Combined Structure and Installation Method of a Semiconductor Device and a Circuit Board

Abstract

In view of the problems in the prior art that general electronic components are installed on a circuit board regardless of power size, resulting in low heat dissipation efficiency of high-power electronic components and difficulty in repairing and replacing high-power components, the present invention provides a combined structure and installation method of a semiconductor device and a circuit board, belonging to the field of semiconductor technology. It includes a circuit board on which low-power semiconductor devices are installed and a heat sink for installing high-power semiconductor devices. The heat sink is installed on the circuit board. There are several through holes on the circuit board for inserting the pins of high-power semiconductor devices. There is a gap between the circuit board and the heat sink. The high-power semiconductor device is installed on the bottom plate between the heat dissipation mechanism and the side plate. The pins of the high-power semiconductor device pass through the bottom plate and the through holes on the circuit board, and pin plug-in parts are sleeved on the pins of the high-power semiconductor device.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a combined structure of a semiconductor device and a circuit board and an installation method. Background Art

[0002] Some electronic components installed on the circuit board have high power and generate a lot of heat, while others have low power and generate relatively little heat. Except for the processor chip, which has a separate heat sink installed, most electronic components are installed on the circuit board, and then a heat sink is installed on the circuit board to dissipate heat for all the electronic components on the circuit board. The connection method between the pins of the electronic components and the circuit board is also that the pins of the electronic components are directly soldered to the pads on the circuit board after the pins are plugged into the circuit board.

[0003] However, in the above scheme, in addition to the processor chip, commonly used electronic components also have high power and high heat generation (high-power components). These electronic components are installed together with other low-power and low-heat electronic components and are cooled by the same radiator. The heat of the high-power components cannot be dissipated in time, which will inevitably affect the service life of the electronic components over time. What's more, the accumulated heat will also affect the normal performance of the surrounding low-power electronic components. And then affect the overall service life of the entire circuit board. In addition, the service life of high-power components is relatively low, and the probability of needing repair and replacement is relatively high. If they are directly welded on the circuit board, when repairing and replacing high-power components, it is necessary to use a welding gun to melt the pins of the high-power components and the welding points of the circuit board in a short time, and pull out the high-power components for replacement before the solder solidifies again. High-power components generally have several pins. To weld and melt all the pins of high-power components from the circuit board in a short period of time requires multiple welding guns and multiple people to work at the same time. However, due to the size of high-power components, the operating space left for the pins of high-power components is very limited. It is very difficult for multiple people and multiple welding guns to weld the pins of high-power components at the same time. As a last resort, in many cases, the entire circuit board can only be replaced as a whole, which increases the cost of maintenance and replacement, and also causes a waste of resources. Summary of the invention

[0004] The present invention aims to solve the problem in the prior art that general electronic components are uniformly installed on a circuit board regardless of power, resulting in low heat dissipation efficiency of high-power electronic components and difficulty in repairing and replacing high-power components. A combination structure of a semiconductor device and a circuit board and an installation method are provided.

[0005] The object of the present invention is achieved by the following technical solutions: A combined structure of a semiconductor device and a circuit board, including a circuit board on which a low-power semiconductor device is installed and a heat sink for installing a high-power semiconductor device. The heat sink is installed on the circuit board. There are several through holes on the circuit board for inserting the pins of the high-power semiconductor device. There is a gap between the circuit board and the heat sink. The heat sink includes a bottom plate, side plates and a heat dissipation mechanism. There is a space between the heat dissipation mechanism and the side plates. The high-power semiconductor device is installed on the bottom plate between the heat dissipation mechanism and the side plates. The pins of the high-power semiconductor device pass through the bottom plate and through the through holes on the circuit board. A pin plug-in is sleeved on the pins of the high-power semiconductor device. The pin plug-in includes a plugging sleeve with a hollow tubular structure with one end closed. A welding ring coaxially arranged with the plugging sleeve is fixedly provided at the non-closed end of the plugging sleeve. The welding ring extends outward relative to the outer side surface of the plugging sleeve. A clamping mechanism for clamping the pins is fixedly arranged in the plugging sleeve. The welding ring is welded to the circuit board.

[0006] In the above solution, the high-power semiconductor device generates more heat. The surface of the high-power semiconductor device is fully attached to the bottom plate of the heat sink, so that the heat dissipated by the high-power semiconductor device can be directly conducted to the heat sink and quickly dissipated. The heat generated by the low-power semiconductor device on the circuit board is less, and its heat can be quickly dissipated through the gap between the circuit board and the heat sink. Moreover, there is a bottom plate of the heat sink between the high-power semiconductor device and the circuit board, and the heat dissipated by the high-power semiconductor device has little influence on the low-power semiconductor device on the circuit board. A pin plug-in is sleeved on the pins of the high-power semiconductor device, and the welding ring of the pin plug-in is welded to the circuit board, which avoids direct welding of the pins to the circuit board, protects the pins, and the surface area of the welding ring of the pin plug-in is larger than the surface area of the pins, making it easier to weld. The use of the pin plug-in also facilitates the maintenance and replacement of semiconductor devices. When an electronic component needs to be replaced, as long as the pin of the electronic component is pulled out from the present invention and the pin of the new electronic component is inserted into the present invention, the replacement can be completed.

[0007] Preferably, the heat dissipation mechanism includes several heat dissipation fins perpendicular to the bottom plate, and the thickness of the heat dissipation fins gradually becomes thinner from the connection end of the heat dissipation fins to the other end. The thick part of the heat dissipation fin can quickly absorb heat, and the thin part of the heat dissipation fin can more quickly dissipate the heat on the heat dissipation fin. The thinner the heat dissipation fin, the less heat exists on the heat dissipation fin, and the more quickly the heat can be released.

[0008] Preferably, several mounting holes for the pins of high-power components to pass through are provided on the bottom plate between the heat dissipation mechanism and the side plates.

[0009] Preferably, the clamping mechanism includes a fixed ring with an annular structure. On one side of the fixed ring facing the closed end of the insertion sleeve, at least two receiving pieces distributed around the center line of the fixed ring are fixedly arranged. There is a gap between adjacent receiving pieces. The receiving pieces are gradually inclined towards the center line of the fixed ring from the end connected to the fixed ring to the other end. The inner side surface of the receiving piece is an arc-shaped structure, and the area formed by all the receiving pieces surrounding is a receiving cavity for clamping the pins of the semiconductor device, and this receiving cavity is a frustum-shaped structure. The frustum-shaped receiving cavity can fit tightly with the outer surface of the component pins.

[0010] Preferably, at least two slots parallel to the center line of the fixed ring are provided at the end of the fixed ring facing away from the receiving pieces. The slots penetrate through the inner and outer side surfaces of the fixed ring. The number of slots is equal to the number of gaps between the receiving pieces, and the slots and the gaps are alternately distributed in sequence. When the pins of the component are inserted into the receiving cavity formed by the receiving pieces, the pins will generate an outward thrust on the receiving pieces. Correspondingly, the end of the receiving piece facing the fixed ring will generate a squeezing force on the connection part of the fixed ring and the receiving piece, forcing the position of the fixed ring between adjacent receiving pieces to deform. If the deformation at this position is difficult to recover, it will directly affect the clamping performance of the receiving piece on the pins. The slots provided on the fixed ring and the gaps between adjacent receiving pieces are alternately distributed in sequence, leaving a deformation space for the fixed ring, which is equivalent to transferring the position on the fixed ring that is prone to deformation, and the deformation at this position has less influence on the receiving piece, enabling the receiving piece to effectively clamp the pins of the component, thereby extending the service life of the receiving piece.

[0011] Preferably, the inner cavity of the insertion sleeve is a cylindrical structure, and the fixed ring is sleeved in the insertion sleeve and has an interference fit with the insertion sleeve.

[0012] Preferably, the circuit board and the radiator are fixedly assembled by press riveting.

[0013] An installation method for a semiconductor device and a circuit board includes the following steps: ①. Insert the pins of the low-power semiconductor device into the through holes on the circuit board and weld them to the circuit board; ②. Assemble the circuit board with the inserted low-power semiconductor device to the radiator by press riveting; ③. Insert the pins of the high-power semiconductor device through the bottom plate of the radiator into the through holes on the circuit board; ④. Trim the pins of all high-power semiconductor devices neatly on the side of the circuit board away from the radiator according to the length of the pin connectors; ⑤. Sleeve the pin connectors on the pins of each high-power semiconductor device; ⑥. Weld and connect the welding rings on the pin connectors to the circuit board. Preferably, the surfaces of the high-power semiconductor device and the bottom plate of the radiator are fully adhered. The adhered contact can conduct heat quickly.

[0014] Preferably, the length of the trimmed pin protruding from the protruding part of the circuit board is greater than the distance from the upper end of the welding ring of the pin connector to the receiving cavity and less than the distance from the upper end of the welding ring of the pin connector to the bottom of the inner cavity of the plug sleeve.

[0015] Compared with the prior art, the present invention has the following beneficial effects: A high-power semiconductor device is directly and adhesively mounted on one side bottom plate of the radiator, and a circuit board with a low-power semiconductor device is mounted on the other side bottom plate. This mounting structure can reduce the influence of the heat generated by the high-power semiconductor device on the low-power semiconductor device and is more conducive to heat dissipation; the pin connector facilitates the repair and replacement of the semiconductor device and does not damage the pins of the semiconductor device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a structural diagram of the present invention;

[0017] Figure 2 is a top view of the radiator;

[0018] Figure 3 is a structural diagram of the pin connector;

[0019] Figure 4 is a front view of the pin connector;

[0020] Figure 5 is a cross-sectional view taken along line A-A of the pin connector;

[0021] Figure 6 is a three-dimensional structural diagram of the clamping mechanism;

[0022] Figure 7 is a usage state diagram of the present invention.

[0023] Reference numerals in the drawings: 1. Circuit board; 2. Radiator; 21. Bottom plate; 22. Side plate; 23. Heat dissipation fins; 24. Mounting hole; 3. Riveting; 4. High-power semiconductor device; 5. Pin; 6. Pin connector; 7. Welding ring; 8. Plug sleeve; 9. Clamping mechanism; 10. Fixed ring; 11. Groove; 12. Receiving piece; 13. Receiving cavity; 14. Low-power semiconductor device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention will be further described below with reference to the embodiments shown in the drawings:

[0025] Embodiment 1

[0026] As Figures 1 to 7As shown in the figure, a combined structure of a semiconductor device and a circuit board includes a circuit board 1 on which a low-power semiconductor device 14 is installed and a heat sink 2 for installing a high-power semiconductor device 4. The circuit board 1 and the heat sink 2 are assembled and fixed by riveting 3. There are several through holes on the circuit board 1 for inserting the pins 5 of the high-power semiconductor device 4. There is a gap between the circuit board 1 and the heat sink 2. The heat sink 2 includes a bottom plate 21, side plates 22 and a heat dissipation mechanism. The heat dissipation mechanism includes several heat dissipation fins 23 perpendicular to the bottom plate 21. The thickness of the heat dissipation fins 23 gradually thins from the connection end of the heat dissipation fins 23 to the other end. There is a gap between the heat dissipation mechanism and the side plates 22. The high-power semiconductor device 4 is installed on the bottom plate 21 between the heat dissipation mechanism and the side plates 22. There are several mounting holes 24 on the bottom plate 21 for the pins 5 of the high-power components 4 to pass through between the heat dissipation mechanism and the side plates 22. The pins 5 of the high-power semiconductor device 4 pass through the bottom plate 21 and the through holes on the circuit board 1. A pin connector 6 is sleeved on the pins 5 of the high-power semiconductor device 4. The pin connector 6 includes a plugging sleeve 8 with a hollow tubular structure with one end closed. A welding ring 7 coaxially arranged with the plugging sleeve 8 is fixedly arranged at the non-closed end of the plugging sleeve 8. The welding ring 7 extends outward relative to the outer side surface of the plugging sleeve 8. A clamping mechanism 9 for clamping the pins 5 is fixedly arranged in the plugging sleeve 8. The welding ring 7 is welded on the circuit board 1. The clamping mechanism 9 includes a fixing ring 10 with a circular ring structure. The fixing ring 10 is sleeved in the plugging sleeve 8 and there is an interference fit between the fixing ring 10 and the plugging sleeve 8. On one side of the fixing ring 10 facing the closed end of the plugging sleeve 8, two receiving pieces 12 distributed around the center line of the fixing ring 10 are fixedly arranged. There is a gap between adjacent receiving pieces 12. The receiving pieces 12 are inclined gradually towards the center line of the fixing ring 10 from the end connected to the fixing ring 10 to the other end. The inner side surface of the receiving pieces 12 is in an arc-shaped structure and the area formed by all the receiving pieces 12 surrounding is a receiving cavity 13 for clamping the pins 5, and the receiving cavity 13 is in a frustum-shaped structure. At the end of the fixing ring 10 facing away from the receiving pieces 12, there are two slots 11 parallel to the center line of the fixing ring 10. The slots 11 penetrate through the inner and outer side surfaces of the fixing ring 10. The number of the slots 11 is equal to the number of the gaps between the receiving pieces 12, and the slots 11 and the gaps are alternately distributed in sequence.The pin 5 of the component is inserted into the receiving cavity 13 formed by the receiving piece 12. The pin 5 will generate an outward thrust on the receiving piece 12. Correspondingly, the end of the receiving piece 12 facing the fixing ring 10 will generate a squeezing force on the connection part of the fixing ring 10 with the receiving piece 12, forcing the fixing ring 10 to deform at the position between adjacent receiving pieces 12. If the deformation at this position is difficult to recover, it will directly affect the clamping performance of the receiving piece 12 on the pin 5. The slots 11 provided on the fixing ring 10 and the intervals between adjacent receiving pieces 12 are alternately distributed in sequence, leaving a deformation space for the fixing ring 10, which is equivalent to transferring the position on the fixing ring 10 that is prone to deformation, and the deformation at this position has less impact on the receiving piece 12, enabling the receiving piece 12 to effectively clamp the pin 5 of the component, thereby extending the service life of the receiving piece 12.

[0027] The installation method based on the above combined structure of the semiconductor device and the circuit board includes the following steps: ①. Insert the pin 5 of the low-power semiconductor device 14 into the through hole on the circuit board 1 and weld it to the circuit board 1; ②. Assemble the circuit board 1 with the inserted low-power semiconductor device 14 through the press riveting 3 and the heat sink 2; ③. Pass the pin 5 of the high-power semiconductor device 4 through the bottom plate 21 of the heat sink 2 and insert it into the through hole on the circuit board 1, and the surfaces of the high-power semiconductor device 4 and the bottom plate 21 of the heat sink 2 are fully attached; ④. On the side of the circuit board 1 away from the heat sink 2, trim all the pins 5 of the high-power semiconductor devices 4 neatly according to the length of the pin connector 6. The length of the protruding part of the trimmed pin 5 relative to the circuit board 1 is greater than the distance from the upper end of the welding ring 7 of the pin connector 6 to the receiving cavity 13 and less than the distance from the upper end of the welding ring of the pin connector 6 to the bottom of the inner cavity of the plug sleeve 8; ⑤. Sleeve the pin connector 6 on each pin 5; ⑥. Weld and connect the welding ring 7 on the pin connector 6 and the circuit board 1.

[0028] Embodiment 2

[0029] As Figures 1 to 7As shown in the figure, a combined structure of a semiconductor device and a circuit board includes a circuit board 1 on which a low-power semiconductor device 14 is installed and a heat sink 2 for installing a high-power semiconductor device 4. The circuit board 1 and the heat sink 2 are assembled and fixed by press riveting 3. There are several through holes on the circuit board 1 for inserting the pins 5 of the high-power semiconductor device 4. There is a gap between the circuit board 1 and the heat sink 2. The heat sink 2 includes a bottom plate 21, side plates 22 and a heat dissipation mechanism. The heat dissipation mechanism includes several heat dissipation fins 23 perpendicular to the bottom plate 21. The thickness of the heat dissipation fins 23 gradually becomes thinner from the connection end of the heat dissipation fins 23 to the other end. There is a space between the heat dissipation mechanism and the side plates 22. The high-power semiconductor device 4 is installed on the bottom plate 21 between the heat dissipation mechanism and the side plates 22. There are several mounting holes 24 on the bottom plate 21 for the pins 5 of the high-power components 4 to pass through between the heat dissipation mechanism and the side plates 22. The pins 5 of the high-power semiconductor device 4 pass through the bottom plate 21 and the through holes on the circuit board 1. A pin connector 6 is sleeved on the pins 5 of the high-power semiconductor device 4. The pin connector 6 includes a plugging sleeve 8 with a hollow tubular structure with one end closed. A welding ring 7 coaxially arranged with the plugging sleeve 8 is fixedly arranged at the non-closed end of the plugging sleeve 8. The welding ring 7 extends outward relative to the outer side surface of the plugging sleeve 8. A clamping mechanism 9 for clamping the pins 5 is fixedly arranged in the plugging sleeve 8. The welding ring 7 is welded on the circuit board 1. The clamping mechanism 9 includes a fixing ring 10 with an annular structure. The fixing ring 10 is sleeved in the plugging sleeve 8 and there is an interference fit between the fixing ring 10 and the plugging sleeve 8. On one side of the fixing ring 10 facing the closed end of the plugging sleeve 8, two receiving pieces 12 distributed around the center line of the fixing ring 10 are fixedly arranged. There is a space between adjacent receiving pieces 12. The receiving pieces 12 are inclined gradually towards the center line of the fixing ring 10 from the end connected to the fixing ring 10 to the other end. The inner side surface of the receiving piece 12 is an arc-shaped structure and the area formed by all the receiving pieces 12 surrounding is a receiving cavity 13 for clamping the pins 5. And the receiving cavity 13 is a frustum-shaped structure. At the end of the fixing ring 10 facing away from the receiving pieces 12, there are two slots 11 parallel to the center line of the fixing ring 10. The slots 11 penetrate the inner and outer side surfaces of the fixing ring 10. The number of the slots 11 is equal to the number of the spaces between the receiving pieces 12, and the slots 11 and the spaces are alternately distributed in sequence.The pin 5 of the component is inserted into the receiving cavity 13 formed by the receiving piece 12. The pin 5 will generate an outward thrust on the receiving piece 12. Correspondingly, the end of the receiving piece 12 facing the fixing ring 10 will generate a squeezing force on the connection part of the fixing ring 10 and the receiving piece 12, forcing the fixing ring 10 to deform at the position between adjacent receiving pieces 12. If the deformation at this position is difficult to recover, it will directly affect the clamping performance of the receiving piece 12 on the pin 5. The slotted openings 11 provided on the fixing ring 10 and the intervals between adjacent receiving pieces 12 are alternately distributed in sequence, leaving a deformation space for the fixing ring 10, which is equivalent to transferring the position on the fixing ring 10 that is prone to deformation, and the deformation at this position has less impact on the receiving piece 12, enabling the receiving piece 12 to effectively clamp the pin 5 of the component, thereby extending the service life of the receiving piece 12.

[0030] The installation method based on the combined structure of the above semiconductor device and circuit board includes the following steps: ①. Insert the pin 5 of the low-power semiconductor device 14 into the through hole on the circuit board 1 and weld it to the circuit board 1; ②. Weld the welding ring 7 of the pin connector 6 to the position on the circuit board 1 where the pin 5 of the high-power semiconductor device 4 needs to be inserted; ③. Assemble the circuit board 1 through riveting 3 and the heat sink 2; ④. After trimming the length of the pin 5 of the high-power semiconductor device 4, pass it through the bottom plate 2 of the heat sink 2 and the through hole on the circuit board 1 and then insert it into the pin connector 6, and the surfaces of the high-power semiconductor device 4 and the bottom plate 21 of the heat sink 2 are fully attached. The length of the protruding part of the trimmed pin 5 relative to the circuit board 1 is greater than the distance from the upper end of the welding ring 7 of the pin connector 6 to the receiving cavity 13 and less than the distance from the upper end of the welding ring of the pin connector 6 to the bottom of the inner cavity of the plug sleeve 8.

[0031] The specific embodiments described in the text are only examples to illustrate the spirit of the present invention. Those skilled in the technical field to which the present invention belongs can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for installing a semiconductor device and a circuit board, characterized in that, Including the following steps: ①. Insert the pins (5) of the low-power semiconductor device (14) into the through-holes on the circuit board (1) and weld them to the circuit board (1); ②. Assemble the circuit board (1) with the inserted low-power semiconductor device (14) and the heat sink (2) by press riveting (3); ③. Insert the pins (5) of the high-power semiconductor device (4) through the bottom plate (21) of the heat sink (2) and into the through-holes on the circuit board (1); ④. Trim neatly all the pins (5) of the high-power semiconductor devices (4) on the side of the circuit board (1) away from the heat sink (2) according to the length of the pin connectors (6); ⑤. Sleeve the pin connectors (6) on each pin (5) of the high-power semiconductor device; ⑥. Weld and connect the welding rings (7) on the pin connectors (6) to the circuit board (1); The installed semiconductor device and circuit board include the circuit board (1) with the installed low-power semiconductor device (14) and the heat sink (2) for installing the high-power semiconductor device (4). The heat sink (2) is installed on the circuit board (1). There are several through-holes on the circuit board (1) for inserting the pins (5) of the high-power semiconductor device (4). There is a gap between the circuit board (1) and the heat sink (2); The heat sink (2) includes a bottom plate (21), side plates (22) and a heat dissipation mechanism. There is a space between the heat dissipation mechanism and the side plates (22); The high-power semiconductor device (4) is installed on the bottom plate (21) between the heat dissipation mechanism and the side plates (22). The pins (5) of the high-power semiconductor device (4) pass through the bottom plate (21) and through the through-holes on the circuit board (1). The pins (5) of the high-power semiconductor device (4) are sleeved with pin connectors (6). The pin connectors (6) include a plugging sleeve (8) with a hollow tubular structure with one end closed. A welding ring (7) coaxial with the plugging sleeve (8) is fixedly arranged at the non-closed end of the plugging sleeve (8). The welding ring (7) extends outward relative to the outer side surface of the plugging sleeve (8); A clamping mechanism (9) for clamping the pins (5) is fixedly arranged in the plugging sleeve (8). The welding ring (7) is welded to the circuit board (1); The clamping mechanism (9) includes a fixing ring (10) with an annular structure. At least two receiving pieces (12) distributed around the center line of the fixing ring (10) are fixedly arranged on one side of the fixing ring (10) facing the closed end of the plugging sleeve (8). There is a space between adjacent receiving pieces (12). The receiving pieces (12) are gradually inclined towards the center line of the fixing ring (10) from the end connected to the fixing ring (10) to the other end. The inner side surface of the receiving piece (12) is an arc-shaped structure and the area formed by all the receiving pieces (12) surrounding is a receiving cavity (13) for clamping the pins (5) of the semiconductor device, and the receiving cavity (13) is a frustum-shaped structure.

2. The installation method of a semiconductor device and a circuit board according to claim 1, characterized in that The surface of the high-power semiconductor device (4) and the bottom plate (21) of the heat sink (2) are fully attached.

3. A method for installing a semiconductor device and a circuit board according to claim 1, characterized in that, The length of the protruding part of the trimmed pin (5) relative to the circuit board (1) is greater than the distance from the upper end of the welding ring (7) of the pin connector (6) to the receiving cavity (13), and less than the distance from the upper end of the welding ring of the pin connector (6) to the bottom of the inner cavity of the plug sleeve (8).

4. A method for installing a semiconductor device and a circuit board according to claim 1, characterized in that, The heat dissipation mechanism includes a plurality of heat dissipation fins (23) perpendicular to the bottom plate (21), and the thickness of the heat dissipation fins (23) gradually decreases from the connection end of the heat dissipation fins (23) to the bottom plate (21) to the other end.

5. A method for installing a semiconductor device and a circuit board according to claim 1, characterized in that, A plurality of mounting holes (24) for the pins (5) of the high-power semiconductor device (4) to pass through are provided on the bottom plate (21) between the heat dissipation mechanism and the side plate (22).

6. A method for installing a semiconductor device and a circuit board according to claim 1, characterized in that, At least two slots (11) parallel to the center line of the fixing ring (10) are provided at the end of the fixing ring (10) facing away from the receiving piece (12). The slots (11) penetrate the inner and outer sides of the fixing ring (10). The number of the slots (11) is equal to the number of intervals between the receiving pieces (12), and the slots (11) and the intervals are alternately distributed in sequence.

7. A mounting method for a semiconductor device and a circuit board according to claim 1, characterized in that, The inner cavity of the plug sleeve (8) is of a cylindrical structure. The fixing ring (10) is sleeved in the plug sleeve (8), and an interference fit is provided between the fixing ring (10) and the plug sleeve (8).

Images