A high temperature reverse bias aging test module for three-level power modules

Abstract

The present invention relates to a high temperature reverse bias aging test module for a three-level power module, including a test fixture and a test circuit, the test fixture includes a bottom PCB board and a clamping assembly, a device to be tested is provided in the clamping assembly, the test circuit is connected to a corresponding device to be tested through the bottom PCB board, the test circuit includes a positive power supply PWR+, a negative power supply PWR-, a single-station positive power supply bridge arm switching relay S5, a single-station negative power supply bridge arm switching relay S7, a single-station intermediate bridge arm switching relay S6 and an MCU, each relay includes two switches in parallel, and the MCU controls the on-off coordination of different switches in the single-station positive power supply bridge arm switching relay S5, the single-station negative power supply bridge arm switching relay S7 and the single-station intermediate bridge arm switching relay S6, so that all single tubes in the device to be tested complete aging test. The present invention improves the aging process efficiency and also reduces the error probability.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature reverse bias aging test of IGBT modules, and more specifically to a high temperature reverse bias aging test module for a three-level power module. Background Art

[0002] At present, the power levels of inverters in the photovoltaic industry and rectifiers in the wind power industry are getting larger and larger, and the size of traditional low-voltage converters is getting larger and larger, and the cost is increasing, which has lost its competitive advantage. In order to solve this bottleneck problem, various companies have increased their R&D investment and adopted the method of increasing the voltage level of the converter and reducing the current to reduce the size and cost of the converter. However, the rated voltage level of the power module cannot meet the use requirements, so a three-level solution is used to replace the original two-level solution. The three-level module has a complex structure and many assessment parameters. During the test process, it is necessary to test under extreme conditions.

[0003] At present, the test methods for three-level power modules mainly include the following two methods: 1. Using the traditional single-tube aging method, even if the devices are aged in parallel, four switches are required, and the aging board needs to be replaced or a different connection method needs to be changed to complete the aging of all single tubes in the three-level module; 2. High-temperature reverse-bias aging uses the ordinary upper and lower bridge aging method, which requires two switches, and the aging board needs to be replaced or a different connection method needs to be changed to complete the aging of all single tubes in the three-level module.

[0004] Traditional test circuits and methods require connecting different bridge arms or single tubes on the test device by replacing the aging board or rewiring. This results in the need to configure multiple aging boards for the same type of three-level module, increasing the cost of use, or requiring the replacement of different connections, which is easy to connect incorrectly. In addition, during the entire three-level module test process, due to the replacement of the aging board or the wiring method, it is necessary to open the oven many times (2-4 times), wait for the oven temperature to reach the temperature, turn on the high voltage to start the test, and turn off the high voltage to end the test (the three-level part of the single tube in the module); cool down, take out the aging board, replace the aging board or rewire, then open the oven, wait for the oven temperature to reach the temperature, turn on the high voltage to start the test, and turn off the high voltage to end the test (the other parts of the three-level module in the module), resulting in low operating efficiency. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a high-temperature reverse bias aging test module for a three-level power module, which does not require replacement of the aging board and can complete the aging of all single tubes in a three-level module with only two switches; the error probability is reduced and the aging processing efficiency is improved.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A high-temperature reverse bias aging test module for a three-level power module, comprising a test fixture and a test circuit, wherein the test fixture comprises a bottom PCB board and a plurality of clamping components fixed on the bottom PCB board, wherein each clamping component is provided with a device to be tested, wherein the test circuit comprises a plurality of groups, wherein each group of test circuits is connected to a corresponding device to be tested through the bottom PCB board, wherein the test circuit comprises a positive power supply PWR+, a negative power supply PWR-, a single-station positive power supply bridge arm switching relay S5, a single-station negative power supply bridge arm switching relay S7 and a single-station intermediate bridge arm switching relay S6, wherein each relay comprises two switches connected in parallel, The single-station positive power bridge arm switching relay S5 is connected to the pins DC+ and N2 / AC2 of the device under test; the single-station negative power bridge arm switching relay S7 is connected to the pins DC- and N1 / AC1 of the device under test; the single-station intermediate bridge arm switching relay S6 is connected to the pins Cx and Cy of the device under test; the test circuit also includes an MCU, which controls the on-off coordination of different switches in the single-station positive power bridge arm switching relay S5, the single-station negative power bridge arm switching relay S7 and the single-station intermediate bridge arm switching relay S6, so that all single tubes in the device under test can be aged in two operations.

[0008] As a preferred solution, the positive power supply PWR+, the positive power supply main relay S1 and the single-station positive power supply bridge arm switching relay S5 are connected in series in sequence, and the single-station positive power supply bridge arm switching relay S5 includes a switch S5A and a switch S5B, the switch S5A is connected to the pin DC+ of the device under test, and the switch S5B is connected to the pin N2 / AC2 of the device under test.

[0009] As a preferred solution, a single-station upper bridge protection relay S3 is provided between the positive power main relay S1 and the single-station positive power bridge arm switching relay S5, and a sampling resistor RIR+ is provided between the positive power main relay S1 and the single-station upper bridge protection relay S3.

[0010] As a preferred solution, the negative power supply PWR-, the negative power supply main relay S2 and the single-station negative power supply bridge arm switching relay S7 are connected in series in sequence, and the single-station negative power supply bridge arm switching relay S7 includes a switch S7A and a switch S7B, the switch S7A is connected to the pin N1 / AC1 of the device under test, and the switch S7B is connected to the pin DC- of the device under test.

[0011] As a preferred solution, a single-station lower bridge protection relay S4 is provided between the negative power main relay S2 and the single-station negative power bridge arm switching relay S7, and a sampling resistor RIR- is provided between the negative power main relay S2 and the single-station lower bridge protection relay S4.

[0012] As a preferred solution, the single-station intermediate bridge arm switching relay S6 is connected to the negative pole of the positive power supply PWR+ and the positive pole of the negative power supply PWR-, and the single-station intermediate bridge arm switching relay S6 includes a switch S6A and a switch S6B, the switch S6A is connected to the pin Cx of the device under test, and the switch S6B is connected to the pin Cy of the device under test.

[0013] As a preferred solution, an upper bridge arm fuse F1, a multiplex fuse F2 and a lower bridge arm fuse F3 are further provided between the single-station positive power bridge arm switching relay S5, the single-station negative power bridge arm switching relay S7 and the device under test.

[0014] As a preferred embodiment, the clamping assembly includes a clamping base and a cover plate, one end of the clamping base is hinged to one end of the cover plate, the other end of the clamping base is clamped to the other end of the cover plate, the device under test is clamped between the clamping base and the cover plate, and a conductive area is also provided on the clamping assembly, and the pins of the device under test are connected to the bottom PCB board through the conductive area.

[0015] As a preferred solution, a locking block seat is fixed to the other end of the cover plate, a locking block extending downward is hinged on the locking block seat, and a locking buckle is fixed to the other end of the clamping base, and the locking block is clamped in the locking buckle.

[0016] As a preferred solution, the cover plate is further provided with a through hole, a heat sink is further fixed on the device under test, and fins on the heat sink pass through the through hole.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention adopts a simultaneous aging test mode of the upper and lower bridges, and at the same time, through switching and control, the pins required by the test device on the aging board in the high-temperature test box are led to the control test circuit board at one time through the bus socket adapter, and the upper and lower bridges are powered on and connected at the same time and the single tubes in the test device are switched by the control test circuit; through the configured test logic sequence, after the circuit of the first test is completed, it is not necessary to stop the oven and replace the aging board or rewire the circuit during the test process, and the circuit of the second test can be directly switched, and the aging of all the single tubes in a three-level module can be completed in two times in total; thereby, the aging process efficiency is improved, and the error probability of manual wiring change required in the existing test process is reduced, and since the replacement of the aging board method is abandoned, the aging cost can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings in the specification, which constitute a part of the present application, are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute a limitation on the present application.

[0020] Figure 1 and Figure 2 It is a schematic diagram of the structure of the bottom PCB board and multiple clamping components at different angles of the present invention;

[0021] Figure 3 It is a schematic diagram of the overall structure of the clamping assembly of the present invention;

[0022] Figure 4 and Figure 5 Schematic diagram of the exploded structure of the clamping assembly at different angles of the present invention;

[0023] Figure 6 This is an overall circuit diagram of a three-level power module used in the present invention;

[0024] Figure 7 The overall circuit diagram of the test circuit used in the present invention;

[0025] Figure 8 This is the equivalent test circuit diagram of the first test of the present invention;

[0026] Fig. 9 This is the equivalent test circuit diagram of the second test of the present invention.

[0027] Figure numerals: 1, bottom PCB board; 2, clamping assembly; 21, heat sink; 20, device under test; 201, pin; 22, clamping base; 221, conduction area; 222, positioning column; 223, hinged seat; 224, hinged column; 23, lock; 24, cover plate; 241, hinged ear; 242, through hole; 25, locking block; 26, locking block seat. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] In addition, in the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more, unless otherwise clearly specified.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0035] like Figure 1 and Figure 2A high-temperature reverse bias aging test module for a three-level power module is shown, comprising a test fixture and a test circuit. The test fixture comprises a bottom PCB board 1, and a plurality of clamping components 2 fixed on the bottom PCB board 1, each clamping component 2 is provided with a device under test 20, and the test circuits are divided into multiple groups, and each group of test circuits is connected to a corresponding device under test 20 through the bottom PCB board 1.

[0036] like Figures 3 to 5 As shown, the clamping assembly 2 includes a clamping base 22 and a cover plate 24, one end of the clamping base 22 is hinged to one end of the cover plate 24, the other end of the clamping base 22 is clamped to the other end of the cover plate 24, the device under test 20 is clamped between the clamping base 22 and the cover plate 24, and a conducting area 221 is also provided on the clamping assembly 2, and the pin 201 of the device under test 20 is connected to the bottom PCB board 1 through the conducting area 221.

[0037] A hinge seat 223 is fixed at one end of the clamping base 22, and hinge columns 224 are straddled on both sides of the hinge seat 223. Two connecting ears 241 extend from both sides of one end of the cover plate 24, and the hinge column 224 passes through the two connecting ears 241. A locking block seat 26 is fixed at the other end of the cover plate 24, and a locking block 25 extending downward is hinged on the locking block seat 26. A locking buckle 23 is fixed at the other end of the clamping base 22, and the locking block 25 is clamped in the locking buckle 23.

[0038] Positioning posts 222 are provided at both ends of the conductive area 221, and positioning holes are provided at both ends of the device under test 20, and two positioning posts pass through the positioning holes; a probe is provided in the conductive area 221, and the pin 201 of the device under test 20 abuts against the corresponding probe in the conductive area 221; a through hole 242 is also provided on the cover plate 24, and a heat sink 21 is also fixed on the device under test 20, and the fins on the heat sink 21 pass through the through hole 242.

[0039] like Figure 6 and Figure 7As shown, the test circuit includes a positive power supply PWR+, a negative power supply PWR-, a single-station positive power supply bridge arm switching relay S5, a single-station negative power supply bridge arm switching relay S7 and a single-station intermediate bridge arm switching relay S6, each relay includes two parallel switches, the single-station positive power supply bridge arm switching relay S5 is connected to the pins DC+ and N2 / AC2 of the device under test 20; the single-station negative power supply bridge arm switching relay S7 is connected to the pins DC- and N1 / AC1 of the device under test 20; the single-station intermediate bridge arm switching relay S6 is connected to the pins Cx and Cy of the device under test 20; the test circuit also includes an MCU, which controls the on-off coordination of different switches among the single-station positive power supply bridge arm switching relay S5, the single-station negative power supply bridge arm switching relay S7 and the single-station intermediate bridge arm switching relay S6, and two operations can complete the aging of all single tubes in the device under test 20.

[0040] The positive power supply PWR+, the positive power supply main relay S1 and the single-station positive power supply bridge arm switching relay S5 are connected in series in sequence, and the single-station positive power supply bridge arm switching relay S5 includes a switch S5A and a switch S5B, the switch S5A is connected to the pin DC+ of the device under test 20, and the switch S5B is connected to the pin N2 / AC2 of the device under test 20. A single-station upper bridge protection relay S3 is also provided between the positive power supply main relay S1 and the single-station positive power supply bridge arm switching relay S5, and a sampling resistor RIR+ is also provided between the positive power supply main relay S1 and the single-station upper bridge protection relay S3.

[0041] The negative power supply PWR-, the negative power supply main relay S2 and the single-station negative power supply bridge arm switching relay S7 are connected in series in sequence, and the single-station negative power supply bridge arm switching relay S7 includes a switch S7A and a switch S7B, the switch S7A is connected to the pin N1 / AC1 of the device under test 20, and the switch S7B is connected to the pin DC- of the device under test 20. A single-station lower bridge protection relay S4 is also provided between the negative power supply main relay S2 and the single-station negative power supply bridge arm switching relay S7, and a sampling resistor RIR- is provided between the negative power supply main relay S2 and the single-station lower bridge protection relay S4.

[0042] The single-station intermediate bridge arm switching relay S6 is connected to the negative pole of the positive power supply PWR+ and the positive pole of the negative power supply PWR-. The single-station intermediate bridge arm switching relay S6 includes a switch S6A and a switch S6B. The switch S6A is connected to the pin Cx of the device under test 20, and the switch S6B is connected to the pin Cy of the device under test 20.

[0043] An upper bridge arm fuse F1 , a multiplex fuse F2 and a lower bridge arm fuse F3 are also provided between the single-station positive power bridge arm switching relay S5 , the single-station negative power bridge arm switching relay S7 and the device under test 20 .

[0044] The high temperature reverse bias aging of the three-level power module adopts the test circuit of the present invention, such as Figure 7 The test circuit in the test configuration can complete the aging of all single tubes in the three-level module through two switches in the test configuration, namely the first test and the second test, without replacing the aging board or changing different connection methods.

[0045] like Figure 8 As shown, in the first test, the positive power supply main relay S1 is energized, the negative power supply main relay S2 is energized, the single-station upper bridge protection relay S3 is energized, the single-station lower bridge protection relay S4 is energized, the switch S5A of the single-station positive power supply bridge arm switching relay S5 is energized, and the switch S5B is disconnected; the switch S7A of the single-station negative power supply bridge arm switching relay S7 is energized, and the switch S7B is disconnected; the switch S6A of the single-station middle bridge arm switching relay S6 is energized, and the switch S6B is disconnected;

[0046] The positive pole of the positive power supply PWR+ passes through the positive power supply main relay S1, the sampling resistor RIR+, the single-station upper bridge protection relay S3, the switch S5A, the fuse F1, and then to the pin DC+ and pin Cx of the device under test DUT, and then to the switch S6A. The negative pole of the positive power supply PWR+ forms an aging loop A1, and the aged device is T1 / D1 in the device under test DUT; the positive pole of the negative power supply PWR- passes through the switch S6A, and then to the pin Cx of the device under test, pin N1 / AC1, the fuse F2, and then to the switch S7A, the single-station lower bridge protection relay S4, the sampling resistor RIR-, the negative power supply main relay S2, and the negative pole of the negative power supply PWR- forms an aging loop A2, and the aged device is T2 / D2 and T5 / D5 in the device under test DUT.

[0047] like Fig. 9 As shown, in the second test, the positive power supply main relay S1 is energized, the negative power supply main relay S2 is energized, the single-station upper bridge protection relay S3 is energized, the single-station lower bridge protection relay S4 is energized, the switch S5A of the single-station positive power supply bridge arm switching relay S5 is disconnected, and the switch S5B is energized; the switch S7A of the single-station negative power supply bridge arm switching relay S7 is disconnected, and the switch S7B is energized; the switch S6A of the single-station middle bridge arm switching relay S6 is disconnected, and the switch S6B is energized;

[0048] The positive pole of the positive power supply PWR+ passes through the positive power supply main relay S1, the sampling resistor RIR+, the single-station upper bridge protection relay S3, the switch S5B, the fuse F2, and then to the pin N2 / AC2 of the device under test, the pin Cy, and then to the switch S6B. The negative pole of the positive power supply PWR+ forms an aging loop B1, and the aged ones are T3 / D3 and T6 / D6 in the device under test DUT; the positive pole of the negative power supply PWR- passes through the switch S6B, and then to the pin Cy of the device under test, the pin DC-, the fuse F3, and then to the switch S7B, the single-station lower bridge protection relay S4, the sampling resistor RIR-, the negative power supply main relay S2, and the negative pole of the negative power supply PWR- forms an aging loop B2, and the aged ones are T4 / D4 in the device under test DUT.

[0049] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0050] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high temperature reverse bias aging test module for a three-level power module, comprising a test fixture and a test circuit, wherein the three-level power module is an ANPC type, the test fixture comprises a bottom PCB board (1), and a plurality of clamping components (2) fixed on the bottom PCB board (1), each clamping component (2) is provided with a device under test (20), the test circuits are multiple groups, each group of test circuits is connected to a corresponding device under test (20) through the bottom PCB board (1), and the characteristics are: The test circuit comprises a positive power supply PWR+, a negative power supply PWR-, a single-station positive power supply bridge arm switching relay S5, a single-station negative power supply bridge arm switching relay S7 and a single-station intermediate bridge arm switching relay S6, each relay comprising two switches connected in parallel, the single-station positive power supply bridge arm switching relay S5 being connected to the pins DC+, N2 and AC2 of the device under test (20); the single-station negative power supply bridge arm switching relay S7 being connected to the pins DC-, N1 and AC1 of the device under test (20); and the single-station intermediate bridge arm switching relay S6 being connected to the pins Cx and Cy of the device under test (20); the test circuit also comprises an MCU, which controls the on-off coordination of different switches in the single-station positive power supply bridge arm switching relay S5, the single-station negative power supply bridge arm switching relay S7 and the single-station intermediate bridge arm switching relay S6, so that all single tubes in the device under test (20) are aged in two operations; The positive power supply PWR+, the positive power supply main relay S1 and the single-station positive power supply bridge arm switching relay S5 are sequentially connected in series, and the single-station positive power supply bridge arm switching relay S5 comprises a switch S5A and a switch S5B, the switch S5A is connected to the pin DC+ of the device under test (20), and the switch S5B is connected to the pin N2 and the pin AC2 of the device under test (20); The negative power supply PWR-, the negative power supply main relay S2 and the single-station negative power supply bridge arm switching relay S7 are sequentially connected in series, and the single-station negative power supply bridge arm switching relay S7 comprises a switch S7A and a switch S7B, the switch S7A is connected to the pin N1 and the pin AC1 of the device under test (20), and the switch S7B is connected to the pin DC- of the device under test (20); The single-station intermediate bridge arm switching relay S6 is connected to the negative pole of the positive power supply PWR+ and the positive pole of the negative power supply PWR-, and the single-station intermediate bridge arm switching relay S6 includes a switch S6A and a switch S6B, the switch S6A is connected to the pin Cx of the device under test (20), and the switch S6B is connected to the pin Cy of the device under test (20).

2. A high temperature reverse bias aging test module for a three-level power module according to claim 1, characterized in that: A single-station upper bridge protection relay S3 is also provided between the positive power main relay S1 and the single-station positive power bridge arm switching relay S5, and a sampling resistor RIR+ is also provided between the positive power main relay S1 and the single-station upper bridge protection relay S3.

3. A high temperature reverse bias aging test module for a three-level power module according to claim 1, characterized in that: A single-station lower bridge protection relay S4 is also provided between the negative power main relay S2 and the single-station negative power bridge arm switching relay S7, and a sampling resistor RIR- is provided between the negative power main relay S2 and the single-station lower bridge protection relay S4.

4. A high temperature reverse bias aging test module for a three-level power module according to claim 1, characterized in that: An upper bridge arm fuse F1 is also provided between the switch S5A of the single-station positive power bridge arm switching relay S5 and the device under test (20), a multiplexed fuse F2 is shared between the switch S5B of the single-station positive power bridge arm switching relay S5 and the device under test (20) and between the switch S7A of the single-station negative power bridge arm switching relay S7 and the device under test (20), and a lower bridge arm fuse F3 is also provided between the switch S7B of the single-station negative power bridge arm switching relay S7 and the device under test (20).

5. A high temperature reverse bias aging test module for a three-level power module according to claim 1, characterized in that: The clamping assembly (2) comprises a clamping base (22) and a cover plate (24); one end of the clamping base (22) is hinged to one end of the cover plate (24); the other end of the clamping base (22) is clamped to the other end of the cover plate (24); the device under test (20) is clamped between the clamping base (22) and the cover plate (24); a conducting area (221) is also provided on the clamping assembly (2); and the pins (201) of the device under test (20) are connected to the bottom PCB board (1) via the conducting area (221).

6. A high temperature reverse bias aging test module for a three-level power module according to claim 5, characterized in that: A locking block seat (26) is fixed to the other end of the cover plate (24), and a locking block (25) extending downward is hinged on the locking block seat (26). A locking buckle (23) is fixed to the other end of the clamping base (22), and the locking block (25) is clamped in the locking buckle (23).

7. A high temperature reverse bias aging test module for a three-level power module according to claim 5, characterized in that: The cover plate (24) is also provided with a through hole (242), and a heat sink (21) is also fixed on the device under test (20), and the fins on the heat sink (21) extend through the through hole (242).

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