the plating tank.

Further, since the mixing tank of the present invention is arranged in a vertical shape, it is compact and does not take up much space, making the layout easy.

[Brief explanation of the drawing]

Figure 1 is a front view schematically showing a conventional plating treatment tank;
3 is a front sectional view showing the mixing tank of the present invention, FIG. 4 is a sectional view of the same plane, and FIG. 5 is a sectional view of the replenisher discharge pipe. . In the drawing, 1 is a plating treatment tank, 4 is a circulation pipe, and 5 is a plating treatment tank.
is the circulating fluid of the metal bath, 8 is the replenisher, 9 is the replenisher tank,
19 is a mixing tank, 20 is an outer tube, 21 and 22 are both upper and lower ends of the outer tube, 23 is an inner tube, 24 is an opening of the inner tube, 25 is an outlet tube, 26 is an inlet tube, and 30 is a discharge of replenisher liquid. tube, 32 is a nozzle.

Claims (1)

[Claims] 1 In a mixing tank in which the solution in the plating treatment tank is refilled and mixed with replenisher while it is being circulated through a circulation pipe, a vertical outer tube and an inner tube are arranged concentrically, and the top and bottom of the outer tube Both ends are sealed, and the inlet pipe of the circulation pipe is connected to the lower side of the outer tube, and the discharge pipe of the replenisher is connected to the upper side of the outer tube, and the inner tube is welded to the outer tube. A mixing tank for plating bath replenisher, characterized in that the upper end is open and the lower end is connected to an outlet pipe of a circulation pipe.