Wafer test seat

Abstract

The utility model provides a wafer test seat, which is mainly used for solving the problems that the existing small probe station or ATE (automatic test equipment) has certain limitation on the size of a wafer and does not support the test of a 12-inch wafer, and a probe head is relatively small and cannot support the test of large current, so that the conduction impedance obtained by the test is inaccurate, and the test efficiency is low. And the technical problem of energy loss of the MOS tube in the actual working process is solved. The device comprises an upper cover and a base. The first probe is installed in the upper cover, and the second probe and the wafer are installed in the base. After the upper cover and the base are buckled, the first probe is in contact with the drain electrode of the wafer, and the second probe is in contact with the grid electrode and the source electrode of the wafer. According to the utility model, the positioning assembly is arranged in the base and is used for positioning wafers with different sizes, part of 12-inch wafers can be sampled, external test equipment can be directly connected for detection, and the use is convenient. The technical problem that existing testing equipment does not support testing of a 12-inch wafer is solved.

Description

Technical Field

[0001] The utility model relates to a MOSFET wafer, in particular to a wafer test seat. Background Art

[0002] MOSFET (power MOSFET) wafers are the fundamental material for MOSFET manufacturing. Currently, wafer-level bare die testing in the industry typically utilizes small probe stations or large automatic test equipment (ATE). Small probe stations typically cost hundreds of thousands of yuan, while large ATE equipment can reach millions. The high cost is a burden for most companies. Small probe stations and ATE equipment have certain limitations on wafer size, and most testing vendors currently do not support testing of 12-inch wafers.

[0003] Small probe stations and ATE test equipment have limitations when testing wafer parameters. For example, when testing the RDSON (on-resistance) parameter, the commonly used test method is to apply a gate-source voltage of 10V or 20V to the power MOS tube; then set the drain current to 10A and 20A, respectively, and measure the on-resistance RDSON of the power MOS tube. However, due to the small size of existing probe heads, they cannot support high current testing and can only use currents of around 1A / 2A for test simulation. The test data obtained from this is of poor reference value. If the on-resistance test is inaccurate, it will cause unnecessary energy loss in the MOS tube during actual operation, which in turn causes overheating. Excessive temperatures may burn the MOS tube and affect its normal operation. Utility Model Content

[0004] The purpose of the utility model is to solve the technical problems that the existing small probe station or ATE test equipment has certain limitations on wafer size and cannot support the test of 12-inch wafers. In addition, the probe head is small and cannot support high current testing, resulting in inaccurate on-resistance obtained from the test and energy loss of MOS tubes during actual operation. A wafer test socket is proposed.

[0005] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0006] A wafer test seat, which is special in that it comprises an upper cover and a base connected in an open-close manner;

[0007] The upper cover includes an upper positioning frame and a first probe assembly; the upper positioning frame is hollow; the first probe assembly is installed in the upper positioning frame; the first probe assembly is used to contact the drain of the wafer when the upper cover is closed;

[0008] The base includes a lower positioning frame, a wafer card slot plate, a positioning assembly, a second probe assembly and a test circuit board;

[0009] One side of the lower positioning frame is hinged to the upper positioning frame; the lower positioning frame is fixedly connected to the test circuit board, the test circuit board is electrically connected to the first probe assembly and also electrically connected to the external terminal test equipment;

[0010] The wafer card slot plate is installed in the lower positioning frame, and is provided with a first groove, a second groove and a third groove on the wafer card slot plate; the first groove is used to mount the wafer; the second groove is located at a top corner of the first groove and is connected to the first groove; the third groove is vertically provided in the middle of the second groove and is connected to the second groove;

[0011] The positioning assembly includes an elastic positioning platform and a limiting buckle; the elastic positioning platform is installed in the second groove; the elastic positioning platform is a stepped structure, including at least two steps, wherein the lowermost step is provided with a multi-layered card slot for respectively clamping a vertex corner of wafers of different sizes; the limiting buckle is installed in the third groove and fixedly connected to the corresponding step for limiting the position of the elastic positioning platform;

[0012] The second probe assembly is installed in the lower positioning frame and connected to the bottom of the wafer card slot plate through a spring screw. One end of the second probe assembly is used to contact the gate and source at the bottom of the wafer, and the other end is fixed to the test circuit board.

[0013] Furthermore, the multi-layer card slot includes a first card slot, a second card slot and a third card slot arranged in layers from top to bottom. The first card slot, the second card slot and the third card slot are all right-angle card slots, and a circular chamfer or a circular open groove is provided at the right angle for clamping a top corner of the wafer.

[0014] Furthermore, a right-angle clamping plate is provided at a top corner of the bottom of the first groove, and the top corner where the right-angle clamping plate is located is diagonally opposite to the top corner where the second groove is located; the upper surface of the right-angle clamping plate is at the same height as the upper surface of the third clamping slot, and a circular chamfer or a circular open groove is provided at the right angle of the inner edge of the right-angle clamping plate, which is used to clamp the two diagonal corners of the same wafer with the third clamping slot.

[0015] Furthermore, the inner wall surface of the first groove includes a conical portion and a straight portion, and the right-angle clamping plate is close to the bottom of the straight portion; the large end of the conical portion faces upward, and the small end is connected to the straight portion; the conical portion is used to cooperate with the first clamping slot to horizontally clamp wafers of the same height; the height of the straight portion is less than the height of the first clamping slot, and is used to cooperate with the second clamping slot to horizontally clamp wafers of the same height.

[0016] Furthermore, the elastic positioning platform includes a first step, a second step and a third step that are lowered in sequence; the first step is higher than the upper surface of the wafer card slot plate, the second step is fixedly connected to the limit buckle, the first card slot is located at the connection between the second step and the third step, and the second card slot and the third card slot are arranged on the third step.

[0017] Furthermore, the first probe assembly includes a first probe seat, a first probe, a bump and an insulating sheet;

[0018] The first probe seat is installed in the upper positioning frame;

[0019] The protrusion is adapted to the straight portion of the first groove and is located on the first probe seat. The insulating sheet is bonded to the outer surface of the protrusion. First through holes are correspondingly provided on the protrusion and the insulating sheet. The first probe is provided on the first probe seat and the head end passes through the first through hole.

[0020] The end of the first probe is electrically connected to the test circuit board of the base through a lead, and the head end of the first probe contacts the drain of the wafer when the upper cover is closed.

[0021] Furthermore, a second through hole is provided at the bottom of the first groove;

[0022] The second probe assembly includes a positioning seat, a second probe and a second probe seat;

[0023] The positioning seat is fixed to the test circuit board by screws, and a lower groove corresponding to the first groove is provided on the positioning seat for mounting the second probe seat;

[0024] The second probe is installed in the second probe seat, one end of which is electrically connected to the test circuit board, and the other end passes through the second through hole of the first groove to contact the gate and source at the bottom of the wafer.

[0025] Furthermore, it also includes a tightening structure, which includes a knob, a thick ring screw, a disc roller and a linking piece located inside the upper positioning frame;

[0026] A semicircular groove is provided in one end surface of the knob, and a threaded hole is provided in the upper positioning frame; the thick ring screw is installed in the threaded hole, one end of the screw is partially installed in the semicircular groove, and the other end is connected to the disc roller;

[0027] The four top corners of the linking piece are connected to the upper positioning frame by four elastic screws respectively; a circular groove is provided on one side of the linking piece, and the circular piece roller can be rotatably installed in the circular groove;

[0028] The first probe seat is fixedly connected to the other side surface of the linking piece by screws.

[0029] Furthermore, the base also includes an insulating base, and the test circuit board is mounted on the insulating base.

[0030] Furthermore, the lower end of the upper positioning frame is provided with two protruding cylindrical pin seats, and the two cylindrical pin seats are respectively provided with first cylindrical pin holes;

[0031] Two raised secondary cylindrical pin seats are provided at one side edge of the upper end of the lower positioning frame, and the two secondary cylindrical pin seats are respectively attached to the outer sides of the two cylindrical pin seats, and are respectively provided with second cylindrical pin holes corresponding to the first cylindrical pin holes;

[0032] A cylindrical pin is inserted into the first cylindrical pin hole and the corresponding second cylindrical pin hole to realize the opening and closing connection between the upper cover and the base.

[0033] Beneficial effects of the utility model:

[0034] 1. The utility model includes an upper cover and a base. The first probe is installed in the upper cover, and the second probe and the wafer are both installed in the base. After the upper cover and the base are buckled together, the first probe contacts the drain of the wafer, and the second probe contacts the gate and source of the wafer. In the utility model, a positioning component is provided in the base for positioning wafers of different sizes. Some 12-inch wafers can be sampled and directly connected to external test equipment for testing, which is easy to use. It solves the technical problem that existing test equipment does not support the test of 12-inch wafers.

[0035] 2. The test socket of this utility model has a simple structure and can be used to test the test circuit board and the general Final Test test equipment, which solves the problem that high current test items cannot be tested and greatly improves the test efficiency.

[0036] 3. The utility model has a tightening component installed on the upper cover, and the first probe on the upper cover can be tightly fitted with the wafer installed on the base by rotating the knob, which solves the problem of inaccurate test results caused by the frequent opening and closing of the existing conventional test seat, which leads to reduced tightness between the upper cover and the base. In addition, for wafers of different sizes, the knob can be appropriately adjusted so that the wafers installed in the first slot, the second slot and the third slot respectively can fit with the first probe and the second probe, thereby improving the reliability of the test.

[0037] 4. The test socket of the present invention can significantly reduce costs and reduce the test cost of wafers by dozens of times. After purchasing the wafers, there is no need to spend time and additional testing fees to test the wafers. Compared with packaging the wafers as finished products and then testing to confirm whether there are any abnormalities, the present invention saves a lot of time and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1This is a schematic diagram of the structure decomposition of a wafer test seat embodiment of the present invention;

[0039] Figure 2 This is a structural diagram of a wafer test seat embodiment of the utility model, in which the upper cover of the test seat embodiment is open;

[0040] Figure 3 for Figure 2 Rear view of;

[0041] Figure 4 for Figure 1 A partial enlarged view of

[0042] Figure 5 This is a schematic structural diagram of a wafer card slot plate in a wafer test seat embodiment of the utility model;

[0043] Figure 6 This is a structural schematic diagram of the elastic positioning platform in a wafer test seat embodiment of the utility model.

[0044] Description of reference numerals:

[0045] 1-knob; 2-thick ring screw; 3-upper positioning frame; 4-wafer roller; 5-connecting plate; 6-first probe seat; 7-lower positioning frame; 8-elastic positioning platform; 9-wafer card slot plate, 91-first groove, 92-second groove, 93-third groove, 94-right-angle card plate; 10-second probe seat; 11-positioning seat; 12-test circuit board; 13-insulating base. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] The utility model discloses a wafer test seat, such as Figure 1 、 Figure 2 As shown, it includes an upper cover, a base and a tightening structure. The tightening structure is installed on the upper cover, and the upper cover and the base are connected in an open-close manner. The tightening structure is used to tightly fit the upper cover and the base when they are buckled together.

[0048] The upper cover includes an upper positioning frame 3 and a first probe assembly; the upper positioning frame 3 is a square structure and is hollow inside. Two raised cylindrical pin seats are provided at the lower end of the upper positioning frame 3, and the two cylindrical pin seats are respectively provided with first cylindrical pin holes. The first probe assembly includes a first probe seat 6, a first probe, a bump and an insulating sheet. The first probe seat 6 is installed inside the upper positioning frame 3. The bump is a cube and is located at the center of the outer side of the first probe seat 6. The insulating sheet is adhered to the outer surface of the bump. First through holes are correspondingly provided on the bump and the insulating sheet, and the first probe passes through the first through hole. The first probe seat 6 is a drain probe seat; the end of the first probe is electrically connected to the test circuit board 12 of the base through a lead, and the head end of the first probe contacts the drain of the wafer when the upper cover is closed.

[0049] like Figure 1 、 Figure 3 As shown, the tightening structure includes a knob 1, a coarse ring screw 2, a disc roller 4 and a linking piece 5. The coarse ring screw 2, the disc roller 4 and the linking piece 5 are all arranged inside the upper positioning frame 3. A semicircular groove is provided in one end face of the knob 1, and a threaded hole is provided in the upper positioning frame 3. The coarse ring screw 2 is installed in the threaded hole, one end portion of which is installed in the semicircular groove, and the other end is connected to the disc roller 4. The four top corners of the linking piece 5 are respectively connected to the upper positioning frame 3 by four elastic screws. A circular groove is provided on one side surface of the linking piece 5, and the disc roller 4 is installed in the circular groove. By rotating the knob, the coarse ring screw 2 rotates along the threaded hole, driving the disc roller 4 to rotate around the axis, and the disc roller 4 drives the linking piece 5 to perform linear motion along the axial direction. The inner side surface of the first probe seat 6 is fixedly connected to the other side surface of the linking piece 5 by screws.

[0050] like Figure 4 As shown, the base includes a lower positioning frame 7 , a wafer card slot plate 9 , a positioning assembly, a second probe assembly, a test circuit board 12 and an insulating base 13 .

[0051] The lower positioning frame 7 is screwed to the test circuit board 12, which is also screwed to the insulating base 13. Six pins extend the wires, allowing connection to external final test equipment (terminal test box) for parameter testing. The wafer holder plate 9 and the second probe assembly are both mounted within the lower positioning frame 7, with the second probe assembly securely connected to the test circuit board 12. The positioning assembly, mounted within the wafer holder plate 9, is used to position wafers of different sizes.

[0052] The lower positioning frame 7 is a square structure with a hollow interior. Two raised secondary cylindrical pin holders are located on one side of the upper edge of the lower positioning frame 7. These secondary cylindrical pin holders fit over the outer sides of the two cylindrical pin holders, each with a corresponding secondary cylindrical pin hole. A cylindrical pin, passing through the secondary cylindrical pin holes and the primary cylindrical pin holes of the two cylindrical pin holders, creates an open-close connection between the upper cover and the base.

[0053] The wafer card slot plate 9 is located in the lower positioning frame 7 and is connected to the positioning seat 11 in the second probe assembly through a spring screw to form a floating device, that is, the wafer card slot plate 9 can float up and down in the vertical direction. Figure 5 As shown, the wafer retaining plate 9 is provided with a first groove 91, a second groove 92, and a third groove 93. The first groove 91 is adapted to fit the protrusion, and a second through-hole is provided at the bottom of the first groove 91. The first groove 91 comprises a tapered portion and a straight portion, with the larger end of the tapered portion facing upward and the smaller end connected to the straight portion. A right-angled retaining plate 94 is provided at one corner of the straight portion to retain one corner of the wafer. A circular opening is provided at the inner right angle of the right-angled retaining plate 94. The positioning assembly includes an elastic positioning platform 8 and a limit buckle. The second groove 92 is located at a diagonal angle of the right-angled retaining plate 94 and communicates with the first groove 91. It is used to mount the elastic positioning platform 8 in the positioning assembly. The third groove 93 is provided perpendicularly to the middle of the second groove 92 and communicates with the second groove 92. It is used to mount the limit buckle in the positioning assembly. The wafer is square, and the elastic positioning platform 8 is used to retain the other corner of the wafer. One corner of the wafer is diagonally opposite another.

[0054] The elastic positioning platform 8 is a stepped structure. In this embodiment, the elastic positioning platform 8 is provided with three layers, including a first step, a second step and a third step that are successively lowered. The first step is slightly higher than the upper surface of the wafer slot plate 9, which is convenient for adjusting the position of the elastic positioning platform 8. After the limit buckle is clamped around the second step, it is installed in the third groove 93 to fix the elastic positioning platform 8. The third step is provided with multiple layers of slots for clamping the other vertex of wafers of different heights. Figure 6As shown, the multi-layer card slot includes a first card slot, a second card slot and a third card slot which are arranged in layers from top to bottom. The first card slot, the second card slot and the third card slot are all right-angled card slots, and circular chamfers or circular open slots are provided at the right angles. The upper surface of the third card slot is at the same height as the upper surface of the right-angle clamping plate 94. The first card slot is provided at the connection between the second step and the third step, and the height of the first card slot is greater than the height of the straight portion. The conical portion is used to cooperate with the first card slot to horizontally clamp wafers of the same height; the straight portion is used to cooperate with the second card slot to horizontally clamp wafers of the same height. By adjusting the position of the elastic positioning platform 8 in the second groove 92, the length of the third step extending into the first groove 91 can be changed. The first card slot, the second card slot and the third card slot can position wafers of different sizes, thereby achieving elastic positioning, and effectively reducing the risk of damage to the wafer during the test process.

[0055] The second probe assembly includes a positioning base 11, a second probe, and a second probe base 10. The positioning base 11 is fixed to the test circuit board 12 via screws. A lower groove corresponding to the first groove 91 is provided at the center of the positioning base 11 for mounting the second probe base 10. The second probe is mounted in the second probe base 10, with one end electrically connected to the test circuit board 12 below and the other end extending through the second through-hole in the first groove 91 to contact the gate and source electrodes at the bottom of the wafer. The second probe serves as a gate and source probe.

[0056] Working process: Place the wafer in the first groove 91 of the wafer card slot plate 9, adjust the position of the elastic positioning platform 8 according to the size of the wafer, and for small-sized wafers, fix it by clamping it at its two diagonal corners through the third card slot and the right-angle card plate 94. For large-sized wafers, fix it by clamping it at its two diagonal corners through the second card slot and the straight part. For larger-sized wafers, fix it by clamping it at its two diagonal corners through the first card slot and the conical part. Snap the upper cover shut and tighten the knob 1 so that the head end of the first probe contacts the drain of the wafer. At the same time, the first probe seat 6 presses the wafer card slot plate 9 downward so that the second probe contacts the gate and source of the wafer.

[0057] Based on the Kelvin test principle, the test circuit board 12 uses a four-wire connection, i.e., two wires are used to measure the voltage across the resistor and the other two wires are used to provide current, thereby eliminating the influence of wiring resistance and contact resistance, improving the accuracy of the measurement, and making the test value of the utility model more accurate and reliable. This solves the problem that the probes of existing probe stations cannot withstand high currents and cannot be tested in high-current projects.

[0058] The test circuit board 12 is directly connected to the MOSFET Final Test test equipment to directly test the various performance parameters of the MOSFET. For example: DC parameters, Eas single pulse avalanche energy, RthJC RthJA thermal resistance test, RG gate resistance test, etc. As shown in Table 1, the measured data of DC parameters include CONT connection status, BVDSS reverse breakdown voltage, VTH threshold voltage, IDSS drain-source leakage current, IGS SF Gate-source forward leakage current, IGS SR The gate-source reverse leakage current, RDSON on-resistance, and VGSth gate threshold voltage are designed to have a maximum RDSON on-resistance of no more than 32mΩ. As can be seen from Table 1, the wafer test socket of the present invention is used to perform a large current (ID=20A) test on the on-resistance of the MOSFET. The RDSON on-resistance of the bare die wafers of ten sets of test data are all lower than the target value, indicating accurate test results.

[0059] Table 1 Measured data of DC parameters

[0060]

Claims

1. A wafer test seat, characterized in that: It includes an upper cover and a base with an opening and closing connection; The upper cover comprises an upper positioning frame (3) and a first probe assembly; the upper positioning frame (3) is hollow inside; the first probe assembly is installed in the upper positioning frame (3); the first probe assembly is used to contact the drain of the wafer when the upper cover is closed; The base comprises a lower positioning frame (7), a wafer card slot plate (9), a positioning assembly, a second probe assembly and a test circuit board (12); One side of the lower positioning frame (7) is hinged to the upper positioning frame (3); the lower positioning frame (7) is fixedly connected to a test circuit board (12); the test circuit board (12) is electrically connected to the first probe assembly and is also electrically connected to an external terminal test device; The wafer card slot plate (9) is installed in the lower positioning frame (7), and the wafer card slot plate (9) is provided with a first groove (91), a second groove (92) and a third groove (93); the first groove (91) is used to install the wafer; the second groove (92) is located at a top corner of the first groove (91) and is connected to the first groove (91); the third groove (93) is vertically arranged on the second groove (92) and is connected to the second groove (92); The positioning assembly includes an elastic positioning platform (8) and a limiting buckle; the elastic positioning platform (8) is installed in the second groove (92); the elastic positioning platform (8) is a stepped structure, including at least two steps, wherein the lowermost step is provided with a multi-layer card slot for respectively clamping a top corner of wafers of different sizes; the limiting buckle is installed in the third groove (93) and is fixedly connected to the corresponding step, and is used to limit the elastic positioning platform (8); The second probe assembly is installed in the lower positioning frame (7) and connected to the bottom of the wafer card slot plate (9) through a spring screw. One end of the second probe assembly is used to contact the gate and source at the bottom of the wafer, and the other end is fixed to the test circuit board (12).

2. The wafer test socket according to claim 1, characterized in that: The multi-layer card slot includes a first card slot, a second card slot and a third card slot which are arranged in layers from top to bottom. The first card slot, the second card slot and the third card slot are all right-angled card slots, and a circular chamfer or a circular opening groove is provided at the right angle for clamping a top corner of the wafer.

3. The wafer test socket according to claim 2, wherein: A right-angled clamping plate (94) is provided at a top corner of the bottom of the first groove (91), and the top corner where the right-angled clamping plate (94) is located is diagonally opposite to the top corner where the second groove (92) is located; the upper surface of the right-angled clamping plate (94) is at the same height as the upper surface of the third clamping groove, and a circular chamfer or a circular opening groove is provided at the right angle of the inner edge of the right-angled clamping plate (94), which is used to clamp the two diagonal corners of the same wafer with the third clamping groove.

4. The wafer test socket according to claim 3, characterized in that: The inner wall surface of the first groove (91) includes a conical portion and a straight portion, and the right-angle clamping plate (94) is close to the bottom of the straight portion; the large end of the conical portion faces upward, and the small end is connected to the straight portion; the conical portion is used to cooperate with the first clamping slot to horizontally clamp wafers of the same height; the height of the straight portion is less than the height of the first clamping slot, and is used to cooperate with the second clamping slot to horizontally clamp wafers of the same height.

5. The wafer test socket according to claim 4, characterized in that: The elastic positioning platform (8) comprises a first step, a second step and a third step which are lowered in sequence; the first step is higher than the upper surface of the wafer slot plate (9), the second step is fixedly connected to the limit buckle, the first slot is located at the connection between the second step and the third step, and the second slot and the third slot are arranged on the third step.

6. The wafer test socket according to claim 5, characterized in that: The first probe assembly comprises a first probe seat (6), a first probe, a bump and an insulating sheet; The first probe seat (6) is installed in the upper positioning frame (3); The convex block is adapted to the straight portion of the first groove (91) and is located on the first probe seat (6), and the insulating sheet is bonded to the outer surface of the convex block; first through holes are correspondingly provided on the convex block and the insulating sheet; the first probe is provided on the first probe seat (6) and the head end passes through the first through hole; The end of the first probe is electrically connected to a test circuit board (12) of the base through a lead, and the head end of the first probe contacts the drain of the wafer when the upper cover is closed.

7. The wafer test socket according to claim 6, characterized in that: A second through hole is provided at the bottom of the first groove (91); The second probe assembly comprises a positioning seat (11), a second probe and a second probe seat (10); The positioning seat (11) is fixed to the test circuit board (12) by screws, and a lower groove corresponding to the first groove (91) is provided on the positioning seat (11) for installing the second probe seat (10); The second probe is installed in the second probe seat (10), one end of which is electrically connected to the test circuit board (12), and the other end passes through the second through hole of the first groove (91) for contacting the gate and source at the bottom of the wafer.

8. The wafer test socket according to claim 7, characterized in that: It also includes a tightening structure, which includes a knob (1), a thick ring screw (2), a disc roller (4) and a linking piece (5) located inside the upper positioning frame (3); A semicircular groove is provided in one end surface of the knob (1), and a threaded hole is provided in the upper positioning frame (3); the coarse ring screw (2) is installed in the threaded hole, one end of the coarse ring screw is installed in the semicircular groove, and the other end is connected to the disc roller (4); The four top corners of the linking piece (5) are connected to the upper positioning frame (3) via four elastic screws respectively; a circular groove is provided on one side surface of the linking piece (5), and the circular piece roller (4) is rotatably mounted in the circular groove; The first probe seat (6) is fixedly connected to the other side of the linking piece (5) by means of screws.

9. The wafer test socket according to claim 1, characterized in that: The base further comprises an insulating base (13), and the test circuit board (12) is mounted on the insulating base (13).

10. The wafer test socket according to claim 1, characterized in that: The lower end of the upper positioning frame (3) is provided with two protruding cylindrical pin seats, and the two cylindrical pin seats are respectively provided with first cylindrical pin holes; Two raised secondary cylindrical pin seats are provided at one side edge of the upper end of the lower positioning frame (7), and the two secondary cylindrical pin seats are respectively attached to the outer sides of the two cylindrical pin seats, and are respectively provided with second cylindrical pin holes corresponding to the first cylindrical pin holes; A cylindrical pin is inserted into the first cylindrical pin hole and the corresponding second cylindrical pin hole to realize the opening and closing connection between the upper cover and the base.

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