JPS5915008B2 - Replenisher mixing tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixing tank for supplying and replenishing a replenishing solution in order to control and adjust the liquid composition in a processing tank for plating, etc.

The printed wiring board is immersed in an electroless plating bath, and electroless copper plating is deposited on the through-hole portions and circuit pattern portions.

In this case, the liquid composition concentration of the plating bath must be controlled within a predetermined range. As an example, the liquid composition of this plating bath is as follows:
Copper sulfate, sodium hydroxide, Rothsiel's salt, formaldehyde, water, etc. are used. Each of these solutions has a specified concentration, and if the concentration exceeds that range, the copper precipitation rate will slow down, the bath quality will become unstable, it will be difficult for electroless copper to adhere to the insulating board, or the adhesive strength will weaken. It becomes a factor that causes fundamental defects such as

In other words, good plating cannot be obtained unless the component ratios of each solution are precisely adjusted, and are therefore extremely strictly controlled. By the way, the plating bath in the plating treatment tank changes from time to time while depositing copper on the printed wiring board, and the concentration of each bath solution changes, so a measuring device for measuring these concentrations is required. An automatic control device is utilized to issue a replenisher supply signal 10 to replenish the missing solution.
FIG. 1 is a diagram showing a conventional apparatus, and numeral 1 is a plating tank, in which printed wiring boards 2 are packed in racks and immersed.

The plating bath 315 is circulated from the plating tank 1 through the circulation pipe 4. This circulating fluid 5 is temperature-controlled by a heat exchanger 5, pressurized by a pump 6, and fed back to the plating tank 1. 8 is a replenisher that dilutes the water-soluble copper salt, formaldehyde, copper complexing salt for complexing the copper salt, alkali metal hydroxide for adjusting the pH of the bath, and sodium hydroxide. Water and the like are stored in each tank 9.

Reference numeral 10 denotes an automatic containment device, which measures the concentration of each solution in the metal bath 3 in the plating tank 1 and automatically controls the concentration to maintain the concentration within a set range.

The signal emitted from this control device 10 operates a solenoid valve 11 provided below the replenisher tank 8. When the solenoid valve 11 opens, the replenisher 8 flows out 30, and when it closes, the flow stops. Stop. The replenisher 8 flows through the replenisher supply pipe 12 and is discharged into the circulation type 4. When the replenisher 8 joins the circulating fluid 5, it must be quickly and uniformly mixed within the circulating pipe 4. This is because some solutions generate self-heating35, which may cause problems such as not being able to mix uniformly and resulting in uniform plating. Conventionally, as shown in FIG. 2, the replenisher supply pipe 12 was welded to the side of the circulation pipe 4.

In this configuration, since the pipe wall has a large fluid resistance, the flow rate is slow and it takes time to mix uniformly with the circulating liquid 5, causing some parts of the pipe 4 to become thick and dark. brought in and the result. In some cases, it was not possible to deposit uniform electrolytic copper. In order to solve the problem of the present invention, the present invention provides a mixing tank in the middle of the circulation pipe so that when the replenishing liquid is supplied to the circulating liquid, it can be mixed quickly and uniformly. Provide a liquid mixing tank.

An embodiment of the present invention will be described based on the drawings. The mixing tank 19 of the present invention has an inner and outer double pipe arranged on a circular center,
The outer tube 20 is an airtight container with both ends 20 and 21 sealed, one end of the inner tube 23 is open 24 (toward the airtight container formed by the outer tube 20), and the other end is treated. It is connected to an outlet pipe 25 which feeds back to the tank 1. Note that the outlet pipe may be branched as necessary. The circulating liquid 5 sent from the processing tank 1 is supplied into the mixing tank 19 from an artificial pipe 26 connected to the outer pipe 20 of the mixing tank 19 .

The inlet pipe 26 is connected to the mixing tank 19 in such a way that the circulating fluid 5 is oriented tangentially to the outer pipe 20, as shown in FIG. The circulating fluid 5 formed by the outer pipe 20 and the inner pipe 23
They are connected along the passage 27. Therefore, the circulating fluid 5 flows counterclockwise in the figure while rotating spirally.
As mentioned above, when the solenoid valve 11 is actuated based on a signal issued by the automatic control device 10, the replenisher 8 refilled into the circulating fluid 5 is opened and a predetermined amount is supplied to the replenisher liquid pipe 30.
The water flows through the tank and is added to the mixing tank 19.

This replenisher pipe 30 is connected facing the axis (normal line) of the mixing tank 19. The tip 31 of the replenisher pipe 30 protrudes to the center of the passage 27 in the mixing tank 19, and the nozzle 32 is bored in the back as shown in FIG. 6 in the flow direction of the circulating fluid 5. There is. The number of replenisher pipes 30 depending on the type of solution to be refilled is installed in the mixing tank 19.
It is preferable that the connections to the pipes 9 be made by changing the height in the longitudinal direction and by changing the connection angles, and the connections of adjacent pipes are separated from each other. The present invention is a replenisher mixing tank having the above configuration, and when the circulating fluid flowing from the processing tank through the circulation pipe is discharged from the artificial pipe into the mixing tank, the circulating fluid flows circumferentially through the passage formed by the inner and outer pipes. Flows in a spiral along the A replenisher pipe is connected normal to the middle of the pipe, and its nozzle is installed on the back side of the flow of circulating fluid so that the replenisher is injected, so the injected replenisher mixes quickly. However, instead of being mixed only in one part, it is now mixed uniformly over the entire surface.

For this reason, it has become possible to uniformly deposit desired electrolytic copper over all parts of the printed wiring board immersed in the processing tank, no matter where in the processing tank it is immersed. The electroless plating technology has been established by providing the replenisher mixing tank of the present invention.

[Brief explanation of the drawing]

Figure 1 is a front view showing the outline of a conventional plating treatment tank, Figure 2
The figure is a sectional view showing the connection of a replenisher supply pipe to a conventional circulation pipe, FIG. 3 is a line diagram showing the flow velocity in the pipe, FIG. 4 is a front sectional view showing the mixing tank of the present invention, and FIG. The plan view and FIG. 6 are cross-sectional views of the replenisher supply pipe. In the drawings, 1 is a processing tank, 4 is a circulation pipe, 5 is a circulating fluid, 8 is a replenisher, 19 is a mixing tank, 20 is an outer pipe, 23 is an inner pipe, 24 is an opening, 25 is an outlet pipe, and 26 is a Inlet pipe, 21
30 is a solution passage, 30 is a replenisher supply pipe, and 32 is a nozzle.

Claims (1)

[Claims] 1. In a mixing tank in which replenisher fluid is mixed with circulating fluid in order to control and adjust the concentration of the fluid in the processing tank within a predetermined range, an inner and outer double pipe is formed on a concentric circle, and this outer pipe has lids on both sides. One of the inner tubes is open in the outer tube, the other protrudes from the outer tube and is connected to the outlet tube, and the inlet tube is connected tangentially to the outer tube so that the circulating fluid forms a spiral motion. , the replenisher pipe is connected in a normal direction from the outer pipe to the inner pipe,
A replenisher mixing tank characterized in that the tank is connected such that its tip is located in the center of a passage formed by the inner and outer tubes.