Radio frequency chip high-frequency performance test technology and clamp thereof

Abstract

The invention provides a radio frequency chip high-frequency performance test process and a clamp. The radio frequency chip high-frequency performance test process comprises the following steps: S1, welding a crimping shaft sleeve to one end of a radio frequency cable; by adopting the scheme of combining the coaxial cable and the PCB, the PCB part can be used for digital signal transmission and product power supply, and the coaxial cable is used for radio frequency signal transmission, so that the microwave interference caused by the use of a PCB microstrip line and the signal influence caused by 90-degree switching between the conductive part and a PCB plane microstrip can be reduced, the high-frequency test requirement of a radio frequency chip is met, and the test efficiency is improved. Through the crimping mode, the problems of long welding time, high operation requirements, unmaintainability and the like in the welding process are solved, the situation that after a radio frequency cable is heated for a long time, the high-frequency test index of the clamp is affected is avoided, the independently designed elastic conductive film serves as a transmission elastic carrier of the clamp, the influence of the conductive film on the radio frequency index is reduced to the minimum, and the reliability of the clamp is improved. The fixture is suitable for double-sided chip layout, and the top of the fixture is also provided with a test assembly, so that double-sided radio frequency chip test can be realized.

Description

Technical Field

[0001] The present invention relates to a testing process and a fixture thereof, in particular to a testing process and a fixture thereof for high frequency performance of a radio frequency chip, and belongs to the technical field of high frequency performance testing of a radio frequency chip. Background Art

[0002] Aerospace equipment has strict requirements on volume and weight. With the development of highly integrated technology, RF highly integrated circuits are widely used due to their small size and light weight. The original modular RF transceiver components or multi-channel amplifiers, phase shifters and other RF devices are packaged into BGA, SIP and QFN chips through semiconductor technology. It has very obvious advantages in terms of volume and cost of use, greatly reducing the volume and weight of the whole equipment, while reducing the power consumption of the whole equipment, and the reliability is higher. It can simplify the assembly steps and is the current mainstream of RF components. There are two main forms of existence: Form 1: standard array package, which looks basically the same as the common BGA / SIP chips on the market, but the array ball points contain RF signal transmission points.

[0003] Form 2 is the custom silicon-based BGA / SIP packaging form. Designers define the signal connection points based on the product's functions or end-customer needs. This type of packaging has no regularity in terms of ball spacing and ball size, and the frequency is very high. Common chips can reach 40GHz.

[0004] At present, the conventional test process uses a probe fixture for testing. The common probe fixture is made of ordinary spring needles. Since ordinary test fixtures can be used as long as the model is turned on, they cannot take into account the important indicators in RF (high frequency, 50Ω impedance, transmission standing wave), resulting in very poor RF performance. Only electrical performance evaluation can be performed. In order to solve this problem, a signal transmission PCB combined with an RF cable can be used for power supply, data transmission and RF signal transmission. However, the existing test process has the following problems when testing RF chips: 1. The RF cable needs to be welded to the gold-plated base of the test fixture. Since the RF chip components are generally large in size, the gold-plated base of the fixture that matches it is also large in size and dissipates heat quickly. It cannot be welded with a soldering iron. It is necessary to use a heating platform to preheat the gold-plated base before using a soldering iron for welding. This method requires a long heating time and has high operating requirements. It is not maintainable. Once the indicators are abnormal, the core part of the fixture will be scrapped. The RF component structure is divided into a central conductor, a dielectric layer, and an outer shielding layer. The dielectric layer plays a key factor in ensuring the RF indicators. Long-term heating will cause the dielectric constant of the dielectric layer to change, thereby affecting the high-frequency test indicators of the fixture; 2. Since the contacts at the bottom of the RF chip are not elastic, a transmission elastic carrier is required in the middle. However, the RF chip is laid out according to the RF characteristics, and its spacing and test point size are very random. There is no standard conductive film that can adapt to it. Although the conductive cloth on the market can adapt, the RF performance is poor and the product is often short-circuited and burned; 3. Since the RF test fixture is a high-precision test fixture, according to the characteristics of RF products, voltage has a great influence on RF indicators. After transmission through the control cable, a voltage drop will occur. When the power supply is unloaded, the voltage drop is not obvious and difficult to test. When the product is placed, a voltage drop occurs, but since the test point of the product is covered, the user cannot test the voltage drop; 4. The RF fixture is a high-speed precision test fixture, and the design and debugging are relatively complex. Users cannot complete the assembly and debugging by themselves. The existing fixture limit frame and fixture accessory fixing frame are a whole. Once the user's device shape tolerance is abnormal, the limit frame needs to be removed, which will cause abnormal fixture indicators.

[0005] Therefore, a RF chip high frequency performance testing process and a fixture thereof are proposed. Summary of the invention

[0006] In view of this, the present invention provides a radio frequency chip high frequency performance testing process and a fixture thereof to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

[0007] The technical solution of the embodiment of the present invention is implemented as follows: A high-frequency performance test process of a radio frequency chip comprises the following steps: S1. Weld the crimping sleeve to one end of the RF cable, and crimp the crimping sleeve to the inside of the test socket; S2. Connect the power cord, voltage test cord and ground cord to the power interface, power voltage drop test port and ground interface respectively; S3, placing the RF chip in the limiting frame so that it contacts the elastic conductive diaphragm, and closing the pressure cover; S4. Manually turn the knob to drive the threaded column to rotate, so that the pressing plate and the pressing block move downward to press the RF chip to be tested and the test PCB tightly; S5. Power on the circuit in the fixture and input the signal to start the high-frequency test of the RF chip.

[0008] Further preferred: In S1, the direct welding method of the traditional test fixture is changed to a crimping method. The coaxial cable is relatively fragile and is prone to abnormal indicators after being squeezed and deformed by external force. Therefore, a crimping sleeve is welded to the coaxial cable to increase the local strength of the cable and prepare for crimping.

[0009] Further preferred: in S2, the power voltage drop test port has a small hole female plug on the outside to prevent the hole from being too large and short-circuiting due to contact with foreign objects, and is internally connected in parallel with the product power supply cable, so that the product can test the accurate voltage drop through the power voltage drop test port under maximum load.

[0010] Further preferred: in S2, the RF fixture housing is made of conductive oxidation, an external grounding interface is set, and the control cable is grounded. According to the situation, the common ground can be selected to meet the grounding requirements and interference requirements of the RF chip.

[0011] Further preferably, in S3, the limiting frame and the fixing frame are designed to be separated, and the user can replace the limiting frames of different sizes at will, and can also replace the limiting frames with balls and without balls.

[0012] Further preferred: in the S3, the elastic conductive diaphragm uses FR4 or FPC flexible board to open holes at the test points of the RF chip, determine the positions of the test connection points, and then use a mold to make a silicon base layer to ensure elasticity. When making the silicone layer, it is necessary to block the test point holes, wait for the silicone layer to solidify, then remove the mold, use conductive glue and gold or silver powder to mix and prepare the conductor, use the mold to inject the prepared conductor into the embryo made in the previous process, wait for solidification to form a conductive column, and finally use the mold to cover the surface elastic protective body.

[0013] In addition, the present invention also provides a fixture for a high-frequency performance test process of a radio frequency chip, comprising a main body component, characterized in that: the main body component comprises a bottom plate, a base, a power interface, a power voltage drop test port, a ground interface, a radio frequency connector, a radio frequency cable and a crimping sleeve; The base is fixedly connected to the upper surface of the base plate by bolts, the power interface, the power voltage drop test port, the ground interface and the RF connector are arranged on the outer side wall of the base, the RF cable is installed at one end of the RF connector, and the crimping sleeve is welded to one end of the RF cable.

[0014] Further preferably: a test assembly is arranged on the top of the main assembly, and the test assembly includes a test seat, a fixing frame, a test PCB, an elastic conductive diaphragm, a limit frame and a limit ring; The fixing frame is fixedly connected to the inner wall of the test socket by bolts, the test PCB is installed on the upper surface of the fixing frame, the elastic conductive diaphragm is installed on the upper surface of the test PCB, the limit frame is arranged on the upper surface of the elastic conductive diaphragm, and the limit frame is fixedly connected to the inside of the fixing frame by bolts.

[0015] Further preferably, the limiting ring is fixedly connected to the inner side wall of the test socket, the RF connector is crimped to the inner side wall of the test socket, and the RF connector is arranged at the bottom of the limiting ring.

[0016] Further preferably: a clamping assembly is arranged on the top of the test assembly, and the clamping assembly comprises a rotating shaft, a torsion spring, a pressure cover, a buckle, a knob, a threaded column, a pressure plate, a guide rod, a first spring, a second spring and a pressure block; The pressure cover is rotatably connected to the top of the test seat through a rotating shaft, the torsion spring is installed on the outer wall of the rotating shaft, the buckle is installed on the top of the pressure cover, the threaded column is threadedly connected to the inner wall of the pressure cover, the knob is fixedly connected to one end of the threaded column, the pressure plate is arranged at the bottom of the threaded column, the four guide rods are fixedly connected to the inside of the pressure cover symmetrically, the first spring is sleeved on the outer wall of the guide rod, the pressure plate is slidably connected to the outer wall of the guide rod, the four second springs are symmetrically installed on the inner wall of the pressure plate, the pressure block is fixedly connected to one end of the second spring, and the pressure block is slidably connected to the inner wall of the pressure plate.

[0017] The embodiment of the present invention has the following advantages due to the adoption of the above technical solution: 1. The present invention adopts a solution of combining coaxial cable and PCB. The PCB part meets the requirements of digital signal transmission and product power supply, and the coaxial cable is used for radio frequency signal transmission. It can reduce the microwave interference caused by the use of PCB microstrip line and the signal influence caused by the 90° transition between the conductive part and the PCB plane microstrip, thereby meeting the high-frequency testing requirements of the radio frequency chip.

[0018] Second, the present invention changes the direct welding method of the traditional test fixture to a crimping method, thereby solving the problems of long welding time, high operation requirements and unmaintainability during the welding process, and avoiding the high-frequency test indicators of the fixture being affected by long-term heating of the RF cable; 3. The present invention uses a self-designed elastic conductive film as the transmission elastic carrier of the fixture, and controls the film thickness between 0.3-3mm according to the radio frequency index, thereby minimizing the influence of the conductive film on the radio frequency index; 4. By adding a power voltage drop test interface to the fixture, the product can test the accurate voltage drop through the power voltage drop test port under maximum load; 5. The limit frame and fixed frame are designed to be separated. Users can replace limit frames of different sizes at will. At the same time, they can also replace limit frames with balls and without balls, which is convenient for users to use; 6. The present invention is also applicable to double-sided chip layout. By setting test components on the bottom and top surfaces of the double-sided chip, double-sided RF chip testing can be achieved.

[0019] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 is a process flow chart of the present invention; Figure 2 It is a structural diagram of the present invention; Figure 3 It is a rear view structural diagram of the present invention; Figure 4 It is the structural diagram of the test PCB of the present invention; Figure 5 It is a structural diagram of the elastic conductive diaphragm of the present invention; Figure 6 It is a structural diagram of the gland of the present invention; Figure 7 It is a structural diagram of the knob of the present invention; Figure 8 It is a cross-sectional structural diagram of the pressing plate of the present invention; Fig. 9 This is a bottom structural diagram of the test socket of the present invention.

[0022] Figure numerals: 10, main assembly; 11, bottom plate; 12, base; 13, power interface; 14, power voltage drop test port; 15, ground interface; 16, RF connector; 17, RF cable; 18, crimping sleeve; 20, test assembly; 21, test socket; 22, fixing frame; 23, test PCB; 24, elastic conductive diaphragm; 25, limit frame; 26, limit ring; 30, clamping assembly; 31, rotating shaft; 32, torsion spring; 33, pressure cover; 34, buckle; 35, knob; 36, threaded column; 37, pressure plate; 38, guide rod; 39, first spring; 310, second spring; 311, pressure block. DETAILED DESCRIPTION

[0023] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0024] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] like Figure 1-9 As shown, an embodiment of the present invention provides a high-frequency performance test process for a radio frequency chip, comprising the following steps: S1. Weld the crimping sleeve to one end of the RF cable, and crimp the crimping sleeve to the inside of the test socket; S2. Connect the power cord, voltage test cord and ground cord to the power interface, power voltage drop test port and ground interface respectively; S3, placing the RF chip in the limiting frame so that it contacts the elastic conductive diaphragm, and closing the pressure cover; S4. Manually turn the knob to drive the threaded column to rotate, so that the pressing plate and the pressing block move downward to press the RF chip to be tested and the test PCB tightly; S5. Power on the circuit in the fixture and input the signal to start the high-frequency test of the RF chip.

[0026] In this embodiment, specifically: in S1, the direct welding method of the traditional test fixture is changed to a crimping method. The coaxial cable is relatively fragile and is prone to abnormal indicators after being squeezed and deformed by external force. Therefore, a crimping sleeve is welded to the coaxial cable to increase the local strength of the cable and prepare for crimping. In addition, the crimping sleeve has the following advantages: 1. The sleeve is small in size and convenient for welding. The heating time is also relatively short and the time is controllable; 2. Crimping is convenient for maintenance. When a defect occurs, it can be pressed out with a tool and re-adjusted and assembled; 3. The crimping sleeve is located at the end of the coaxial cable, and its appearance is a stepped cylindrical shape with a relatively small volume, which is directly connected to the single The root component shield is welded, and the position can be easily moved back and forth, which is convenient for adjusting the RF phase. This indicator is also an important indicator of the RF chip; 4. The crimping process is relatively simple, and there is no special requirement for personnel. Just use a small press to press the assembled sleeve assembly into the gold-plated base of the fixture. The above structure directly uses the center conductor of the coaxial cable for RF signal transmission, which can ensure the effective transmission of the RF signal. At the same time, the coaxial cable shielding layer is integrated with the chip grounding through the crimping sleeve, which plays a better shielding and anti-interference role, allowing the RF indicators to be transmitted through the coaxial cable, ensuring the indicator performance.

[0027] In this embodiment, specifically: in S2, the outside of the power voltage drop test port is a small hole female plug to prevent the hole from being too large and short-circuiting with foreign objects, and the inside is connected in parallel with the product power supply cable, so that the product can test the accurate voltage drop through the power voltage drop test port under maximum load.

[0028] In this embodiment, specifically: in S2, the RF fixture housing is made of conductive oxidation, an external grounding interface is set, and the control cable is grounded. According to the situation, the common ground can be selected to meet the grounding requirements and interference requirements of the RF chip.

[0029] In this embodiment, specifically: in S3, the limiting frame and the fixed frame are designed to be separated, and the user can replace the limiting frames of different sizes at will, and can also replace the limiting frames with balls and without balls.

[0030] In this embodiment, specifically: in S3, the elastic conductive diaphragm uses FR4 or FPC flexible board to open holes at the test points of the RF chip, determine the positions of the test connection points, and then use a mold to make a silicon base layer to ensure elasticity. When making the silicone layer, it is necessary to block the test point holes, wait for the silicone layer to solidify, then remove the mold, use conductive glue and gold or silver powder to mix and prepare the conductor, use the mold to inject the prepared conductor into the embryo made in the previous process, wait for solidification to form a conductive column, and finally use the mold to cover the surface elastic protective body. Since thickness is the key factor affecting RF indicators, a 0.3-3mm RF conductive film is made by mold opening. After simulation calculation, it is found that the conductive film in this range can minimize the impact, and different frequencies are suitable according to different thicknesses. The actual test effect is good, and it can be matched and produced according to the RF chip indicators and test points.

[0031] In addition, the present invention also provides a fixture for a high-frequency performance test process of a radio frequency chip, comprising a main component 10, the main component 10 comprising a bottom plate 11, a base 12, a power interface 13, a power voltage drop test port 14, a ground interface 15, a radio frequency connector 16, a radio frequency cable 17 and a crimping sleeve 18; The base 12 is fixedly connected to the upper surface of the base plate 11 by bolts, the power interface 13, the power voltage drop test port 14, the ground interface 15 and the RF connector 16 are arranged on the outer wall of the base 12, the RF cable 17 is installed at one end of the RF connector 16, and the crimping sleeve 18 is welded to one end of the RF cable 17.

[0032] In this embodiment, specifically: a test assembly 20 is arranged on the top of the main assembly 10, and the test assembly 20 includes a test seat 21, a fixing frame 22, a test PCB 23, an elastic conductive diaphragm 24, a limit frame 25 and a limit ring 26; The fixing frame 22 is fixedly connected to the inner wall of the test socket 21 by bolts, the test PCB 23 is installed on the upper surface of the fixing frame 22, the elastic conductive diaphragm 24 is installed on the upper surface of the test PCB 23, and the limit frame 25 is arranged on the upper surface of the elastic conductive diaphragm 24. The limit frame 25 is fixedly connected to the inside of the fixing frame 22 by bolts.

[0033] In this embodiment, specifically: the limiting ring 26 is fixedly connected to the inner wall of the test socket 21 , the RF connector 16 is crimped to the inner wall of the test socket 21 , and the RF connector 16 is disposed at the bottom of the limiting ring 26 .

[0034] In this embodiment, specifically: a clamping assembly 30 is arranged on the top of the test assembly 20, and the clamping assembly 30 includes a rotating shaft 31, a torsion spring 32, a pressure cover 33, a buckle 34, a knob 35, a threaded column 36, a pressure plate 37, a guide rod 38, a first spring 39, a second spring 310 and a pressure block 311; The pressure cover 33 is rotatably connected to the top of the test seat 21 through the rotating shaft 31, the torsion spring 32 is installed on the outer wall of the rotating shaft 31, the buckle 34 is installed on the top of the pressure cover 33, the threaded column 36 is threadedly connected to the inner wall of the pressure cover 33, the knob 35 is fixedly connected to one end of the threaded column 36, the pressure plate 37 is arranged at the bottom of the threaded column 36, the four guide rods 38 are fixedly connected to the inside of the pressure cover 33 symmetrically, the first spring 39 is sleeved on the outer wall of the guide rod 38, the pressure plate 37 is slidably connected to the outer wall of the guide rod 38, the four second springs 310 are symmetrically installed on the inner wall of the pressure plate 37, the pressure block 311 is fixedly connected to one end of the second spring 310, and the pressure block 311 is slidably connected to the inner wall of the pressure plate 37. The present invention is also applicable to the double-sided chip layout. The test assembly 20 is arranged on the bottom and top surfaces of the double-sided chip to realize the double-sided RF chip test.

[0035] When the present invention is working: the crimping sleeve 18 is welded to one end of the RF cable 17, and the crimping sleeve 18 is crimped to the inside of the test socket 21, the power line, the voltage test line and the ground line are respectively connected to the power interface 13, the power voltage drop test port 14 and the ground interface 15, the RF chip is placed in the limit frame 25 so that it contacts the elastic conductive diaphragm 24, and the pressure cover 33 is closed, the pressure cover 33 is fixed by the buckle 34, the knob 35 is manually rotated to drive the threaded column to rotate 36, so that the pressure plate 37 and the pressure block 311 move downward, and with the assistance of the first spring 39 and the second spring 310, the RF chip to be tested is pressed against the test PCB23, the test circuit in the fixture is energized and the signal is input, the test frequency is set to 67GHz, and the high-frequency test of the RF chip is started.

[0036] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A radio frequency chip high frequency performance test process, characterized in that: The following steps are involved: S1. Weld the crimping sleeve to one end of the RF cable, and crimp the crimping sleeve to the inside of the test socket; S2. Connect the power cord, voltage test cord and ground cord to the power interface, power voltage drop test port and ground interface respectively; S3, placing the RF chip in the limiting frame so that it contacts the elastic conductive diaphragm, and closing the pressure cover; S4. Manually turn the knob to drive the threaded column to rotate, so that the pressing plate and the pressing block move downward to press the RF chip to be tested and the test PCB tightly; S5. Power on the circuit in the fixture and input the signal to start the high-frequency test of the RF chip.

2. A radio frequency chip high frequency performance testing process according to claim 1, characterized in that: In S1, the direct welding method of the traditional test fixture is changed to a crimping method. The coaxial cable is relatively fragile and is prone to abnormal indicators after being squeezed and deformed by external force. Therefore, a crimping sleeve is welded to the coaxial cable to increase the local strength of the cable and prepare for crimping.

3. The high frequency performance testing process of a radio frequency chip according to claim 1, characterized in that: In S2, the power voltage drop test port has a small female plug on the outside to prevent the hole from being too large and short-circuiting with foreign objects. The inside is connected in parallel with the product power supply cable, so that the product can test the accurate voltage drop through the power voltage drop test port under maximum load, which is used as a basis for voltage compensation to test the actual performance of the product.

4. The high frequency performance testing process of a radio frequency chip according to claim 1, characterized in that: In S2, the RF fixture housing is made of conductive oxide, an external grounding interface is provided, and the control cable is grounded. A common ground can be selected according to the situation to meet the grounding requirements and interference requirements of the RF chip.

5. The high frequency performance testing process of a radio frequency chip according to claim 1, characterized in that: In the S3, the limiting frame and the fixed frame are designed to be separated, and the user can replace the limiting frames of different sizes at will, and can also replace the limiting frames with balls and those without balls.

6. The high frequency performance testing process of a radio frequency chip according to claim 1, characterized in that: In the S3, the elastic conductive diaphragm uses FR4 or FPC flexible board to open holes at the test points of the RF chip, determine the positions of the test connection points, and then use a mold to make a silicon base layer to ensure elasticity. When making the silicone layer, it is necessary to block the test point holes. After the silicone layer is cured, remove the mold, use conductive glue and gold or silver powder to mix and prepare the conductor, use the mold to inject the prepared conductor into the embryo made in the previous process, wait for it to solidify to form a conductive column, and finally use the mold to cover the surface elastic protective body.

7. A fixture for high frequency performance testing of radio frequency chips according to any one of claims 1 to 6, comprising a main body component (10), characterized in that: The main body component (10) comprises a bottom plate (11), a base (12), a power interface (13), a power voltage drop test port (14), a ground interface (15), a radio frequency connector (16), a radio frequency cable (17) and a crimping sleeve (18); The base (12) is fixedly connected to the upper surface of the base plate (11) by means of bolts; the power interface (13), the power voltage drop test port (14), the ground interface (15) and the radio frequency connector (16) are arranged on the outer side wall of the base (12); the radio frequency cable (17) is installed at one end of the radio frequency connector (16); and the crimping sleeve (18) is welded to one end of the radio frequency cable (17).

8. The fixture for high frequency performance testing of radio frequency chips according to claim 7 is characterized in that: A test assembly (20) is arranged on the top of the main body assembly (10), and the test assembly (20) comprises a test seat (21), a fixing frame (22), a test PCB (23), an elastic conductive diaphragm (24), a limit frame (25) and a limit ring (26); The fixing frame (22) is fixedly connected to the inner wall of the test seat (21) by means of bolts, the test PCB (23) is mounted on the upper surface of the fixing frame (22), the elastic conductive diaphragm (24) is mounted on the upper surface of the test PCB (23), the limit frame (25) is arranged on the upper surface of the elastic conductive diaphragm (24), and the limit frame (25) is fixedly connected to the inside of the fixing frame (22) by means of bolts.

9. The fixture for high frequency performance testing of radio frequency chips according to claim 8, characterized in that: The limiting ring (26) is fixedly connected to the inner side wall of the test socket (21), the radio frequency connector (16) is crimped to the inner side wall of the test socket (21), and the radio frequency connector (16) is arranged at the bottom of the limiting ring (26).

10. The fixture for high frequency performance testing of radio frequency chips according to claim 9, characterized in that: A clamping assembly (30) is disposed on the top of the test assembly (20), and the clamping assembly (30) comprises a rotating shaft (31), a torsion spring (32), a pressure cover (33), a buckle (34), a knob (35), a threaded column (36), a pressure plate (37), a guide rod (38), a first spring (39), a second spring (310) and a pressure block (311); The pressure cover (33) is rotatably connected to the top of the test seat (21) via a rotating shaft (31), the torsion spring (32) is installed on the outer side wall of the rotating shaft (31), the buckle (34) is installed on the top of the pressure cover (33), the threaded column (36) is threadedly connected to the inner side wall of the pressure cover (33), the knob (35) is fixedly connected to one end of the threaded column (36), the pressure plate (37) is arranged at the bottom of the threaded column (36), and the four guides are The guide rod (38) is fixedly connected to the inner side of the pressure cover (33) symmetrically, the first spring (39) is sleeved on the outer side wall of the guide rod (38), the pressure plate (37) is slidably connected to the outer side wall of the guide rod (38), four second springs (310) are symmetrically installed on the inner side wall of the pressure plate (37), the pressure block (311) is fixedly connected to one end of the second spring (310), and the pressure block (311) is slidably connected to the inner side wall of the pressure plate (37).

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