A gallium nitride power module with multiple substrate hybrid integration and compatible metal heat sink

Abstract

The application relates to the field of power semiconductor devices and automobile electronics, in particular to a gallium nitride power module with multi-substrate hybrid integration and compatible metal heat sink, which comprises: GaN chips, including upper pipe GaN chips and lower pipe GaN chips; a DPC substrate arranged between the upper pipe GaN chips and the lower pipe GaN chips, serving as a GaN chip carrier and capable of passing large current; an FPC driving signal carrier connected with the DPC substrate and the GaN chips, integrating driving devices and passive devices; a primary heat sink substrate, which is selected from double-sided metallized diamond substrates; a secondary heat sink substrate, which performs secondary heat dissipation on the gallium nitride power module; and a cooling plate used for heat exchange with the secondary heat sink substrate. The application innovatively proposes a hybrid 3D packaging structure. The excellent structural characteristics make the power module meet driving integration, negative pressure protection integration, full-size heat sink and metal pole plate compatibility while ensuring the minimization of material thermal resistance, and greatly improve the heat dissipation performance.

Description

Technical Field

[0001] This invention relates to the fields of power semiconductor devices and automotive electronics, and more particularly to a gallium nitride power module that is multi-substrate hybrid integrated and compatible with metal heat sinks. Background Technology

[0002] With the rapid development of the new energy industry, power electronic conversion systems are widely used in various important scenarios such as rail transit, UAV electric drive, robot electric drive, and electric vehicles. As a crucial component of core hardware such as inverters and ESC systems, the performance of power modules directly affects the reliability and efficiency of the system. In recent years, the emergence of wide-bandgap semiconductor gallium nitride (GaN) devices has brought revolutionary changes to power converters. Compared with other devices, gallium nitride high electron mobility transistors (GaNHEMTs) have smaller gate charge and on-resistance, enabling higher power density and efficiency. However, the fast switching speed of GaNHEMTs makes them more sensitive to parasitic parameters. Parasitic inductance and capacitance not only increase switching losses but also cause serious electromagnetic interference (EMI) problems.

[0003] Currently, various power module designs with integrated gate drivers have been proposed. For example, one approach integrates decoupling capacitors and drivers on one side of a printed circuit board (PCB), places a GaNHEMT on the other side, and solders it to the GaNHEMT substrate using direct-bonded copper substrate (DBC) or active metal brazing substrate (AMB) to form a heat dissipation path. Another double-sided heat dissipation structure uses direct-plated copper substrate (DPC) for electrical connection and heat dissipation on the top of the GaNHEMT and both sides of the substrate. Furthermore, there are designs that integrate driver devices using flexible printed circuit boards (FPC) and add pads to the substrate side to achieve a complete heat sink area. These solutions improve the integration and heat dissipation performance of power modules to some extent, but some problems still exist.

[0004] In existing technologies, interconnection via bonding wires introduces a significant amount of parasitic inductance, reducing reliability and lifespan. For example, single-sided heat dissipation solutions cannot adequately reduce junction-to-case thermal resistance; double-sided heat dissipation structures, due to the increased height of the sub-board and its extremely poor thermal conductivity, result in high overall parasitic inductance and insufficient heat dissipation for the power module; alloy pads soldered onto the GaN substrate introduce extremely high thermal resistance, reducing heat dissipation performance. Furthermore, the thermal conductivity of the DBC substrate is much lower than that of the vapor chamber, increasing thermal resistance and reducing the vapor chamber's effectiveness in cooling the chip. Summary of the Invention

[0005] The purpose of this invention is to provide a gallium nitride power module that integrates multiple substrates and is compatible with metal heat sinks, thereby solving the problems of poor heat dissipation on one side and large overall parasitic inductance and insufficient heat dissipation caused by the double-sided heat dissipation structure in the prior art.

[0006] To achieve the above objectives, the present invention provides a GaN chip, including an upper GaN chip and a lower GaN chip, wherein the bottom of the GaN chip is a device substrate; The DPC substrate is placed between the upper GaN chip and the lower GaN chip to serve as a GaN chip carrier, allowing high current to pass through and providing heat dissipation. FPC drive signal carrier, connected to DPC substrate and GaN chip, used to integrate drive devices and passive devices; Copper strips are used to connect the GaN chip substrate and the source electrode; Copper pads are placed at the four corners of the FPC drive signal carrier to provide additional support; they are also placed on the DPC substrate to provide additional support and additional heat dissipation pathways. The primary heat sink substrate is a double-sided metallized diamond substrate, which is placed on the outside of the upper GaN chip to provide primary heat dissipation for the upper GaN chip and to insulate the substrate from the outside. The secondary heat sink substrate is disposed on the outside of the upper diamond substrate for secondary heat dissipation of the upper GaN chip, and is directly disposed on the outside of the lower GaN chip for primary heat dissipation of the lower GaN chip. Cooling plates are located on the outer side of the upper and lower secondary heat sink substrates and are used for heat exchange with the secondary heat sink substrates. The cooling plates are either liquid cooling plates or air-cooled fins.

[0007] In some embodiments of this application, the gallium nitride power module adopts a vertically arranged half-bridge structure, and the substrates of the upper and lower GaN chips are cooled sequentially through the upper and lower primary heat sink substrates and secondary heat sink substrates.

[0008] In some embodiments of this application, the GaN chip adopts a lateral die design, which can eliminate the parasitic and thermal resistance introduced by monolithic packaging.

[0009] In some embodiments of this application, the upper GaN chip substrate and the copper pillars on the source pin side of the upper GaN chip are connected to a double-sided metallized diamond substrate to obtain a structure in which the substrate and the source are connected, which is used to reduce the dynamic on-resistance and to insulate the upper GaN substrate from the heat sink substrate; the lower GaN chip substrate is directly connected to the secondary heat sink substrate.

[0010] In some embodiments of this application, the DPC substrate is a ceramic substrate used to connect the upper and lower GaN chips, providing support, heat dissipation, and matching thermal expansion coefficients.

[0011] In some embodiments of this application, the FPC drive signal carrier is used to integrate drive devices, signal pins and four corner supports, and is connected to the DPC substrate through a pad interface.

[0012] In some embodiments of this application, a copper substrate is connected to the DPC substrate to form additional heat dissipation pathways and support.

[0013] In some embodiments of this application, the area of ​​the secondary heat sink substrate completely covers the gallium nitride power module, and the secondary heat sink substrate is one of a phase change heat sink plate, a copper plate, an aluminum plate, or a metal graphene substrate.

[0014] The advantages and beneficial effects of this invention compared to the prior art are: 1. This invention uses GaN bare die and multi-substrate hybrid packaging. GaN bare die is used to eliminate the thermal resistance and parasitic inductance caused by monolithic packaging. At the same time, the characteristics of various substrates are compared and studied, and different substrates are mixed and used.

[0015] 2. This invention innovatively proposes a hybrid 3D packaging structure. Its superior structural characteristics enable the power module to meet the requirements of drive integration, negative voltage protection integration, full-size heat sink, and metal plate compatibility while minimizing material thermal resistance.

[0016] 3. This invention achieves direct integration of a phase change heat spreader onto a high-voltage GaN bare core, possessing complete and excellent electrical performance. By utilizing the integrated phase change heat spreader, the severe localized heat concentration phenomenon in the GaN bare core is greatly alleviated, significantly improving the heat dissipation performance of the power module.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a gallium nitride power module that is multi-substrate hybrid integrated and compatible with metal heat sinks, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a multi-substrate 3D hybrid integrated packaging structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a conventional planar layout scheme in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the vertical layout scheme used in an embodiment of the present invention; Figure 5 This is a schematic diagram of the heat transfer path according to an embodiment of the present invention. Detailed Implementation

[0019] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing the 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, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the present invention provides a gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks, comprising: GaN chips include upper-side GaN chips and lower-side GaN chips, with the bottom of the GaN chip serving as the device substrate. The DPC substrate is placed between the upper GaN chip and the lower GaN chip to serve as a GaN chip carrier, allowing high current to pass through and providing heat dissipation. FPC drive signal carrier, connected to DPC substrate and GaN chip, used to integrate drive devices and passive devices; Copper strips are used to connect the GaN chip substrate and the source electrode; Copper pads are placed at the four corners of the FPC drive signal carrier to provide additional support; they are also placed on the DPC substrate to provide additional support and additional heat dissipation pathways. The primary heat sink substrate is a double-sided metallized diamond substrate, which is placed on the outside of the upper GaN chip to provide primary heat dissipation for the upper GaN chip and to insulate the substrate from the outside. The secondary heat sink substrate is disposed on the outside of the upper diamond substrate for secondary heat dissipation of the upper GaN chip, and is directly disposed on the outside of the lower GaN chip for primary heat dissipation of the lower GaN chip. Cooling plates are located on the outer side of the upper and lower secondary heat sink substrates and are used for heat exchange with the secondary heat sink substrates. The cooling plates are either liquid cooling plates or air-cooled fins.

[0022] In some embodiments of this application, the gallium nitride power module adopts a vertically arranged half-bridge structure, and the substrates of the upper and lower GaN chips are cooled sequentially through the upper and lower primary heat sink substrates and secondary heat sink substrates.

[0023] In some embodiments of this application, the GaN chip adopts a lateral die design, which can eliminate the parasitic and thermal resistance introduced by monolithic packaging.

[0024] In some embodiments of this application, the upper GaN chip substrate and the copper pillars on the source pin side of the upper GaN chip are connected to a double-sided metallized diamond substrate to obtain a structure in which the substrate and the source are connected, which is used to reduce the dynamic on-resistance and to insulate the upper GaN substrate from the heat sink substrate; the lower GaN chip substrate is directly connected to the secondary heat sink substrate.

[0025] In some embodiments of this application, the DPC substrate is a ceramic substrate used to connect the upper and lower GaN chips, providing support, heat dissipation, and matching thermal expansion coefficients.

[0026] In some embodiments of this application, the FPC drive signal carrier is used to integrate drive devices, signal pins and four corner supports, and is connected to the DPC substrate through a pad interface.

[0027] In some embodiments of this application, a copper substrate is connected to the DPC substrate to form additional heat dissipation pathways and support.

[0028] In some embodiments of this application, the area of ​​the secondary heat sink substrate completely covers the gallium nitride power module, and the secondary heat sink substrate is one of a phase change heat sink plate, a copper plate, an aluminum plate, or a metal graphene substrate.

[0029] The advantages and beneficial effects of this invention compared to the prior art are: 1. This invention uses GaN bare die and multi-substrate hybrid packaging. GaN bare die is used to eliminate the thermal resistance and parasitic inductance caused by monolithic packaging. At the same time, the characteristics of various substrates are compared and studied, and different substrates are mixed and used.

[0030] 2. This invention innovatively proposes a hybrid 3D packaging structure. Its superior structural characteristics enable the power module to meet the requirements of drive integration, negative voltage protection integration, full-size heat sink, and metal plate compatibility while minimizing material thermal resistance.

[0031] 3. This invention achieves direct integration of a phase change heat spreader onto a high-voltage GaN bare core, possessing complete and excellent electrical performance. By utilizing the integrated phase change heat spreader, the severe localized heat concentration phenomenon in the GaN bare core is greatly alleviated, significantly improving the heat dissipation performance of the power module.

[0032] The system implementation of the present invention will be described in detail below with reference to specific embodiments.

[0033] The first step is to perform a multi-substrate selection design: FPC uses polyimide (PI) film as the insulating layer, with a thermal conductivity of 0.2 W / m·K and a breakdown field strength of 300 kV / mm. The copper foil thickness is typically <1 oz. A four-layer FPC has a total thickness of <0.3 mm, is bendable, and offers the highest wiring density. DPC substrates use ceramic as the insulating medium. When using aluminum nitride (AlN), the thermal conductivity of the DPC substrate can reach 170 W / m·K, allowing it to also serve as a heat sink substrate. However, due to process limitations, DPC can currently only be fabricated as a two-layer board, with a minimum board thickness of approximately 0.5 mm. Diamond is considered to have great application potential due to its breakdown voltage >10 kV / mm and thermal conductivity greater than 1400 W / m·K. However, limited by metallization processes, the metal layer can typically only be grown to 0.5 μm, and the cost is high, thus its use is relatively limited. Phase change heat exchangers can be considered a type of metal substrate. Their main heat transfer method is to complete phase change heat transfer through an internal vapor chamber. The theoretical thermal conductivity of the vapor chamber can reach 10,000 W / m·K.

[0034] Based on the characteristics of each material, a multi-substrate hybrid packaging strategy is proposed, the key points of which are as follows: 1. DPC substrate as power signal carrier: The DPC substrate needs to be directly connected to the GaN die and pass through a large current. The excellent thermal conductivity and matching CTE of the AlN dielectric DPC substrate can improve the thermal conduction and reliability of the power module.

[0035] 2. FPC as a drive signal carrier: The drive substrate connects the driver and passive devices. It does not need to carry high power but has high requirements for wiring density. At the same time, the low thermal conductivity of PI can effectively prevent the heat of the power substrate from coupling to the gate driver and causing it to overheat.

[0036] 3. Double-sided metallized diamond substrate as primary heat sink substrate: Diamond is used for initial heat dissipation of the GaN die and for insulation from the outside. Simultaneously, the thin metal layer on its surface can be used for interconnection between the GaN substrate and the source. To avoid high costs, the diamond area is only slightly larger than the GaN die and is only used in the upper GaN transistor of a half-bridge.

[0037] 4. Phase change heat sink as primary / secondary heat sink substrate: GaN bare wafers have small area and high heat flux density. Phase change heat sinks can quickly disperse hot spots and improve heat exchange efficiency.

[0038] The second step is to conduct a hybrid 3D integrated structure design: Conventional 2D integration means that a height difference exists between power devices and other devices. The heat sink, while in close contact with the power device, cannot cover other devices, which significantly reduces the heat sink area and severely degrades heat dissipation performance. To address these issues, this invention proposes a multi-substrate 3D hybrid integrated packaging structure, such as... Figure 2 As shown. This solution has the following technological breakthroughs: (1) Half-bridge vertical layout: thermal decoupling + compatible metal substrate: Figure 3 (a) is a conventional planar layout scheme, which places the upper and lower power devices side by side in parallel. The advantage of this scheme is that it minimizes the vertical spacing of the power loop, but the disadvantage is that severe thermal coupling will form between the substrates of the upper and lower devices. The thermal resistance of the power device substrate is lower than that of the pin side, so in actual operation, most of the heat is transferred through the substrate side. The thermal coupling on the substrate side causes the junction temperature of the device to rise, and the device characteristics degrade and the reliability is reduced. Figure 3 (b) shows that conventional planar thermal decoupling requires the introduction of a large number of metal pads, which introduces additional thermal resistance and is not conducive to heat transfer. At the same time, the heat sinks on the upper and lower tube substrate sides need to be connected to the same substrate, so the substrate must have insulating properties and a metal substrate cannot be used.

[0039] like Figure 4 The invention shown uses a vertical layout to divide the upper and lower transistor substrates into two independent heat sinks for complete thermal decoupling. This allows the lower transistor's 0V substrate to use a separate metal heat sink substrate for heat dissipation, overcoming the physical limitation of low thermal conductivity in insulating substrate materials. The upper transistor uses a diamond substrate of only 0.3mm as the primary insulating heat sink, eliminating thermionic effects while isolating the high potential of the upper transistor and minimizing thermal resistance. Furthermore, copper blocks with independent isolation potentials are added outside the half-bridge circuit. These copper blocks provide additional heat conduction paths for the GaN device, transferring heat from the pin side to the heat spreader, further reducing thermal resistance. Simultaneously, these large-area copper blocks act as auxiliary supports, distributing the pressure of the housing on the GaN device and reinforcing the support to improve mechanical strength.

[0040] (2) 3D layered structure: Drive integration + full-size heat sink: This invention innovatively utilizes the inherent thickness (1mm) of the DPC substrate, combined with the top tube (0.28mm) and diamond thickness (0.3mm) introduced in the vertical layout, resulting in a total thickness that perfectly matches the thickness of the thickest isolated drive (1.35mm). This allows the invention to achieve complete drive and negative voltage protection integration while ensuring the power device substrate is as close as possible to the heat sink housing. The drive and negative voltage components are successfully integrated into the power module, and the maximum height of the substrate is slightly higher than the thickest isolated drive device, ensuring full coverage of the heat sink. The rectangular blocks at the four corners of the FPC are used for mechanical support. Through this structure, the heat sink area can fully cover all components. The integration of negative voltage protection and drive significantly improves the stability of the drive signal, and the full-size heat sink improves the heat exchange efficiency between the external cold plate and the housing, reducing the junction temperature.

[0041] The third step is the integration of the phase change heat exchange plate: The 3-D integration scheme proposed in this invention converts the area of ​​the driving component into the area of ​​the heat sink, achieving full-size vapor chamber integration. For example... Figure 5 As shown, the red arrows indicate the heat flow path, and the blue arrows indicate the phase change steam propagation path. The phase change heat exchanger can rapidly conduct heat from a 12.54 mm² heat source to a 713 mm² heat exchanger shell. When exchanging heat with the external cold plate, the heat flux density is reduced by more than 50 times, thus reducing the heat treatment pressure on the external cold plate.

[0042] Meanwhile, the invention also reuses the outer copper shell of the heat spreader for electrical functions, forming an additional current path besides the FPC, thus solving the problem that the copper layer of the FPC is too thin to carry large currents. Figure 5 The blue arrows indicate additional co-flow paths formed by reusing the heat exchanger.

[0043] The fourth step is to assemble and manufacture the power module: To ensure stable assembly of the multi-substrate structure, the present invention provides the following assembly scheme: 1. First, use solder paste with a melting point of 220°C to solder the GaN bare die, copper block and diamond to the DPC substrate.

[0044] 2. Solder the logic driver devices on the FPC using 138°C solder paste, and use four corner clamps to flatten the FPC during the process to prevent warping.

[0045] 3. Connect the DPC and FPC at the interface using 138℃ solder paste.

[0046] 4. Solder the four corner copper pillars, decoupling capacitors, and interfaces on the FPC.

[0047] 5. Using 138℃ solder paste, solder one side of the heat spreader to the outer surface of the diamond and copper parts, using clamps for fixation during the process.

[0048] 6. Use a clamp to secure the other side heat spreader to the lower tube substrate and the back of the FPC.

[0049] In summary, the 3-D hybrid heat sink integrated GaN power module structure proposed in this invention has the following significant advantages: 1. Compatible with heat sink substrates on metal surfaces.

[0050] 2. Using GaN die design eliminates parasitic and thermal resistance introduced by monolithic packaging.

[0051] 3. Double-sided heat sinks that fully cover the power module.

[0052] 4. With its low profile and fully utilized internal space, the overall power module is only slightly taller than the tallest device in the module.

[0053] 5. The phase change heat exchanger provides ultra-high heat uniformity and improves hotspot handling capabilities.

[0054] 6. Integration of drive components and negative pressure components.

[0055] 7. Internal loop magnetic cancellation design, parasitic inductance <0.8nH.

[0056] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. 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 still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks, characterized in that, include: GaN chips include upper-side GaN chips and lower-side GaN chips, with the bottom of the GaN chip serving as the device substrate. The DPC substrate is placed between the upper GaN chip and the lower GaN chip to serve as a GaN chip carrier, allowing high current to pass through and providing heat dissipation. Drive devices and passive devices; FPC drive signal carrier, connected to DPC substrate and GaN chip, used to integrate drive devices and passive devices; Copper strips are used to connect the device substrate and source of a GaN chip; Copper pads are placed at the four corners of the FPC drive signal carrier to provide additional support; It is also mounted on the DPC substrate to provide additional support and additional heat dissipation pathways; The primary heat sink substrate is a double-sided metallized diamond substrate, which is set on the outside of the upper GaN chip to provide primary heat dissipation for the upper GaN chip and to insulate the device substrate from the outside. A phase change heat spreader is disposed on the outside of the upper diamond substrate for secondary heat dissipation of the upper GaN chip, and is directly disposed on the outside of the lower GaN chip for primary heat dissipation of the lower GaN chip. Cooling plates are located on the outer side of the upper and lower phase change heat exchange plates and are used for heat exchange with the phase change heat exchange plates. The cooling plates are liquid-cooled plates or air-cooled fins.

2. The gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 1, characterized in that, The gallium nitride power module adopts a vertically arranged half-bridge structure, and the device substrates of the upper and lower GaN chips are cooled sequentially through primary heat sink substrates and phase change heat sinks on the upper and lower sides.

3. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 1, characterized in that, The GaN chip adopts a lateral die design, which can eliminate the parasitic and thermal resistance introduced by monolithic packaging.

4. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 3, characterized in that, The device substrate of the upper GaN chip and the copper pillars on the source pin side of the upper GaN chip are connected to a double-sided metallized diamond substrate to obtain a structure in which the substrate and the source are connected. This structure is used to reduce the dynamic on-resistance and to insulate the device substrate of the upper GaN chip from the heat sink substrate through the diamond substrate. The device substrate of the lower GaN chip is directly connected to the phase change heat sink.

5. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 4, characterized in that, The DPC substrate is a ceramic substrate used to connect the upper GaN chip and the lower GaN chip, providing support, heat dissipation, and matching thermal expansion coefficient.

6. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 1, characterized in that, The FPC drive signal carrier is connected to the DPC substrate through a pad interface.

7. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 1, characterized in that, A copper substrate is connected to the DPC substrate to form additional heat dissipation pathways and support.

8. A gallium nitride power module with multi-substrate hybrid integration and compatibility with metal heat sinks according to claim 1, characterized in that, The area of ​​the phase change heat spreader completely covers the gallium nitride power module.

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