A press-fit silicon carbide power module packaging structure

Abstract

This invention relates to a press-fit silicon carbide power module packaging structure, belonging to the field of power semiconductor device technology. This structure is a single-tube structure with multiple chips connected in parallel. The silicon carbide chips are double-sided welded, with the chip drain welded to a drain substrate for reliable fixation and good electrothermal connection. Simultaneously, the chip source electrode is extended by welding source metal pillars. A flexible interconnect material is used between the source metal pillars and the source substrate to achieve pressureless electrothermal connection. An insulating support shell provides mechanical support for the module's internal structure while achieving electrical insulation. The chip's gate and Kelvin source are led out through a flexible PCB board fixed to the insulating support shell. The module's internal structure achieves reliable sealing through multiple design features, including controlling the length of the metal pillars, setting up dam-like barriers, and filling with silicone gel, thereby ensuring normal operation of the module in any orientation. This invention also allows for the application of higher external clamping forces to reduce the contact thermal resistance between the module and the heat sink.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor device technology and relates to a press-fit silicon carbide power module packaging structure. Background Technology

[0002] Press-fit power modules are circuit modules that achieve electrothermal connection between power semiconductor chips and metal substrates through mechanical pressure. They have advantages such as large capacity and ease of series connection, and are therefore widely used in converter valves for flexible DC transmission. With the increase in voltage and power levels of flexible DC transmission systems, traditional silicon-based IGBT press-fit modules are difficult to support the construction of converter valves with higher voltage and larger capacity due to their own voltage withstand and capacity limitations.

[0003] Silicon carbide MOSFETs offer advantages such as high voltage withstand capability and fast switching speed, making them a popular choice in various power converters. However, silicon carbide chips are harder and more brittle than silicon-based chips, making them prone to failure in press-fit packages due to uneven pressure distribution and stress concentration. Furthermore, silicon carbide chips have a smaller area than silicon-based chips, resulting in higher heat flux and placing greater demands on thermal design. In traditional press-fit modules, the chip bears the entire external clamping force, and the contact thermal resistance and contact resistance on the chip surface are coupled with the magnitude of the clamping force. Higher clamping forces can reduce contact thermal resistance and contact resistance, but the chip is more prone to breakage; conversely, lower clamping forces increase the unevenness of heat distribution, affecting module reliability. Therefore, traditional press-fit packaging structures are not suitable for silicon carbide chips and cannot fully utilize their potential. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a press-fit silicon carbide power module packaging structure with double-sided chip welding and internal chip pressure-free interconnection. While establishing a good electrothermal connection path, it decouples the external clamping force from the contact pressure on the chip surface, thereby achieving decoupling of the internal force field and electrothermal field of the module. At the same time, it allows the application of higher external clamping force to reduce the contact thermal resistance between the module and the heat sink, thereby effectively reducing the junction-current thermal resistance of the power module.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A press-fit silicon carbide power module packaging structure includes an insulating support shell 3, a drain substrate 2, a silicon carbide chip 6, a source metal pillar 8, a source substrate 4, a flexible interconnect material 9, and a flexible PCB board 5.

[0006] This packaging structure is a single-tube structure with multiple chips connected in parallel. The silicon carbide chip 6 is double-sided soldered, and the chip drain is soldered onto the drain substrate 2 to achieve reliable chip fixation and good electrothermal connection. Simultaneously, the chip source is extended by soldering source metal pillars 8, with the extended portion used for pressureless connection, insulation, and sealing design. Flexible interconnect material 9 is used between the source metal pillars 8 and the source substrate 4 to achieve pressureless electrothermal connection. The insulating support shell 3 provides mechanical support within the packaging structure while achieving electrical insulation. The chip's gate and Kelvin source are led out through a flexible PCB board 5 fixed to the insulating support shell 3. The internal packaging structure achieves reliable sealing through multiple designs, including controlling the length of the source metal pillars 8, setting up dam-like barriers, and filling with silicone gel, thereby ensuring normal operation of the module in any orientation. This packaging structure uses PEEK countersunk insulated screws for mechanical fixation, providing insulation gaps while ensuring mechanical strength.

[0007] This packaging structure achieves decoupling of the chip from the external clamping force while establishing a good electrothermal connection through double-sided welding and the use of flexible interconnect materials. The packaging structure uses an insulating support shell to withstand the external clamping force, decoupling the clamping force applied to the surface of the press-fit module from the contact pressure on the silicon carbide chip inside the module. This eliminates the contact pressure on the chip, improving the reliability of the press-fit silicon carbide power module. Simultaneously, the flexible interconnect material decouples the force field and electro-thermal multi-physics field within the module, ensuring that the electro-thermal field distribution inside the module is unaffected by the magnitude of the external clamping force, thus improving the uniformity of the internal electro-thermal distribution. Furthermore, after decoupling the internal and external pressures, the external clamping force can be further increased, which helps reduce the contact thermal resistance between the power module and the heat sink, thereby effectively reducing the junction-current thermal resistance of the power module.

[0008] Preferably, the source substrate 2 has a groove cut at the position corresponding to the source metal pillar 8 to hold the flexible interconnect material 9 and accommodate the source metal pillar 8, forming a connection interface between the source metal pillar 8, the flexible interconnect material 9, and the source substrate 2 within the groove.

[0009] Preferably, the groove edge of the source substrate 2 is designed with a dam-like protrusion to prevent the flexible interconnect material 9 from overflowing when the source metal pillar 8 is inserted, while enhancing the sealing performance of the groove edge when the silicon gel is injected.

[0010] Preferably, the drain substrate 2 has a circular hole in the center for injecting silicon gel into the package structure after the package structure is assembled.

[0011] Preferably, silicon gel is injected inside the packaging structure to seal the flexible interconnect material 9 within the groove of the source substrate 2, while enhancing the electrical insulation performance inside the packaging structure.

[0012] Preferably, the insulating support shell 3 has a support structure inside that is directly connected to the drain substrate 2 and the source substrate 4 to bear the clamping force applied to the packaging structure, so that the chip does not bear the contact pressure.

[0013] Preferably, the gate and Kelvin source of the chip are connected to the flexible PCB board 5 by bonding wires and led out to connect to an external driving circuit; the flexible PCB board 5 is fixed on the insulating support shell 3.

[0014] Preferably, the encapsulation structure is mechanically fixed using PEEK countersunk insulated screws, which provides an insulating gap while ensuring mechanical strength.

[0015] Preferably, the drain substrate 2, source substrate 4, and source metal pillar 8 are made of copper, molybdenum, or a molybdenum-copper alloy. The insulating support shell 3 is made of FR4, various ceramics, or GPO-3. The flexible interconnect material 9 is any one or more of gallium-based liquid metal, bismuth-based liquid metal, conductive paste, ion-conductive gel, metal nanoparticles, or graphite nanoparticles, which have good electrical conductivity and certain thermal conductivity.

[0016] The beneficial effects of this invention are as follows: Addressing the problem of chip contact pressure and internal electro-thermal-mechanical multi-physics coupling in existing press-fit power modules, this invention achieves decoupling of the chip from the external clamping force while establishing a good electro-thermal connection through double-sided welding of the silicon carbide chip and the use of flexible interconnect materials. The module uses an insulating support shell to withstand the external clamping force, decoupling the clamping force applied to the surface of the press-fit module from the contact pressure experienced by the silicon carbide chip inside the module. This eliminates the contact pressure on the chip, improving the reliability of the press-fit silicon carbide power module. Simultaneously, the flexible interconnect material decouples the force field from the electro-thermal multi-physics field within the module, ensuring that the internal electro-thermal field distribution is unaffected by the magnitude of the external clamping force, thus improving the uniformity of the internal electro-thermal distribution. Furthermore, after decoupling the internal and external pressures, the external clamping force can be further increased, which helps reduce the contact thermal resistance between the power module and the heat sink, thereby effectively reducing the junction-current thermal resistance of the power module.

[0017] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1The circuit structure diagram of the press-fit silicon carbide power module packaging structure provided in the embodiment of the present invention is shown. Figure 2 This is an isometric side view of the press-fit silicon carbide power module packaging structure provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the press-fit silicon carbide power module packaging structure provided in an embodiment of the present invention; Figure 4 This is a top view of the drain double-sided welding component provided in an embodiment of the present invention; Figure 5 This is an isometric view of the drain double-sided welding component provided in an embodiment of the present invention; Figure 6 This is a top view of the insulating support shell provided in an embodiment of the present invention; Figure 7 This is an isometric side view of the insulating support shell provided in an embodiment of the present invention; Figure 8 This is an assembly diagram of the double-sided welded component, the insulating support shell, and the gate-source lead wire provided in the embodiments of the present invention; Figure 9 This is a top view of the source substrate provided in an embodiment of the present invention; Figure 10 This is an isometric side view of the source substrate provided in an embodiment of the present invention; Figure 11 This is an exploded view of the assembly of the drain double-sided welding assembly and the source substrate provided in an embodiment of the present invention.

[0019] Reference numerals: 1- PEEK insulating screw, 2- drain substrate, 3- insulating support shell, 4- source substrate, 5- flexible PCB, 6- silicon carbide chip, 7- bonding wire, 8- source metal pillar, 9- flexible interconnect material. Detailed Implementation

[0020] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0021] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0022] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0023] Please see Figures 1 to 11 This invention provides a press-fit silicon carbide power module packaging structure, the single-tube packaging structure of which is as follows: Figure 1 As shown, a single switching unit consists of four silicon carbide chips, which are centrally symmetrically distributed, and the entire power module contains four silicon carbide chips.

[0024] In this embodiment, the drains of all silicon carbide chips in a single switching unit are connected to a single point, and the drain power terminal (D) is brought out. All sources are connected together, and the source power terminal (S) is brought out. All gates are brought out to the signal terminal (G).

[0025] Figure 2 The diagram shows an isometric side view of a press-fit silicon carbide power module package structure. The upper part is the drain substrate 2, on which a double-sided soldered chip is fixed. The middle part is an insulating support shell 3, providing electrical insulation and mechanical support. The lower part is the source substrate 4, filled with flexible interconnect material 9. Silicon gel is filled inside the package structure for insulation and sealing. The gate and Kelvin source are led out through a flexible PCB board 5. The package structure is secured by four PEEK countersunk insulated screws.

[0026] Figure 3The internal structure of a press-fit silicon carbide power module package is shown. The silicon carbide chip is double-sided welded, with the chip drain welded to the drain substrate 2 for reliable fixation, and the chip source welded to the source metal pillars 8 to extend the electrode. The cavity of the source substrate 4 is filled with flexible interconnect material 9. The source metal pillars 8 and the source substrate 4 are connected without pressure via the flexible interconnect material 9. The flexible interconnect material 9 has good electrical conductivity and a certain thermal conductivity, which can eliminate contact pressure on the chip while achieving good electrothermal contact, decoupling the external clamping force and the pressure on the chip. In traditional press-fit modules, the chip bears the entire clamping force, which may lead to breakage due to stress concentration. Simultaneously, the contact resistance and contact thermal resistance of the chip surface are related to the clamping force; a lower clamping force can lead to uneven distribution of the electrothermal field. Silicon carbide chips have a higher Young's modulus and heat flux, therefore traditional press-fit packaging is not suitable for silicon carbide chips. The connection structure, combining double-sided welding with flexible interconnect materials, achieves reliable chip fixation and good electrothermal contact, while also decoupling the external clamping force from the internal electro-thermal-mechanical field of the module. Furthermore, this embodiment features a multi-layered sealing structure. The surface of the flexible interconnect material is slightly lower than the source substrate cavity, and the cavity surface is designed with dam-like protrusions to prevent leakage of the flexible interconnect material. Silicon gel fills the module's interior, further enhancing its sealing performance.

[0027] Figure 4 The diagram shows the welded components of the drain substrate, silicon carbide chip, and source metal pillars. The chip drain is welded onto the substrate for reliable fixation and good electrothermal connection. The chip source electrode is extended via welded metal pillars, which increase the insulation gap and provide a sealing design for the flexible interconnect material. The drain substrate 2 features bumps to reduce the impact of substrate thermomechanical stress on the chip and solder, while preventing solder layer overflow during welding and subsequent insulation damage. The base area of ​​the metal pillars is determined by the source region of the chip and is slightly smaller than the source region to prevent solder overflow. Figure 5 This is a top view of the welded section, providing a more intuitive view of the bottom design of the source metal pillar 8. The central circular hole is a through-hole used for injecting silicone gel after the package structure is assembled.

[0028] Figure 6 The diagram shows the insulating support housing used to provide electrical and mechanical insulation. The through holes around the perimeter are for securing PEEK countersunk insulating bolts; the raised edge contours around the perimeter are used to fix the substrate position during package assembly; the central circular hole is used to inject silicone gel after module assembly. The two central square protrusions are used to fix the flexible PCB board 5 and provide internal support and withstand external clamping forces after module assembly. Figure 7 This is a top view of the insulating support shell 3.

[0029] Figure 8The diagram shows the assembly of the double-sided soldering assembly, the insulating support shell, and the gate-source leads. The insulating support shell 3 is fixed on the drain substrate 2, and the flexible PCB is embedded in the insulating support shell 3. The gate and Kelvin source of the chip are connected to the flexible PCB through bonding wires.

[0030] Figure 9 The image shows a source substrate with cavities and dam-like protrusions. Threaded holes around the perimeter are used for connecting PEEK countersunk insulating screws; the cavities are used to fill the flexible interconnect material; the dam-like protrusions are used to prevent leakage of the flexible interconnect material 9. Figure 10 This is an isometric side view of the source substrate 4.

[0031] Figure 11 The image shows an exploded view of the drain double-sided soldering assembly and the source substrate. The chip source metal pillars are inserted into the flexible interconnect material of the source substrate. They are secured around the perimeter with PEEK countersunk screws. Finally, silicone gel is poured through the central hole of the drain substrate to achieve better insulation and sealing.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A press-fit silicon carbide power module packaging structure, characterized in that, It includes an insulating support shell, a drain substrate, a silicon carbide chip, a source metal pillar, a source substrate, flexible interconnect materials, and a flexible PCB board; This packaging structure is a single-tube structure with multiple chips connected in parallel. The silicon carbide chips are soldered on both sides, and the chip drain is soldered on the drain substrate to fix the chip and achieve good electrothermal connection. At the same time, the chip source is extended by soldering source metal pillars. The extended part is used for pressureless connection, insulation and sealing design. Flexible interconnect material is used between the source metal pillars and the source substrate to achieve pressureless electrothermal connection. The insulating support shell provides mechanical support for the internal packaging structure while achieving electrical insulation; the chip's gate and Kelvin source are led out through a flexible PCB board fixed on the insulating support shell; the internal packaging structure achieves reliable sealing through multiple designs such as controlling the length of the source metal pillars, setting up dam-like barriers, and filling with silicone gel, thereby ensuring that the module can work normally in any posture.

2. The press-fit silicon carbide power module packaging structure according to claim 1, characterized in that, The source substrate has a groove cut at the position corresponding to the source metal pillar to hold the flexible interconnect material and accommodate the source metal pillar, forming a connection interface between the source metal pillar, the flexible interconnect material, and the source substrate within the groove.

3. The press-fit silicon carbide power module packaging structure according to claim 2, characterized in that, The source substrate has a dam-like protrusion at the groove edge to prevent the flexible interconnect material 9 from overflowing when the source metal pillar is inserted.

4. The press-fit silicon carbide power module packaging structure according to any one of claims 1 to 3, characterized in that, The drain substrate has a circular hole in the center, which is used to inject silicon gel into the package structure after the package structure is assembled.

5. The press-fit silicon carbide power module packaging structure according to claim 3, characterized in that, Silicon gel is injected into the package structure to seal the flexible interconnect material within the trench of the source substrate, while also enhancing the electrical insulation performance inside the package structure.

6. The press-fit silicon carbide power module packaging structure according to claim 1, characterized in that, The insulating support shell has an internal support structure that is directly connected to the drain substrate and the source substrate to bear the clamping force applied to the packaging structure, so that the chip does not bear the contact pressure.

7. The press-fit silicon carbide power module packaging structure according to claim 1, characterized in that, The gate and Kelvin source of the chip are connected to the flexible PCB board and led out by bonding wires for connection to external driving circuits.

8. The press-fit silicon carbide power module packaging structure according to claim 1, characterized in that, The encapsulation structure is mechanically secured using PEEK countersunk insulated screws.

9. The press-fit silicon carbide power module packaging structure according to claim 1, characterized in that, The drain substrate, source substrate, and source metal pillar are made of copper, molybdenum, or a molybdenum-copper alloy; the insulating support shell is made of FR4, various ceramics, or GPO-3; and the flexible interconnect material is any one or more of gallium-based liquid metal, bismuth-based liquid metal, conductive paste, ion-conductive gel, metal nanoparticles, or graphite nanoparticles that have good electrical and thermal conductivity.

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