IGBT device busbar connection structure and method

Abstract

The present invention relates to a busbar connection structure and method for an IGBT device. The connection structure includes at least a shorting block and a contact spring; at least two contact springs are respectively attached to the busbar and the test fixture to reduce or isolate the stray inductance in the connection structure; wherein the circuit loop formed by the busbar and the test fixture is connected in parallel layers under the attachment of the contact springs. The present invention connects the circuit loop in parallel layers by providing a shorting block and a contact spring, and superimposes the current sensor Rogowski coil, thereby shortening the current loop length, thereby minimizing the loop length, minimizing the parasitic inductance, and eliminating the stray magnetic field as much as possible to achieve the reduction of stray inductance. The reduction of stray inductance can reduce the peak voltage generated when the IGBT device is turned off with a large di / dt, prevent the IGBT device from being broken down, and increase the service life and switching loss of the IGBT device. Lower stray inductance also makes the dynamic parameters measured in the dynamic test of the IGBT device more accurate.

Description

Technical Field

[0001] The present invention relates to the field of IGBT testing technology, and in particular to an IGBT device busbar connection structure and method. Background Art

[0002] IGBT device dynamic testing is essential for evaluating the dynamic parameters of IGBTs. Half-bridge switching dynamic testing is performed using a low-stray inductance busbar to inductor circuit to the IGBT. This provides information on the IGBT's switching parameters and the reverse recovery characteristics of the internal anti-parallel diode, providing crucial information for evaluating IGBT switching performance, such as switching frequency, switching losses, dead time, and drive power. Whether in testing or in actual applications, stray inductance in the power circuit significantly impacts the IGBT's switching characteristics. During turn-off with a large di / dt, stray inductance generates high voltage spikes, which not only impact the IGBT's lifespan and switching losses but may even cause IGBT breakdown. Greater stray inductance increases the voltage spike, so reducing stray inductance in the circuit is essential. Low stray inductance during IGBT dynamic testing allows for more accurate measurement of IGBT device dynamic parameters.

[0003] In current dynamic test equipment, there are two main methods for connecting the dynamic test busbar to the test fixture. One method uses wires connected to a connector; the other method involves welding a copper block to the busbar, installing spring terminals on the support block on the fixture, soldering and filling them, and then plugging them together. Both of these current detection modules require separate installation, resulting in a longer circuit loop. Both existing connection loops have relatively large parasitic inductances, are complex to produce and assemble, and are costly.

[0004] Chinese patent CN107733246A discloses a current-sharing parallel IGBT module assembly, which includes: a heat sink having a front and a back; a plurality of IGBT modules, which are paired with an adapter board and fixedly mounted on the front of the heat sink in a line; a parallel copper busbar, which is placed above the plurality of IGBT modules and fixedly connected to the AC ends of one or more IGBT modules in the middle of the plurality of IGBT modules; an AC output copper busbar, which is overlapped above the parallel copper busbar and fixedly connects the two ends of the AC output copper busbar to the two ends of the parallel copper busbar, and short-circuits the AC output ends of the modules on the outside of the plurality of IGBT modules to the two ends of the AC output copper busbar, respectively, wherein the middle portion of the AC output copper busbar does not contact the middle portion of the parallel copper busbar and has a gap, so that the current flowing through the parallel copper busbar and the current flowing through the AC output copper busbar overlap in the horizontal direction, but flow in opposite directions.

[0005] Chinese patent CN202949351U discloses a copper busbar mounting structure for parallel switch tube modules. The copper busbar mounting structure includes a busbar and a rectangular current equalizing plate. The current equalizing plate evenly connects the output terminals of the three switch tubes. The busbar aggregates the current passing through the three switch tube modules in parallel. The connection points between the busbar and the current equalizing plate are respectively set at 1 / 6 of the left and right ends of the current equalizing plate. This makes the output resistance of the three switch tube modules equal, thus effectively preventing the occurrence of current deviation in a single switch tube module and the resulting tube explosion phenomenon. This patent uses regular copper busbar processing to reduce material consumption, low cost, and low processing difficulty.

[0006] The drawbacks of the two aforementioned patents are that connecting several IGBTs in parallel does not reduce the length of the current loop and instead causes the current loop to be too long. Although the patents achieve a low-inductance effect of the stacked busbars by, for example, varying the positions and distance ratios of the copper busbars and by using opposite current flows, thereby reducing the stray inductance caused by the leads, the longer current loop length results in a relatively large parasitic stray inductance, which cannot effectively improve the accuracy of dynamic parameter testing of the IGBTs. Instead, the structures described in the patents are cumbersome and costly to produce and assemble. The test fixtures provided are not easy to replace in a timely manner based on the type of IGBTs. Reducing the number of connecting components while adjusting the length of the copper busbars to create a more compact connection is not an effective method for reducing the length of the current loop, and its effect is unpredictable. Reducing the stray inductance of the leads while increasing the stray inductance of the loop is putting the cart before the horse and cannot solve the problems of dynamic testing of the IGBTs and the susceptibility of the IGBTs to breakdown due to high spike voltages.

[0007] In addition, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making the present invention, but due to space limitations, not all details and contents are listed in detail. However, this does not mean that the present invention does not have the characteristics of these prior arts. On the contrary, the present invention already has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art to the background technology. Summary of the Invention

[0008] To address the shortcomings of the prior art, the present invention provides an IGBT device busbar connection structure, comprising at least a shorting block and a contact spring. At least two of the contact springs are adapted to fit the busbar and test fixture, respectively, to reduce or isolate stray inductance within the connection structure. The circuit loop formed by the busbar and test fixture is connected in parallel layers by the contact springs. The present invention connects the circuit loop in parallel layers by providing a shorting block and contact springs, and superimposes a current sensor Rogowski coil, thereby shortening the current loop length. This reduces stray inductance by minimizing loop length, minimizing parasitic inductance, and minimizing stray magnetic fields.

[0009] According to a preferred embodiment, the busbar and test fixture are each provided with contact areas that mate with the contact springs; at least two of the contact areas mate with at least two of the contact springs to form a parallel stack. This parallel stack reduces stray inductance in the circuit. This reduction in stray inductance can also reduce the voltage spikes generated during IGBT device turn-off due to high di / dt, preventing IGBT breakdown and increasing the device's lifespan and switching losses.

[0010] According to a preferred embodiment, at least two of the contact springs are separated, and an insulating sheet is provided in between to prevent breakdown between the two short-circuit blocks. The insulating sheet is used to prevent the two contact springs from contacting each other.

[0011] According to a preferred embodiment, a coil for shortening the current loop is provided at the contact section between the shorting block and the insulating sheet. The coil can be a Rogowski coil of a current sensor. The superposition of the Rogowski coils of the current sensor facilitates shortening the current loop length.

[0012] According to a preferred embodiment, the structure further comprises a supporting capacitor and an absorbing capacitor, which constitute the busbar and are used to provide energy required for dynamic testing of the connection structure at different voltages.

[0013] According to a preferred embodiment, the test fixture is provided with at least two IGBT modules and a high voltage resistance layer.

[0014] According to a preferred embodiment, the IGBT module includes an upper-bridge IGBT module under test and a lower-bridge IGBT module under test. The upper-bridge IGBT module under test and the lower-bridge IGBT module under test use inductor self-inductance to detect the switching parameters of the lower-bridge IGBT module under test and the reverse recovery characteristics of the upper-bridge IGBT module under test during the opening and closing stages of the connection structure. Since it is necessary to evaluate the switching performance of the IGBT module, such as important data such as switching frequency, switching loss, dead time, and driving power, it is necessary to separately set wires or set spring terminals on the upper-bridge IGBT under test and the lower-bridge IGBT under test for connection, resulting in a longer loop of the test circuit structure, thereby causing parasitic stray inductance in the connection loop, and the switching performance finally detected fluctuates and is inaccurate. Therefore, the present invention solves the problem of dynamic testing of switching performance of the traditional half-bridge dual-pulse IGBT test circuit structure and reduces switching loss by setting a connection structure.

[0015] According to a preferred embodiment, the contact spring between the busbar and the test fixture reduces the stray inductance in the circuit loop in a stacked parallel stray inductance manner, wherein the formula is:

[0016] L / m=μ×h / W

[0017] Where L is the stray inductance, μ is the coefficient, h is the stack spacing, m is the unit length, and w is the stack width.

[0018] The present invention relates to a busbar connection method for an IGBT device, the method comprising at least: reducing or isolating stray inductance in a connection structure by respectively affixing at least two contact springs to a busbar and a test fixture; wherein a circuit loop formed by the busbar and the test fixture is connected in parallel layers under the affixation of the contact springs.

[0019] According to a preferred embodiment, the busbar and the test fixture are respectively provided with contact areas matching the contact springs. The method further comprises: at least two of the contact areas are fitted with at least two of the contact springs to form the parallel stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a side cross-sectional view of an IGBT device connection structure according to a preferred embodiment of the present invention;

[0021] Figure 2 This is an axial schematic diagram of an IGBT device connection structure according to a preferred embodiment of the present invention;

[0022] Figure 3 This is another side cross-sectional view of an IGBT device connection structure according to a preferred embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of a current loop of an IGBT device connection structure according to a preferred embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the structure principle of a traditional half-bridge dual-pulse IGBT test circuit provided by the present invention;

[0025] Figure 6 This is a structural schematic diagram of multiple contact areas of an IGBT device connection structure according to a preferred embodiment of the present invention;

[0026] Figure 7 This is a schematic diagram of calculating the coplanar stray inductance of an IGBT device connection structure according to a preferred embodiment of the present invention.

[0027] Reference Signs List

[0028] 1: Support capacitor; 2: Absorption capacitor; 3: Current detection unit; 4: Upper bridge IGBT under test; 5: Lower bridge IGBT under test; 11: Busbar; 12: Coil; 13: Shorting block; 14: Contact spring; 15: High-voltage layer; 16: Test fixture; 17: Contact area; 18: Insulation sheet; 171: First contact area; 172: Second contact area; 173: Third contact area; 174: Fourth contact area. DETAILED DESCRIPTION

[0029] IGBT device dynamic testing is essential for evaluating the dynamic parameters of IGBTs. Half-bridge switching dynamic testing is performed using a low-stray inductance busbar to inductor circuit to the IGBT. This provides information on the IGBT's switching parameters and the reverse recovery characteristics of the internal anti-parallel diode, providing crucial information for evaluating IGBT switching performance, such as switching frequency, switching losses, dead time, and drive power. Whether in testing or in actual applications, stray inductance in the power circuit significantly impacts the IGBT's switching characteristics. During turn-off with a large di / dt, stray inductance generates high voltage spikes, which not only impact the IGBT's lifespan and switching losses but may even cause IGBT breakdown. Greater stray inductance increases the voltage spike, so reducing stray inductance in the circuit is essential. Low stray inductance during IGBT dynamic testing allows for more accurate measurement of IGBT device dynamic parameters.

[0030] The following is a detailed description with reference to the accompanying drawings.

[0031] Example 1

[0032] The present invention aims to provide a low-stray-inductance connection structure and method between an IGBT device busbar and a dynamic test fixture, thereby reducing stray inductance in a test loop.

[0033] like Figure 5 The figure shows a schematic diagram of the structure principle of a conventional half-bridge dual-pulse IGBT test circuit in the prior art.

[0034] like Figure 5 As shown, the conventional half-bridge dual-pulse IGBT test circuit structure includes a support capacitor 1, a snubber capacitor 2, a current sensing unit 3, an upper bridge IGBT under test 4, and a lower bridge IGBT under test 5. Support capacitor 1 and snubber capacitor 2 form a dynamic test busbar, which provides the energy required for dynamic testing of the test circuit at different voltages. Both the upper and lower bridges include an IGBT module. The current sensing unit is, for example, a current probe. Figure 5The figure shows the circuit structure when the test circuit dynamically tests the dynamic parameters of the lower-bridge IGBT module. Therefore, in this case, the upper-bridge IGBT under test can also be called the upper-bridge diode under test. In the traditional half-bridge dual-pulse IGBT test circuit structure, due to the need to evaluate the switching performance of the IGBT module during the start-up phase, such as switching frequency, switching loss, dead time, driving power and other important data, it is necessary to set separate wires or spring terminals on the upper-bridge IGBT under test and the lower-bridge IGBT under test for connection, resulting in a longer loop of the test circuit structure, which leads to parasitic stray inductance of the connection loop, and the switching performance finally detected fluctuates and is inaccurate. Therefore, there is an urgent need for a new IGBT device connection structure to solve the problem of dynamic testing of switching performance of the traditional half-bridge dual-pulse IGBT test circuit structure and reduce switching loss.

[0035] like Figure 1 FIG. 1 is a side cross-sectional view of an IGBT device connection structure of the present invention. Figure 6 Shown is a structural schematic diagram of the IGBT device connection structure.

[0036] like Figure 1 and Figure 6 As shown, the IGBT device connection structure includes at least a short-circuit block 13 and a contact spring 14. At least two contact springs 14 reduce or isolate the stray inductance in the test circuit in a manner that fits the busbar 11 and the test fixture 16 respectively. The circuit loop formed by the busbar 11 and the test fixture 16 is connected in parallel layers under the fit of the contact springs 14. The above-mentioned short-circuit block is, for example, a short-circuit copper block. It should be noted that due to the wide variety of IGBT packaging types, the test fixture involves replacing different test fixtures. For the present invention, different test fixtures are not a restriction condition for the IGBT device connection structure of the present invention. The IGBT device connection structure of the present invention is still easy to replace and has the characteristics of low stray inductance connection. As Figure 2 and Figure 4 In the illustrated contact spring 14, when the contact spring 14 is compressed and elastically deformed, causing the shorting block 13 to contact the contact area 17, the compressed coverage area of ​​the contact spring 14 is smaller than the area of ​​the contact area 17, thereby preventing an increase in stray inductance. Preferably, the contact spring 14 is divided into several spring segments in a direction parallel to the shorting block 13 and perpendicular to the connection line between the busbar 11 and the test fixture 16. This balances the elastic potential energy of the contact spring 14 and prevents the area of ​​the contact spring 14 from changing beyond a predetermined value while in the elastically deformed state.

[0037] According to a preferred embodiment, at least two contact springs 14 are arranged separately from each other, and an insulating sheet 18 is provided between the two contact springs 14 to avoid breakdown between the two short-circuit blocks 13. The insulating sheet 18 is also used to fix the coil 12. It should be noted that the length and width of the contact spring 14 and the insulating sheet 18 can be freely set according to needs. Preferably, the contact spring 14 can be a concave spring with a copper sheet in the middle, and the width of the concave spring after compression is greater than the maximum length of the concave spring. Preferably, the contact spring 14 can also be another concave spring. Figure 2 As shown, at least two slots are milled into shorting block 13, with the minimum distance between the two slots being less than the minimum unstressed length of the concave spring. Regardless of the method used to position contact spring 14, the goal is to ensure that the compressed spring fits the shorting block 13 as closely as possible. Preferably, contact spring 14 employs contact insulation to insulate the upper and lower shorting blocks 13 when they are closed.

[0038] According to a preferred embodiment, a coil 12 is provided at the contact section between the short-circuit block 13 and the insulating sheet. The coil 12 can be a Rogowski coil of a current sensor. The superposition of the Rogowski coils of the current sensor is conducive to shortening the length of the current loop. The coil 12 is used to detect the current in the circuit loop. Two (Rogowski) coils 12 are mounted on the short-circuit block 13 made of a conductive material in a current-isolated manner, wherein the current flowing through the short-circuit block 13 is roughly perpendicular to the annular surface enclosed by the coil 12, and is used to measure the current flowing from the contact area 17 to the test fixture 16 in a mutual inductance manner. By integrating the coil 12 into the short-circuit block 13, the circuit design is simplified, and the purpose of shortening the current loop length is effectively achieved.

[0039] according to Figure 1 The test fixture 16 is used to fix the IGBT modules to be tested that are arranged in pairs, wherein the busbar 11 and the test fixture 16 together constitute an IGBT test circuit, the support capacitor 1 and the absorption capacitor 2 set on the busbar 11 serve as current applicators, and the upper bridge IGBT module and the lower bridge IGBT module set on the test fixture 16 serve as current receivers.

[0040] According to a preferred embodiment, contact areas 17 that match the contact springs 14 are respectively provided on the busbar 11 and the test fixture 16. At least two contact areas 17 are fitted with at least two contact springs 14 to form a parallel stack. The busbar 11 is provided with contact areas 17 on the top surface of the upper and lower surfaces, respectively, which are made of copper and serve as power supply terminals. The contact area on the test fixture 16 needs to be welded with a 0.1mm copper block to prevent contact wear. By setting the copper contact area 17 to an area protruding from the copper conductive area, a wear margin can be provided. However, this also causes additional stray inductance, and the contact area 17 needs to be calculated because of its non-negligible area size.

[0041] When conducting a test, the test fixture 16 can be provided with a replaceable IGBT module to be tested. The test fixture 16 is also provided with a high-voltage layer 15, wherein the top and bottom layers of the busbar 11 and the test fixture 16 are copper-clad to reduce inductance. The high-voltage layer 15 is located between the top and bottom layers of the busbar 11 and the test fixture 16 to composite the busbar 11 and the test fixture 16. The material of the high-voltage layer 15 can be selected according to the current in the circuit. For example, when the current is small, the high-voltage layer 15 can be an FR-4 epoxy resin PCB. When the current is large, the high-voltage layer 15 needs to be composited with a busbar. The high-voltage layer 15 serves as an insulating layer, and its insulating material is selected from suitable materials according to the usage conditions (temperature, withstand voltage strength, dielectric constant, thermal conductivity, etc.).

[0042] like Figure 6 As shown, the circular and square pieces on the left are support capacitor 1 and absorption capacitor 2 respectively. The connection method of support capacitor 1 and absorption capacitor 2 is the same as that of the prior art, thereby forming a busbar 11. The two rectangular pieces in the middle are two contact areas 17. The porous square piece on the right is the IGBT module of the upper bridge and the lower bridge. When testing at least two IGBT modules located on the test fixture 16, the contact spring 14 for connecting the short-circuit block 13 forms a parallel stack in a manner of clamping the busbar 11 and the test fixture 16 on both sides vertically, wherein the parallel stack refers to Figure 4 The upper shorting block is shown as the first layer, the busbar 11 and test fixture 16 form the second layer, and the lower shorting block is the third layer to form a parallel stack. The current in this parallel stack flows from the support capacitor 1 and the absorption capacitor 2 on the busbar 11, through the upper shorting block, the upper bridge IGBT module to be tested, and the lower bridge IGBT module to be tested, to the lower shorting block, and finally back to the busbar 11, thus forming a current loop with opposite current directions in the stack.

[0043] The present invention connects the circuit loops in parallel layers by providing shorting blocks 13 and contact springs 14, and superimposes the current sensor Rogowski coils 12, thereby shortening the current loop length. This reduces stray inductance by minimizing the loop length, minimizing parasitic inductance, and eliminating stray magnetic fields as much as possible. Reducing stray inductance can reduce the spike voltage generated during large di / dt turn-off in IGBT devices, prevent IGBT device breakdown, and increase the service life and switching losses of IGBT devices. Furthermore, lower stray inductance can also make the dynamic parameters measured during dynamic testing of IGBT devices more accurate.

[0044] In the current dynamic test equipment, there are mainly two ways to connect the dynamic test busbar (support capacitor 1 and absorption capacitor 2) and the test fixture 16 (adapted IGBT module, etc.). One is to use a wire to connect to the connector; the other is to weld a copper block on the busbar, install a spring terminal on the support block on the fixture, and then weld and fill it, and then connect the two together. Both of the above-mentioned current detection related modules need to be added separately, which makes the circuit loop longer. The parasitic stray inductance of the two existing connection loops is relatively large, and it is relatively cumbersome in production and assembly, and the cost is also high.

[0045] The current flow in the existing technology is as follows: when the half-bridge dual-pulse IGBT test circuit is turned on, support capacitor 1 and absorption capacitor 2 provide the energy required for testing. The inductor current flows toward the lower-bridge IGBT under test, thereby measuring the relevant switching parameters of the lower-bridge IGBT under test. When the half-bridge dual-pulse IGBT test circuit is turned off, the inductor current cannot undergo sudden changes, so it flows in the reverse direction through the diode built into the upper-bridge IGBT under test, thereby measuring the reverse recovery characteristics of the upper-bridge IGBT under test.

[0046] The present invention reduces stray inductance by using the principle of stacked parallel stray inductance through the contact spring 14 provided between the busbar 11 and the test fixture 16. After the upper and lower short-circuit blocks 13 are closed, the current flow of the present invention is as follows: Figure 4 As shown, the flow passes through the busbar 11 , the upper shorting block, the test fixture 16 , the lower shorting block and returns to the busbar 11 in sequence.

[0047] The use process of the present invention is as follows: after the busbar 11 is fixed, the test fixture 16 is pushed horizontally. The busbar 11 and the test fixture 16 are on the same horizontal plane. The contact spring 14 on the short-circuit block 13 is pushed up and down by, for example, a cylinder or other pushing module, thereby contacting the contact areas 17 located on the busbar 11 and the test fixture 16 respectively. After the test fixture 16 is placed in the specified position, at least two short-circuit blocks 13 are squeezed vertically above and vertically below the busbar 11 and the test fixture 16 toward the middle, thereby placing the circuit loop in a parallel stack, so as to utilize the principle of electromagnetic coupling to reduce the stray inductance in the circuit loop.

[0048] According to a preferred embodiment, Figure 7 The stacked parallel stray inductance formula shown in FIG. 1 is shown in FIG. 2 . The present invention reduces stray inductance by minimizing loop length and minimizing parasitic inductance. The formula is:

[0049] L / m=μ×h / w

[0050] Where L is the stray inductance, μ is the coefficient, h is the stack spacing, m is the unit length, and w is the stack width.

[0051] Example 2

[0052] This embodiment is a further improvement and / or supplement to embodiment 1, and repeated contents are not repeated here. In the absence of conflict or contradiction, the whole and / or part of the preferred implementation manners of other embodiments can be used as a supplement to this embodiment.

[0053] The present invention provides a low-inductance connection structure and method between an IGBT device busbar and a dynamic test fixture, reducing stray inductance in the test loop. The present invention utilizes a parallel stack formed by two shorting blocks 13 and contact areas 17, allowing circuit loops to connect within the parallel stack. Furthermore, the current sensor Rogowski coil 12 is superimposed, shortening the current loop length. This reduces stray inductance by minimizing loop length, minimizing parasitic inductance, and minimizing stray magnetic fields.

[0054] like Figure 6As shown, a low-inductance connection structure between an IGBT device busbar and a dynamic test fixture includes at least a first contact area 171, a second contact area 172, a third contact area 173, and a fourth contact area 174. The first, second, third, and fourth contact areas 171, 172, 173, and 174 are bulk copper conductors. Preferably, testing an IGBT device requires only that the tester apply polarity to one of the first, second, third, and fourth contact areas 171, 172, 173, and 174, while simultaneously or sequentially applying the same and / or opposite polarity to at least one of the remaining contact areas. The IGBT device testing process involves: when applying polarity to any one contact area and simultaneously or sequentially applying the same and / or opposite polarity to at least one of the remaining contact areas, a processing module calculates the stray inductance between the resulting interlaced polarity test areas to minimize parasitic inductance and select a multi-operating-mode loop.

[0055] The first, second, third, and fourth contact regions 171, 172, 173, and 174 of the present invention form a mixed polarity test area based on polarity assignment and polarity conversion, providing multiple operating conditions and varying stray inductance impacts for IGBT device testing. Prior art half-bridge dual-pulse IGBT test circuits exist, but these circuits rely on frequent busbar and connection structure replacement to achieve multi-condition testing for IGBT dynamic parameter testing under multiple operating conditions. Frequent busbar replacement increases testing time and wear, leading to increased busbar wear. Therefore, these technical solutions rely on ensuring sufficient busbar copper or replacing the connection structure for multi-condition testing. The copper and connection structure are limiting test requirements. Therefore, while requiring multi-condition testing, this inevitably increases IGBT testing costs to a significant degree. This inability to meet the test conditions for multiple IGBT device testing simultaneously also results in significant cost penalties. Different from the technical solutions of the above-mentioned prior art, the present invention provides a solution for obtaining various working conditions for testing IGBTs based on changing the polarity of several contact areas, and changing the polarity of several contact areas can reduce the stray inductance of the additional circuit under any polarity condition and facilitate calculation. Since the method of changing the polarity of several contact areas is easy to implement, the test conditions of multiple working conditions no longer rely on replacing the busbar and / or connection structure. At the same time, the method of changing the polarity of several contact areas ensures the versatility of the structure to the greatest extent. Therefore, the present invention provides a solution that avoids the tediousness of replacing the busbar and / or connection structure caused by the need to perform multiple working condition tests on the basis of meeting the dynamic test requirements of IGBT devices, which is conducive to the universal testing of IGBT devices.

[0056] like Figure 6 As shown, the first contact area 171 and the second contact area 172 are spaced adjacent to each other on the busbar 11. The third contact area 173 and the fourth contact area 174 are spaced adjacent to each other on the test fixture 16. On an imaginary common plane, the first contact area 171 and the second contact area 172, together with the third contact area 173 spaced adjacent to the first contact area 171 and the fourth contact area 174 spaced adjacent to the second contact area 172 and the third contact area 173, form a test area with mixed polarity. Existing half-bridge dual-pulse IGBT test circuits use a technical solution that provides different busbars and test fixtures to test the IGBT under multiple operating conditions. This utilizes structural changes to obtain the dynamic parameters of the IGBT, resulting in the need for frequent replacement of the busbars and test fixtures. The main issues that increase costs are the operational performance of the replacement device and the wear and tear on the busbars and fixtures. In actual operation, testers are limited by the changes in the test circuit and stray inductance, making it difficult to achieve multiple dynamic tests on IGBTs through a single test operation. That is, due to the uncontrollable test circuit and stray inductance, when they want to test IGBTs under different working conditions, the test work cannot be carried out quickly and it is difficult to ensure the reliability and effectiveness of the test structure. Different from the technical solutions of the above-mentioned prior art, the present invention provides a solution for obtaining various operating conditions of testing IGBTs based on changing the polarity of several contact areas, wherein the first contact area 171, the second contact area 172, the third contact area 173 and the fourth contact area 174 set by the present invention are based on polarity giving and polarity conversion to form polarity mixed test areas, which provide operating conditions in several situations for the testing of IGBT devices and bring accurately calculable stray inductance, that is, the tester changes the test circuit by instantaneous switching of polarity during a single test, and changes the test circuit a second time by instantaneous switching again when the tester performs the next test. During this period, the stray inductances of the test circuit changed once and the test circuit changed twice are different but calculable, thereby ensuring the accuracy of the IGBT test.

[0057] Preferably, by presetting the feedback signal and the response of the polarity conversion object, when the tester completes the test operation under the test loop, one or more of the first contact area 171, the second contact area 172, the third contact area 173, and the fourth contact area 174 instantaneously switches polarity to obtain a changed test loop. The processing module transmits the first feedback signal to the display module based on the obtained changed test loop. The display module responds at the same time as receiving the first feedback signal, for example, by highlighting the polarity conversion object (i.e., the contact area with changed polarity). The tester can clearly understand the test loop corresponding to the polarity change based on the response of the polarity conversion object in the display module; based on the tester's active activation of the processing module, one or more of the first contact area 171, the second contact area 172, the third contact area 173, and the fourth contact area 174 instantaneously switches polarity again to obtain a second changed test loop. Based on the needs of the tester, the tester can decide the interval between the first change of the test loop and the second change of the test loop by the time of the active activation behavior. For example, the interval can be kept after the test loop can be tested several times, so as to obtain several sets of dynamic parameters that are sufficient to reflect the IGBT to be tested under the working conditions.

[0058] Preferably, a first shorting block is provided between the first contact region 171 and the third contact region 173, and a second shorting block is provided between the second contact region 172 and the fourth contact region 174, adjacent to the first shorting block. The first, second, third, and fourth contact regions 171, 172, 173, and 174 are arranged in a manner that is isolated from each other and coplanar. Preferably, the instantaneous switching of polarity of one or more of the first, second, third, and fourth contact regions 171, 172, 173, and 174 can be performed in a clock sequence. For example, under a first clock, the polarities of the first, second, third, and fourth contact regions 171, 172, 173, and 174 are: the first contact region 171 is positive, the second contact region 172 is negative, the third contact region 173 is positive, and the fourth contact region 174 is negative. In the next clock cycle, the polarities of first contact region 171, second contact region 172, third contact region 173, and fourth contact region 174 are: first contact region 171 is negative, second contact region 172 is positive, third contact region 173 is negative, and fourth contact region 174 is positive. This technical solution enables testers to perform periodic IGBT testing and monitor IGBT dynamic parameters under multiple operating conditions. It should be noted that a first shorting block is provided between first contact region 171 and third contact region 173, and a second shorting block is provided between second contact region 172 and fourth contact region 174 to connect the busbar to the test fixture.

[0059] Preferably, the stray inductance is calculated differently between contact areas of different polarities and different connections. Preferably, the processing module calculates the stray inductance based on polarity assignment and polarity conversion. For example, in the case of a first clock, the top layer of the first contact area 171 and the bottom layer of the first contact area 171 form a parallel stack, while the top layer of the third contact area 173 and the bottom layer of the third contact area 173 form a parallel stack. The stray inductance is calculated as follows:

[0060] L / m=μ×h / w

[0061] Where L is the stray inductance, μ is the coefficient, h is the stack spacing, m is the unit length, and w is the stack width. The stack spacing refers to the distance between the upper and lower shorting blocks or the upper and lower contact areas. The stack width refers to the width of the busbar, test fixture, or contact area. A conservative stack spacing (h) between the metal plate spacing and the parallel conductors (busbar 11 and / or test fixture 16) is approximately 1 / 10 the short-term dielectric strength of an FR-4 epoxy PCB. For example, the short-term dielectric breakdown of an FR-4 epoxy PCB is approximately 20 kV / mm, and the conservative operating rating is 2 kV / mm, which corresponds to a short-term dielectric breakdown spacing of 0.6 mm at 1.2 kV. The inductance of the above-mentioned geometric structure is a ratio of the upper length and is directly proportional to the stack spacing (h) and inversely proportional to the stack width (w). The stack spacing h refers to the distance between the upper and lower shorting blocks or the upper and lower contact areas, and the stack width w refers to the width of the shorting blocks or contact areas. For example, when w = 20 mm, h = 0.6 mm, and μ = 1.25667 nH / mm, substituting these into the above equation yields L / m (i.e., stray inductance per unit length) as 0.0377 nH / mm. The key factors influencing this are: 1. The smaller the stack spacing h, the smaller the stray inductance L; and 2. The wider the stack width w, the smaller the stray inductance L. Preferably, the processing module calculates the stray inductance between the first contact region 171 and the third contact region 173 and / or between the second contact region 172 and the fourth contact region 174 using the parallel stack formula before and after the test loop is modified.

[0062] Preferably, before and after the test loop is changed, the processing module further calculates the stray inductance between the first contact area 171 and the second contact area 172 and / or between the third contact area 173 and the fourth contact area 174 based on the coplanarity of the contact areas. The calculation of the stray inductance is as follows:

[0063]

[0064] Wherein, L is the stray inductance, μ is the coefficient, t is the coplanar spacing, m is the unit length, w′ is the contact area width, and cosh is the hyperbolic cosine function. The above-mentioned coplanar spacing refers to the spacing between the first contact area 171 and the second contact area 172 or between the third contact area 173 and the fourth contact area 174. The above-mentioned contact area width refers to the width of the longer side of the first contact area 171, the second contact area 172, the third contact area 173 or the fourth contact area 174, that is, the width of the contact area in the same direction as the coplanar spacing. For example, when w'=20mm, t=3mm (plane safety spacing) and μ=1.1828nH / mm, L / m (that is, the stray inductance per unit length) can be obtained from the above formula to be 0.2167nH / mm. The above-mentioned μ are all variable coefficients.

[0065] Preferably, the processing module accurately measures the dynamic parameters of the IGBT by solving for stray inductance using an optimized method based on at least four contact areas of different polarities and the above formula. Preferably, the processing module selects stacking calculation and / or coplanar calculation based on at least the polarity-converted test loop to obtain the stray inductance of the test loop after the polarity conversion. Preferably, the present invention also includes a storage module. The processing module and the storage module are connected via a wired or wireless connection. The storage module can be replaced by a remote server. The storage module is used to store information such as the test loop status, contact area polarity conversion, and test parameters related to the object under test. As described above, the present invention changes the test loop by assigning and converting polarity to multiple contact areas, and by employing different stray inductance calculation methods, accurately derives the dynamic parameters of the IGBT under test. The structure and method of the present invention, which utilizes changes in the test loop to complete IGBT testing under different operating conditions, are more adaptable than traditional IGBT test circuits and can be used for IGBT testing in various situations. It is a more universal test structure and is not susceptible to interference from stray inductance. It should be noted that while the present invention exemplarily proposes the use of at least four contact areas for polarity assignment and switching, this does not preclude the use of six, eight, or even more paired contact areas, employing a similar structure to simulate IGBT testing environments under various operating conditions. The present invention can form an even number of contact areas to enable multiple dynamic tests under different operating conditions during a single IGBT cycle, while also calculating the stray inductance for different test loops and polarities based on the aforementioned formula to improve the accuracy of test parameters. For example, when the first contact area 171 is the positive pole, the second contact area 172 is the positive pole, the third contact area 173 is the negative pole, and the fourth contact area 174 is the negative pole, the processing module first calculates the stray inductance of the first contact area 171 and the third contact area 173 and the second contact area 172 and the fourth contact area 174 through stacking, and then calculates the coplanarity and superimposes the stray inductance between the first contact area 171 and the second contact area 172 and between the third contact area 173 and the fourth contact area 174 to obtain the stray inductance of the entire connection structure for IGBT dynamic testing.

[0066] Example 3

[0067] This embodiment is a further improvement of Embodiment 1 and / or Embodiment 2, and repeated contents will not be repeated here.

[0068] Since the busbar 11, the test fixture 16, and the short-circuit block 13 need to be relatively fixed in space, there are cases where some alignment errors occur, which makes it impossible to form parallel stacks and even affects the test effect of the IGBT. Therefore, how to align the busbar 11, the test fixture 16, and the short-circuit block 13 in space is a problem that needs to be solved by the present invention. When aligning the busbar 11, the test fixture 16, and the short-circuit block 13, due to the small size of the devices and the narrow space, high-precision instruments are required to align and calibrate them. However, this can easily increase costs, and multiple alignments can easily cause damage to the IGBT.

[0069] According to a preferred embodiment, in order to ensure excellent test performance of the IGBT device connection structure of the present invention while solving the alignment of the busbar 11, the test fixture 16 and the shorting block 13, the present invention provides an alignment unit for performing precise alignment during use of the IGBT device connection structure.

[0070] According to a preferred embodiment, after the busbar 11 is placed, the image module of the alignment unit records the image of the busbar. Preferably, the image module completes the image recording in the positive projection direction at least from directly above and to the side of the busbar to obtain the spatial position of the busbar. Preferably, the processing module of the alignment unit obtains the positions of the supporting capacitor 1 and the absorption capacitor 2 from the recorded busbar image, and then uses the positions of the supporting capacitor 1 and the absorption capacitor 2 to form a grid to divide the busbar. After the division is completed, the position in the grid is the spatial position of the busbar. Preferably, the test fixture and the short-circuit block are moved into the grid, so that the assembled test fixture and the short-circuit block are aligned with the busbar in turn.

[0071] The present invention provides an IGBT device alignment method for aligning the connections between a busbar 11, a test fixture 16, and a shorting block 13. The alignment process at least includes precisely controlling the spatial positions of the busbar 11, the test fixture 16, and the shorting block 13. Preferably, the specific method for detecting the spatial positions of the busbar 11, the test fixture 16, and the shorting block 13 can be:

[0072] Using an imaging module to capture images of the busbar 11, the test fixture 16, and the shorting block 13;

[0073] Processing the image captured by the image module to obtain the plane where the busbar 11 is located and the projections of the test fixture 16 and the short-circuit block 13 on the plane;

[0074] Establish a rectangular coordinate system with the supporting capacitor 1 or the absorbing capacitor 2 of the busbar 11 as the origin and the absorbing capacitor 2 or the supporting capacitor 1 as the reference point;

[0075] The projections of the test fixture 16 and the shorting block 13 on the plane where the busbar 11 is located are placed in a rectangular coordinate system to determine the relative spatial positions of the busbar 11 , the test fixture 16 and the shorting block 13 .

[0076] According to a preferred embodiment, after the projections of the test fixture 16 and the short-circuit block 13 on the plane where the busbar 11 is located are placed in a rectangular coordinate system, it is possible to judge whether the test fixture 16 is on the same horizontal plane as the busbar 11, whether the test fixture 16 is spaced a preset distance from the busbar 11, whether the contact areas 11 on the test fixture 16 and the busbar 11 match each other, and whether the contact spring 14 on the short-circuit block 13 matches the contact areas 11 respectively, based on the distance between the projections, so as to adjust the spatial positions of the busbar 11, the test fixture 16 and the short-circuit block 13.

[0077] According to a preferred embodiment, when the projection does not match the fixed busbar 11, it indicates that the test fixture 16 and / or the short-circuit block 13 are not aligned with the busbar 11, and the position of the test fixture 16 and / or the short-circuit block 13 needs to be adjusted by, for example, a robotic arm; when the projection matches the fixed busbar 11, it indicates that the test fixture 16 and / or the short-circuit block 13 are aligned with the busbar 11, and the short-circuit block 13 can be pressed down toward the busbar 11 and the test fixture 16 to form a parallel stack. In particular, the pressing distance of at least two short-circuit blocks 13 can also be obtained from a rectangular coordinate system. It should be noted that the above-mentioned rectangular coordinate system includes at least three, namely, rectangular coordinate systems in three directions directly above the busbar and at least two adjacent sides.

[0078] According to a preferred embodiment, when the spatial position of the busbar 11, the test fixture 16 and the short-circuit block 13 is detected, the imaging module captures images of the busbar 11, the test fixture 16 and the short-circuit block 13 at a preset distance, and sends the captured images to a server or other device.

[0079] According to a preferred embodiment, the support capacitors 1 and the absorption capacitors 2, while forming the busbar, also form an easily identifiable origin and reference point on the image. Specifically, a straight line extending along the extension of the connection line formed by the support capacitors 1 and the absorption capacitors 2 forms a grid-like rectangular coordinate system for the busbar 11. This grid-like rectangular coordinate system is used to determine the spatial position of the busbar 11, the test fixture 16, and the shorting block 13.

[0080] According to a preferred embodiment, the processing module segments the busbar 11 image captured by the imaging module to serve as a reference for determining the spatial position of the test fixture 16 and the shorting block 13. Preferably, the processing module segments the busbar 11 image captured by the imaging module by quickly identifying a straight line connecting the support capacitor 1 as the origin and the absorption capacitor 2 as the reference point. Preferably, the processing module segments the busbar 11 image captured by the imaging module using the support capacitor 1 as the origin and the absorption capacitor 2 as the reference point to determine the spatial position of the busbar 11.

[0081] According to a preferred embodiment, the processing module can also segment the busbar 11 image in the following manner: That is, the processing module uses the rectangular edges of the busbar 11 as spatial features to segment the busbar 11 image into a grid-like rectangular coordinate system.

[0082] According to a preferred embodiment, the processing module places the images of the test fixture 16 and the shorting block 13 in a rectangular coordinate system based on the image shooting distance and the spatial position of the busbar 11, so as to determine the relative spatial positions of the test fixture 16 and the shorting block 13 and the busbar 11. Preferably, when placing the images of the test fixture 16 and the shorting block 13 in the rectangular coordinate system, it is necessary to ensure that the IGBT module on the test fixture 16 and the contact spring 14 of the shorting block 13 are simultaneously located in the rectangular coordinate system, thereby ensuring that the reference system of the test fixture 16 and the shorting block 13 coincides with the reference system of the busbar 11, and avoiding the test fixture 16 and the shorting block 13 from projecting too large on the plane, thereby affecting the judgment of their spatial positions and causing misjudgment.

[0083] According to a preferred embodiment, when placing the images of the test fixture 16 and the short-circuit block 13 in a rectangular coordinate system based on the image shooting distance and the spatial position of the busbar 11 to determine the relative spatial position of the test fixture 16 and the short-circuit block 13 to the busbar 11, the processing module judges the images of the test fixture 16 and the short-circuit block 13 at least twice, and the relative positions of the images of the test fixture 16 and the short-circuit block 13 to the rectangular coordinate system are different in the two judgments. Preferably, the images of the test fixture 16 and the short-circuit block 13 in the second judgment can be obtained by rotating the images in the first judgment by any angle. Preferably, the relative positional relationship among the busbar 11, the test fixture 16 and the short-circuit block 13 can be determined only when and only when the results of the two judgments match. When judging the relative positional relationship among the busbar 11, the test fixture 16 and the short-circuit block 13, the present invention establishes at least three rectangular coordinate systems in three directions directly above the busbar and on at least two adjacent sides, and each rectangular coordinate system is rotated at any angle for multiple judgments, thereby avoiding misjudgment caused by image coincidence errors, especially coincidence errors between the test fixture 16 and the short-circuit block 13.

[0084] According to a preferred embodiment, the processing module segments the busbar 11 image captured by the imaging module by quickly identifying a straight line connecting the support capacitor 1 as the origin and the absorption capacitor 2 as the reference point. Preferably, the processing module segments the image using the support capacitor 1 as the origin and the absorption capacitor 2 as the reference point to determine the spatial position of the busbar 11, thereby shortening image processing time. The misalignment relationship between images can be simply and clearly displayed through a grid, and the spatial position relationship can be grasped and position alignment can be performed without further distance detection.

[0085] The stacking of the busbar 11, the test fixture 16 and the short-circuit block 13 obviously requires high precision. Compared with other docking methods, the present invention completes the docking work by establishing a grid-type rectangular coordinate system. The low precision of the docking will constitute a risk event of IGBT failure in future dynamic tests of IGBT, especially in half-bridge tests. In particular, for the upper bridge IGBT under test and the lower bridge IGBT under test, the risk cannot be ignored. In order to ensure the high precision of alignment, the present invention introduces an alignment unit to achieve improvements to the three, and uses the support capacitor 1, the absorption capacitor 2 and the outer contour of the busbar 11 on the busbar 11 as the calibration of the rectangular coordinate system, thereby achieving high-precision alignment. The regular arrangement of the support capacitor 1, the absorption capacitor 2 and the outer contour of the busbar 11 creates a high-precision alignment work for the alignment unit, and the regularity gives the rectangular coordinate system a reference object. Based on this, after receiving relevant knowledge training, the user can effectively use the alignment unit to connect the busbar 11, the test fixture 16 and the short-circuit block 13. It is feasible to use a graphic detection method to determine the spatial position for alignment, and its alignment accuracy is significantly improved. The network-type rectangular coordinate system also reduces the required accuracy of the graphics. For example, a 1080P resolution is sufficient to confirm the positional relationship between the busbar 11, the test fixture 16 and the short-circuit block 13; and for smaller connection structures, 4K and above resolutions are also sufficient for this high-precision alignment work. This embodiment improves an alignment method for an IGBT device connection structure, which can specifically be a method for determining the spatial position using a graphic recognition method.

[0086] The present invention solves the image distortion problem caused by the image module, including pincushion distortion, etc., through a number of rectangular coordinate systems and multiple judgment processes for each rectangular coordinate system. Image distortion can easily cause a large projection error in the grid-type rectangular coordinate system, and its error may even affect the projection deviation caused by the position deviation of the busbar 11, the test fixture 16, and the short-circuit block 13. Therefore, the present invention solves the image distortion problem with the help of a number of rectangular coordinate systems and multiple judgment processes for each rectangular coordinate system. That is to say, in an embodiment of the present invention, not only is the rectangular coordinate system aligned for the busbar 11, the test fixture 16, and the short-circuit block 13, but the image distortion problem is also solved based on the limitations of several judgments to provide a more efficient and more convenient alignment process. It should be noted that the above-mentioned image distortion is not only used in the embodiment of the present invention, but also in other situations, such as when the human eye judges whether it is aligned or not, there is also an image distortion problem, which results in the low precision of the traditional alignment method.

[0087] Throughout the text, the features referred to as “preferably” are merely optional and should not be understood as having to be set. Therefore, the applicant reserves the right to abandon or delete the relevant preferred features at any time.

[0088] It should be noted that the above-mentioned specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also fall within the scope of the disclosure of the present invention and fall within the scope of protection of the present invention. Those skilled in the art should understand that the present invention specification and its drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The present invention specification contains multiple inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", which means that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application based on each inventive concept.

Claims

1. An IGBT device busbar connection structure, characterized in that: The connection structure comprises two upper and lower short-circuit blocks (13) and four contact springs (14) arranged separately from each other for connecting the short-circuit blocks (13); The two contact springs (14) on the upper and lower short-circuit blocks (13) are respectively fitted to the busbar (11) and the test fixture (16) to reduce or isolate the stray inductance in the connection structure; The circuit loop formed by the busbar (11) and the test fixture (16) is connected in parallel stacking under the contact spring (14), and the busbar (11) and the test fixture (16) are respectively provided with a contact area (17) matching the contact spring (14); wherein, The four contact areas (17) and the four contact springs (14) form the parallel stack in a manner of respectively clamping the busbar (11) and the test fixture (16) on both sides in the vertical direction. The parallel stack is compositely formed by an upper short-circuit block as a first layer, a second layer consisting of the busbar (11) and the test fixture (16), and a lower short-circuit block as a third layer.

2. The IGBT device busbar connection structure according to claim 1, characterized in that: The two contact springs (14) on each of the upper and lower short-circuit blocks (13) are separated, and an insulating sheet (18) is provided in the middle for preventing breakdown between the two short-circuit blocks (13).

3. The IGBT device busbar connection structure according to claim 2, characterized in that: The contact section between the short-circuit block (13) and the insulating sheet (18) is provided with a coil (12) for shortening the length of the current loop.

4. The IGBT device busbar connection structure according to claim 1, characterized in that: The structure further comprises a supporting capacitor (1) and an absorption capacitor (2), wherein: The supporting capacitor (1) and the absorption capacitor (2) constitute the busbar (11) for providing energy required for dynamic testing of the connection structure at different voltages.

5. The IGBT device busbar connection structure according to claim 1, characterized in that: The test fixture (16) is provided with two IGBT modules; wherein, the test fixture (16) is also provided with a high voltage resistance layer (15).

6. The IGBT device busbar connection structure according to claim 5, characterized in that: The IGBT module comprises an upper bridge IGBT module (4) to be tested and a lower bridge IGBT module (5) to be tested, wherein: The upper bridge IGBT module (4) under test and the lower bridge IGBT module (5) under test utilize inductor self-inductance to detect switching parameters of the lower bridge IGBT module (5) under test and reverse recovery characteristics of the upper bridge IGBT module (4) under test during the opening and closing phases of the connection structure.

7. The IGBT device busbar connection structure according to claim 1, characterized in that: The contact spring (14) between the busbar (11) and the test fixture (16) reduces the stray inductance in the circuit loop in the form of stacked parallel stray inductance, wherein the formula is: L / m=μ×h / w; Where L is the stray inductance, μ is the inductance, h is the stacking distance, m is the unit length, and w is the stacking width.

8. A connection method for the IGBT device busbar connection structure according to any one of claims 1 to 7, characterized in that: The method comprises: The two contact springs (14) on the upper and lower short-circuit blocks (13) are respectively fitted to the busbar (11) and the test fixture (16) to reduce or isolate the stray inductance in the connection structure; The circuit loop formed by the busbar (11) and the test fixture (16) is connected in parallel layers under the contact of the contact spring (14).

Images