A multi-flow channel heat sink substrate design method for power module heat source layout

Abstract

The application discloses a multi-flow channel heat uniform substrate design method for a power module heat source layout, and belongs to the technical field of power semiconductor packaging. The design method comprises the following steps: obtaining the shell profile of the heat uniform substrate according to the type of the power module to be cooled; the shell of the heat uniform substrate comprises an evaporation end top plate and a condensation end cavity base; first supporting metal columns are arranged on the condensation end cavity base at positions corresponding to the heat sources of each chip of the power module, and a plurality of second supporting metal columns are uniformly arranged on the remaining positions of the condensation end cavity base; the wicking core is sintered on the lower surface of the evaporation end top plate and the inner surface of the condensation end cavity base, and the foam copper ring is wrapped outside all the first supporting metal columns and part of the second supporting metal columns; and finally, the evaporation end top plate and the condensation end cavity base are assembled to form a closed cavity. The application is based on the phase change heat transfer and capillary driving principle, and the liquid phase flow resistance is greatly reduced through the multi-liquid channel design, so that the evaporation and condensation efficiency is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor packaging technology, specifically relating to a design method for a multi-channel heat dissipation substrate for power module heat source layout. Background Technology

[0002] With the rapid development of high-voltage, high-power applications such as electric vehicles, new energy power generation, and data center power supplies, power modules, as core components of power conversion, are continuously evolving towards higher power density, miniaturization, and higher reliability. While wide-bandgap semiconductor devices, represented by silicon carbide (SiC) and gallium nitride (GaN), possess excellent switching performance and high-temperature tolerance, their typically small chip area leads to a significant increase in local heat flux density. Meanwhile, traditional silicon-based IGBT modules still dominate in high-power applications, and their multi-chip parallel structure also faces the problem of significant thermal coupling effects. Therefore, all types of power modules urgently require efficient thermal management technologies.

[0003] In high-power multi-chip power modules, the strong thermal coupling effect caused by the close arrangement of multiple chips can easily lead to uneven junction temperature distribution within the module, forming localized hot spots. This temperature non-uniformity not only accelerates the thermo-mechanical fatigue aging of the packaging materials but also causes current imbalances between chips and uneven electrical stress during switching, severely restricting the long-term reliability and power output capability of the module. This problem is particularly prominent in high-voltage, high-power applications, and thermal management of multi-chip parallel structures remains a common technical challenge regardless of the semiconductor materials used.

[0004] To address the aforementioned thermal management challenges, the industry has developed a variety of advanced heat dissipation technologies. Integrated liquid cooling technologies (such as direct substrate cooling and embedded microchannels) can significantly reduce the junction-to-case thermal resistance of modules, but their complex structure requires high standards for insulation design and coolant flow uniformity, and they are difficult to effectively improve thermal coupling between multiple chips and in-plane temperature uniformity. While double-sided cooling technologies and high thermal conductivity packaging materials can improve overall heat dissipation capabilities, they are still essentially limited by solid-to-solid heat conduction mechanisms, and their effects on localized hot spots and lateral heat diffusion between chips are limited.

[0005] Vapor chambers (VCs), as passive heat dissipation components based on gas-liquid phase change heat and capillary-driven reflux, possess extremely high equivalent thermal conductivity (reaching 12~28.8 kW / (m·K)) and excellent lateral heat diffusion capabilities, effectively suppressing local hot spots and improving temperature uniformity in the heat source area. However, existing research on power module integration using vapor chambers largely focuses on medium power levels (≤300W) or simplified chip layouts. For high-voltage, high-power modules with numerous chips and strong thermal coupling, systematic design and verification are lacking. Therefore, there is an urgent need for a vapor chamber substrate design method that can adapt to multi-chip heat source layouts, has multiple liquid reflux channels, and is compatible with existing power module packaging processes, in order to achieve efficient thermal management and optimized temperature uniformity of high-voltage, high-power modules. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a design method for a multi-channel heat dissipation substrate for power module heat source layout.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention discloses a design method for a multi-channel heat dissipation substrate for the layout of heat sources in power modules, the method comprising the following design steps: S1: Obtain the outer shell outline of the heat dissipation substrate according to the type of power module to be cooled, wherein the outer shell of the heat dissipation substrate includes an evaporation end top plate and a condensation end cavity base. S2: Based on the layout of the heat source of each chip in the power module, first supporting metal pillars are arranged on the condensing end cavity base at the positions corresponding to the heat source of each chip, and multiple second supporting metal pillars are evenly arranged at the remaining positions on the condensing end cavity base. S3: Sinter the liquid-absorbing core on the lower surface of the top plate of the evaporation end and the inner surface of the cavity base of the condensation end. S4: Wrap a foam copper ring around all the first supporting metal columns and part of the second supporting metal columns, wherein the thickness of the foam copper ring wrapped around the first supporting metal columns is greater than the thickness of the foam copper ring wrapped around the second supporting metal columns. S5: Assemble the evaporator top plate and the condenser cavity base to form a sealed cavity, so that the foam copper ring contacts and connects with the liquid absorption core of the evaporator top plate and the condenser cavity base, so as to form multiple parallel evaporation-condensation circulation paths under the drive of capillary force.

[0008] Furthermore, in S1, a liquid injection pipe for injecting a working fluid into the heat spreader substrate is installed on the condenser cavity base; wherein the working fluid is a mixture of water, acetone and ethanol.

[0009] Furthermore, the foamed copper ring is a ring-shaped component made of foamed copper material; for all the second supporting metal columns, the foamed copper ring is spaced around the outer periphery of the second supporting metal column, that is, one foamed copper ring is set every other second supporting metal column, so that a steam flow area is formed between two adjacent second supporting metal columns; the thickness of the foamed copper ring wrapped around the second supporting metal column is 0.8-1.2mm; the thickness of the foamed copper ring wrapped around the first supporting metal column is 1.3-1.6mm, and the distance between adjacent foamed copper rings is greater than or equal to 5mm.

[0010] Secondly, the present invention also discloses a multi-channel heat spreader substrate generated using the aforementioned design method, comprising an evaporation end top plate, a condensation end cavity base, a liquid absorbent core, a first supporting metal pillar, a second supporting metal pillar, and a foam copper ring; the evaporation end top plate and the condensation end cavity base are assembled to form a sealed cavity, the first supporting metal pillar is arranged at the position corresponding to the heat source of each chip in the power module on the condensation end cavity base, and a plurality of second supporting metal pillars are evenly arranged at the remaining positions on the condensation end cavity base; the lower surface of the evaporation end top plate and the inner surface of the condensation end cavity base are both sintered with liquid absorbent cores, and all the first supporting metal pillars and some of the second supporting metal pillars are wrapped with a foam copper ring; wherein, a liquid injection pipe is installed on the condensation end cavity base.

[0011] Thirdly, the present invention discloses a method for heat dissipation of a power module using the aforementioned heat dissipation substrate, comprising the following steps: In a vacuum environment, the sealed cavity is first evacuated through the injection pipe. Then, the heat spreader substrate and the DBC layer of the power module are reflow soldered to bring the top plate of the evaporation end of the heat spreader substrate into contact with the DBC layer. Next, a preset mass of liquid working fluid is injected into the sealed cavity through the injection pipe. After the working fluid injection is completed, the sealed cavity is evacuated a second time through the injection pipe, and the heat spreader substrate is heated to allow the non-condensable gas in the sealed cavity to be discharged through the injection pipe. Finally, the injection pipe is cut off and sealed. During the operation of the power module, the heat generated by multiple chip heat sources in the power module is transferred to the evaporation side of the heat spreader substrate through the DBC layer, causing the liquid working fluid in the wick on the evaporation side to absorb heat and vaporize. The vaporized working fluid diffuses to the condensation side in the sealed cavity and releases heat to condense and form a liquid working fluid. Under the action of capillary force, the condensed liquid working fluid flows back to the wick on the evaporation side through the wick on the condensation side and the foam copper ring sleeved on the outside of the supporting metal column, so as to heat the power module through the gas-liquid phase change cycle and multiple parallel evaporation-condensation cycle paths.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a non-uniform structural design oriented towards the heat source. Specifically, copper pillars are placed directly below the heat source and wrapped with thick foamed copper rings to enhance the supply of working fluid and shorten the heat transfer path. Meanwhile, copper pillars are placed in non-heat source areas and wrapped with thin foamed copper rings to balance auxiliary heat dissipation and the unobstructed flow of vapor channels. This overcomes the problem of uneven temperature distribution among multiple chips that is difficult to effectively alleviate in existing technologies. As a result, it achieves the technical effects of precise thermal management, effective mitigation of thermal coupling effects, and improved uniformity of heat source temperature in the module.

[0013] This invention employs a multi-channel parallel design, dividing the traditional single-path long liquid return channel into multiple parallel short loops by wrapping a foamed copper ring around the copper pillar. This overcomes the problems of high flow resistance, easy local drying, low evaporation and condensation efficiency, and limited heat source power caused by the single and excessively long liquid flow path in existing heat spreader technologies. Consequently, it achieves significant reductions in liquid flow resistance, avoidance of local drying, improved evaporation and condensation efficiency, and effectively ensures stable operation of the phase change heat cycle under high power.

[0014] This invention employs a heat dissipation substrate design that is highly compatible with existing packaging processes. Its external dimensions are basically the same as those of traditional copper substrates, allowing for direct replacement. It provides passive heat dissipation, eliminates insulation issues, and does not require changes to the existing power module's DBC layout, chip arrangement, or packaging process. Furthermore, it is applicable to various types of power modules, including SiC, IGBT, and GaN. Therefore, it overcomes the problems of high industrialization difficulty and poor compatibility caused by the need to modify packaging processes or adjust module layouts for novel heat dissipation structures in existing technologies. As a result, it achieves the technical advantages of not requiring changes to existing processes, direct replacement, wide applicability, and broad industrialization prospects.

[0015] 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 study, or may be learned from the practice of the invention. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the multi-channel heat dissipation substrate for power module heat source layout according to the present invention. Figure 2 This is a heat source distribution diagram of the power module in one embodiment of the present invention; Figure 3 This is a layout diagram of the supporting copper pillars and foam copper rings in one embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the working principle of a heat-spreading substrate in one embodiment of the present invention. Figure 5 This is a flowchart illustrating the fabrication process of a heat-spreading substrate integrated power module according to one embodiment of the present invention. Figure 6 This is a flowchart illustrating the fabrication process of an integrated power module on a heat-spreading substrate according to one embodiment of the present invention. Figure 7 A comparison graph showing the thermal resistance of a heat spreader substrate and a pure copper substrate at different temperatures. Figure 8 A comparison of the steady-state junction temperatures of 8 chips on a pure copper substrate and a heat-spreading substrate. Figure 9 A comparison of the thermal performance of a pure copper substrate and a heat spreader substrate under twice the heating power. Detailed Implementation

[0017] 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.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and 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.

[0019] 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.

[0020] This invention addresses the heat source layout characteristics of power module chips (i.e., power modules) by providing a multi-channel heat dissipation substrate design method for power module heat source layout. This method aims to solve the problems of significant thermal coupling effect caused by parallel layout of multiple chips, uneven junction temperature distribution between chips, formation of local hot spots, and accelerated thermo-mechanical fatigue failure of packaging materials.

[0021] To achieve the above objectives, the present invention provides the following technical solution: Option 1: This invention provides a multi-channel heat dissipation substrate design method for power module chip heat source layout, including the following design steps: S1: Referencing the conventional substrate morphology of existing power modules, determine the external shape (i.e., the shell outline) of the heat spreader substrate, prepare the evaporation end top plate and the condensation end cavity base of the heat spreader substrate, and leave a liquid injection pipe on the bottom of the condensation end cavity. The liquid injection pipe is used to inject working fluid into the heat spreader substrate. Here, the external shape refers to the outer dimensions of the heat spreader substrate, the position of the mounting holes of the heat spreader substrate, and the position of the positioning notch. S2: Determine the arrangement scheme of the internal support copper pillars of the heat dissipation substrate according to the layout of the multiple chip heat sources in the power module; specifically, according to the layout of the multiple chip heat sources in the power module, arrange the first support copper pillars at the positions corresponding to each chip heat source on the condensing end cavity base, and arrange multiple second support copper pillars evenly at the remaining positions on the condensing end cavity base. S3: A liquid-absorbing core is sintered on the lower surface of the top plate of the evaporator end and the inner surface of the base of the condenser end cavity; wherein, holes are pre-reserved at the corresponding positions of the supporting copper pillar on the two capillary structures of the top liquid-absorbing core (i.e., the liquid-absorbing core sintered on the lower surface of the top plate of the evaporator end) and the bottom liquid-absorbing core (i.e., the liquid-absorbing core sintered on the inner surface of the base of the condenser end cavity), so that no liquid-absorbing core will be sintered on the supporting copper pillar. S4: Based on the heat source distribution of the power module, wrap porous foam copper rings (i.e. foam copper rings) of different sizes around all the first support copper pillars and part of the second support copper pillars. S5: The evaporator top plate and the condenser cavity base are permanently sealed by 800℃ high-temperature brazing, forming a sealed cavity capable of withstanding subsequent processing (such as reflow welding and vacuuming). The foamed copper ring contacts and connects with the liquid-absorbing core of the evaporator top plate and the condenser cavity base, forming multiple parallel short evaporation-condensation circulation paths driven by capillary force. This shortens the phase change heat transfer circuit, reduces the liquid flow resistance in the foamed copper ring and the liquid-absorbing core, and improves evaporation and condensation efficiency.

[0022] Among them, the liquid wick and the foamed copper ring are commonly used capillary structure materials in the field of heat spreaders / heat pipes.

[0023] Furthermore, the top and bottom suction cores adopt an asymmetrical structural design. The top suction core has a thinner structure with lower porosity to provide high capillary force and reduce thermal resistance, while the bottom suction core has a thicker structure with higher porosity to facilitate reduced flow resistance and provide sufficient liquid return channels. Specifically, the thickness of the top suction core is 0.25-0.4 mm and the porosity is 0.6-0.8; the thickness of the bottom suction core is 0.5-0.8 mm and the porosity is 0.85-0.95.

[0024] Furthermore, the arrangement of the supporting copper pillars includes placing at least one first supporting copper pillar directly below each chip heat source to quickly conduct heat from local hot spots, while simultaneously arranging multiple second supporting copper pillars evenly in other areas (i.e., non-chip heat source areas) to enhance the overall structural strength and heat diffusion capability. Specifically, the multiple second supporting pillars are arranged at intervals to meet the requirements of supporting the heat spreader cavity and accommodating the vapor flow space within the heat spreader. The diameter of both the first and second supporting copper pillars is 2.6 mm, and their height ranges from 2.0 to 2.5 mm.

[0025] Furthermore, the dimensions of the foamed copper rings surrounding the first and second supporting copper pillars are designed based on the heat flux density of their respective locations. A thicker foamed copper ring is used to wrap the first supporting copper pillars in the chip's heat source area, enhancing the working fluid supply and evaporation efficiency in this area, while maintaining a distance of at least 5mm between adjacent foamed copper rings to ensure both working fluid return and unobstructed vapor passage. A thinner foamed copper ring is used to wrap the second supporting copper pillars in non-heat source areas, with one foamed copper ring placed every other second supporting copper pillar. Specifically, the foamed copper rings are annular components made of foamed copper material; the thickness of the foamed copper rings surrounding the first supporting copper pillars is 1.3-1.6mm, and the thickness of the foamed copper rings surrounding the second supporting copper pillars is 0.8-1.2mm, with a porosity between 0.8 and 0.9.

[0026] Furthermore, the shape of the heat spreader substrate is basically the same as that of the conventional substrate (i.e., traditional copper substrate) of the existing power module. The present invention also performs nickel plating on the outer surface of the heat spreader substrate to form a nickel plating layer for improving solder wettability. After nickel plating on the outer surface of the heat spreader substrate, it can directly replace the traditional copper substrate and be reflow soldered and integrated with the DBC (Direct Bonded Copper) layer of the power module, which is compatible with the existing power module packaging process.

[0027] Option 2: Figure 1 As shown, the present invention provides a heat-spreading substrate designed and generated using the above method, comprising an evaporation end top plate, a condensation end cavity base, a liquid-absorbing core, a first supporting copper pillar, a second supporting copper pillar, and a foam copper ring; the evaporation end top plate and the condensation end cavity base are assembled to form a sealed cavity, the first supporting metal pillar is arranged at the position corresponding to the heat source of each chip in the power module on the condensation end cavity base, and a plurality of second supporting metal pillars are evenly arranged at the remaining positions on the condensation end cavity base; the lower surface of the evaporation end top plate and the inner surface of the condensation end cavity base are both sintered with a liquid-absorbing core, and all the first supporting metal pillars and some of the second supporting metal pillars are wrapped with a foam copper ring; Option 3: The present invention also provides a method for heat dissipation of a power module using the above-mentioned heat dissipation substrate, comprising the following steps: In a vacuum environment, the sealed cavity is first evacuated through the injection pipe. Then, the heat spreader substrate and the DBC layer of the power module are reflow soldered, bringing the top plate of the evaporation end of the heat spreader substrate into contact with the DBC layer. Next, a predetermined mass of liquid working fluid is injected into the sealed cavity through the injection pipe. The mass of the injected working fluid... The calculation formula is: in, For the working fluid density, , , , , , These are the volume of the evaporation end wick, the porosity of the evaporation end wick, the total volume of the copper foam ring, the porosity of the copper foam ring, and the volume and porosity of the condensation end wick.

[0028] After the liquid working fluid injection is completed, the sealed cavity is evacuated a second time through the injection pipe, and the heat spreader is heated so that the non-condensable gas in the sealed cavity is discharged through the injection pipe; finally, the injection pipe is cut off and sealed. During the operation of the power module, the heat generated by multiple chip heat sources in the power module is transferred to the evaporation side of the heat spreader substrate through the DBC layer, causing the liquid working fluid in the wick on the evaporation side to absorb heat and vaporize. The vaporized working fluid diffuses to the condensation side in the sealed cavity and releases heat to condense and form a liquid working fluid. Under the action of capillary force, the condensed liquid working fluid flows back to the wick on the evaporation side through the wick on the condensation side and the foam copper ring sleeved on the outside of the supporting metal column, so as to heat the power module through the gas-liquid phase change cycle and multiple parallel evaporation-condensation cycle paths.

[0029] The key to the homogenization method of the present invention is to arrange the liquid injection process after reflow welding to avoid the working fluid from vaporizing and failing due to the high temperature of reflow welding. At the same time, the double vacuum sealing ensures that there are no non-condensable gas residues in the cavity, thus guaranteeing the long-term stability of phase change heat transfer.

[0030] This embodiment provides a design method for a multi-channel heat dissipation substrate of a common commercial Economial packaged all-SiC power module. The method includes the following design steps: S1: Referencing the shape of the commercial copper substrate of a common commercial Economial packaged all-SiC power module, the geometry of the multi-channel heat sink is determined. The dimensions of this commercial copper substrate are 122mm × 62mm × 3mm. The external geometry of the heat sink described in this invention is kept as consistent as possible with this substrate to ensure compatibility with the all-SiC power module packaging process and heatsink interface.

[0031] S2: Based on the layout of multiple chip heat sources in the all-SiC power module, determine the arrangement scheme of the supporting copper pillars and porous liquid wick inside the heat spreader substrate. For example... Figure 2 As shown, the all-SiC power module in this embodiment adopts a half-bridge structure. Each bridge arm consists of 8 SiC MOSFET chips and 8 SBD diode chips connected in parallel, with chip sizes of 4.14mm × 4.96mm and 4.25mm × 4.25mm, respectively. Based on the chip layout, 32 copper pillars with a radius of 1.3mm are placed directly below the chip heat source, corresponding to 16 SiC MOSFETs and 16 SiC SBD chips; 88 copper pillars are evenly arranged in other non-heat source areas to enhance the overall structural strength and heat dissipation capability.

[0032] S3: A liquid-absorbing core is sintered on the lower surface of the top plate of the evaporator end and the inner surface of the base of the condenser end cavity; wherein, holes are pre-reserved at the corresponding positions of the supporting copper pillar on the two capillary structures of the top liquid-absorbing core (i.e., the liquid-absorbing core sintered on the lower surface of the top plate of the evaporator end) and the bottom liquid-absorbing core (i.e., the liquid-absorbing core sintered on the inner surface of the base of the condenser end cavity), that is, no liquid-absorbing core is sintered on the supporting copper pillar.

[0033] S4: Based on the heat source distribution of the power module, foam copper rings of different sizes are wrapped around the outside of multiple supporting copper pillars. For example... Figure 3 As shown, while ensuring that the distance between adjacent foam copper rings exceeds 5mm, 32 supporting copper pillars directly below the chip heat source are wrapped with foam copper rings with a thickness of 1.5mm to enhance the working fluid supply and evaporation efficiency in the heat source area; in the supporting copper pillars in other areas, a foam copper ring with a thickness of 0.9mm is set every other supporting copper pillar, for a total of 39, to provide an auxiliary heat transfer channel while keeping the vapor chamber unobstructed.

[0034] S5: The evaporator top plate and the condenser cavity base are permanently sealed by 800℃ high-temperature brazing, forming a sealed cavity capable of withstanding subsequent processing (such as reflow welding, vacuuming). The foamed copper ring contacts and connects with the liquid-absorbing core of the evaporator top plate and the condenser cavity base, forming multiple parallel short evaporation-condensation circulation paths driven by capillary force. Figure 4 As shown, the foamed copper ring connects the liquid suction core on the evaporation side (i.e., the liquid suction core on the top plate of the evaporation end) and the liquid suction core on the condensation layer side (i.e., the liquid suction core on the base of the condensation end cavity), dividing the traditional single-path long liquid return channel into multiple parallel short loops, thereby shortening the phase change heat transfer loop, reducing the liquid phase flow resistance in the porous medium, and improving the evaporation and condensation efficiency.

[0035] The specific design and power module heat dissipation method of this embodiment are as follows: Figure 5 and Figure 6 As shown, it includes the following steps: S1: The thickness of the top plate of the evaporation end is 0.6mm, the thickness of the base of the condensing end cavity is 2.9mm, the height of the supporting copper column is 2.3mm, and a liquid injection pipe is left on the bottom 9 of the condensing end cavity; specifically, the thickness of the bottom plate of the condensing end cavity base is 0.6mm, and the final heat spreader is a sealed cavity with a total thickness of 3.5mm. S2: Based on the layout of multiple chip heat sources in the power module, determine the arrangement scheme of the internal support copper pillars of the heat dissipation substrate, and machine the designed support copper pillars on the condensation end cavity base. S3: A liquid-absorbing core is sintered on the lower surface of the evaporator top plate and the inner surface of the condenser cavity base. A 0.28mm thick wire mesh structure with a porosity of 0.7 is sintered on the lower surface of the evaporator top plate as the evaporator liquid-absorbing core; and a 0.6mm thick wire mesh structure with a porosity of 0.9 is sintered on the inner surface of the condenser cavity base as the condenser liquid-absorbing core. In addition, a 1.42mm high foamed copper ring with a porosity of 0.85 is sintered around the supporting copper pillars. The supporting copper pillars in the heat source area are wrapped with a 1.5mm thick foamed copper ring, while those in the non-heat source area are wrapped with a 0.9mm thick foamed copper ring.

[0036] S4: The evaporator top plate and the condenser cavity base are sealed and assembled using a high-temperature brazing process to form a closed cavity. The brazing temperature is 800℃ to ensure the airtightness and structural strength of the cavity.

[0037] S5: The assembled structure is nickel-plated with a thickness of 3μm to enhance the solderability of subsequent welding processes.

[0038] S6: The sealed cavity is evacuated for the first time in a vacuum environment through the injection pipe to prevent oxidation of the liquid suction core during subsequent processing.

[0039] S7: Reflow soldering is performed on the heat spreader substrate and the DBC layer of the power module to complete the packaging of the heat spreader substrate and the power module. The reflow soldering temperature is 250℃.

[0040] S8: Open the injection tube pre-installed on the base of the condenser cavity and inject the working fluid. The working fluid used in this embodiment is a mixture of 95% water, 5% acetone and ethanol. This mixture has good thermophysical properties in the range of 30~200℃, and the filling mass is 4.7g.

[0041] S9: Perform a second vacuuming process on the heat-spreading substrate and heat the heat-spreading substrate to 80~100℃ to remove non-condensable gases.

[0042] S10: Cut and seal the injection tube to complete the final encapsulation of the heat spreader substrate. During the operation of the power module, the heat generated by multiple chip heat sources in the power module is transferred to the evaporation side of the heat spreader substrate through the DBC layer, causing the liquid working fluid in the wick on the evaporation side to absorb heat and vaporize. The vaporized working fluid diffuses to the condensation side in the sealed cavity and releases heat to condense and form a liquid working fluid. Under the action of capillary force, the condensed liquid working fluid flows back to the wick on the evaporation side through the wick on the condensation side and the foam copper ring sleeved on the outside of the supporting metal column, so as to heat the power module through the gas-liquid phase change cycle and multiple parallel evaporation-condensation cycle paths.

[0043] The key to the homogenization method of the present invention is to arrange the liquid injection process after reflow welding to avoid the working fluid from vaporizing and failing due to the high temperature of 250°C. At the same time, the double vacuum sealing ensures that there are no non-condensable gas residues in the cavity, thus ensuring the long-term stability of phase change heat transfer.

[0044] This embodiment verifies the technical effects of the present invention through experiments. Following the design method described in the embodiment, a heat-spreading substrate is integrated with a power module prototype, and multiple electrothermal performance tests are conducted on it against a conventional copper substrate of the power module prototype.

[0045] Thermal resistance testing was conducted using the dual-interface method. Figure 7 The display shows that at 25°C, the traditional copper substrate (i.e. Figure 7 The thermal resistances of the copper-based substrate and the vapor chamber substrate of the present invention are 0.0108 °C / W and 0.0095 °C / W, respectively. The thermal resistance of the vapor chamber substrate of the present invention is 12.67% lower than that of the conventional copper substrate. Moreover, the thermal resistance of the substrate of the present invention continues to decrease as the substrate temperature increases, reaching its lowest point at 100 °C / W, which is more than 46% lower than that of the conventional copper substrate.

[0046] In the embodiment where the power module is an all-SiC power module, the DC heating test results are as follows: Figure 8 As shown, the horizontal axis numbers #1, #2, #3, #4, #5, #6, #7, and #8 represent the first, second, third, fourth, fifth, sixth, seventh, and eighth SiC MOSFET chips in the upper bridge arm of the all-SiC power module, respectively. Under a heating power of 330W, the traditional copper substrate (i.e....) Figure 8 The pure copper substrate module in the present invention and the heat-spreading substrate of the present invention (i.e., Figure 8 The heat spreader substrate modules in this invention all reach a steady state after heating for 240 seconds. The highest junction temperature of a traditional copper substrate is 112°C, and the maximum temperature difference between chips is 11.2°C. The highest junction temperature of the heat spreader substrate of this invention is about 100°C, and the temperature difference between chips is controlled within 3°C. The junction temperature comparison curve clearly demonstrates the temperature uniformity advantage of this invention.

[0047] Figure 9This demonstrates the traditional copper substrate (i.e., 660W) under twice the heating power (i.e., 2 times the heating power). Figure 9 The copper substrate module in the present invention and the heat dissipation substrate of the present invention (i.e., Figure 9 A comparison of the thermal performance of the vapor chamber module in this invention. Using 175°C as the junction temperature limit, the traditional copper substrate reaches the limit in 55.8 seconds, while the vapor chamber module of this invention extends the safe operating time to 179 seconds, more than three times the limit. This demonstrates that the invention has significant thermal buffering capability under overload conditions and is of great value in improving the thermal reliability of power modules.

[0048] In summary, this invention, based on the phase change heat transfer mechanism, designs a multi-channel heat dissipation substrate structure oriented towards the heat source, which significantly improves the heat dissipation performance and temperature uniformity of the power module. At the same time, it is highly compatible with existing packaging processes and has broad prospects for industrial applications.

[0049] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the invention and not to limit it. Although the invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the invention.

[0050] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for multi-streamer uniform heat substrate design for power module heat source layout, characterized in that, This method includes the following design steps: S1: Obtain the outer shell outline of the heat dissipation substrate according to the type of power module to be cooled, wherein the outer shell of the heat dissipation substrate includes an evaporation end top plate and a condensation end cavity base. S2: Based on the layout of the heat source of each chip in the power module, first supporting metal pillars are arranged on the condensing end cavity base at the positions corresponding to the heat source of each chip, and multiple second supporting metal pillars are evenly arranged at the remaining positions on the condensing end cavity base. S3: Sinter the liquid-absorbing core on the lower surface of the top plate of the evaporation end and the inner surface of the cavity base of the condensation end. S4: Wrap a foam copper ring around all the first supporting metal columns and part of the second supporting metal columns, wherein the thickness of the foam copper ring wrapped around the first supporting metal columns is greater than the thickness of the foam copper ring wrapped around the second supporting metal columns. S5: Assemble the evaporator top plate and the condenser cavity base to form a sealed cavity, so that the foam copper ring contacts and connects with the liquid absorption core of the evaporator top plate and the condenser cavity base, so as to form multiple parallel evaporation-condensation circulation paths under the drive of capillary force.

2. The design method of claim 1, wherein, In S1, a liquid injection pipe for injecting working fluid into the heat spreader substrate is also installed on the condenser cavity base; wherein the working fluid is a mixture of water, acetone and ethanol.

3. The method of claim 1, wherein, Both the first and second supporting metal pillars are copper pillars; the first and second supporting metal pillars are directly formed on the bottom surface of the condenser end cavity base by machining.

4. The design method according to claim 1, characterized in that, The thickness of the liquid-absorbing core sintered on the lower surface of the evaporator top plate is 0.25-0.4 mm, and the porosity is 0.6-0.8; the thickness of the liquid-absorbing core sintered on the inner surface of the condenser cavity base is 0.5-0.8 mm, and the porosity is 0.85-0.

95.

5. The method according to claim 1, characterized in that, The foamed copper ring is a ring-shaped component made of foamed copper material with a porosity of 0.8-0.

9. For all the second supporting metal columns, the foamed copper ring is spaced around the outer periphery of the second supporting metal column, that is, one foamed copper ring is set every other second supporting metal column, so that a steam flow area is formed between two adjacent second supporting metal columns. The thickness of the foamed copper ring wrapped around the second supporting metal column is 0.8-1.2mm. The thickness of the foam copper ring wrapped around the first supporting metal column is 1.3-1.6mm, and the distance between adjacent foam copper rings is greater than or equal to 5mm.

6. The method according to claim 1, characterized in that, The outer surface of the heat-spreading substrate is nickel-plated to form a nickel plating layer for improving solder wettability.

7. A multi-channel heat spreader substrate generated using the design method of claim 1, characterized in that, The device includes an evaporator top plate, a condenser cavity base, a liquid absorbent core, a first supporting metal column, a second supporting metal column, and a copper foam ring. The evaporator top plate and the condenser cavity base are assembled to form a sealed cavity. The first supporting metal column is arranged on the condenser cavity base at the position corresponding to the heat source of each chip in the power module, and multiple second supporting metal columns are evenly arranged at other positions on the condenser cavity base. The lower surface of the evaporator top plate and the inner surface of the condenser cavity base are both sintered with liquid absorbent cores. All the first supporting metal columns and some of the second supporting metal columns are wrapped with a copper foam ring. A liquid injection pipe is installed on the condenser cavity base.

8. A method for heat dissipation of a power module using the heat dissipation substrate of claim 7, characterized in that, Includes the following steps: In a vacuum environment, the sealed cavity is evacuated for the first time through the injection pipe. Then, the heat spreader substrate and the DBC layer of the power module are reflow soldered so that the top plate of the evaporation end of the heat spreader substrate comes into contact with the DBC layer. Next, a preset mass of working fluid is injected into the sealed cavity through the injection pipe. After the working fluid injection is completed, the sealed cavity is evacuated for the second time through the injection pipe, and the heat spreader substrate is heated so that the non-condensable gas in the sealed cavity is discharged through the injection pipe. Finally, the injection pipe is cut off and sealed. During the operation of the power module, the heat generated by multiple chip heat sources in the power module is transferred to the evaporation side of the heat spreader substrate through the DBC layer, causing the liquid working fluid in the wick on the evaporation side to absorb heat and vaporize. The vaporized working fluid diffuses to the condensation side in the sealed cavity and releases heat to condense and form a liquid working fluid. Under the action of capillary force, the condensed liquid working fluid flows back to the wick on the evaporation side through the wick on the condensation side and the foam copper ring sleeved on the outside of the supporting metal column, so as to heat the power module through the gas-liquid phase change cycle and multiple parallel evaporation-condensation cycle paths.

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