Transient high-efficiency heat dissipation system and method for power module

Abstract

The present invention discloses a transient high-efficiency heat dissipation system and method for power modules. The system includes a metal cavity close to the power module, a heat pipe array, and a plurality of phase change material modules with different thermal conductivities arranged in the metal cavity. The phase change material modules are arranged according to the heat flux density in the metal cavity to balance the heat flux non-uniformity on the surface of the power module during transient overcurrent. The evaporation section of the heat pipe array is embedded in the metal cavity and the phase change material module; the heat pipe is filled with a working fluid and a phase change microcapsule that can move with the working fluid; the phase change microcapsule absorbs external heat flow together with the working fluid, and is carried by the working fluid in the heat pipe to complete the heat cycle between the evaporation section and the condensation section. The system of the present invention has both steady-state and transient heat dissipation functions, can improve the heat storage capacity under the same volume, balance the heat non-uniformity, add micro phase change capsules to the heat pipe to prevent the heat pipe from drying out, and increase the maximum heat transfer power of the heat pipe.

Description

Technical Field

[0001] The invention belongs to the field of power electronic device packaging, and in particular relates to a transient high-efficiency heat dissipation system for a power module and a method thereof. Background Art

[0002] In the context of the energy revolution, the construction of smart energy grids is imperative, which puts forward higher requirements on the safety, reliability, controllability, flexibility and new energy carrying capacity of the grid. To this end, the new power system is forming a "double high" development trend of "high proportion of renewable energy" and "high proportion of power electronic equipment". Compared with traditional synchronous generators, new renewable energy units and power electronic equipment have the defects of low inertia, weak anti-interference, low overload capacity and high output volatility, and are prone to transient overcurrent conditions during operation. Under overcurrent conditions, the surface heat flux density of the chip exceeds the rated heat flux density by several times, and a large amount of overload heat flow cannot be effectively dissipated by the heat sink, and it continues to accumulate near the heat source surface, causing the chip junction temperature to rise rapidly, seriously affecting the operating stability and expected life of power electronic devices. Therefore, the thermal bottleneck caused by overcurrent has become an important constraint on the power electronics and renewable energy grid connection of new power systems. Due to the limitations of process and insulation requirements, the existing technical solutions cannot integrate phase change materials (PCM) on the upper surface of the chip near the heat source surface. Generally, a hollow copper block layer is added to the side of the direct bonding copper (DBC) far from the chip heat source surface, and PCM is injected. Limited by the poor thermal conductivity of PCM (thermal conductivity is more than one order of magnitude less than that of common metals), on the one hand, directly integrating PCM in the heat transfer path from the chip junction to the heat sink will make the junction current thermal resistance too high, resulting in a decrease in steady-state heat dissipation performance. On the other hand, after the PCM begins to melt, there is a liquid film between the molten heat source and the solid-phase PCM. The melting rate will decrease rapidly with the increase of the liquid film thickness, resulting in a small amount of PCM melted per unit time. Therefore, the existing technical solutions will also add a metal skeleton to the PCM, using the higher thermal conductivity of the metal to reduce the junction current thermal resistance and ensure steady-state heat dissipation performance. At the same time, the outer surface of the metal skeleton is used to melt the PCM to expand the wetting area. However, this solution is relatively limited in optimizing the above technical problems. Limited by the low heat conduction rate, the surface temperature distribution of the metal skeleton is uneven at the beginning of the flow, and the effective wetting area above the melting point of PCM is small. Therefore, the melting rate and latent heat of PCM are low. In addition, due to the decrease in the effective thermal conductivity area on the heat transfer path, it is difficult to avoid the impact of replacing the solid metal layer with a metal skeleton structure filled with PCM on the junction thermal resistance.

[0003] Heat pipes transfer heat from the evaporation section to the condensation section through the phase change of the internal working fluid. However, if the thermal power of the evaporation section is too high, the internal working fluid may completely change phase to gas and cannot flow back to the evaporation section through the capillary wick to complete the thermal cycle. In this case, the heat pipe will lose its ability to quickly transfer heat. The current power modules / devices generate high and relatively concentrated heat. For example, Si IGBT has a surface heat flux density of up to 100 W / cm 2 As mentioned above, if a transient overcurrent condition occurs, taking a three-fold overcurrent as an example, the heat loss can reach five times that of a steady-state condition. The high heat flux density at this time is very likely to exceed the maximum heat transfer power limit of the heat pipe, causing the heat pipe to become ineffective.

[0004] Power modules / devices consist of various electrical components, and their surface heat flux densities are not the same. Due to the weak heat diffusion effect, the surface temperature uniformity under the DBC is often poor. Taking Si IGBT as an example, the Infineon module FS75R12KE3 has a surface heat flux density of 135.1 W / cm2 under the conditions of DC bus voltage 600 V, output current 400 A, switching frequency 2 kHz, and output frequency 50 Hz. 2 The surface heat flux density of the diode chip is 43.8 W / cm 2 , the temperature of the DBC bottom surface directly below the IGBT chip should be higher than that of the diode chip under steady-state conditions. Under transient overcurrent conditions, taking triple overcurrent as an example, the heat flux difference between the IGBT and diode chip surfaces can reach 456 W / cm 2 , resulting in a certain difference in the temperature rise rate near the heat source surface of the two, the temperature and heat flow are uneven, and the thermal management solution design is difficult. In summary, due to the slow thermal response speed of the existing method and the limitation of the chip working junction temperature, the power of the applicable electronic devices is extremely limited. Otherwise, the excessive heat flux density in a short period of time will cause the chip junction temperature to exceed the limit, affecting its operating life and reliability. Adding PCM increases the junction current thermal resistance, resulting in the module's improved overcurrent resistance, but the steady-state heat dissipation performance decreases, the junction temperature increases, and its long-term operating stability is affected. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention proposes a transient high-efficiency heat dissipation system and method for a power module.

[0006] To solve the technical problem, on the one hand, the present invention provides a transient high-efficiency heat dissipation system for a power module, which comprises: a metal cavity, a heat pipe array, and a plurality of phase change material modules with different thermal conductivities arranged in the metal cavity;

[0007] The metal cavity is arranged close to the power module, and a plurality of phase change material modules with different thermal conductivities are arranged according to the heat flux density in the metal cavity, wherein the cavity area corresponding to the high heat flux zone is arranged with a phase change material module with low thermal conductivity and low phase change latent heat, and the low heat flux zone is arranged with a phase change material module with high thermal conductivity and low phase change latent heat, and the phase change material modules with different thermal conductivities are separated by a partition wall;

[0008] The heat pipe array comprises a plurality of heat pipes arranged in an array, the evaporation section of the heat pipe array is embedded in a metal cavity and a phase change material module; the heat pipe is filled with a working fluid and phase change microcapsules that can move with the working fluid; the phase change microcapsules are composed of an outer shell and internal phase change particles.

[0009] Furthermore, the thermal conductivity of the phase change material of the phase change material module with low thermal conductivity and high phase change latent heat is ≤ 10W / (m·K), and the phase change latent heat is ≥ 100 J / g; the thermal conductivity of the phase change material of the phase change material module with high thermal conductivity and low phase change latent heat is > 10 W / (m·K), and the phase change latent heat is < 100 J / g. The melting point of the phase change material in each phase change material module is 1-2K higher than the steady-state temperature of the heat flow zone in which it is located.

[0010] On the other hand, the present invention also provides a transient high-efficiency heat dissipation method based on the system, comprising:

[0011] A pre-punched metal cavity is integrated on a power module that needs to perform transient and efficient heat dissipation; the metal cavity is partitioned according to the heat flux density of each area of ​​the power module, and then a heat pipe array is inserted into the metal cavity and fixed, and the end of the evaporation section of the heat pipe array is flush with the top surface of the metal cavity; each partition of the metal cavity is filled with phase change material to form a phase change material module with different thermal conductivities, wherein the cavity area corresponding to the high heat flow area of ​​the power module is filled with a phase change material with low thermal conductivity and high phase change latent heat, and the low heat flow area of ​​the power module is filled with a phase change material with high thermal conductivity and low phase change latent heat;

[0012] When the power module generates transient thermal overcurrent, part of the heat flow is directly transferred to the heat pipe array, and the heat pipe transfers the heat from the evaporation section to the condensation section through the phase change of the internal working fluid; the phase change microcapsules inside the heat pipe also absorb the external heat flow and are carried by the working fluid in the heat pipe to complete the heat cycle between the evaporation section and the condensation section, with latent heat of phase change in the evaporation section and solidification in the condensation section;

[0013] Transient thermal overcurrent generates non-uniform heat flow on the surface of the power module. The high heat flux density area of ​​the power module is equipped with phase change materials with low thermal conductivity and high phase change latent heat to store latent heat with low heat storage rate and high heat storage amount. The low heat flux density area is equipped with phase change materials with high thermal conductivity and low phase change latent heat to store latent heat with higher heat storage rate and lower heat storage amount. Metal materials with high thermal conductivity are arranged outside the active area of ​​the chip with only diffuse heat flow to store sensible heat with higher heat storage rate and lower heat storage amount, thereby balancing the non-uniform heat flow on the surface of the power module.

[0014] Under the initial steady-state conditions, a small part of the heat flux will be transferred from the heat pipe surface to the PCM until thermal equilibrium is reached. After the overcurrent condition occurs, a large amount of overload heat flux is input from the heat source surface to the PCM through the heat pipe, causing it to store latent heat through phase change. After the overcurrent condition ends, the surface temperature of the heat pipe will drop below the melting point of the PCM. At this time, the PCM solidifies and releases heat, which is transferred to the heat sink at the condensation end through the heat pipe.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention uses heat pipes to dissipate heat in power modules. Compared with traditional air-cooled heat sinks, it can reduce the junction thermal resistance and junction temperature of the chip, has better steady-state heat dissipation capability, and takes into account the sensible heat of the packaging structure, thereby improving its own current capacity to a certain extent.

[0017] (2) The present invention integrates PCM around the evaporation section of the heat pipe and uses the heat pipe to replace the traditional metal frame to expand the wetted area. Since the heat transfer speed of the heat pipe is much faster than that of the metal frame, its surface temperature will uniformly and quickly exceed the melting point of PCM at the beginning of the flow, thereby improving the melting rate and latent heat of PCM.

[0018] (3) The present invention integrates the PCM around the evaporation section of the heat pipe. Since the heat flow is almost entirely transferred from the heat pipe to the condensation end instead of through the PCM, the integrated PCM has almost no effect on the junction thermal resistance.

[0019] (4) The thermal response speed of the heat storage method adopted is negatively correlated with the heat flux density. From high heat flux to low heat flux, low thermal conductivity PCM, higher thermal conductivity PCM, and sensible heat structure are integrated in sequence, which can greatly improve the heat storage capacity under the condition of the same volume.

[0020] (5) The present invention adds micro phase change capsules to the cooling fluid of the heat pipe to avoid the heat pipe from drying out in applications with high heat flux density and to increase the maximum heat transfer power of the heat pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a positive three-axis view of the transient high-efficiency heat dissipation system of the present invention.

[0022] Figure 2 A schematic diagram of a power module according to an embodiment.

[0023] Figure 3 A schematic diagram of another power module according to an example embodiment.

[0024] Figure 4 It is an exploded view of the assembly of the transient high-efficiency heat dissipation system of the present invention.

[0025] Figure 5 is a schematic diagram of the side wall of the metal chamber.

[0026] Figure 6 Schematic diagram of the installation of phase change modules with different thermal conductivities in the embodiment.

[0027] Figure 7 The embodiment is an enlarged cross-sectional view of a phase change microcapsule.

[0028] In the figure, 1. power module, 11. IGBT chip 12. diode chip, 13. MOSFET chip, 2. copper-clad ceramic board, 21. copper layer on copper-clad ceramic board, 22. ceramic layer of copper-clad ceramic board, 23. copper layer on copper-clad ceramic board, 3. metal cavity, 31. top surface of cavity, 4. phase change material module, 41. partition wall, 421. upper internal PCM, 422. upper external PCM, 431. lower internal PCM, 432. lower external PCM, 5. heat pipe, 51. heat pipe evaporation section, 52. heat pipe insulation section, 53. heat pipe condensation section, 531. heat pipe condensation section seal, 6. fins, 7. phase change microcapsules, 71. shell, 72. PCM particles. DETAILED DESCRIPTION

[0029] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0030] Under the guiding ideology of coordinated optimization of steady-state heat dissipation performance and transient flow capacity, the present invention adopts phase change material heat storage and heat pipe heat dissipation technology. The heat flow is rapidly dissipated from the heat source surface to the condensation end by utilizing the characteristics of high thermal conductivity and high heat conduction rate of the heat pipe. The condensation end is integrated with a radiator, which can be used for convection heat exchange with the cooling medium by various methods such as air cooling, liquid cooling, and impact jet. This solution does not limit the heat dissipation method of the heat pipe condensation section, and air cooling is used as an example in the embodiment. Phase change material is integrated in the evaporation section of the heat pipe, and heat pipes are used instead of traditional metal skeletons to expand the wetted area of ​​PCM melting and increase the latent heat of PCM per unit time.

[0031] Heat storage methods are mainly divided into latent heat and sensible heat. The latent heat capacity of the same substance is much higher than the sensible heat, but the rate of phase change latent heat is lower than the latent heat of heating. At present, common PCM generally shows a trend that the higher the thermal conductivity (the faster the melting rate), the lower the unit latent heat. For example, paraffin and liquid metal, the thermal conductivity of paraffin is only 0.2 W / (m·K), the unit latent heat is 220 J / g, and the liquid metal (LM108) is 35 W / (m·K), and the unit latent heat is 45 J / g. In order to balance the non-uniformity of heat flow on the surface of the module / device chip and improve the efficiency of the heat storage structure, the guiding principle should be to arrange materials with slow heat storage rate and high heat storage rate at higher heat flow, and to arrange materials with fast heat storage rate and low heat storage rate at lower heat flow.

[0032] Specifically, the application objects of the present invention are high-power power electronic devices, including various power chips / devices made of various semiconductor materials such as silicon carbide, silicon, gallium nitride, gallium arsenide, aluminum nitride, etc., including power diodes, power transistors, power field effect transistors (MOSFET), insulated gate bipolar transistors (IGBT), etc.

[0033] like Figure 1 , Figures 4 to 7 As shown, the transient high-efficiency heat dissipation system of the present invention comprises a metal cavity 3, a heat pipe array and a plurality of phase change material modules 4 with different thermal conductivities arranged in the metal cavity;

[0034] The metal cavity 3 is arranged close to the power module 1, and a plurality of phase change material modules 4 with different thermal conductivities are arranged according to the heat flux density in the metal cavity, wherein the cavity area corresponding to the high heat flux zone is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the low heat flux zone is arranged with a phase change material module with high thermal conductivity and low phase change latent heat, and the phase change material modules with different thermal conductivities are separated by a partition wall 41; the heat pipe array includes a plurality of heat pipes 5 arranged in an array, and the evaporation section of the heat pipe array is embedded in the metal cavity 3 and the phase change material module 4; the heat pipe 5 is filled with a working fluid and a phase change microcapsule 7 that can move with the working fluid; the phase change microcapsule 7 is composed of an outer shell 71 and internal PCM particles 72.

[0035] like Figure 2 As shown, the power module 1 takes a silicon-based IGBT as an example, which is composed of an IGBT chip 11 and a diode chip 12. The chip is connected to the upper copper layer of the copper-clad ceramic board by reflow soldering or silver sintering. In order to make the heat flow on the upper surface of the copper-clad ceramic board DBC as uniform as possible, the IGBT chip 11 and the diode chip 12 are arranged in an interlaced manner, but the arrangement is not fixed and can be arranged arbitrarily. The thickness of the copper-clad ceramic board 2 is not fixed, and the ceramic layer can use materials such as aluminum oxide or aluminum nitride.

[0036] The metal cavity 3 of the present invention is integrated below the DBC of the IGBT module, and the connection method can be direct welding or sintering. A supporting substrate can be integrated into the lower layer of the DBC by welding or sintering, and then the substrate is connected to the cavity by sintering or welding. The material of the substrate can be various materials such as copper, aluminum, carbon, etc., and the thickness is determined according to the actual situation of the power module / device. The material of the metal cavity 3 can be various materials such as copper, aluminum, iron, alloy, etc. Taking the copper cavity as an example, it is composed of multiple wall surfaces, and the side wall surface thickness and height are relatively large. It will be fixed in combination with the heat pipe and the heat sink later. The top surface near the chip end is used to insert the sealing end of the heat pipe. At the same time, the high thermal conductivity of the copper block is used to enhance the temperature uniformity of the lower surface of the copper block, providing basic conditions for the subsequent uniform melting of the phase change material. Holes are punched on the side walls, bottom and top of the metal cavity 3, and the heat pipe array with integrated air-cooling fins 6 is inserted therein as a whole. Since the seals at both ends of the heat pipes are irregular in shape, a small amount of material with high thermal conductivity, such as liquid metal, thermal grease, etc., can be filled to enhance thermal contact. Taking liquid metal as an example, liquid phase liquid metal is filled into the pores, and after solidification, it plays a role in mechanical fastening and thermal contact.

[0037] Since the melting rate of PCM is low, the spacing of the heat pipe array should be small. The closely packed heat pipe array can expand the wetted area of ​​PCM melting and increase the melting amount. At the same time, the maximum heat transfer power of the heat pipe is limited. During the transient thermal overcurrent period, the heat loss of the power module / device is high. The use of closely packed heat pipe arrays can distribute a large amount of heat flow to more heat pipes, so that the average heat transfer power of each heat pipe decreases. On the other hand, the present invention adds micro phase change capsules 7 to the cooling fluid working medium of the heat pipe. The capsule structure is composed of an outer shell 71 and internal PCM particles 72. The outer shell can constrain the PCM particles from leaking after melting. The diameter is preferably in the order of microns. The internal PCM particles should be closely arranged on the inner surface of the outer shell to better absorb the external heat flow. The phase change microcapsules can be carried by the working medium in the heat pipe to complete the heat cycle between the evaporation section and the condensation section. The phase change material in the capsule changes phase in the evaporation section to store heat and solidifies in the condensation section. Compared with traditional heat pipes, the addition of phase change microcapsules can increase the maximum heat transfer power of the heat pipe and avoid the heat pipe from drying out in applications with high heat flux density.

[0038] Phase change materials are filled into each partition of the metal cavity 3 to form phase change material modules 4 with different thermal conductivities, wherein the chamber area corresponding to the high heat flow area of ​​the power module is filled with phase change materials with low thermal conductivity and high phase change latent heat, and the low heat flow area of ​​the power module is filled with phase change materials with high thermal conductivity and low phase change latent heat. In some embodiments of the present invention, the internal area of ​​the metal cavity 3 is horizontally partitioned by partition walls according to the different heat flux densities of each area of ​​the power module, and the height of each phase change material module 4 is the same as the height of the metal cavity 3. The chamber area corresponding to the high heat flow area of ​​the power module 1 is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the chamber area corresponding to the low heat flow area of ​​the power module 1 is arranged with a phase change material module with high thermal conductivity and low phase change latent heat.

[0039] In other embodiments of the present invention, the internal area of ​​the metal cavity 3 is partitioned in the horizontal and vertical directions by partition walls according to the different heat flux densities of various areas of the power module, wherein in the horizontal partitioning, the chamber area corresponding to the high heat flow area is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the chamber area corresponding to the low heat flow area is arranged with a phase change material module with high thermal conductivity and low phase change latent heat; in the vertical partitioning, the partition close to the power module is arranged with a phase change material module with low thermal conductivity, high phase change latent heat and a relatively high melting point, and the partition far from the power module is arranged with a phase change material module with high thermal conductivity, low phase change latent heat and a relatively low melting point.

[0040] The thickness and melting point of the PCM in the phase change material module 4 are determined by the specific heat loss of the power module 1, the duration of the overcurrent period and the overcurrent multiple. The melting point of the PCM should be as close as possible to but higher than the highest temperature of the inner wall of the metal cavity 3 and the outer surface of the heat pipe 5, so as to avoid melting under steady-state operating conditions and shorten the thermal response time required for sensible heat temperature rise. Due to the weak thermal diffusion effect, the temperature distribution of the entire device in the horizontal direction is uneven. The temperature at the far chip will be lower than that below the diode chip, and the temperature below the diode chip will be lower than that below the IGBT chip. At the same time, during the transient heat loss step period, the heat flux density below the IGBT chip is much higher than that of the diode chip. Therefore, in order to further speed up the response speed of the heat storage structure and improve the heat storage capacity, PCM materials with different melting points and thermal conductivities can be used at various locations according to the gradient of temperature and heat flux density.

[0041] Regarding the selection of phase change materials, in one embodiment of the present invention, the thermal conductivity of the phase change material of the phase change material module with low thermal conductivity and high phase change latent heat is ≤ 10 W / (m·K), and the phase change latent heat is ≥ 100 J / g; the thermal conductivity of the phase change material of the phase change material module with high thermal conductivity and low phase change latent heat is > 10 W / (m·K), and the phase change latent heat is < 100 J / g. To further meet the demand for steady-state heat dissipation, the melting point of the phase change material in each phase change material module is higher than the steady-state temperature of the heat flow zone in which it is located, but shall not exceed 5K, preferably 1-2K higher.

[0042] For example, in a specific embodiment of the present invention, a graphite / paraffin composite phase change material is placed under the IBGT chip, and liquid metal is placed under the diode chip. At the same time, the temperature in the vertical direction will also change to a certain extent, and a PCM material with a lower melting point can be used near the radiator end. In order to further improve the thermal response speed of PCM, a small metal skeleton or copper foam can be placed between the gaps of the heat pipe, and the PCM is filled into the heat pipe-metal skeleton / copper foam coupling structure. Due to the weak thermal diffusion effect, the thermal response speed of the heat storage structure farther away from the chip is slow, and it performs poorly in applications with short-term steps in heat flux density. Therefore, a structure for storing heat in a sensible heat manner can be added here. The structure is generally a solid metal or other high thermal conductivity material with a thermal conductivity of the order of hundreds of W / (m·K) or above.

[0043] The thickness of the PCM should be as low as possible while meeting the latent heat demand during the overcurrent period, taking into account the device cost and the actual overcurrent period. The simulation numerical model of the present invention is as follows: Assume that the wind speed at the inlet of the air-cooled fins at the condensation end of the heat pipe is 2m / s, the incoming flow temperature is 278.15 K, and the boundary condition of the heat source surface is the heat flux of the upper surface of the IGBT chip is 70 W / cm 2 , the heat flux density on the diode surface is 20 W / cm 2 , the overcurrent condition is 3 times the overcurrent of 1.5 s (5 times the heat loss). The results are as follows: the highest junction temperature of the chip under steady-state conditions is 342 K, the highest junction temperature during the overcurrent time is 409 K, the PCM melting rate is 88%, and the latent heat is 1090 J. According to the test data, it is more appropriate to set the PCM thickness to 10-12 mm under this condition. If the overcurrent period may increase or decrease, the PCM thickness can be increased or decreased accordingly.

[0044] like Figure 3 As shown, the power module 1 can also be a MOSFET, which is composed of multiple MOSFET chips, and its arrangement is not fixed. The transient high-efficiency heat dissipation system of the present invention can also arrange the phase change material module 4 in different zones according to the heat flow on the surface of the power module 1, and its arrangement principle is the same as that of the silicon-based IGBT.

[0045] like Figure 4In the embodiment, holes are evenly punched on the top surface 31 of the metal cavity. The distribution, spacing and number of the holes are not fixed. For example, 6 holes are provided in both the horizontal and vertical directions. The hole diameter should be slightly larger than the size of the heat pipe 5 to be inserted later. One or more peripheral through holes will penetrate the side wall of the cavity in the vertical direction. The top surface 31 of the cavity is connected to the lower copper layer 23 of the DBC by welding or sintering. Through holes with a diameter slightly larger than the diameter of the heat pipe 5 are punched on the surface of the fin 6. The center of the through hole of each fin 6 should be aligned with the center of the through hole of the metal cavity 3. If there is an offset, the heat pipe 5 cannot be directly inserted. The side wall thickness of the metal cavity 3 should be relatively large, preferably with the diameter of one to two heat pipes. After the heat pipe 5 is inserted into the metal cavity 3, the high thermal conductivity of the heat pipe 5 is used to evenly transport the heat flow to various parts of the side wall of the cavity, and the heat is stored in the form of sensible heat. The heat pipes 5 are inserted into the fin through holes in sequence and fixed by welding or piercing the fins. The number of integrated fins 6 varies according to the heat dissipation requirements of the condensation section, and the thickness, shape, surface structure, and spacing between the fins can all vary. The arrangement can be uniform or non-uniform. The spacing between the heat pipes 5 in the heat pipe array should be relatively small, preferably 1-3 mm, depending on the length of the thermal overcurrent period and the heat flux density on the surface of the power module. Considering that the seal 531 at the condensation end of the heat pipe will cause the length of the condensation end to be invalid, a gap should be left between the bottom fin and the bottom side of the heat pipe. The heat pipe array after the integrated fins 6 is inserted into the cavity through hole as a whole. In order to ensure good thermal contact and a certain mechanical strength between the heat pipe evaporation section 51 and the metal cavity 3, the gap can be filled with liquid metal material in the liquid phase, which is connected after solidification; it can also be filled with high thermal conductivity materials such as thermal conductive silicone grease. There is no specific requirement for the temperature of the condensation end 53 of the heat pipe, but the startup temperature should be higher than the lowest surface temperature of the heat pipe evaporation section 51 under the steady-state operation of the power module 1, so that it can start normally. When the heat flux density on the surface of the power module 1 increases, the overloaded heat flux will be quickly transferred to the condensation section through the heat pipe.

[0046] like Figure 5 Embodiment: After completing the connection of other devices, the liquid phase phase change material module 4 is opened from the upper and lower positions of the cavity side wall and then injected into the PCM. Considering the influence of PCM gravity, it will be injected from the lower opening, and the upper opening is used to exhaust air and excess PCM. The specific filling thickness is determined by the actual working conditions.

[0047] In the case of poor uniformity of temperature / heat flux density in the horizontal / vertical direction, different PCMs can be used in the horizontal direction, different PCMs can be used in the vertical direction, or different PCMs can be used in both the horizontal and vertical directions. The number of PCMs in each direction is not fixed, and their physical properties can be different melting points, thermal conductivities, and latent heat quantities. The types of PCMs can be organic compounds such as graphite / paraffin composite phase change materials, or high thermal conductivity PCMs such as liquid metals. For example, organic compound PCMs with relatively low thermal conductivity, relatively slow melting rate, and relatively high unit latent heat can be used at high heat flux density, and liquid metal PCMs with relatively high thermal conductivity, relatively fast melting rate, and relatively low unit latent heat can be used at low heat flux density. Figure 6 In the embodiment, four types of PCM are used, namely, upper internal PCM 421, upper external PCM 422, lower internal PCM 431, and lower external PCM 432, which are separated by a phase change material partition wall 41. The material of the phase change material partition wall 41 can be various solids such as copper or AlSiC.

[0048] like Figure 7 Embodiment: The present invention adds a micro phase change capsule 7 to the cooling fluid of the heat pipe. The capsule structure is composed of an outer shell 71 and internal PCM particles 72. The outer shell 71 can constrain the PCM particles from leaking after melting. The diameter is preferably in the micrometer order and can be a compound material such as silicon dioxide. The internal PCM particles 72 are tightly arranged on the inner surface of the outer shell, and the melting point should be close to and lower than the evaporation section temperature of the heat pipe to better absorb external heat flow. The shape of the micro phase change capsule can be various geometric shapes such as round and elliptical, and the surface can be added with grooves, protrusions and other structures to enhance heat exchange.

[0049] The application scenarios of the present invention are various steady-state / transient working conditions where the chip power consumption is stable or changes, including overcurrent, overload, surge current, module / device failure, etc. When the present invention is applied and a transient thermal overcurrent is generated in the power module, part of the heat flow is directly transferred to the heat pipe array, and the heat pipe transfers the heat from the evaporation section to the condensation section through the internal working fluid phase change; the phase change microcapsules inside the heat pipe also absorb the external heat flow and are carried by the working fluid in the heat pipe to complete the thermal cycle between the evaporation section and the condensation section, the latent heat of the phase change in the evaporation section, and solidification in the condensation section;

[0050] On the other hand, transient thermal overcurrent produces non-uniform heat flow on the surface of the power module. The high heat flux density area of ​​the power module uses phase change materials with low thermal conductivity and high phase change latent heat to store latent heat with a low heat storage rate and a high heat storage amount. The low heat flux density area uses phase change materials with high thermal conductivity and low phase change latent heat to store latent heat with a higher heat storage rate and a lower heat storage amount. Metal materials with high thermal conductivity are arranged outside the active area of ​​the chip where there is only diffuse heat flow to store sensible heat with a higher heat storage rate and a lower heat storage amount.

[0051] The condensing end radiator of the heat pipe in the present invention can be various heat dissipation modes such as air cooling and liquid cooling. The starting temperature and working fluid filling rate of the heat pipe vary according to the three-dimensional temperature distribution of the device / module under steady-state conditions and the maximum heat transfer power requirement.

[0052] like Figure 4 In the embodiment, a non-stratified liquid metal phase change material (thermal conductivity is 35 W / (m·K), latent heat is 45 J / g), the melting point is set to 320 K, the air cooling fin inlet wind speed at the condensation end of the heat pipe is 2 m / s, the incoming flow temperature is 278.15K, and the boundary condition of the heat source surface is the heat flux of 70 W / cm on the upper surface of the IGBT chip 2 , the heat flux density on the diode surface is 20 W / cm 2 The overcurrent condition is 3 times the overcurrent of 1.5 s. The results show that the latent heat is 1078 J within the overcurrent period of 1.5 s.

[0053] like Figure 6 In the embodiment, the melting point of the PCM inside the upper layer is set to 320 K, and a graphite / paraffin composite phase change material (thermal conductivity is 6 W / (m·K) and latent heat is 150 J / g) is used. The melting point of the PCM outside the upper layer is set to 319 K, and a liquid metal phase change material (thermal conductivity is 35 W / (m·K) and latent heat is 45 J / g) is used. The thickness of the upper PCM is 6 mm, the melting point of the PCM inside the lower layer is set to 312 K, and a liquid metal phase change material is used. The melting point of the PCM outside the lower layer is 311 K, and a liquid metal phase change material is used, and the thickness is also 6 mm. The results show that the latent heat of this embodiment is 2100 J within a flow period of 1.5 s, which is relatively Figure 4 The embodiment improved by 94.8%.

[0054] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A transient high-efficiency heat dissipation system for power modules, characterized in that: include: A metal cavity, a heat pipe array, and phase change material modules with various thermal conductivities arranged in the metal cavity; The metal cavity is arranged close to the power module, and a plurality of phase change material modules with different thermal conductivities are arranged according to the heat flux density in the metal cavity, wherein the cavity area corresponding to the high heat flux zone is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the low heat flux zone is arranged with a phase change material module with high thermal conductivity and low phase change latent heat, and the phase change material modules with different thermal conductivities are separated by a partition wall; The heat pipe array comprises a plurality of heat pipes arranged in an array, the evaporation section of the heat pipe array is embedded in a metal cavity and a phase change material module; the heat pipe is filled with a working fluid and phase change microcapsules that can move with the working fluid; the phase change microcapsules are composed of an outer shell and internal phase change particles.

2. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The inner area of ​​the metal cavity is horizontally partitioned by partition walls according to the different heat flux densities of various areas of the power module. The height of each phase change material module is the same as the height of the metal cavity. The cavity area corresponding to the high heat flow area of ​​the power module is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the cavity area corresponding to the low heat flow area of ​​the power module is arranged with a phase change material module with high thermal conductivity and low phase change latent heat; the melting point of the phase change material in each phase change material module is 1-2K higher than the steady-state temperature of the heat flow area where it is located.

3. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The inner area of ​​the metal cavity is partitioned in the horizontal and vertical directions by partition walls according to the different heat flux densities of various areas of the power module. In the horizontal partitioning, the chamber area corresponding to the high heat flux area is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the chamber area corresponding to the low heat flux area is arranged with a phase change material module with high thermal conductivity and low phase change latent heat; in the vertical partitioning, the partition close to the power module is arranged with a phase change material module with low thermal conductivity and high phase change latent heat, and the partition far from the power module is arranged with a phase change material module with high thermal conductivity and low phase change latent heat.

4. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The thermal conductivity of the phase change material of the phase change material module with low thermal conductivity and high phase change latent heat is ≤ 10 W / (m·K), and the phase change latent heat is ≥ 100 J / g; the thermal conductivity of the phase change material of the phase change material module with high thermal conductivity and low phase change latent heat is > 10 W / (m·K), and the phase change latent heat is < 100 J / g.

5. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The thickness of the side wall of the metal cavity is greater than the diameter of the heat pipe, and a vertically penetrating heat pipe mounting hole is provided on the side wall of the metal cavity; the heat pipes of the outer circle of the heat pipe array are arranged in the heat pipe mounting holes of the side wall, and they and the heat pipes penetrate the bottom surface, phase change material module and top surface of the metal cavity; the ends of the evaporation sections of all the heat pipes in the heat pipe array are flush with the top surface of the metal cavity.

6. The transient high-efficiency heat dissipation system for power modules according to claim 5, characterized in that: The heat pipe and the metal cavity are mechanically fastened and thermally contacted by reflow soldering. The sealing shape of the heat pipe evaporation section is irregular, and the gap between the heat pipe and the metal cavity is filled with high melting point liquid metal or thermal conductive silicone grease for thermal contact; the top of the metal cavity and the lower surface of the DBC are mechanically fastened and thermally contacted by reflow soldering / sintering.

7. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The heat pipe is a cylindrical heat pipe or a flat heat pipe, the spacing between the heat pipes is 1-3 mm, the volume filling amount of the working fluid in the heat pipe is 40%-70%, and the filling amount of the phase change microcapsule is 0.05%-2% of the weight of the working fluid.

8. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The diameter of the phase change microcapsule is 10um-100um, the internal phase change particles are closely arranged on the inner surface of the shell, and the melting point of the internal phase change particles is close to and lower than the working temperature of the evaporation section of the heat pipe.

9. The transient high-efficiency heat dissipation system for power modules according to claim 1, characterized in that: The condensing end of the heat pipe array is provided with a plurality of groups of fins for heat dissipation, and the surface of the fin is provided with a through hole array whose aperture matches the outer diameter of the heat pipe, and the heat pipe array is fixed through the through hole array.

10. A transient high-efficiency heat dissipation method based on the system according to any one of claims 1 to 9, characterized in that: The method comprises: A pre-punched metal cavity is integrated on a power module that needs to perform transient and efficient heat dissipation; the metal cavity is partitioned according to the heat flux density of each area of ​​the power module, and then a heat pipe array is inserted into the metal cavity and fixed, and the end of the evaporation section of the heat pipe array is flush with the top surface of the metal cavity; each partition of the metal cavity is filled with phase change material to form a phase change material module with different thermal conductivities, wherein the cavity area corresponding to the high heat flow area of ​​the power module is filled with a phase change material with low thermal conductivity and high phase change latent heat, and the low heat flow area of ​​the power module is filled with a phase change material with high thermal conductivity and low phase change latent heat; When the power module generates transient thermal overcurrent, part of the heat flow is directly transferred to the heat pipe array, and the heat pipe transfers the heat from the evaporation section to the condensation section through the phase change of the internal working fluid; the phase change microcapsules inside the heat pipe also absorb the external heat flow and are carried by the working fluid in the heat pipe to complete the thermal cycle between the evaporation section and the condensation section, absorbing heat in the evaporation section and solidifying in the condensation section; On the other hand, transient thermal overcurrent produces non-uniform heat flow on the surface of the power module. The high heat flux density area of ​​the power module is equipped with phase change materials with low thermal conductivity and high phase change latent heat to store latent heat with a low heat storage rate and a high amount of heat storage. The low heat flux density area is equipped with phase change materials with high thermal conductivity and low phase change latent heat to store latent heat with a higher heat storage rate and a lower amount of heat storage. Metal materials with high thermal conductivity are arranged outside the active area of ​​the chip where there is only diffuse heat flow to store sensible heat with a higher heat storage rate and a lower amount of heat storage, thereby balancing the non-uniform heat flow on the surface of the power module.

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