Gallium nitride liquid cooling integrated power module based on diamond substrate and packaging method

Abstract

The invention discloses a gallium nitride liquid cooling integrated power module based on a diamond substrate and a packaging method. The gallium nitride liquid cooling integrated power module comprises a decoupling capacitor, an electrical connection substrate, a gallium nitride chip and the diamond substrate which are sequentially stacked and connected. The diamond substrate is also provided with a metal interconnection block which is on the same horizontal plane with the gallium nitride chip. The diamond substrate is connected with the metal interconnection block and the gallium nitride chip through a conductive metal film layer and a silver sintering layer. According to the power module, the diamond is used as an assembly of the substrate, the bottom plate and the radiator, the characteristics of ultrahigh heat conductivity, high hardness, high stability, high electric insulativity and the like of the diamond are fully utilized, the heat transfer path in the heat dissipation process is greatly reduced, and the advanced heat management requirements of portability, compactness and integration are expected to be met.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated power modules, and in particular to a gallium nitride liquid-cooled integrated power module based on a diamond substrate and a packaging method. Background Art

[0002] Compared with traditional silicon-based semiconductor materials, wide bandgap semiconductor materials represented by gallium nitride have advantages such as wider bandgap width, higher withstand voltage and higher switching frequency. Among them, gallium nitride high electron mobility transistor (HEMT) is recognized as the most ideal high-frequency power device at present and is widely used in consumer electronics and defense military fields.

[0003] With the development of technology, the characteristic size of GaN chips continues to decrease, the power density continues to rise, and the heat flux density increases sharply. If the generated heat cannot be dissipated in time, the device temperature will rise, affecting the performance and working reliability of the device. In addition, the self-heating effect of GaN devices (the performance of the device will degrade or even cause the device to fail in high temperature and high field environments) means that the improvement of GaN device performance must solve the reliability problem caused by heat dissipation difficulties.

[0004] Gallium nitride power module packaging technology mainly includes single-sided DBC packaging, DBC / PCB hybrid packaging, double-sided DBC packaging and embedded packaging. Single-sided DBC packaging uses aluminum bonding wires to achieve electrical connection between the chip and the substrate. The disadvantage is that it will introduce a large parasitic inductance of the power loop, poor high-frequency performance, and poor mechanical strength of the bonding wire, which is the main reason for the failure of traditional bonding wire power modules.

[0005] The DBC / PCB hybrid package combines the advantages of the DBC substrate and the PCB substrate. It not only enhances heat dissipation and reduces the module junction-case thermal resistance through the high thermal conductivity of the DBC substrate, but also retains the PCB substrate with high wiring flexibility to reduce the parasitic inductance of the power circuit.

[0006] Double-sided DBC packaging places the chip between two DBC substrates, which can achieve efficient double-sided heat dissipation, but the disadvantage is that the wiring flexibility of DBC is poor. Embedded packaging embeds the GaN chip directly into the substrate, which can effectively save space and increase power density, but the manufacturing process is complex and the module thermal resistance is high.

[0007] CN118315381A discloses a flexible gallium nitride power module and its packaging method. The flexible gallium nitride power module includes a substrate, a first conductive layer and a second conductive layer, a polyimide material is filled between the first conductive layer and the second conductive layer to form a polyimide dielectric layer, and the first conductive layer is electrically connected to the second conductive layer through a plurality of solder joints; there are at least two GaN devices, which are arranged on one side of the first conductive layer; there is at least one decoupling capacitor, which is arranged between two adjacent GaN devices; the first conductive layer is respectively connected to the GaN device and the decoupling capacitor through an interconnect solder layer; the decoupling capacitor forms a power loop with its two adjacent GaN devices. Low packaging parasitic parameters and low chip stress are used to ensure that the power module operates safely and efficiently at high frequency and high power density, solving the problem that the parasitic inductance of the existing packaging method is difficult to further reduce.

[0008] CN116387251A discloses a double-sided heat dissipation packaging structure of a gallium nitride power module, the structure includes an upper DBC substrate and a lower DBC substrate and a plurality of gallium nitride chips sandwiched therebetween, the lower DBC substrate includes a lower first copper layer, a lower insulating layer, and a lower second copper layer from top to bottom, the gallium nitride chip is welded on the lower first copper layer, wherein the lower first copper layer is etched into a specific shape for matching the electrical connection of the gallium nitride chip, the upper DBC substrate includes an upper first copper layer, an upper insulating layer, and an upper second copper layer from bottom to top, and a transition structure is also included between the upper first copper layer and the gallium nitride chip, the transition structure includes, from bottom to top, a double-sided insulating heat dissipation tape directly in contact with the upper surface of the gallium nitride and a metal pad directly in contact with the upper first copper layer. Compared with the traditional structure, a transition structure consisting of a double-sided insulating heat dissipation tape and a metal pad is added to dissipate heat on the upper surface of the chip, and the transition structure has better height adaptability and adjustability, and can effectively solve the size mismatch problem in the manufacturing process.

[0009] If the above packaging method is used to package the GaN chip, it needs to be connected to the base plate after packaging. The base plate is the key part connecting the power module and the cooling system, and it mainly plays the role of heat dissipation and mechanical support. The module with the base plate installed is then connected to the radiator.

[0010] The heat transfer path of the above packaging method is "chip-solder-DBC substrate-solder-base plate-solder-heat sink". The heat transfer path is long and the heat dissipation efficiency is low, which cannot meet the growing heat dissipation needs of gallium nitride power modules.

[0011] In summary, the existing cooling methods for GaN packaging are mostly indirect cooling or remote cooling, with long heat transfer paths, and the heat generated by the chip cannot be dissipated in time. Heat accumulation will affect the working performance and reliability of the chip, causing chip performance degradation or even failure. In addition, remote cooling methods (large system volume, size, weight and cost, etc.) cannot meet the heat dissipation needs of miniaturized and integrated electronic devices. Summary of the invention

[0012] The present invention aims at the problem of insufficient heat dissipation performance in the packaging of gallium nitride power modules and provides a gallium nitride liquid-cooled integrated power module structure and packaging method based on a diamond substrate. The power module uses diamond as a combination of a substrate, a bottom plate and a heat sink, which greatly reduces the heat transfer path during the heat dissipation process and is expected to meet the advanced thermal management requirements of lightness, compactness and integration.

[0013] To achieve the above object, the technical solution adopted by the present invention is: A gallium nitride liquid-cooled integrated power module based on a diamond substrate, comprising a decoupling capacitor, an electrical connection substrate, a gallium nitride chip and a diamond substrate which are stacked and connected in sequence; a metal interconnection block which is on the same level as the gallium nitride chip is also provided on the diamond substrate; The diamond substrate is connected to the metal interconnection block and the gallium nitride chip through a conductive metal film layer and a silver sintering layer.

[0014] In the present invention, the problem of the long heat dissipation path of the traditional gallium nitride power module is addressed. The diamond substrate has the functions of electrical insulation, mechanical support, heat transfer and dissipation (the substrate, base plate and heat sink in the traditional solution are integrated into one), and the "chip-substrate-base plate-heat sink" heat dissipation structure is reduced to a "chip-diamond substrate" structure. This packaging method fully utilizes the characteristics of diamond such as ultra-high thermal conductivity, high hardness, high stability, and high electrical insulation, greatly reduces the heat transfer path in the heat dissipation process, and is expected to meet the advanced thermal management requirements of lightness, compactness, and integration.

[0015] Preferably, the connection between the diamond substrate and the metal interconnection block and the gallium nitride chip specifically includes: depositing a conductive metal film layer on the surface of the diamond substrate, coating the conductive metal film layer with silver paste, and then sintering and connecting it with the metal interconnection block and the gallium nitride chip.

[0016] Preferably, the diamond substrate is integrated with embedded heat dissipation microchannels, which can further enhance the heat dissipation effect of the diamond substrate and improve the system integration and compactness.

[0017] Preferably, the conductive metal film layer includes a metal adhesion layer and a main metal layer, the metal adhesion layer is close to the diamond substrate; the metal adhesion layer includes a titanium or chromium film layer with a thickness of 5-50 nanometers; the main metal layer material includes one or more of gold, silver, copper, etc., with a thickness of more than 100 nanometers, preferably a thickness of 100 nanometers to 10 microns.

[0018] Preferably, the material of the conductive metal film layer includes one or more of gold, silver, copper, etc., and can be prepared by magnetron sputtering, electron beam evaporation, electroplating and other processes; in order to improve the bonding strength between the metal film and the substrate, before sputtering the main metal layer, it is necessary to sputter a layer of titanium, chromium, etc. as an adhesion layer to enhance the interface adhesion.

[0019] Silver sintering technology requires that both sides of the connection interface are made of metal to ensure a good sintering effect and reliable interface connection. Therefore, a layer of metal film must be sputtered on the diamond surface first.

[0020] Preferably, the thickness of the diamond substrate needs to be determined according to the power level of the module and the heat dissipation requirements of the module. The depth of the embedded microchannel directly affects the heat dissipation performance, and the remaining substrate thickness after etching the microchannel determines the insulation strength and mechanical support capacity of the substrate.

[0021] Preferably, the electrical connection substrate includes one or more of DBC (Direct bonded copper), AMB (Active metal brazing), IMS (Insulated metal substrate), DPC (Direct Plated Copper), TPC (Thick-printed copper), and PCB (Printed circuit board).

[0022] The present invention also provides a packaging method for the gallium nitride liquid-cooled integrated power module based on a diamond substrate, comprising the steps of: Step 1, depositing a conductive metal film layer on the surface of a diamond substrate; Step 2, coating silver paste on the conductive metal film layer at positions corresponding to the gallium nitride chip and the metal interconnection block and drying the paste, and then sequentially placing the gallium nitride chip and the metal interconnection block on the silver paste, and sintering them into one body through silver; Step 3: Connect the electrical connection substrate and the decoupling capacitor in sequence on the gallium nitride chip and the metal interconnection block through a silver sintering or reflow soldering process.

[0023] Preferably, before step 1, the packaging method further comprises: preparing embedded heat dissipation microchannels on the diamond substrate by using a method such as picosecond laser.

[0024] Preferably, the coverage area of ​​the embedded microchannel should correspond to the location of the GaN chip and can be appropriately expanded to optimize the heat dissipation effect and improve the overall thermal management performance; Preferably, the embedded microchannel width, fin width, microchannel depth and other parameters need to be optimized in the early design stage through finite element simulation, theoretical calculation and analysis to ensure that its comprehensive performance in terms of heat dissipation performance, flow characteristics, structural strength and insulation performance is optimal; Preferably, a manifold layer is provided below the diamond substrate to optimize the uniform distribution of the fluid in the microchannels while reducing the flow pressure drop and improving the cooling efficiency.

[0025] Preferably, the surface deposition method in step 1 includes one or more of magnetron sputtering, electron beam evaporation, electroplating and the like.

[0026] Preferably, the silver sintering process in step 2 needs to ensure the accurate positioning of the gallium nitride chip and the metal interconnection block, and a frame can be used to assist in positioning to ensure a stable and reliable connection between the diamond and the chip.

[0027] The present invention proposes a new gallium nitride power module packaging method, which can greatly improve the module's thermal management capabilities and significantly reduce the module size. The traditional "chip-substrate-base plate-heat sink" structure is replaced by a diamond substrate embedded with microchannels. The silver sintering process used in the packaging process has the advantages of high thermal conductivity, high mechanical strength, excellent high temperature performance, and low temperature sintering. It can significantly improve the heat dissipation path of the power module and is conducive to the development requirements of micro-sized devices.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The packaging technology proposed in this invention is based on module-level electrical-thermal collaborative design, which enables the diamond substrate to simultaneously have electrical functions such as electrical connection and electrical insulation, mechanical functions such as mechanical support, and thermal functions such as heat diffusion and heat dissipation. This design significantly improves the heat dissipation capacity of the GaN power module while effectively reducing the module size, which is conducive to achieving advanced thermal management requirements of lightness, compactness, and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the gallium nitride liquid-cooled integrated power module based on a diamond substrate in Example 1, wherein 1 is a diamond substrate, 2 is a gallium nitride chip, 3 is an electrical connection substrate, and 4 is a decoupling capacitor.

[0030] Figure 2 Schematic diagram of the structure of depositing a conductive metal film layer and silver paste on the surface of a diamond substrate in Example 1, wherein 11 is a conductive metal film layer, 12 is a silver paste for connecting metal interconnect blocks, and 13 is a silver paste for connecting gallium nitride chips.

[0031] Figure 3 Schematic diagram of the process flow of the packaging method of the gallium nitride liquid-cooled integrated power module based on the diamond substrate in Example 1.

[0032] Figure 4 Schematic diagram of the structure of the traditional GaN liquid-cooled integrated power module in Comparative Example 1, 5 is a DBC substrate, 6 is a copper base plate, and 7 is a heat sink.

[0033] Figure 5 This is a comparison chart of the maximum chip surface temperature in the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1.

[0034] Figure 6 This is a comparison diagram of the chip surface temperature difference in the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1.

[0035] Figure 7 This is a comparison chart of the overall module volume of the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0037] The raw materials used in the following specific embodiments are all purchased from the market.

[0038] Example 1 like Figure 1 and Figure 2 As shown, a gallium nitride liquid-cooled integrated power module based on a diamond substrate comprises a decoupling capacitor 4, an electrical connection substrate 3, a gallium nitride chip 2 and a diamond substrate 1 which are stacked and connected in sequence; a metal interconnection block is arranged on a diamond substrate 1 with a thickness of 1 mm, and is at the same level as the gallium nitride chip 2; 10 nanometers of titanium and 200 nanometers of gold are sequentially deposited between the diamond substrate 1 and the metal interconnection block and the gallium nitride chip 2 by magnetron sputtering as a conductive metal film layer for subsequent sintering connection, wherein 11 is a schematic diagram of the conductive metal film layer, and 12 and 13 are silver paste coating areas for silver sintering. 12 is used to connect the metal interconnection block (a silver-plated copper block is used in this embodiment), and 13 is used to connect the gallium nitride chip 2. An embedded heat dissipation microchannel is arranged in the diamond substrate 1, which can significantly improve the heat dissipation effect of the substrate.

[0039] like Figure 3 As shown, a packaging method of a gallium nitride liquid-cooled integrated power module based on a diamond substrate comprises the following steps: Step 1, using a picosecond laser method to etch an embedded heat dissipation microchannel with a width of 60 microns and a depth of 500 microns on a diamond substrate; removing impurities on the diamond surface by ultrasonic cleaning; Step 2, using a magnetron sputtering process to sequentially deposit two regions of 10 nanometer titanium thin film layers and 200 nanometer gold as conductive metal thin film layers on the surface of the diamond substrate; Step 3, coating silver paste on the metal interconnect block and the conductive metal film layer corresponding to the gallium nitride chip; Step 4, placing the gallium nitride chip and the metal interconnection block at the corresponding position of the conductive metal film layer coated with silver paste, and sintering them into one body through silver; Step 5, coating silver paste on the upper surface of the gallium nitride chip and the metal interconnection block, and performing secondary silver sintering to electrically connect the substrate; Step 6: Connect the decoupling capacitors to the electrical connection substrate through a reflow process, and package to obtain a gallium nitride liquid-cooled integrated power module based on a diamond substrate.

[0040] Depending on the actual structure of the power module, the packaging process may be different. For example, when the drive circuit is integrated, the last step requires the simultaneous installation of components such as the driver, power supply, resistors, and capacitors.

[0041] The side of the diamond substrate etched with microchannels needs to be sealed with the cover plate. For diamond substrates with straight microchannel design, it can be sealed with the cover plate by gaskets plus bolts or double-sided tape. For manifold microchannel design, it is necessary to additionally manufacture a manifold layer to connect the microchannel with the manifold layer and the cover plate layer in sequence.

[0042] Comparative Example 1 Taking the traditional liquid-cooled integrated power module of GaN chip as a comparison, its structure is as follows Figure 4 As shown, it includes a decoupling capacitor 4, an electrical connection substrate 3, a gallium nitride chip 2, a DBC substrate 5, a copper base plate 6 and a heat sink 7 which are stacked and connected in sequence, and each part is connected in sequence by silver sintering or reflow soldering.

[0043] It is worth noting that in an actual power module, the base plate and the heat sink may be larger than the DBC to obtain better heat dissipation and mechanical support effects. The illustrations in this embodiment are only for structural illustration and are not limited to size. Figure 1 and Figure 4 The structure shown only shows a schematic diagram of the simplest power module arrangement structure, that is, a half-bridge structure formed by two GaN chips, with only one decoupling capacitor integrated in the module. More complex circuit structures (such as full bridge, etc.) can be deduced in the same way. The chip arrangement position can be determined based on the thermal-electrical-mechanical joint multi-physics field simulation.

[0044] Performance Testing The thermal performance of the gallium nitride liquid-cooled integrated power modules of Example 1 and Comparative Example 1 was simulated using COMSOL finite element simulation software, and the module volumes were calculated and compared. The simulation results are as follows: Figure 5-Figure 7 shown. Figure 5 This is a comparison chart of the maximum chip surface temperature in the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1. Figure 6 This is a comparison diagram of the chip surface temperature difference in the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1. Figure 7 This is a comparison chart of the overall module volume of the gallium nitride liquid-cooled integrated power module of Example 1 and Comparative Example 1.

[0045] It can be seen that compared with the traditional "chip-solder-substrate-solder-bottom plate-solder-heat sink" packaging solution in Comparative Example 1, the "chip-solder-diamond substrate" packaging solution in Example 1 of the present invention reduces the maximum temperature of the chip surface by 46.3%, the chip surface temperature difference by 74.0%, and the total volume of the module by 62.1%.

Claims

1. A gallium nitride liquid-cooled integrated power module based on a diamond substrate, characterized in that: It comprises a decoupling capacitor, an electrical connection substrate, a gallium nitride chip and a diamond substrate which are stacked and connected in sequence; the diamond substrate is also provided with a metal interconnection block which is on the same level as the gallium nitride chip; The diamond substrate is connected to the metal interconnection block and the gallium nitride chip through a conductive metal film layer and a silver sintering layer.

2. The gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 1, characterized in that: The connection between the diamond substrate and the metal interconnection block and the gallium nitride chip specifically includes: depositing a conductive metal film layer on the surface of the diamond substrate, coating the conductive metal film layer with silver paste, and then sintering and connecting it with the metal interconnection block and the gallium nitride chip.

3. The gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 1, characterized in that: An embedded heat dissipation microchannel is integrated in the diamond substrate.

4. The gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 1, characterized in that: The conductive metal film layer includes a metal adhesion layer and a main metal layer, and the metal adhesion layer is close to the diamond substrate.

5. The gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 4, characterized in that: The material of the metal adhesion layer includes a titanium or chromium thin film layer with a thickness of 5-50 nanometers; the material of the main metal layer includes one or more of gold, silver, copper, etc. with a thickness of more than 100 nanometers.

6. The gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 1, characterized in that: The electrical connection substrate includes one or more of DBC, AMB, IMS, DPC, TPC, and PCB.

7. The packaging method of a gallium nitride liquid-cooled integrated power module based on a diamond substrate according to any one of claims 1 to 6, characterized in that: Includes steps: Step 1, depositing a conductive metal film layer on the surface of a diamond substrate; Step 2, coating silver paste at the location where the gallium nitride chip and the metal interconnection block are connected on the conductive metal film layer and drying the paste, and then placing the gallium nitride chip and the metal interconnection block on the silver paste and sintering them into one body through silver; Step 3: Connect the electrical connection substrate and the decoupling capacitor in sequence on the gallium nitride chip and the metal interconnection block through a silver sintering or reflow soldering process.

8. The packaging method of the gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 7, characterized in that: The packaging method further comprises, before step 1, preparing embedded heat dissipation microchannels on the diamond substrate using a picosecond laser.

9. The packaging method of the gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 7, characterized in that: A manifold layer is disposed below the diamond substrate.

10. The packaging method of the gallium nitride liquid-cooled integrated power module based on a diamond substrate according to claim 7, characterized in that: The surface deposition method in step 1 includes one or more of magnetron sputtering, electron beam evaporation, and electroplating.

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