A press-fit semiconductor power module

Abstract

The present invention discloses a press-fit semiconductor power module in the technical field of power semiconductor devices, comprising an emitter conductor and M emitter bosses, wherein N emitter bosses are welded to the surface of the emitter conductor by solder, and N≤M, and the solder forms a welding layer after welding, and the welding layer undergoes plastic deformation when the pressure between the emitter boss and the emitter conductor reaches a specified value, and the Young's modulus in the emitter boss and the emitter conductor is greater than the Young's modulus of the welding layer. The present invention reduces the stress imbalance between chips in the working state of the press-fit IGBT module by welding the emitter boss to the surface of the emitter conductor by solder, thereby improving the force consistency between chips and the reliability of the press-fit module.

Description

Technical Field

[0001] The invention relates to a press-connected semiconductor power module, belonging to the technical field of power semiconductor devices. Background Art

[0002] Insulated Gate Bipolar Transistor (IGBT) is a new type of power semiconductor device that combines the advantages of MOS transistors and bipolar transistors, and has excellent current capacity, switching speed and voltage resistance.

[0003] With the increase in the design capacity of power electronic systems and the increase in the demand for application fields, the performance of IGBT modules has become increasingly important. The packaging technology of traditional welded IGBT modules is cumbersome. Affected by processes such as welding, potting, and wire bonding, it is difficult to significantly increase its power level. There are also many hidden dangers of failure such as solder fatigue, solder layer voids, and aluminum bonding wire shedding. Therefore, it is difficult to meet the needs of large-scale power systems such as high-voltage direct current transmission and flexible alternating current transmission. The crimped IGBT modules with higher power levels and reliability solve this problem. The design of high-power crimped IGBT devices without leads and double-sided heat dissipation greatly increases the device capacity and reliability. The demand for high-power density and high-reliability applications such as flexible direct current transmission and large-scale offshore wind power generation is gradually increasing.

[0004] Press-fit IGBT devices apply a certain amount of mechanical pressure from the outside to ensure good contact between the components inside the device, forming a stable conductive and thermal conduction channel. The intervention of external mechanical pressure makes the internal physical field of the press-fit device more complicated. The surface of the conductor electrode of the device shell will be warped due to the external mechanical pressure. At the same time, the thermal stress at the operating temperature will also cause inconsistent deformation of various parts of the IGBT device, resulting in different pressures on different chips during operation. If the chip is subjected to excessive force, the surface metal layer will be squeezed excessively, damaging the terminal and even causing the chip to break. If the chip is subjected to too little force, the contact resistance and contact thermal resistance between components will increase. The heat generated by the chip cannot be transferred in time, increasing the possibility of thermal failure of the module and affecting the reliability of the module. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a press-fit semiconductor power module. By soldering the emitter boss to the surface of the emitter conductor through solder, the stress imbalance between the chips in the working state of the press-fit IGBT module is reduced, the force consistency between the chips and the reliability of the press-fit module are improved.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0007] The present invention provides a press-fit semiconductor power module, comprising an emitter conductor and M emitter bosses, wherein N emitter bosses are welded to the surface of the emitter conductor by solder, and N≤M, and the solder forms a welding layer after welding, and the welding layer undergoes plastic deformation when the pressure between the emitter boss and the emitter conductor reaches a specified value, and the Young's modulus in the emitter boss and the emitter conductor is greater than the Young's modulus of the welding layer.

[0008] Furthermore, the emitter boss, the solder layer and the emitter conductor are connected into one by vacuum reflow soldering.

[0009] Furthermore, the solder layer adopts SAC, SnSb series lead-free solder or SnPb series lead-containing solder.

[0010] Furthermore, the end of the emitter boss away from the emitter conductor is connected to a molybdenum sheet assembly, the welding layer, the emitter boss and the molybdenum sheet assembly form a sub-module, the power module also includes a pressure-bearing limit frame and a collector conductor, and the sub-module can be inserted into the pressure-bearing limit frame, the emitter conductor and the collector conductor are respectively located on both sides of the pressure-bearing limit frame, and the collector conductor and the emitter conductor are crimped with a tube cover on one side away from the pressure-bearing limit frame, and a tube shell is provided on the outside of the tube cover, the collector conductor and the emitter conductor.

[0011] Furthermore, the molybdenum sheet assembly includes a collector molybdenum sheet and an emitter molybdenum sheet, and a semiconductor chip is sandwiched between the two, the emitter molybdenum sheet is close to the emitter boss and the collector molybdenum sheet is close to the collector conductor.

[0012] Furthermore, the semiconductor chip, the emitter-level molybdenum sheet and the collector molybdenum sheet are connected by contact, welding or by a sintering process.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The novel crimping module structure proposed in the present invention changes the traditional contact connection between the emitter boss and the base into welding of the emitter boss and the base. In view of the inconsistent deformation of different chips under working conditions, the emitter boss and the solder layer are added as a buffer layer, and the emitter boss is soldered to the surface of the emitter conductor through solder through vacuum reflow soldering. The solder thickness is adjusted for compensation, so that the height of each sub-module is consistent under working conditions. It is used to improve the uneven force on the chip caused by the inconsistent height of various parts of the device under mechanical pressure and thermal stress. It can also reduce the contact surface to improve the operating reliability of the crimping module and solve the stress balance problem in the rigid crimping module. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the compression-type IGBT packaging structure provided in the first embodiment of the present invention;

[0016] Figure 2 yes Figure 1 A magnified schematic diagram of the structure of the neutron module.

[0017] In the figure: 1. sub-module; 2. collector conductor; 3. emitter conductor; 4. tube shell; 5. upper tube cover; 6. lower tube cover; 7. pressure limit frame; 11. semiconductor chip; 12. collector molybdenum sheet; 13. emitter molybdenum sheet; 14. emitter boss; 15. welding layer. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0019] Example:

[0020] See also Figure 1 A press-fit semiconductor power module, the structure of which includes, from the back, an upper tube cover 5, a collector conductor 2, a sub-module 1, an emitter conductor 3, a lower tube cover 6, a tube shell 4, a pressure-bearing limit frame 7 and other parts. The layers are press-fitted together by applying pressure at both ends of the module, wherein the collector conductor 2 and the emitter conductor 3 are respectively located on both sides of the pressure-bearing limit frame 7, the upper tube cover 5 is located on the side of the collector conductor 2 away from the pressure-bearing limit frame 7, the lower tube cover 6 is located on the side of the emitter conductor 3 away from the pressure-bearing limit frame 7, the tube shell 4 is sleeved on the outer sides of the upper tube cover 5, the collector conductor 2, the emitter conductor 3 and the lower tube cover 6, and the sub-module 1 is embedded in Inside the pressure-limiting frame 7, the sub-module 1 includes a collector molybdenum sheet 12, a semiconductor chip 11, an emitter molybdenum sheet 13, an emitter boss 14 and a solder layer 15. The collector molybdenum sheet 12, the semiconductor chip 11, the emitter molybdenum sheet 13, and the emitter boss 14 are installed in the pressure-limiting frame 7. The emitter boss 14 and the solder layer 15 are connected together with the emitter conductor 3. The solder layer 15 can be made of but not limited to lead-free solders such as SAC and SnSb and lead-containing solders such as SnPb. These solders are suitable for electronic packaging and have a small Young's modulus. When the stress on the conductors on both sides is relatively large, the solder layer will undergo plastic deformation to release the stress. The semiconductor chip 11 is located between the emitter-level molybdenum sheet 13 and the collector molybdenum sheet 12, and the three form a molybdenum sheet assembly. The emitter-level molybdenum sheet 13 is close to the emitter boss 14 and the collector molybdenum sheet 12 is close to the collector conductor 2. The connection between the semiconductor chip 11 and the emitter-level molybdenum sheet 13 and the collector molybdenum sheet 12 can be a contact connection, a welding connection, or a connection through a sintering process.

[0021] When this type of press-fit semiconductor power module is actually installed, first place the upper tube cover 5 in the tube shell 4, place the collector conductor 2 on the upper tube cover 5, and place the pressure-bearing limit frame 7 on the collector conductor 2, then solder the sub-module 1 on the surface of the emitter conductor 3 by soldering, then buckle the emitter conductor 3 side with the sub-module 1 on the pressure-bearing limit frame 7, and finally cover the lower tube cover 6.

[0022] In order to solve the problem of inconsistent deformation of different parts of the press-fit IGBT module when it is in operation, this embodiment adds an emitter boss 14 and a solder layer 15 as a buffer layer, and connects the emitter boss 14, the solder layer 15 and the emitter conductor 3 into one by vacuum reflow soldering. By adjusting the thickness of the solder layer 15 corresponding to different chips, the stress imbalance between the chips in the press-fit IGBT module when it is in operation can be reduced, the force consistency between the chips can be improved, the contact surface can be reduced, the operating reliability of the press-fit module can be improved, and the stress balance problem in the rigid press-fit module can be solved.

[0023] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A press-fit semiconductor power module, Its characteristics are: It includes an emitter conductor and M emitter bosses, N of the emitter bosses are welded to the surface of the emitter conductor by solder, and N≤M, the solder forms a solder layer after welding, the solder layer undergoes plastic deformation when the pressure between the emitter boss and the emitter conductor reaches a specified value, and the Young's modulus in the emitter boss and the emitter conductor is greater than the Young's modulus of the solder layer.

2. The press-fit semiconductor power module according to claim 1, Its characteristics are: The emitter boss, the solder layer and the emitter conductor are connected into one body through vacuum reflow soldering.

3. The press-fit semiconductor power module according to claim 1, Its characteristics are: The solder layer adopts SAC, SnSb series lead-free solder or SnPb series lead-containing solder.

4. The press-fit semiconductor power module according to claim 1, Its characteristics are: The end of the emitter boss away from the emitter conductor is connected to a molybdenum sheet assembly, and the welding layer, the emitter boss and the molybdenum sheet assembly form a submodule. The power module also includes a pressure-bearing limit frame and a collector conductor, and the submodule can be inserted into the pressure-bearing limit frame. The emitter conductor and the collector conductor are respectively located on both sides of the pressure-bearing limit frame, and the collector conductor and the emitter conductor are crimped with a tube cover on one side away from the pressure-bearing limit frame, and a tube shell is provided on the outside of the tube cover, the collector conductor and the emitter conductor.

5. The press-fit semiconductor power module according to claim 4, Its characteristics are: The molybdenum sheet assembly comprises a collector molybdenum sheet and an emitter molybdenum sheet, and a semiconductor chip is sandwiched between the two. The emitter molybdenum sheet is close to the emitter boss and the collector molybdenum sheet is close to the collector conductor.

6. The press-fit semiconductor power module according to claim 5, Its characteristics are: The semiconductor chip, the emitter-level molybdenum sheet and the collector-electrode molybdenum sheet are connected by contact, welding or by a sintering process.

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