CN212640606U

CN212640606U - Rapid cooling system for wafer plating solution

Info

Publication number: CN212640606U
Application number: CN202021945516.0U
Authority: CN
Inventors: 张萍; 李宗颖; 周浩; 李勇刚; 刘凯
Original assignee: Hebei Guangchuang Electronic Technology Co ltd
Current assignee: Hebei Guangchuang Electronic Technology Co ltd
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2021-03-02
Anticipated expiration: 2030-09-08

Abstract

The utility model belongs to the field of semiconductor chip processing equipment, concretely relates to quick cooling system of wafer plating solution, the defect that the wafer plating efficiency is low in the prior art is solved, and a high-efficiency quick cooling system of wafer plating solution capable of realizing quick cooling discharge is provided, which comprises a plating solution tank, a circulating pipeline in the plating solution tank, a heat exchanger, a heater, a compressed air inlet, a compressed air pipeline, a pure water inlet, a pure water pipeline, a circulating pump and a control valve, wherein the plating solution tank is communicated with the circulating pipeline in the plating solution tank, a heat exchange branch pipeline and a circulating discharge branch pipeline are arranged on the circulating pipeline in the plating solution tank, the heat exchange branch pipeline is communicated with the heat exchanger, and the circulating pump is positioned on the heat exchange; the pipeline is provided with a control valve; the heater is connected with the heat exchanger through a pipeline.

Description

Rapid cooling system for wafer plating solution

Technical Field

The utility model belongs to semiconductor chip processing equipment field, concretely relates to rapid cooling system of wafer plating bath.

Background

During the fabrication of semiconductor integrated circuits, semiconductor wafers are typically subjected to a number of process steps, such as film deposition, etching, polishing, etc. These process steps become important sites for contamination generation. In order to maintain the wafer surface clean and remove contaminants deposited on the wafer surface during the various process steps, the wafer surface after each process step must be cleaned. Therefore, the cleaning process becomes the most common process step in the integrated circuit fabrication process, and aims to effectively control the contamination level of each step to achieve the goal of each process step.

The wafer production equipment in the prior art can only realize stable production of wafers with the size of 8 inches or less basically, and when the size of the wafer is increased, the prior art can not perform uniform and stable high-quality treatment on the surface of the wafer.

The crystal rounding plating equipment is characterized in that a chemical plating solution is prepared in a chemical plating process, and then a heater is used for heating to a specified temperature for chemical plating. When the chemical plating solution needs to be replaced, the chemical plating solution is required to be cooled and then discharged because the chemical plating solution is too high in temperature and directly discharged to damage pipelines. The traditional equipment is used for waiting for the natural cooling of the chemical plating solution, and the process is slow and long, thereby influencing the wafer yield. If the wafer production efficiency is improved, the technical problem to be solved in the prior art is needed.

SUMMERY OF THE UTILITY MODEL

In order to solve the defect of low efficiency of the wafer plating equipment in the prior art, the utility model provides an automatic rapid cooling system of wafer plating solution.

The utility model provides a technical scheme that its technical problem adopted as follows: a rapid cooling system for wafer plating solution comprises a plating solution tank, a circulating pipeline in the plating solution tank, a heat exchanger, a heater, a compressed air inlet, a compressed air pipeline, a pure water inlet, a pure water pipeline, a circulating pump and a control valve, wherein the plating solution tank is communicated with the circulating pipeline in the plating solution tank; a heat exchange circulating pipeline is arranged between the circulating discharge branch pipeline and the heat exchanger, and a control valve is arranged on the heat exchange circulating pipeline and is a circulating pneumatic control valve; the heater is connected with the heat exchanger through a pipeline; the compressed air inlet is arranged at the inlet end of a compressed air pipeline, the compressed air pipeline is communicated with a circulating pipeline in the plating solution tank, and a control valve is arranged on the compressed air pipeline; the end of the pure water pipeline is a pure water inlet, and the pure water pipeline is connected with the heat exchanger.

The pure water purification device is characterized by further comprising a compressed air first pipeline, wherein the compressed air first pipeline is communicated with the compressed air pipeline and the part, which is not connected with the heat exchanger, of the pure water pipeline, a pure water injection electromagnetic valve is arranged on the compressed air first pipeline, and a pure water injection pneumatic control valve is arranged at the communication position of the compressed air first pipeline and the pure water pipeline.

The pure water purifier is characterized by further comprising a compressed air second pipeline, the compressed air second pipeline is communicated with the compressed air pipeline and the pure water pipeline discharge heat exchanger, the part close to the pure water discharge port is communicated, a pure water discharge electromagnetic valve is arranged on the compressed air second pipeline, and a pure water discharge pneumatic control valve is arranged at the communication position of the compressed air first pipeline and the pure water pipeline.

The heat exchanger is characterized by further comprising a compressed air third pipeline, the compressed air third pipeline is communicated with the heat exchanger and the heat exchange circulating pipeline, a circulating electromagnetic valve is arranged on the compressed air third pipeline, and a circulating pneumatic control valve is arranged at the position communicated with the heat exchange circulating pipeline.

The plating solution circulating system is characterized by further comprising a compressed air fourth pipeline, wherein the compressed air fourth pipeline is communicated with the circulating discharge branch pipeline, a plating solution discharging electromagnetic valve is arranged on the compressed air fourth pipeline, and a plating solution discharging pneumatic control valve is arranged at the position communicated with the circulating discharge branch pipeline.

The compressed air pipeline is communicated with a circulating pipeline in the plating solution tank, an internal discharge magnetic valve is arranged on a fifth compressed air pipeline, and an internal discharge pneumatic control valve is arranged at the communication position of the compressed air pipeline and the circulating pipeline in the plating solution tank.

The plating solution tank comprises a plating solution tank outer tank and a plating solution tank inner tank, the plating solution tank outer tank is nested on the outer side of the upper part of the plating solution tank inner tank, and plating solution inlets and outlets are arranged at the bottoms of the plating solution tank outer tank and the plating solution tank inner tank.

The heat exchanger comprises a chemical plating solution return port, a sealing cover plate, a heater hot water return port, a sealing screw, a room-temperature pure water outlet, a shell, a room-temperature pure water inlet, a heater hot water inlet, a heat exchanger bracket, a chemical plating solution inlet, a capillary tube, a top flow distribution plate and a bottom flow distribution plate; the shell is fixed on a heat exchanger support, a top splitter plate is arranged at the top end of the shell, a bottom splitter plate is arranged at the bottom end of the shell and fixed by a sealing screw, the top splitter plate and the bottom splitter plate are double layers, the inner layer is a plate with a plurality of through holes, the outer layer is provided with an inlet and an outlet, a gap is formed between the inner layer and the outer layer, the inlet and the outlet at the top of the outer layer of the top splitter plate are chemical plating solution return ports, and the inlet and the outlet at the bottom of the outer layer of the bottom splitter; a capillary tube is arranged in a closed space formed by the shell, the top splitter plate and the bottom splitter plate, and two ends of the capillary tube are respectively communicated with the through holes on the top splitter plate and the bottom splitter plate; a room temperature pure water inlet is arranged below the room temperature pure water outlet arranged above the side surface of the shell.

The pure water discharge valve and the pure water discharge port are arranged on a pure water pipeline, the pure water discharge port is one end far away from the pure water inlet, and the pure water discharge valve is close to the pure water discharge port; the plating solution discharging port is arranged at the tail end of the branch circulating discharging pipeline, and the plating solution discharging valve is positioned on the branch circulating discharging pipeline and close to the plating solution discharging port.

The beneficial effects of the utility model reside in that:

the chemical plating solution tank uses a circulating pump to circulate liquid, the liquid is pumped into a heat exchanger to carry out heat exchange, the circulating water part is divided into two groups, one group is provided with hot water by a heater and is used by heating after being replaced with chemical plating solution, and the other group is connected into pure water at room temperature to carry out rapid cooling when the chemical plating solution needs to be replaced. Because pure water is expensive, in order to save the pure water, a pure water saving function is set in the program, namely the pure water is not opened all the time, but the opening time is a, the closing time is b, so that the pure water stays in the heat exchanger for b time, and the pure water is replaced after the pure water and the chemical plating solution fully exchange heat.

The utility model discloses well all gas accuse valves are controlled by corresponding solenoid valve, and the solenoid valve is controlled by master control system, and master control system control solenoid valve break-make promptly, and solenoid valve control compressed air break-make, compressed air is the gas accuse valve break-make of controlling again, can make electrical system and pipe-line system keep apart like this, prevents that electrical system from being corroded, influences equipment stability.

The technology solves the technical problem which can not be solved in the prior art, can be used for manufacturing wafers with the size of more than 8 inches, particularly wafers with the size of 12 inches or more, and is suitable for popularization and application.

Drawings

FIG. 1 is a schematic structural view of example 1;

FIG. 2 is a schematic view of the heat exchanger according to embodiment 1;

FIG. 3 is a schematic side view of a heat exchanger according to example 1

FIG. 4 is a schematic sectional view of a heat exchanger according to example 1.

In the drawings:

1-plating bath external tank, 2-plating bath internal tank, 3-internal discharge gas control valve, 4-circulating pump, 5-pure water injection pneumatic control valve, 6-heat exchanger, 7-pure water injection manual valve, 8-pure water injection electromagnetic valve, 9-compressed air pressure reducing valve, 10-heater, 11-pure water discharge manual valve, 12-chemical plating bath discharge manual valve, 13-pure water discharge electromagnetic valve, 14-chemical plating bath discharge electromagnetic valve, 15-circulating pneumatic control valve, 16-pure water discharge pneumatic control valve, 17-chemical plating bath discharge pneumatic control valve, 18-circulating electromagnetic valve, 19-internal discharge electromagnetic valve, 20-chemical plating bath return port, 21-sealing cover plate, 22-heater hot water return port, 23-sealing screw, 24-room temperature pure water discharge port, 25-PP shell, 26-room temperature pure water inlet, 27-heater hot water inlet, 28-heat exchanger bracket, 29-plating solution inlet, 30-capillary tube, 31-top splitter plate, 32-bottom splitter plate, 33-plating solution tank internal circulation pipeline, 34-heat exchange branch pipeline, 35-circulation discharge branch pipeline, 36-heat exchange circulation pipeline, 37-compressed air first pipeline, 38-compressed air second pipeline, 39-compressed air third pipeline, 40-compressed air fourth pipeline, 41-pure water discharge port, 42-plating solution discharge port, 43-pure water inlet, 44-compressed air inlet, 45-compressed air pipeline and 46-pure water pipeline.

Detailed Description

Embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Example 1:

referring to fig. 1-4, a schematic structural diagram of a rapid cooling system for wafer plating solution of this embodiment is shown:

a rapid cooling system for wafer plating solution comprises a plating solution tank, a circulating pipeline 33 in the plating solution tank, a heat exchanger 6, a heater 10, a compressed air inlet 44, a compressed air pipeline 45, a pure water inlet 43, a pure water pipeline 46, a circulating pump and a control valve, wherein the plating solution tank is communicated with the circulating pipeline 33 in the plating solution tank, the circulating pipeline in the plating solution tank is provided with a heat exchange branch pipeline 34 and a circulating discharge branch pipeline 35, the heat exchange branch pipeline 34 is communicated with the heat exchanger 6, and the circulating pump 4 is positioned on the heat exchange branch pipeline 34; a heat exchange circulating pipeline 36 is arranged between the circulating discharge branch pipeline 35 and the heat exchanger 6, and a control valve is arranged on the heat exchange circulating pipeline 36 and is a circulating pneumatic control valve 15; the heater 10 is connected with the heat exchanger 6 through a pipeline; the compressed air inlet 44 is arranged at the inlet end of a compressed air pipeline 45, the compressed air pipeline 45 is communicated with the plating solution tank internal circulation pipeline 33, a control valve is arranged on the compressed air pipeline 45 and is an internal discharge magnetic valve 19, and an internal discharge pneumatic control valve is arranged at the communication part of the compressed air pipeline 45 and the plating solution tank internal circulation pipeline 33; the pure water pipe 46 has a pure water inlet 43 at its end, and the pure water pipe 46 is connected to the heat exchanger 6.

The device also comprises a compressed air first pipeline 37, the compressed air first pipeline is communicated with the compressed air pipeline and the part of the pure water pipeline which is not connected with the heat exchanger, a pure water injection electromagnetic valve 8 is arranged on the compressed air first pipeline, and a pure water injection pneumatic control valve 5 is arranged at the communication position of the compressed air first pipeline and the pure water pipeline.

And the device also comprises a compressed air second pipeline 38, wherein the compressed air second pipeline is communicated with the compressed air pipeline and the pure water pipeline discharge heat exchanger and a part close to the pure water discharge port, the compressed air second pipeline is provided with a pure water discharge electromagnetic valve 13, and a pure water discharge pneumatic control valve 16 is arranged at the communication part of the compressed air first pipeline and the pure water pipeline.

The heat exchanger further comprises a compressed air third pipeline 39, the compressed air third pipeline is communicated with the heat exchanger and the heat exchange circulating pipeline, a circulating electromagnetic valve 18 is arranged on the compressed air third pipeline, and a circulating pneumatic control valve 15 is arranged at the position communicated with the heat exchange circulating pipeline.

The plating bath chemical plating device further comprises a compressed air fourth pipeline 40, wherein the compressed air fourth pipeline is communicated with the circulating discharge branch pipeline, a plating bath chemical plating discharge electromagnetic valve 14 is arranged on the compressed air fourth pipeline, and a plating bath chemical plating discharge pneumatic control valve 17 is arranged at the position communicated with the circulating discharge branch pipeline.

And the pure water discharge valve 11 and the pure water discharge port 41 are further included, the pure water discharge valve 11 and the pure water discharge port 41 are arranged on the pure water pipeline, the pure water discharge port 41 is one end far away from the pure water inlet 43, and the pure water discharge valve 11 is close to the pure water discharge port 41.

The device also comprises a plating solution discharge valve 12 and a plating solution discharge port 42, wherein the plating solution discharge port 42 is arranged at the tail end of the branch circulation discharge pipeline 35, and the plating solution discharge valve 12 is positioned on the branch circulation discharge pipeline 35 and is close to the plating solution discharge port 42.

The plating solution tank comprises a plating solution tank outer tank 1 and a plating solution tank inner tank 2, the plating solution tank outer tank is nested on the outer side of the upper part of the plating solution tank inner tank, and plating solution inlets and outlets are arranged at the bottoms of the plating solution tank outer tank and the plating solution tank inner tank.

The heat exchanger comprises a chemical plating solution return port 20, a sealing cover plate 21, a heater hot water return port 22, a sealing screw 23, a room-temperature pure water drainage port 24, a shell 25, a room-temperature pure water inlet 26, a heater hot water inlet 27, a heat exchanger bracket 28, a chemical plating solution inlet 29, a capillary tube 30, a top splitter plate 31 and a bottom splitter plate 32; the shell 25 is fixed on a heat exchanger support 28, a top splitter plate is arranged at the top end of the shell, a bottom splitter plate is arranged at the bottom end of the shell and fixed by a sealing screw 23, the top splitter plate and the bottom splitter plate are double-layer, the inner layer is plate-shaped and provided with a plurality of through holes, the outer layer is provided with an inlet and an outlet, a gap is formed between the inner layer and the outer layer, the inlet and the outlet at the top of the outer layer of the top splitter plate are chemical plating solution return ports, and the inlet and the outlet at the bottom of the outer layer; a capillary tube is arranged in a closed space formed by the shell, the top splitter plate and the bottom splitter plate, and two ends of the capillary tube are respectively communicated with the through holes on the top splitter plate and the bottom splitter plate; a room temperature pure water inlet is arranged below the room temperature pure water outlet arranged above the side surface of the shell; a hot water return port 22 of the heater is arranged above the side surface of the shell, and a hot water inlet 27 of the heater is arranged below the side surface of the shell.

After the proportioned chemical plating solution is added manually, a circulating pump 4 and a circulating air control valve 15 are opened, the chemical plating solution starts to circulate, the solution is pumped from the outer tank 1 of the gold-plating and palladium-plating tank into a chemical plating solution inlet 29 of a heat exchanger 6, the solution comes out from a chemical plating solution return port 20 of the heat exchanger 6 and returns to the inner tank 2 of the gold-plating and palladium-plating tank, and the inner tank 2 returns to the outer tank 1 after overflowing; adding enough water into the heater 10, opening the heater 10, circularly pumping the water into a heater hot water inlet 27 of the heat exchanger 6, returning the water to the heater from a heater hot water return port 22 of the heat exchanger 6, heating at the same time, and exchanging heat between the heated hot water and the chemical plating solution in the heat exchanger 6 to heat the chemical plating solution; when the chemical plating solution is replaced, the chemical plating solution is cooled firstly, at the moment, the circulation of the chemical plating solution is not closed, the heater 10 is closed, the pure water injection air control valve 5, the pure water injection manual valve 7, the pure water discharge manual valve 11 and the pure water discharge air control valve 16 are opened, the operation is kept for a seconds (the time can be set), the pure water at the room temperature is injected into the room-temperature pure water inlet 26 of the heat exchanger 6, and the residual hot water in the room-temperature pure water inlet is discharged to the factory through the room-temperature pure water discharge port 24; after the heat exchanger 6 is filled with room temperature pure water, the pure water injection air control valve 5, the pure water injection manual valve 7, the pure water discharge manual valve 11 and the pure water discharge air control valve 16 are closed, b seconds (time can be set) are kept, after the pure water and the chemical plating solution are subjected to sufficient heat exchange, the pure water injection air control valve 5, the pure water injection manual valve 7, the pure water discharge manual valve 11 and the pure water discharge air control valve 16 are opened, a seconds (time can be set) are kept, and the like, until the temperature of the chemical plating solution is reduced to be lower than the discharge temperature, the pure water injection air control valve 5, the pure water injection manual valve 7, the pure water discharge manual valve 11 and the pure water discharge air. At this time, the internal discharge pneumatic control valve 3, the chemical plating solution discharge manual valve 12, the circulation pneumatic control valve 15 and the chemical plating solution discharge pneumatic control valve 17 can be opened, and the chemical plating solution is discharged to the recycling bin through the chemical plating solution discharge port 42.

The chemical plating solution is injected into the heat exchanger 6 from the inlet 29, and is divided into tens of PFA capillaries by the bottom dividing plate 32, and then the tens of PFA capillaries are converged into the chemical plating solution outlet 20 by the top dividing plate 31. Pure water at room temperature is fed into the heat exchanger through a port 26, fills the cavity of the whole heat exchanger, and flows out of the heat exchanger through an outlet 24. The heat exchange is carried out through the temperature difference between the pure water and the chemical plating solution, the heat exchange is uniform, and the condition of high local temperature cannot occur; the heat exchange efficiency is high; the capillary material is PFA, and the corrosion resistance is good.

Of course, the foregoing is a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations are also considered to be the protection scope of the present invention.

Claims

1. A rapid cooling system of wafer plating solution is characterized in that: the plating solution tank is communicated with the circulating pipeline in the plating solution tank, a heat exchange branch pipeline and a circulating discharge branch pipeline are arranged on the circulating pipeline in the plating solution tank, the heat exchange branch pipeline is communicated with the heat exchanger, and the circulating pump is positioned on the heat exchange branch pipeline; a heat exchange circulating pipeline is arranged between the circulating discharge branch pipeline and the heat exchanger, and a control valve is arranged on the heat exchange circulating pipeline and is a circulating pneumatic control valve; the heater is connected with the heat exchanger through a pipeline; the compressed air inlet is arranged at the inlet end of a compressed air pipeline, the compressed air pipeline is communicated with a circulating pipeline in the plating solution tank, and a control valve is arranged on the compressed air pipeline; the end of the pure water pipeline is a pure water inlet, and the pure water pipeline is connected with the heat exchanger.

2. The rapid cooling system for wafer plating solution according to claim 1, wherein: the heat exchanger comprises a chemical plating solution return port, a sealing cover plate, a heater hot water return port, a sealing screw, a room-temperature pure water outlet, a shell, a room-temperature pure water inlet, a heater hot water inlet, a heat exchanger bracket, a chemical plating solution inlet, a capillary tube, a top flow distribution plate and a bottom flow distribution plate; the shell is fixed on a heat exchanger support, a top splitter plate is arranged at the top end of the shell, a bottom splitter plate is arranged at the bottom end of the shell and fixed by a sealing screw, the top splitter plate and the bottom splitter plate are double layers, the inner layer is a plate with a plurality of through holes, the outer layer is provided with an inlet and an outlet, a gap is formed between the inner layer and the outer layer, the inlet and the outlet at the top of the outer layer of the top splitter plate are chemical plating solution return ports, and the inlet and the outlet at the bottom of the outer layer of the bottom splitter; a capillary tube is arranged in a closed space formed by the shell, the top splitter plate and the bottom splitter plate, and two ends of the capillary tube are respectively communicated with the through holes on the top splitter plate and the bottom splitter plate; a room temperature pure water inlet is arranged below the room temperature pure water outlet arranged above the side surface of the shell.

3. The rapid cooling system for wafer plating solution according to claim 1, wherein: the pure water purification device is characterized by further comprising a compressed air first pipeline, wherein the compressed air first pipeline is communicated with the compressed air pipeline and the part, which is not connected with the heat exchanger, of the pure water pipeline, a pure water injection electromagnetic valve is arranged on the compressed air first pipeline, and a pure water injection pneumatic control valve is arranged at the communication position of the compressed air first pipeline and the pure water pipeline.

4. The rapid cooling system for wafer plating solution according to claim 1, wherein: the pure water purifier is characterized by further comprising a compressed air second pipeline, the compressed air second pipeline is communicated with the compressed air pipeline and the pure water pipeline discharge heat exchanger, the part close to the pure water discharge port is communicated, a pure water discharge electromagnetic valve is arranged on the compressed air second pipeline, and a pure water discharge pneumatic control valve is arranged at the communication position of the compressed air first pipeline and the pure water pipeline.

5. The rapid cooling system for wafer plating solution according to claim 1, wherein: the heat exchanger is characterized by further comprising a compressed air third pipeline, the compressed air third pipeline is communicated with the heat exchanger and the heat exchange circulating pipeline, a circulating electromagnetic valve is arranged on the compressed air third pipeline, and a circulating pneumatic control valve is arranged at the position communicated with the heat exchange circulating pipeline.

6. The rapid cooling system for wafer plating solution according to claim 1, wherein: the plating solution circulating system is characterized by further comprising a compressed air fourth pipeline, wherein the compressed air fourth pipeline is communicated with the circulating discharge branch pipeline, a plating solution discharging electromagnetic valve is arranged on the compressed air fourth pipeline, and a plating solution discharging pneumatic control valve is arranged at the position communicated with the circulating discharge branch pipeline.

7. The rapid cooling system for wafer plating solution according to claim 1, wherein: the plating solution tank comprises a plating solution tank outer tank and a plating solution tank inner tank, the plating solution tank outer tank is nested on the outer side of the upper part of the plating solution tank inner tank, and plating solution inlets and outlets are arranged at the bottoms of the plating solution tank outer tank and the plating solution tank inner tank.

8. The rapid cooling system for wafer plating solution according to claim 1, wherein: the heat exchanger comprises a chemical plating solution return port, a sealing cover plate, a heater hot water return port, a sealing screw, a room-temperature pure water outlet, a shell, a room-temperature pure water inlet, a heater hot water inlet, a heat exchanger bracket, a chemical plating solution inlet, a capillary tube, a top flow distribution plate and a bottom flow distribution plate; the shell is fixed on a heat exchanger support, a top splitter plate is arranged at the top end of the shell, a bottom splitter plate is arranged at the bottom end of the shell and fixed by a sealing screw, the top splitter plate and the bottom splitter plate are double layers, the inner layer is a plate with a plurality of through holes, the outer layer is provided with an inlet and an outlet, a gap is formed between the inner layer and the outer layer, the inlet and the outlet at the top of the outer layer of the top splitter plate are chemical plating solution return ports, and the inlet and the outlet at the bottom of the outer layer of the bottom splitter; a capillary tube is arranged in a closed space formed by the shell, the top splitter plate and the bottom splitter plate, and two ends of the capillary tube are respectively communicated with the through holes on the top splitter plate and the bottom splitter plate; a room temperature pure water inlet is arranged below the room temperature pure water outlet arranged above the side surface of the shell.

9. The rapid cooling system for wafer plating solution according to claim 1, wherein: the pure water discharge valve and the pure water discharge port are arranged on a pure water pipeline, the pure water discharge port is one end far away from the pure water inlet, and the pure water discharge valve is close to the pure water discharge port; the plating solution discharging port is arranged at the tail end of the branch circulating discharging pipeline, and the plating solution discharging valve is positioned on the branch circulating discharging pipeline and close to the plating solution discharging port.