A pressure welding tool for power module and welding process thereof

Abstract

The present invention provides a pressure welding tool for a power module and a welding process thereof, and relates to the field of power semiconductor technology. The power module includes an AMB ceramic copper-clad liner, a welding piece and a heat dissipation copper substrate. The tool includes a pressure plate jig, the pressure plate jig includes a jig body, a first mounting cavity is arranged on one side of the jig body, a welding jig is arranged in the first mounting cavity, the welding jig includes a jig body, a limiting pressure block is arranged on one side of the welding jig, a second mounting cavity is arranged on one side of the limiting pressure block, the AMB ceramic copper-clad liner and the welding piece are arranged in the second mounting cavity, the heat dissipation copper substrate is stacked and arranged on one side of the welding piece, an arc is arranged on one side of the heat dissipation copper substrate, a heat conduction jig includes a copper bottom plate, a third mounting cavity is arranged in the middle of the copper bottom plate, and a heat dissipation copper substrate is arranged in the third mounting cavity. The present invention naturally fits the heat conduction jig with the heat dissipation copper substrate, so that the product welding surface is heated more evenly, the melting and distribution of the welding piece are controlled to be symmetrical, and the stress warping of the AMB ceramic copper-clad liner during the welding stage is controlled.

Description

Technical Field

[0001] The invention relates to the technical field of power semiconductors, and in particular to a pressure welding tool for a power module and a welding process thereof. Background Art

[0002] With the continuous development of third-generation semiconductor technology, the demand for packaging materials for high-power IGBT modules is also increasing. The AMB process technology of aluminum nitride and silicon nitride ceramics combined with oxygen-free copper sheets has gradually become the mainstream. This technology not only increases the thermal conductivity and interlayer adhesion, but also improves the overall reliability of the product. Therefore, this ceramic substrate shows significant advantages in high-power and high-current application scenarios, and has gradually become the preferred choice for heat dissipation circuit boards for mid-to-high-end IGBT modules.

[0003] The characteristics of AMB ceramic copper clad liner have caused major challenges to stability in traditional packaging technology. In the conventional DCB welding process, AMB ceramic copper clad liner is used for welding. The material characteristics of AMB ceramic copper clad liner lead to welding delamination, significantly reduced void yield, uneven distribution of solder on the welding surface, and also lead to the defect of inconsistent height of the circuit surface of AMB ceramic copper clad liner. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a pressure welding tool for a power module and a welding process thereof, so as to improve the product yield stability of AMB materials and the uniformity of solder distribution between the welding surfaces of the AMB ceramic copper-clad liner and the heat dissipation copper substrate.

[0005] The technical solution adopted by the present invention is:

[0006] A pressure welding tool for a power module, wherein the power module comprises an AMB ceramic copper-clad liner, a welding sheet and a heat dissipation copper substrate, and the pressure welding tool for the power module comprises:

[0007] A pressing plate jig, the pressing plate jig comprising a first jig body, positioning holes are arranged around the first jig body, and a first mounting cavity is arranged on a side surface of the first jig body;

[0008] A welding jig, the welding jig is arranged in the first installation cavity, the welding jig comprises a second jig body, a limiting pressure block is arranged on a side of the second jig body away from the first installation cavity, and a second installation cavity is arranged on a side of the limiting pressure block away from the second jig body;

[0009] The AMB ceramic copper-clad liner is arranged in the second installation cavity, and a circuit pattern is arranged on a side of the AMB ceramic copper-clad liner close to the second installation cavity;

[0010] The welding sheet is arranged in the second mounting cavity and is stacked with the AMB ceramic copper-clad liner;

[0011] The heat dissipation copper substrate is stacked and arranged on the side of the welding piece away from the AMB ceramic copper-clad liner, and the side of the heat dissipation copper substrate away from the welding piece is provided with an arc;

[0012] A heat-conducting fixture, the heat-conducting fixture comprises a copper base plate, the copper base plate is provided with positioning locking pieces at positions corresponding to the positioning holes, the positioning locking pieces are plugged into the positioning holes provided corresponding thereto, a third mounting cavity with a matching shape is provided in the middle of the copper base plate at a position corresponding to the heat-dissipating copper substrate, a heat-dissipating copper substrate is provided in the third mounting cavity, and the heat-dissipating copper substrate has a curved side close to the third mounting cavity.

[0013] Preferably, the pressure welding tooling of the power module is described, wherein the pressure plate jig comprises a first jig body, and jig code plate mounting grooves are arranged at both ends of a side of the first jig body away from the first mounting cavity, and four groups of matching hole assemblies are arranged on the first jig body between the two jig code plate mounting grooves, and the four groups of matching hole assemblies are arranged in pairs on the upper and lower sides of the first jig body, and the two groups of matching hole assemblies on the upper and lower sides are mirror-symmetrical about the central axis of the first jig body, and each group of matching hole assemblies includes a plurality of matching holes, and a plurality of reserved pressure pins arranged at intervals are arranged on the first jig body between the four groups of matching hole assemblies, and four corner pressure pins are arranged around both sides of the reserved pressure pins, and a first compression spring is sleeved on the side of the four corner pressure pins close to the first mounting cavity.

[0014] Preferably, the pressure welding fixture of the power module is provided with flexible switches on both side walls of the first fixture body, the flexible switch comprises an extension section, a first connecting section and a second connecting section, the first connecting section and the second connecting section are respectively provided at both ends of the extension section, the extension section extends to the side of the first fixture body away from the first mounting cavity, the first connecting section and the second connecting section are fixed to the two side walls of the first fixture body through mounting columns, a connecting column is provided in the middle of the first connecting section and the second connecting section perpendicular to the side of the first fixture body, a first groove is provided on the first fixture body corresponding to the position of each connecting column, the connecting column extends into the first groove, a spring is sleeved on the connecting column, the other end of the spring is connected to the inner wall of the first groove, a second groove is provided at the position of the first fixture body corresponding to the extension section, and the flexible switch moves left and right through the action of the spring.

[0015] Preferably, the pressure welding tooling of the power module is provided with a plurality of fixed columns arranged at intervals on the side of the second jig body close to the first installation cavity, the fixed columns penetrate the second jig body and extend to the side of the second jig body away from the first installation cavity, a guide column is provided on the bottom surface of the second jig body between two adjacent fixed columns, a fixing hole is provided on the limiting pressure block corresponding to the position of each of the fixed columns, the fixing hole is plug-matched with the fixed column arranged corresponding thereto, a guide hole is provided on the limiting pressure block corresponding to the position of each of the guide columns, the guide hole is matched with the guide column arranged corresponding thereto; a circuit pattern is provided on the side of the AMB ceramic copper-clad liner close to the second installation cavity; a pressure pin lower pressure groove is provided on the second jig body corresponding to the position of each of the four corner pressure pins, and the four corner pressure pins are matched with the pressure pin lower pressure groove arranged corresponding thereto.

[0016] Preferably, the power module has a pressure welding tool, wherein flexible compression spring columns are further arranged around the second fixture body, compression spring grooves are arranged on the limiting pressure block at positions corresponding to the positions of the flexible compression spring columns, the number of the flexible compression spring columns is consistent with the number of the compression spring grooves and are plugged in one-to-one, and a second compression spring is arranged on the side of the flexible compression spring column and the fixed column close to the limiting pressure block.

[0017] Preferably, in the pressure welding tooling of the power module, mounting holes are arranged on the heat dissipation copper substrate, and positioning columns are arranged around one side of the second fixture body close to the limiting pressure block at positions corresponding to the mounting holes, and the positioning columns cooperate with the mounting holes arranged correspondingly thereto.

[0018] Preferably, the pressure welding tooling of the power module is such that the shape of the limiting pressure block is a rectangular frame structure, a connecting piece is arranged in the middle of the rectangular block along the width direction, and avoidance slopes are arranged on the limiting pressure blocks on both sides of the connecting piece, and the slope of the avoidance slope is 20-40°, and the connecting piece divides the second mounting cavity into two mounting cavities, and AMB ceramic copper-clad lining plates and welding sheets are sequentially stacked in each mounting cavity, and a jig QR code encoding area is arranged at both ends of the side of the second jig body away from the limiting pressure block.

[0019] Preferably, the pressure welding tooling of the power module is described, wherein anti-fool pins are provided at positions corresponding to the matching holes on the copper base plate, the anti-fool pins are plug-fitted with the matching holes arranged corresponding thereto, and locking notches are provided on the side walls of the positioning lock fasteners; positioning grooves are provided around the side of the copper base plate away from the third mounting cavity, the middle part of the upper end of the heat dissipating copper base plate protrudes upward, and the positions of the third mounting cavity corresponding to the upward protrusions of the heat dissipating copper base plate are both recessed upward, and the curvatures of the heat dissipating copper base plate and the third mounting cavity are both 0.4-0.7°.

[0020] The present invention also provides a welding process for a pressure welding tool applied to a power module, comprising the following steps:

[0021] Step S1. Place the first mounting cavity of the pressing plate fixture upward on the operating table;

[0022] Step S2. Install the limit pressing block onto the second fixture body, then place the welding fixture with the limit pressing block facing upward into the first installation cavity of the pressure plate fixture, and press the four corner pressing pins down into the pressing pin pressing grooves;

[0023] Step S3. Place the AMB ceramic copper-clad liner with the circuit pattern on the side facing downward in the second mounting cavity;

[0024] Step S4. placing the solder sheet in the second mounting cavity and stacking it with the AMB ceramic copper-clad liner;

[0025] Step S5. The heat dissipation copper substrate is stacked with the raised surface facing upward on the side of the soldering piece away from the AMB ceramic copper-clad liner, and the mounting holes and the positioning columns are correspondingly plugged;

[0026] Step S6. Place the upwardly protruding side of the heat dissipation copper substrate in the third installation cavity of the heat conductive fixture, insert the foolproof pin of the heat conductive fixture into the matching hole, and then insert the positioning lock fastener downward into the positioning hole and press it tightly, and finally lock it with a flexible switch to obtain an assembled welding fixture assembly;

[0027] Step S7. Insert the positioning lock fastener of the heat-conducting fixture downward into the positioning hole and press it tightly, and then lock it through the flexible switch to obtain an assembled welding fixture assembly;

[0028] Step S8. After the product is welded, take out the welding jig assembly from the equipment welding carrier, open the flexible switches on both sides of the pressure plate jig, take out the thermal conductive jig, and obtain the power module.

[0029] Preferably, in the welding process, the welding parameters in step S6 are: the heating rate in the welding heating stage is 1-3°C / s, when the temperature of the welding cavity reaches 205-215°C, the cavity of the welding equipment is evacuated to <5mbar, the cavity of the welding equipment begins to be filled with formic acid with a purity of ≥97% until the pressure reaches 550-650mbar, and then the oxide on the surface of the welding material is reduced, and the reduction treatment time is 60-90s; thereafter, the welding equipment continues to heat up to a maximum temperature that is 20-30°C higher than the melting point of the solder, and after the welding reaches the maximum temperature, the welding equipment is evacuated to <10mbar to degas the welding layer, and the vacuum pressure is maintained for 60-90s during the degassing treatment, and then the pressure is released, and the pressure release rate is 40-60mbar / s, and the temperature is lowered after the welding is completed, and the cooling rate is 1-3°C / s.

[0030] Advantages of the present invention:

[0031] The pressurized welding fixture of the power module of the present invention is provided with a third mounting cavity of a shape matching at a position corresponding to the heat dissipation copper substrate in the middle of the heat conductive jig, and the heat dissipation copper substrate is provided in the third mounting cavity, and the heat dissipation copper substrate has an arc side close to the third mounting cavity, so that the heat conductive jig and the heat dissipation copper substrate can be naturally fitted together, so that the heating of the product welding surface can be more uniform, and the melting and distribution of the welding piece can be controlled symmetrically; by providing flexible switches on both side walls of the jig body, the AMB ceramic copper clad liner can be limited in all directions at the beginning of product assembly, so that the AMB ceramic copper clad liner and the heat dissipation copper substrate can be closely fitted from normal temperature to high temperature, and the stress warping of the AMB ceramic copper clad liner in the high temperature welding stage can be effectively controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the pressing plate fixture of the present invention.

[0033] Figure 2 It is a cross-sectional view of the pressing plate jig of the present invention.

[0034] Figure 3 It is a structural schematic diagram of the welding jig of the present invention.

[0035] Figure 4 It is a cross-sectional view of the welding jig of the present invention.

[0036] Figure 5 It is a schematic structural diagram of the position limiting pressing block of the present invention.

[0037] Figure 6 It is a schematic structural diagram of the heat-conducting fixture of the present invention.

[0038] Figure 7 It is a cross-sectional view of the heat-conducting fixture of the present invention.

[0039] Figure 8 This is an exploded view of the welding jig assembly of the present invention before assembly.

[0040] Fig. 9 It is a schematic diagram of the structure of the welding jig assembly of the present invention after assembly.

[0041] Fig.10 It is a schematic structural diagram of a power module with a pressure welding fixture after the flexible switch is locked in a locking notch.

[0042] Fig.11 For the present invention Fig.10 Cross-sectional view of .

[0043] Fig.12 This is a welding process diagram of the pressure welding tooling of the power module of the present invention.

[0044] Fig.13 A microscope image of an AMB ceramic copper-clad liner of a power module in the prior art.

[0045] Fig.14 This is a microscope image of the AMB ceramic copper-clad liner of the power module of Example 2.

[0046] Fig.15 A visual diagram of a power module of the prior art.

[0047] Fig.16 This is a visual picture of the power module of Example 2.

[0048] Fig.17 This is an X-ray image of the AMB ceramic copper-clad liner in the power module of the prior art.

[0049] Fig.18 This is an X-ray image of the AMB ceramic copper-clad liner in the power module of Example 2.

[0050] Fig.19 This is a graph showing the IMC growth test of the power module of Example 2.

[0051] Fig. 20 for Fig.19 Local IMC growth test diagram. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with specific embodiments.

[0053] Example 1

[0054] like Figure 1-Figure 11 A pressure welding tool for a power module, the power module includes an AMB ceramic copper-clad liner 3, a welding piece 4 and a heat dissipation copper substrate 5, and the pressure welding tool for the power module includes:

[0055] A pressing plate fixture 1, the pressing plate fixture 1 comprises a first fixture body 11, positioning holes 12 are arranged around the first fixture body 11, and a first installation cavity 18 is arranged on a side surface of the first fixture body 11;

[0056] A welding jig 2, the welding jig 2 is arranged in the first mounting cavity 18, the welding jig 2 comprises a second jig body 21, a limiting pressing block 24 is arranged on a side of the second jig body 21 away from the first mounting cavity 18, and a second mounting cavity 25 is arranged on a side of the limiting pressing block 24 away from the second jig body 21;

[0057] The AMB ceramic copper-clad liner 3 is disposed in the second installation cavity 25, and a circuit pattern is disposed on one side of the AMB ceramic copper-clad liner 3 close to the second installation cavity 25;

[0058] The welding piece 4 is arranged in the second installation cavity 25 and is stacked with the AMB ceramic copper-clad liner 3;

[0059] The heat dissipation copper substrate 5 is stacked and arranged on the side of the welding piece 4 away from the AMB ceramic copper-clad liner 3, and the side of the heat dissipation copper substrate 5 away from the welding piece 4 is provided with an arc;

[0060] The heat-conducting fixture 6 includes a copper base plate 61, and the copper base plate 61 is provided with positioning locking pieces 62 corresponding to the positions of the positioning holes 12. The positioning locking pieces 62 are plugged into the positioning holes 12 corresponding thereto. A third mounting cavity 64 is provided in the middle of the copper base plate 61, and the heat-dissipating copper substrate 5 has an arc-shaped side facing away from the welding piece 4 and is provided in the third mounting cavity 64.

[0061] The pressure plate jig 1 includes a first jig body 11, and the first jig body 11 is away from the first installation cavity 18. The pressure plate jig 1 includes jig code plate installation grooves 13 at both ends of the first jig body 11 away from the first installation cavity 18, and four groups of matching hole assemblies are arranged on the first jig body 11 between the two jig code plate installation grooves 13. The four groups of matching hole assemblies are arranged in pairs on the upper and lower sides of the first jig body 11, and the two groups of matching hole assemblies on the upper and lower sides are mirror-symmetrical about the central axis of the first jig body 11. Each group of matching hole assemblies includes a plurality of matching holes 14, and a plurality of reserved pressure pins 15 arranged at intervals are arranged on the first jig body 11 between the four groups of matching hole assemblies. Four corner pressure pins 16 are arranged around the two sides of the reserved pressure pins 15, and a first compression spring 19 is sleeved on the side of the four corner pressure pins 16 close to the first installation cavity 18.

[0062] A flexible switch 17 is arranged on both side walls of the first fixture body 11, and the flexible switch 17 includes an extension section 171, a first connecting section 172 and a second connecting section 173. The first connecting section 172 and the second connecting section 173 are arranged at both ends of the extension section 171, and the extension section extends to the side of the first fixture body 11 away from the first installation cavity 18. The first connecting section 172 and the second connecting section 173 are fixed to the two side walls of the first fixture body 11 through the installation column 20. A connecting column 174 is arranged perpendicular to the side of the first fixture body 11 between the first connecting section 172 and the second connecting section 173. A first groove is arranged on the first fixture body 11 at a position corresponding to each of the connecting columns. The connecting column 174 extends into the first groove. A spring 175 is sleeved on the connecting column, and the other end of the spring is connected to the inner wall of the groove. A second groove 176 is arranged at a position corresponding to the extension section of the first fixture body 11, and the flexible switch 17 can move left and right through the action of the spring.

[0063] A plurality of fixed columns 22 arranged at intervals are provided on one side of the second jig body 21 close to the first mounting cavity 18. The fixed columns 22 penetrate the second jig body 21 and extend to the side of the second jig body 21 away from the first mounting cavity 18. A guide column 23 is provided on the bottom surface of the second jig body 21 between two adjacent fixed columns 22. A limiting pressure block 24 is provided on the side of the second jig body 21 away from the first mounting cavity 18. A second mounting cavity 25 is provided on the side of the limiting pressure block 24 away from the second jig body 21. Fixed holes are provided on the limiting pressure block 24 corresponding to the positions of the fixed columns 22. The fixed holes are plug-matched with the corresponding fixed columns 22. Guide holes are provided on the limiting pressure block 24 corresponding to the positions of the guide columns 23. The guide holes are matched with the corresponding guide columns 23. A pressing pin lowering groove 26 is provided on the second jig body 21 corresponding to the positions of the four-corner pressing pins 16. The four-corner pressing pins 16 are matched with the pressing pin lowering groove 26.

[0064] When assembling the matching hole 14 with the thermal conductive fixture, the anti-mistake pin 63 is used. After direct verification, the position of the matching hole 14 is uniformly matched. If the matching is wrong during the production process, it cannot be assembled normally. The fixture code plate installation slot 13 is the fixture code plate installation area, which is convenient for equipment code scanning and fixture maintenance management after assembly. The mounting column 20 is a locking structure mounting column. The reserved pressure pin 15 is reserved for pressure pins for special products. Pressure pins can be added to perform pressure point welding on the center area of ​​the AMB ceramic copper-clad lining board. The flexible switch 17 is a flexible switch that is demolded after welding.

[0065] Flexible compression spring columns 27 are also arranged around the second fixture body 21, and compression spring grooves are arranged on the limiting pressure block 24 at positions corresponding to the positions of the flexible compression spring columns 27. The number of the flexible compression spring columns 27 is consistent with the number of the compression spring grooves and they are plugged in one by one. A second compression spring 28 is arranged on the side of the flexible compression spring column 27 and the fixed column 22 close to the limiting pressure block 24.

[0066] The heat dissipation copper substrate 5 is provided with mounting holes 51 , and positioning posts 29 are provided around one side of the second fixture body 21 close to the limiting pressure block 24 at positions corresponding to the mounting holes 51 , and the positioning posts 29 cooperate with the mounting holes 51 provided corresponding thereto.

[0067] The shape of the limiting pressure block 24 is a rectangular frame structure, a connecting piece 30 is arranged in the middle of the rectangular parallelepiped along the width direction, and avoidance slopes 31 are arranged on the limiting pressure blocks 24 on both sides of the connecting piece 30, and the slope of the avoidance slope 31 is 20-40°. The connecting piece 30 divides the second installation cavity 25 into two installation cavities, and an AMB ceramic copper-clad lining plate 3 and a welding sheet 4 are stacked in sequence in each installation cavity. A fixture two-dimensional code encoding area 32 is arranged at both ends of the side of the second fixture body 21 away from the limiting pressure block 24.

[0068] The two-dimensional code encoding area 32 of the jig is convenient for the production system to scan and record traceability. The pressure pin pressing groove 26 applies pressure evenly at the four corners of the second jig body 21 through the four-corner pressure pins 16 to ensure the flatness of the jig. The flexible compression spring column 27 enables the limit pressure block to ensure a certain flexible pressure during operation, so that the AMB ceramic copper-clad lining plate 3 and the welding piece and the heat dissipation copper substrate fit closely; the guide column 23 is used to ensure that the position of the limit pressure block under pressure in the vertical direction is within the control range; the avoidance slope 31 prevents the second jig body 21 from pressing down the arc, resulting in the limit pressure block pressing down and colliding and failing to press to the bottom, thereby causing the AMB ceramic copper-clad lining plate 3 to fail in suspension, and the avoidance slope 31 improves the plane flatness of the second jig body 21 and the limit pressure block, thereby further ensuring the matching degree of the AMB ceramic copper-clad lining plate 3 and the second mounting cavity 25 in the limit pressure block; the positioning column 29 cooperates with the mounting hole 51 to ensure that the position of the AMB ceramic copper-clad lining plate 3 on the heat dissipation copper substrate 5 during the welding process is within the process control range.

[0069] Anti-foolproof pins 63 are arranged at positions corresponding to the matching holes 14 on the copper bottom plate 61, and the anti-foolproof pins 63 are plugged into and matched with the matching holes 14 arranged corresponding thereto, and locking notches 65 are arranged on the side walls of the positioning lock fastener 62; positioning grooves 66 are arranged around the side of the copper bottom plate 61 away from the third mounting cavity 64; the middle part of the upper end of the heat dissipating copper substrate 5 is convex upward, and the third mounting cavity 64 is concave upward corresponding to the upward convex position of the heat dissipating copper substrate 5, and the curvature of the heat dissipating copper substrate 5 and the third mounting cavity 64 are both 0.4-0.7°.

[0070] The copper bottom plate 61 ensures the thermal conductivity of the heat-conducting jig and improves the efficiency of the welding process. Because the product structures are different, it is necessary to distinguish the welding jigs. By setting the anti-fool pin 63, it is prevented that the jigs are mixed in batches and used incorrectly, resulting in product scrapping; the third installation cavity 64 is the contact surface between the heat-conducting jig 6 and the heat-dissipating copper substrate 5. The third installation cavity 64 is provided with an arc surface structure with the same arc as the heat-dissipating copper substrate 5 to ensure that the contact surface of the copper substrate can be evenly heated when the product is welded.

[0071] Example 2

[0072] like Figure 1-Figure 12 A welding process of a power module with a pressure welding tool comprises the following steps:

[0073] Step S1. Place the first mounting cavity 18 of the pressing plate fixture 1 upward on the operating table;

[0074] Step S2. Install the limit pressing block 24 on the second fixture body 21, and then place the welding fixture 2 with the limit pressing block 24 facing upward in the first installation cavity 18 of the pressure plate fixture, and press the four corner pressing pins 16 down into the pressing pin pressing groove 26;

[0075] Step S3. Place the AMB ceramic copper-clad liner 3 with the side provided with the circuit pattern facing downward in the second mounting cavity 25;

[0076] Step S4. Place the soldering sheet 4 in a stacked manner in the second mounting cavity 25 and stack it with the AMB ceramic copper-clad liner 3;

[0077] Step S5. The heat dissipation copper substrate 5 is stacked with the raised surface facing upward on the side of the soldering piece 4 away from the AMB ceramic copper-clad liner 3, and the mounting holes 51 and the positioning columns 29 are correspondingly plugged;

[0078] Step S6. Place the upwardly protruding side of the heat dissipation copper substrate 5 in the third installation cavity 64 of the heat conductive fixture 6, insert the foolproof pin 63 of the heat conductive fixture 6 into the matching hole 14, and then insert the positioning lock fastener 62 downward into the positioning hole 12 and press it tightly, and finally lock it through the flexible switch 17 to obtain the assembled welding fixture assembly;

[0079] Step S7. Install the welding fixture assembly onto the welding equipment for welding, and the welding parameters are: the heating rate in the welding heating stage is 2°C / s, when the temperature of the welding cavity reaches 210°C, the welding equipment cavity is evacuated to <5mbar, and the welding equipment cavity begins to be filled with formic acid with a purity of ≥97% until the pressure reaches 600mbar, and then the oxide on the surface of the welding material is reduced, and the reduction treatment time is 60s; thereafter, the welding equipment continues to heat up to a maximum temperature that is 25°C higher than the melting point of the solder. After the welding reaches the maximum temperature, the welding equipment is evacuated to <10mbar to degas the welding layer. During the degassing treatment, the vacuum pressure is maintained for 80s, and then the pressure is released at a rate of 50mbar / s. After the welding is completed, the temperature is lowered at a rate of 2°C / s.

[0080] Step S8. After the product is welded, take out the welding jig assembly from the equipment welding carrier, open the flexible switches 17 on both sides of the pressure plate jig 1, take out the thermal conductive jig 6, and obtain the power module.

[0081] Fig.13 A microscope image of an AMB ceramic copper-clad liner of a power module in the prior art; Fig.14It is a microscope image of the AMB ceramic copper-clad liner of the power module of Example 2, a and b are two AMB ceramic copper-clad liner in the power module; Fig.15 A visual diagram of a power module of the prior art; Fig.16 It is a visual inspection picture of the power module of Example 2, a and b are two AMB ceramic copper-clad lining boards in the power module; Fig.17 It is an X-ray image of the AMB ceramic copper-clad liner in the power module of the prior art, a and b are two AMB ceramic copper-clad liner in the power module; Fig.18 : is an X-ray image of the AMB ceramic copper-clad liner in the power module of Example 2, a and b are two AMB ceramic copper-clad liner in the power module; Fig.19 This is an IMC growth test diagram of the power module of Example 2; Fig. 20 for Fig.19 The local IMC growth test diagram, where Fig.19 7 is a chip, 8 is a solder layer, 9 and 11 are copper layers of the AMB ceramic copper-clad liner, 10 is a ceramic layer of the AMB ceramic copper-clad liner, Fig. 20 8 is the solder layer, and 9 is the copper layer of the AMB ceramic copper-clad liner.

[0082] from Fig.13 and Fig.15 It can be concluded that the solder on the welding surface of the AMB ceramic copper-clad liner and the heat dissipation copper substrate is uneven, and the solder distribution is not thin at both ends of the module and thick in the middle. The uneven solder distribution on the welding surface also leads to inconsistent height of the circuit surface of the AMB ceramic copper-clad liner; Fig.17 It can be concluded that after the AMB ceramic copper clad liner is welded using traditional welding tooling, the solder uniformity of the welding surface between the AMB ceramic copper clad liner and the heat dissipation copper substrate deteriorates, the finishing void rate exceeds the standard, and the welding results do not meet the process requirements.

[0083] from Fig.14 and Fig.16 It can be concluded that the solder on the welding surface of the AMB copper-clad liner is evenly distributed, and the side of the AMB ceramic copper-clad liner 3 with the circuit pattern has no staggered layers. Fig.18 It can be concluded that after the sample was tested by X-ray equipment, no holes were found on the welding surface of the material, and the hole rate was greatly reduced; in the prior art, the IMC size of the solder layer is required to be less than 10μm. Fig.19 and Fig. 20 It can be concluded that the IMC size of the solder layer is between 2.41-3.75 μm, the IMC of the solder layer grows uniformly, and the welding process meets the product design specifications and process requirements.

[0084] The present invention uses a welding jig to locate the welding position of the AMB ceramic copper-clad lining board, and the flexible switch applies uniform pressure to the four sides of the AMB ceramic copper-clad lining board, so that the AMB ceramic copper-clad lining board is tightly fitted with the curved heat-dissipating copper substrate at the beginning of assembly, and the second installation cavity limits the height of the AMB ceramic copper-clad lining board, so that after the welding piece is melted, the secondary distribution of the solder can be more uniform, so as to achieve the best welding effect.

[0085] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A pressure welding tool for a power module, characterized in that: The power module comprises an AMB ceramic copper-clad liner (3), a welding sheet (4) and a heat-dissipating copper substrate (5), and the pressure welding tooling of the power module comprises: A pressure plate jig (1), the pressure plate jig (1) comprising a first jig body (11), positioning holes (12) being arranged around the first jig body (11), and a first mounting cavity (18) being arranged on a side surface of the first jig body (11); A welding jig (2), the welding jig (2) being arranged in the first mounting cavity (18), the welding jig (2) comprising a second jig body (21), a limiting pressure block (24) being arranged on a side of the second jig body (21) facing away from the first mounting cavity (18), and a second mounting cavity (25) being arranged on a side of the limiting pressure block (24) facing away from the second jig body (21); The AMB ceramic copper-clad liner (3) is arranged in the second installation cavity (25), and a circuit pattern is arranged on a side of the AMB ceramic copper-clad liner (3) close to the second installation cavity (25); The welding sheet (4) is arranged in the second mounting cavity (25) and is stacked with the AMB ceramic copper-clad liner (3); The heat dissipation copper substrate (5) is stacked on a side of the welding sheet (4) facing away from the AMB ceramic copper-clad liner (3), and a side of the heat dissipation copper substrate (5) facing away from the welding sheet (4) is provided with an arc; A heat-conducting fixture (6), the heat-conducting fixture (6) comprising a copper base plate (61), the copper base plate (61) being provided with positioning lock pieces (62) corresponding to the positions of the positioning holes (12), the positioning lock pieces (62) being plugged into the positioning holes (12) corresponding thereto, a third mounting cavity (64) of a matching shape being provided in the middle of the copper base plate (61) corresponding to the position of the heat-dissipating copper substrate (5), the heat-dissipating copper substrate (5) being provided in the third mounting cavity (64), and a curved side surface of the heat-dissipating copper substrate (5) being close to the third mounting cavity (64).

2. The pressure welding tool for power module according to claim 1, characterized in that: The pressure plate jig (1) comprises a first jig body (11), wherein both ends of a side of the first jig body (11) facing away from the first installation cavity (18) are provided with jig code plate installation grooves (13), and four groups of matching hole assemblies are provided on the first jig body (11) between the two jig code plate installation grooves (13), and the four groups of matching hole assemblies are arranged in pairs on the upper side and the lower side of the first jig body (11), and the two groups of matching hole assemblies on the upper side and the lower side are mirror-symmetrical about the central axis of the first jig body (11), and each group of matching hole assemblies includes a plurality of matching holes (14), and a plurality of reserved pressure pins (15) arranged at intervals are provided on the first jig body (11) between the four groups of matching hole assemblies, and four corner pressure pins (16) are arranged around both sides of the reserved pressure pins (15), and a first compression spring (19) is sleeved on the side of the four corner pressure pins (16) close to the first installation cavity (18).

3. The pressure welding tool for power module according to claim 1, characterized in that: Flexible switches (17) are arranged on both side walls of the first fixture body (11); the flexible switch (17) comprises an extension section (171), a first connecting section (172) and a second connecting section (173); the first connecting section (172) and the second connecting section (173) are arranged at two ends of the extension section (171); the extension section extends to the side of the first fixture body (11) away from the first mounting cavity (18); the first connecting section (172) and the second connecting section (173) are fixed to both side walls of the first fixture body (11) via mounting columns (20); A connecting column (174) is arranged between the first connecting section (172) and the second connecting section (173) perpendicular to the side surface of the first fixture body (11); a first groove is arranged on the first fixture body (11) at a position corresponding to each of the connecting columns (174); the connecting column (174) extends into the first groove; a spring (175) is sleeved on the connecting column; the other end of the spring (175) is connected to the inner wall of the first groove; a second groove (176) is arranged at a position of the first fixture body (11) corresponding to the extension section; and the flexible switch (17) moves left and right under the action of the spring.

4. The pressure welding tool for power module according to claim 2, characterized in that: A plurality of fixed columns (22) arranged at intervals are provided on one side of the second jig body (21) close to the first installation cavity (18). The fixed columns (22) penetrate the second jig body (21) and extend to the side of the second jig body (21) facing away from the first installation cavity (18). A guide column (23) is provided on the bottom surface of the second jig body (21) between two adjacent fixed columns (22). A fixing hole is provided on the limiting pressure block (24) at a position corresponding to each of the fixed columns (22). The fixing hole and the corresponding fixed column (22) are plugged in and matched. A guide hole is provided on the limiting pressure block (24) at a position corresponding to each of the guide columns (23). The guide hole and the corresponding guide column (23) are matched. A pressing pin lower pressing groove (26) is provided on the second jig body (21) at a position corresponding to each of the four corner pressing pins (16). The four corner pressing pins (16) are matched with the corresponding pressing pin lower pressing groove (26).

5. The pressure welding tool for power module according to claim 1, characterized in that: Flexible compression spring columns (27) are also arranged around the second fixture body (21), compression spring grooves are arranged on the position-limiting pressure block (24) corresponding to the positions of the flexible compression spring columns (27), the number of the flexible compression spring columns (27) is consistent with the number of the compression spring grooves and they are plugged in one-to-one, and a second compression spring (28) is arranged on the side of the flexible compression spring column (27) and the fixed column (22) close to the position-limiting pressure block (24).

6. The pressure welding tool for power module according to claim 1, characterized in that: Mounting holes (51) are provided on the heat dissipation copper substrate (5), and positioning columns (29) are provided at positions corresponding to the mounting holes (51) on the four sides of one side of the second fixture body (21) close to the limiting pressure block (24), and the positioning columns (29) cooperate with the mounting holes (51) provided corresponding thereto.

7. The pressure welding tool for power module according to claim 1, characterized in that: The limiting pressure block (24) is in the shape of a rectangular parallelepiped frame structure, a connecting piece (30) is arranged in the middle of the rectangular parallelepiped along the width direction, avoidance slopes (31) are arranged on the limiting pressure blocks (24) on both sides of the connecting piece (30), and the slope of the avoidance slopes (31) is 20-40 degrees, the connecting piece (30) divides the second installation cavity (25) into two installation cavities, and an AMB ceramic copper-clad lining plate (3) and a welding sheet (4) are sequentially stacked in each installation cavity, and a fixture two-dimensional code encoding area (32) is arranged at both ends of a side of the second fixture body (21) away from the limiting pressure block (24).

8. The pressure welding tool for power module according to claim 2, characterized in that: Anti-mistake pins (63) are arranged at positions corresponding to the matching holes (14) on the copper bottom plate (61), and the anti-mistake pins (63) are plugged into and matched with the matching holes (14) arranged corresponding thereto, and locking notches (65) are arranged on the side walls of the positioning lock fastener (62); positioning grooves (66) are arranged around a side of the copper bottom plate (61) away from the third installation cavity (64); the middle part of the upper end of the heat dissipation copper base plate (5) is upwardly protruding, and the third installation cavity (64) is upwardly concave corresponding to the upward protruding position of the heat dissipation copper base plate (5), and the curvature of the heat dissipation copper base plate (5) and the third installation cavity (64) are both 0.4-0.7°.

9. A welding process for a pressure welding tool for a power module according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1. Place the first mounting cavity (18) of the pressing plate fixture (1) on an operating table with the first mounting cavity (18) facing upward; Step S2. Install the limiting pressure block (24) onto the second fixture body (21), then place the welding fixture (2) with the limiting pressure block (24) facing upwards into the first installation cavity (18) of the pressure plate fixture (1), and press the four corner pressure pins (16) down into the pressure pin lower pressure grooves (26); Step S3. placing the AMB ceramic copper-clad liner (3) with the side provided with the circuit pattern facing downward in the second mounting cavity (25) of the limiting pressing block (24); Step S4. placing the solder sheet (4) in the second mounting cavity (25) and stacking it with the AMB ceramic copper-clad liner (3); Step S5. The heat dissipation copper substrate (5) is stacked with the convex surface facing upward on the side of the soldering piece (4) away from the AMB ceramic copper-clad liner (3), and the mounting holes (51) and the positioning columns (29) are correspondingly plugged in; Step S6. Place the upwardly protruding side of the heat dissipation copper substrate (5) in the third installation cavity (64) of the heat conductive jig (6), insert the foolproof pin (63) of the heat conductive jig (6) into the matching hole (14), then insert the positioning lock fastener (62) downward into the positioning hole (12) and press it, and finally lock it with the flexible switch (17) to obtain an assembled welding jig assembly; Step S7. Install the welding jig assembly onto the welding equipment for welding; Step S8. After the product is welded, the welding jig assembly is removed from the equipment welding carrier, the flexible switches (17) on both sides of the pressure plate jig (1) are opened, and the heat conductive jig (6) is removed to obtain the power module.

10. The welding process according to claim 9, characterized in that: The welding parameters in step S7 are as follows: the heating rate in the welding heating stage is 1-3°C / s, when the temperature of the welding cavity reaches 205-215°C, the cavity of the welding equipment is evacuated to <5mbar, the cavity of the welding equipment begins to be filled with formic acid with a purity of ≥97% until the pressure reaches 550-650mbar, and then the oxide on the surface of the welding material is reduced, and the reduction treatment time is 60-90s; thereafter, the welding equipment continues to heat up to a maximum temperature that is 20-30°C higher than the melting point of the solder. After the welding reaches the maximum temperature, the welding equipment is evacuated to <10mbar to degas the welding layer, and the vacuum pressure is maintained for 60-90s during the degassing treatment, and then the pressure is released, and the pressure release rate is 40-60mbar / s. After the welding is completed, the temperature is lowered, and the cooling rate is 1-3°C / s.

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