Horizontal double-sided electroplating equipment for panel and semiconductor circuit

Abstract

The utility model provides horizontal double-sided electroplating equipment for a panel and a semiconductor circuit, which comprises a machine table with a circular ring rotating structure, and an electroplating mechanism is arranged in the middle of the circular ring rotating structure. The lower cavity structure is fixed to the machine table, the middle cavity structure surrounds the periphery of the lower cavity structure, the upper cavity structure is arranged above the middle cavity structure in a lifting fit mode, the middle cavity structure is arranged on the circular ring rotating structure in a rotating fit mode, and the upper cavity structure is arranged above the middle cavity structure in a lifting fit mode. The lower end of the upper cavity structure and the upper end of the lower cavity structure are respectively divided into a plurality of concentric annular independent anode areas; and the middle cavity structure comprises a plurality of cathode connecting sheets arranged on the circular ring rotating structure, a cathode ring arranged at the upper ends of the plurality of cathode connecting sheets, and a cathode conduction clamp module arranged on the cathode ring. The utility model relates to the field of TVG electroplating technology.

Description

Technical Field

[0001] This utility model relates to the field of TVG electroplating process, and in particular to a horizontal double-sided electroplating device for panels and semiconductor circuits. Background Technology

[0002] In the panel and semiconductor manufacturing industries, especially in applications involving through-glass via (TGV) technology, the horizontal double-sided electroplating process has extremely stringent requirements for high uniformity and high precision coatings. However, existing technologies still have many shortcomings in practical applications, and these defects directly affect the electroplating quality and production efficiency of TGV structures.

[0003] First, traditional horizontal electroplating equipment typically uses a fixed anode structure, which cannot dynamically adjust the current density changes in different areas during TGV electroplating. Due to the high aspect ratio of the TGV structure, the electric field distribution in the central and edge areas is uneven, resulting in significant differences in coating thickness, which seriously affects the reliability of subsequent micro-interconnects. In addition, most existing electroplating solution supply systems use a single flow mode, which cannot adjust the flow ratio of the upper and lower spray plates according to the special requirements of the TGV structure, resulting in insufficient uniformity of electroplating solution filling in the holes, which easily leads to voids or uneven coating.

[0004] Secondly, the cathode structure of existing equipment is usually statically designed, which cannot achieve workpiece rotation. During the TGV electroplating process, due to the uneven distribution of electric field and solution flow, the fixed cathode will cause inconsistent deposition of the coating on the hole wall. Especially in the deep hole area, the coating is prone to be thin or even not coated. At the same time, the electroplating solution mixing efficiency of traditional equipment is low and the additives are unevenly distributed, which further aggravates the fluctuation of coating crystal quality and affects the electrical performance and mechanical strength of the TGV structure.

[0005] In addition, the liquid level control accuracy of existing horizontal electroplating equipment is insufficient. Residual electroplating solution during loading and unloading can easily contaminate the contact area between the fixture and the workpiece, resulting in unstable contact resistance during subsequent electroplating processes and affecting process consistency. The traditional step-by-step electroplating and etching process not only increases process time but also introduces the risk of contamination due to multiple clamping, reducing the yield of TGV structures.

[0006] Therefore, the inventor urgently needs to design a horizontal double-sided electroplating device for panels and semiconductor circuits to solve the above problems. Utility Model Content

[0007] To address the shortcomings of the existing technology, this utility model provides a horizontal double-sided electroplating equipment for panels and semiconductor circuits, aiming to solve the problems of poor coating uniformity, incomplete filling of deep holes, uneven distribution of electroplating solution, and insufficient process control precision in the application of horizontal double-sided electroplating technology in TGV (Through Glass Through-Video) applications.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a horizontal double-sided electroplating equipment for panels and semiconductor circuits, comprising a machine base with a circular rotating structure, an electroplating mechanism disposed in the middle of the circular rotating structure, the electroplating mechanism comprising a lower cavity structure fixed on the machine base, a middle cavity structure surrounding the lower cavity structure, and an upper cavity structure that is vertically fitted above the middle cavity structure, forming a closed electroplating space, wherein the middle cavity structure is rotatably fitted on the circular rotating structure, the lower end of the upper cavity structure and the upper end of the lower cavity structure are both divided into multiple concentric ring-shaped independent anode regions, the middle cavity structure includes a plurality of cathode connecting pieces disposed on the circular rotating structure, a cathode ring disposed on the upper end of the plurality of cathode connecting pieces, and a cathode conduction fixture module mounted on the cathode ring, the cathode conduction fixture module being located between the lower end of the upper cavity structure and the lower cavity structure.

[0009] Based on the above, the beneficial effects of a horizontal double-sided electroplating equipment for panels and semiconductor circuits are that it solves the problems of poor coating uniformity, incomplete deep hole filling, uneven electroplating solution distribution, and insufficient process control precision in the application of horizontal double-sided electroplating technology in TGV (Through Glass Via) in the prior art; mainly reflected in:

[0010] 1. This utility model, through multiple concentric annular independent anode regions set in the upper and lower cavity structures, combined with the cathode conduction fixture module and circular rotating structure in the middle cavity structure, achieves independent current control of the electroplating area, effectively solving the problem of poor coating uniformity caused by uneven current density distribution in TGV applications. Each anode region can independently adjust the current according to the coating requirements of different parts of the workpiece, while the rotating cathode structure further homogenizes the electric field distribution.

[0011] 2. This utility model adopts an electroplating solution supply system composed of an upper spray plate and a lower spray plate. It achieves precise control of the upper and lower flow rates through independent supply pipelines. With the flow regulating valve group and pressure sensor in the flow control module, it can adjust the upper and lower spray ratio according to the deep hole characteristics of the TGV structure, thus solving the problem of incomplete filling of deep holes.

[0012] 3. The Venturi mixer of the electroplating solution supply system adopted by this utility model effectively improves the mixing uniformity of the electroplating solution. The liquid in the electroplating tank return pipe and the chemical addition pipe are fully mixed through the low-pressure zone formed by the circulation return pipe and then fed into the electroplating solution storage tank, which solves the problem of uneven distribution of electroplating solution in traditional technology.

[0013] 4. This utility model adopts a low-level drain tank and a stepped high-level drain tank for drain control, which ensures the level accuracy during loading and unloading of plates and electroplating, and solves the problem of insufficient process control accuracy.

[0014] Furthermore, the electroplating mechanism also includes an electroplating solution supply system, which includes an upper spray plate disposed in the upper cavity structure and a lower spray plate disposed in the lower cavity structure. The upper spray plate and the lower spray plate are respectively connected to the electroplating solution storage tank through independent supply pipelines.

[0015] Based on the above, the beneficial effects of the electroplating solution supply system are that the flow rates of the upper and lower spray plates can be precisely controlled separately. This allows for adjustment of the ratio and intensity of the upper and lower sprays according to the specific requirements of the TGV structure. When processing TGV structures with high aspect ratios, the flow rate of the lower spray plate can be increased to enhance the supply of electroplating solution to the bottom of the deep hole, while the flow rate of the upper spray plate can be appropriately adjusted to ensure the plating quality in the orifice area. This effectively solves the problem that traditional single-spray systems struggle to simultaneously ensure the uniformity of plating at the bottom and orifice of deep holes. Furthermore, the independent supply pipeline design avoids mutual interference between the upper and lower sprays, ensuring the stability and accuracy of flow control.

[0016] Furthermore, the electroplating solution supply system also includes a flow control module, which includes flow regulating valve groups and pressure sensors installed on each supply pipeline. The flow regulating valve groups consist of multiple small-diameter solenoid valves connected in parallel.

[0017] Based on the above, the beneficial effects of the flow control module are that it provides multi-level flow regulation through the combination of different numbers of solenoid valves. Compared with the traditional single regulating valve, it has a more precise flow control capability. The setting of the pressure sensor can provide real-time feedback on pipeline pressure changes, ensuring the stability of flow control. This modular design is particularly suitable for the need for different flow rates in different areas in the TGV electroplating process. For example, in deep hole electroplating, the flow ratio of the upper and lower spray plates can be precisely adjusted to optimize the flow state of the electroplating solution in the hole, thereby improving the uniformity of the coating coverage at the bottom of the deep hole.

[0018] Furthermore, the electroplating solution supply system also includes a Venturi mixer, the input end of which is connected to the electroplating solution return pipe and the additive replenishment pipe, and the output end of which is connected to the electroplating solution storage tank.

[0019] Based on the above, the beneficial effects of the Venturi mixer are that it overcomes the problem of uneven mixing that exists in traditional direct mixing methods. The high-speed jet action of the Venturi mixer ensures that the electroplating solution and additives are fully and uniformly mixed before entering the electroplating solution storage tank at the output end, ensuring the consistency of solution composition. At the same time, this structure avoids the backflow risk that may occur in traditional three-way mixing, which not only improves the mixing efficiency but also ensures the reliability of system operation, providing a stable electroplating solution environment for TGV electroplating.

[0020] Furthermore, the cathode conduction fixture module includes a fixture mounting ring fixed on the cathode ring, a plurality of conductive contacts evenly distributed circumferentially on the inner side of the fixture mounting ring, and a workpiece fixture detachably mounted on the fixture mounting ring and electrically connected to the conductive contacts.

[0021] Based on the above, the beneficial effects of the cathode conduction fixture module are that it ensures the uniform distribution of current on the workpiece surface, effectively avoiding the problem of uneven current density caused by traditional single-point contact. The detachable workpiece fixture design not only facilitates the quick replacement of workpieces of different specifications, but also ensures the stability of electrical contact through the reliable connection between the conductive contact and the fixture. Especially for the TGV electroplating process, the multi-point contact characteristics of this module can significantly improve the uniformity of the bottom plating coverage of the deep hole structure, while the rotation function further optimizes the symmetry of the electric field distribution.

[0022] Furthermore, the circular rotating structure includes a fixed base fixed to the machine base, a slewing bearing mounted on the fixed base, and a drive motor connected to the outer ring of the slewing bearing via a gear transmission mechanism.

[0023] Based on the above, the beneficial effects of the circular rotating structure are that it enables the cathode conduction fixture module to drive the workpiece to rotate at a uniform speed, effectively eliminating the difference in coating thickness caused by uneven electric field distribution in traditional fixed electroplating. Especially for the TGV electroplating process, the rotational motion can promote the uniform flow of the electroplating solution in the deep hole structure, improve the uniformity of coating coverage in the hole, and the gear transmission mechanism design also facilitates precise control of the rotation speed, which can be flexibly adjusted according to different process requirements, further optimizing the electroplating effect.

[0024] Furthermore, the upper cavity structure achieves lifting and lowering movement through a lifting drive mechanism installed on the machine base. The lifting drive mechanism includes a guide column fixed on the machine base, a lifting platform slidably fitted on the guide column, and a motor assembly that drives the lifting platform to move up and down along the guide column.

[0025] Based on the above, the beneficial effects of the lifting drive mechanism are that the lifting platform is driven up and down along the guide column by the motor assembly, which realizes the smooth lifting of the upper cavity structure, making it easy to open the cavity for product loading and unloading operations. This structural design allows the upper cavity to be raised to provide sufficient operating space when loading and unloading sheets, and can be accurately lowered during electroplating to form a closed electroplating space with the middle cavity, effectively simplifying the TGV electroplating process.

[0026] Furthermore, the lower cavity structure includes a low-level drain trough disposed on the outer ring of the concentric annular independent anode region and a stepped high-level drain trough around the upper part of the inner wall of the lower cavity structure. The lower ends of the low-level drain trough and the stepped high-level drain trough are both connected to a drain pipe. A solenoid valve is installed on the drain pipe. A liquid level monitoring sensor is installed on the inner wall of the lower cavity structure.

[0027] Based on the above, the dual drainage structure of the low-level drain tank and the stepped high-level drain tank provides the advantage of precise control of the liquid level during electroplating, in conjunction with solenoid valves and level monitoring sensors. The low-level drain tank is used for rapid drainage during loading and unloading of wafers, ensuring the liquid level drops to a safe position; the stepped high-level drain tank maintains a stable working liquid level during electroplating. The solenoid valve configuration makes liquid level switching faster and more reliable, while the level monitoring sensor enables real-time monitoring of the liquid level.

[0028] To more clearly illustrate the above-mentioned features of this utility model and the objectives it aims to achieve, the present utility model will be further described below in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0029] Figure 1 : This is a perspective view of the present invention;

[0030] Figure 2 This is a schematic diagram of the installation of the Venturi mixer of this utility model;

[0031] Figure 3 This is a schematic diagram of the installation of the flow control module of this utility model;

[0032] Figure 4 This is a schematic diagram showing the combination of the lower cavity structure and the middle cavity structure of this utility model;

[0033] Figure 5 This is a cross-sectional schematic diagram of the present invention.

[0034] Figure 6 : This is a schematic diagram of the lower cavity structure of this utility model;

[0035] Figure 7 : This is a schematic diagram of the central cavity structure of this utility model;

[0036] Figure 8 : This is a schematic diagram of the upper cavity structure of this utility model;

[0037] Figure 9 : This is a schematic diagram of the concentric annular independent anode region of the upper cavity structure of this utility model.

[0038] Reference numerals: 1-Machine base, 11-Circular rotating structure, 111-Fixed base, 112-Slewing bearing, 113-Drive motor, 114-Transmission gear, 2-Electroplating mechanism, 21-Lower cavity structure, 211-Low liquid level drain tank, 212-Stepped high liquid level drain tank, 213-Drainage pipeline, 214-Solenoid valve, 22-Middle cavity structure, 221-Cathode connection piece, 222-Cathode ring, 223-Cathode conduction fixture module, 2231-Fixture installation 2232-Conductive contact, 2233-Workpiece clamp, 23-Upper cavity structure, 3-Electroplating solution supply system, 31-Upper spray plate, 32-Lower spray plate, 33-Flow control module, 331-Flow regulating valve group, 332-Pressure sensor, 34-Venturi mixer, 341-Electroplating solution return pipe, 342-Replenishment pipe, 4-Lifting drive mechanism, 41-Guide column, 42-Lifting platform, 43-Motor assembly, 100-Concentric annular independent anode area. Detailed Implementation

[0039] like Figures 1-9 As shown, a horizontal double-sided electroplating apparatus for panels and semiconductor circuits includes a machine base 1 with a circular rotating structure 11. An electroplating mechanism 2 is disposed in the middle of the circular rotating structure 11. The electroplating mechanism 2 consists of a lower cavity structure 21 fixed to the machine base 1, a middle cavity structure 22 surrounding the lower cavity structure 21, and an upper cavity structure 23 that is vertically fitted above the middle cavity structure 22, forming a sealed electroplating space. The middle cavity structure 22 is rotatably fitted to the circular rotating structure 11. 1. The lower end of the upper cavity structure 23 and the upper end of the lower cavity structure 21 are both divided into multiple concentric ring-shaped independent anode regions 100. The middle cavity structure 22 includes a plurality of cathode connecting pieces 221 disposed on the circular rotating structure 11, a cathode ring 222 disposed on the upper end of the plurality of cathode connecting pieces 221, and a cathode conducting clamp module 223 mounted on the cathode ring 222. The cathode conducting clamp module 223 is located between the lower end of the upper cavity structure 23 and the lower cavity structure 21.

[0040] In this embodiment, the electroplating mechanism 2 further includes an electroplating solution supply system 3. The electroplating solution supply system 3 includes an upper spray plate 31 disposed on the upper cavity structure 23 and a lower spray plate 32 disposed on the lower cavity structure 21. The upper spray plate 31 and the lower spray plate 32 are respectively connected to the electroplating solution storage tank through independent liquid supply pipelines.

[0041] In this embodiment, the electroplating solution supply system 3 further includes a flow control module 33. The flow control module 33 includes a flow regulating valve group 331 and a pressure sensor 332 disposed on each supply pipeline. The flow regulating valve group 331 is composed of multiple small-diameter solenoid valves connected in parallel.

[0042] In this embodiment, the electroplating solution supply system 3 further includes a Venturi mixer 34. The input end of the Venturi mixer 34 is connected to the electroplating solution return pipe 341 and the replenishment pipe 342, and the output end of the Venturi mixer 34 is connected to the electroplating solution storage tank.

[0043] In this embodiment, the cathode conduction fixture module 223 includes a fixture mounting ring 2231 fixed on the cathode ring 222, a plurality of conductive contacts 2232 evenly distributed circumferentially on the inner side of the fixture mounting ring 2231, and a workpiece fixture 2233 detachably mounted on the fixture mounting ring 2231 and electrically connected to the conductive contacts 2232.

[0044] In this embodiment, the circular rotating structure 11 includes a fixed base 111 fixed on the machine base 1, a slewing bearing 112 mounted on the fixed base 111, and a drive motor 113 connected to the outer ring of the slewing bearing 112 via a transmission gear 114.

[0045] In this embodiment, the upper cavity structure 23 achieves lifting and lowering movement through a lifting drive mechanism 4 installed on the machine base 1. The lifting drive mechanism 4 includes a guide column 41 fixed on the machine base 1, a lifting platform 42 slidably engaged with the guide column 41, and a motor assembly 43 that drives the lifting platform 42 to move up and down along the guide column 41.

[0046] In this embodiment, the lower cavity structure 21 includes a low-level drain trough 211 disposed on the outer ring of the concentric annular independent anode region 100 and a stepped high-level drain trough 212 around the upper end of the inner wall of the lower cavity structure 21. The lower ends of the low-level drain trough 211 and the stepped high-level drain trough 212 are both connected to the drain pipe 213. The drain pipe 213 is equipped with a solenoid valve 214. A liquid level monitoring sensor is disposed on the inner wall of the lower cavity structure 21.

[0047] This utility model also discloses a horizontal double-sided electroplating process for panels and semiconductor circuits, including the following steps:

[0048] S1: Install the workpiece to be electroplated onto the cathode conduction fixture module 223;

[0049] S2: Control the lifting drive mechanism 4 to lower the upper cavity structure 23 and seal it with the middle cavity structure 22;

[0050] S3: Electroplating solution is injected into the electroplating space to the set liquid level through the electroplating solution supply system 3;

[0051] S4: Start the circular rotating structure 11 to drive the central cavity structure 22 and the workpiece to rotate;

[0052] S5: Apply independently controlled current to each concentric ring-shaped independent anode region 100 for electroplating;

[0053] S6: After electroplating is completed, drain the electroplating solution and raise the upper cavity structure 23 to remove the workpiece.

[0054] In this embodiment, a dual-pulse power supply is used in step S5 to provide power, and positive electroplating pulses and reverse etching pulses are applied alternately.

[0055] In summary, the specific implementation of this utility model is as follows: First, the motor assembly 43 of the lifting drive mechanism 4 drives the lifting platform 42 to rise along the guide column 41, so that the upper cavity structure 23 is in the open state. The operator installs the workpiece to be processed onto the workpiece fixture 2233 of the cathode conduction fixture module 223 to ensure good contact between the workpiece and the conductive contact 2232. After the installation is completed, the motor assembly 43 drives the lifting platform 42 to fall, so that the upper cavity structure 23 and the middle cavity structure 22 form a closed electroplating space.

[0056] Next, the circular rotating structure 11 on the machine tool 1 starts, in which the fixed seat 111 provides support, and the slewing bearing 112 starts to operate under the drive of the drive motor 113 through the transmission gear 114. The middle cavity structure 22 rotates accordingly, driving the cathode ring 222 and the cathode conduction fixture module 223 to move synchronously.

[0057] The electroplating solution supply system 3 then starts working. The Venturi mixer 34 fully mixes the liquid in the electroplating solution return pipe 341 and the replenishment pipe 342 and then inputs it into the electroplating solution storage tank. The variable frequency chemical pump adjusts the mixed electroplating solution through the flow control module 33. The flow regulating valve group 331 accurately controls the flow based on the feedback from the pressure sensor 332. The solution is injected into the closed electroplating space composed of the lower cavity structure 21, the middle cavity structure 22 and the upper cavity structure 23 through the upper spray plate 31 and the lower spray plate 32 respectively. The liquid level monitoring sensor monitors the liquid level change in real time. When the set value is reached, the solenoid valves 214 on the low liquid level drain tank 211 and the stepped high liquid level drain tank 212 adjust their openings accordingly to maintain a stable liquid level.

[0058] When the electroplating process officially begins, the dual-pulse power supply 8 applies a program-controlled current to each concentric ring-shaped independent anode region 100. At the same time, the cathode conduction fixture module 223 provides a uniform current distribution to the workpiece through the fixture mounting ring 2231 and the conductive contact 2232. During the forward electroplating pulse stage, metal ions are deposited on the workpiece surface; during the reverse etching pulse stage, the protrusions on the plating surface are eliminated. The entire process continues until the preset electroplating time is reached.

[0059] After the process is completed, the solenoid valve 214 on the drain pipe 213 is opened to drain the electroplating solution to a low level. The lifting drive mechanism 4 is started again to raise the upper cavity structure 23. The operator can then remove the electroplated workpiece from the cathode conduction fixture module 223 to prepare for the next processing cycle.

[0060] The above description is only the optimal solution embodiment of this utility model and is not intended to limit this utility model. Various modifications or substitutions made by those skilled in the art to this utility model without departing from the essence and protection scope of this utility model should also be within the protection scope of this utility model.

Claims

1. A horizontal double-sided electroplating apparatus for panel and semiconductor wiring, comprising a machine table (1) with a circular ring rotating structure (11), characterized in that: The middle part of the circular ring rotating structure (11) is provided with an electroplating mechanism (2), which is composed of a lower cavity structure (21) fixed on the machine table (1), a middle cavity structure (22) surrounding the periphery of the lower cavity structure (21), and an upper cavity structure (23) matched with the upper part of the middle cavity structure (22), which together form a closed electroplating space, wherein the middle cavity structure (22) is rotationally matched with the circular ring rotating structure (11), the lower end of the upper cavity structure (23) and the upper end of the lower cavity structure (21) are both divided into a plurality of concentric ring-shaped independent anode areas (100), the middle cavity structure (22) includes a plurality of cathode connecting pieces (221) arranged on the circular ring rotating structure (11), a cathode ring (222) arranged on the upper end of the plurality of cathode connecting pieces (221), and a cathode conduction clamp module (223) mounted on the cathode ring (222), and the cathode conduction clamp module (223) is located between the lower end of the upper cavity structure (23) and the upper end of the lower cavity structure (21).

2. The apparatus according to claim 1, wherein: The electroplating mechanism (2) further comprises an electroplating liquid supply system (3), which comprises an upper spray disc (31) arranged on the upper cavity structure (23) and a lower spray disc (32) arranged on the lower cavity structure (21), and the upper spray disc (31) and the lower spray disc (32) are respectively connected with an electroplating liquid storage tank through independent liquid supply pipelines.

3. A horizontal double-sided electroplating apparatus for panel and semiconductor wiring according to claim 2, wherein: The electroplating liquid supply system (3) further comprises a flow control module (33), which comprises a flow regulating valve group (331) and a pressure sensor (332) arranged on each liquid supply pipeline, and the flow regulating valve group (331) is composed of a plurality of small-diameter electromagnetic valves connected in parallel.

4. The apparatus according to claim 3, wherein: The electroplating liquid supply system (3) further comprises a Venturi mixer (34), the input end of the Venturi mixer (34) is connected with an electroplating liquid return pipe (341) and a liquid supplement pipe (342), and the output end of the Venturi mixer (34) is connected with the electroplating liquid storage tank.

5. The horizontal double-sided electroplating equipment for panels and semiconductor circuits according to claim 1, characterized in that: The cathode conduction clamp module (223) comprises a clamp mounting ring (2231) fixed on the cathode ring (222), a plurality of conductive contact pieces (2232) uniformly distributed on the inner side of the clamp mounting ring (2231), and a workpiece clamp (2233) detachably mounted on the clamp mounting ring (2231) and electrically connected with the conductive contact pieces (2232).

6. The apparatus according to claim 1, wherein: The circular ring rotating structure (11) comprises a fixed seat (111) fixed on the machine table (1), a slewing bearing (112) mounted on the fixed seat (111), and a driving motor (113) connected with the outer ring of the slewing bearing (112) through a transmission gear (114).

7. The apparatus according to claim 1, wherein: the faceplate is made of a material having a high thermal conductivity. The upper cavity structure (23) is lifted by a lifting driving mechanism (4) fixed on the machine table (1), which comprises a guide column (41) fixed on the machine table (1), a lifting platform (42) slidingly fitted on the guide column (41), and a motor assembly (43) driving the lifting platform (42) to move up and down along the guide column (41).

8. The apparatus according to claim 1, wherein: The lower cavity structure (21) comprises a low liquid level drainage groove (211) arranged outside the outer ring of the concentric ring-shaped independent anode area (100) and a stepped high liquid level drainage groove (212) arranged around the upper end of the inner wall of the lower cavity structure (21), the lower ends of the low liquid level drainage groove (211) and the stepped high liquid level drainage groove (212) are connected with a drainage pipeline (213), the drainage pipeline (213) is provided with an electromagnetic valve (214), and a liquid level monitoring sensor is arranged on the inner wall of the lower cavity structure (21).

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