Strong overcurrent power device packaging structure filled with phase change material

Abstract

The invention belongs to the field of power systems, and discloses a strong overcurrent power device packaging structure filled with a phase change material, and the structure comprises a bottom housing, a top housing, a SiC MOSFET chip, a chip substrate, a device pin, an insulator and a phase change liquid, the device pin is welded on a housing side plate through the insulator, and the phase change liquid is welded on the housing side plate through the insulator. The bottom shell and the top shell are welded through a sealing gasket to form a device shell, and the interior of the device is filled with phase change liquid to immerse the SiC MOSFET chip and all bonding wires. The problem that thermal expansion coefficients in solid phase change materials are not matched is solved, the overcurrent capacity of the power device is remarkably improved, and the power device can be applied to various overcurrent occasions such as short-time overcurrent occasions and long-time overcurrent occasions.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the technical field of power systems, and in particular relates to a packaging structure of a strong overcurrent power device filled with phase change material. Background Art

[0002] Traditional power systems are mainly based on coal energy and synchronous motors, with strong overload capacity and stability. However, with the adjustment of energy structure and technological progress, new power systems are characterized by a high proportion of new energy and widespread application of power electronic equipment. Power electronic equipment runs through all aspects of the new power system, from power generation, transmission to distribution, and its stability and reliability are directly related to the safe and stable operation and operation and maintenance costs of the power system.

[0003] One of the unavoidable problems in new power systems is AC short-circuit faults. When an AC short circuit occurs in the system, the power converter used in new energy sources needs to assume reactive support for the power grid and enter an overloaded operating state. During the short circuit, the system will produce overcurrent and the voltage will drop sharply. However, unlike the synchronous machine in the traditional power system, the core power module of the power converter in the new power system is limited by its design capacity and operating temperature, and its overload capacity is much lower than that of the synchronous generator. Existing power modules are difficult to provide sufficient overcurrent support capacity in AC short circuit faults, which can easily lead to large-scale grid disconnection and endanger the stable operation of the power system.

[0004] Most existing commercial silicon-based (Si) IGBT devices can only withstand overcurrents of about 2 times the rated current and lasting for 1 millisecond. In contrast, silicon carbide (SiC) MOSFET devices have improved overcurrent tolerance, but their 100-millisecond overcurrent operation capability is only about 1.2 times the rated current. The overcurrent capability of power semiconductor devices is limited by the safe operating area (SOA) of the device. Therefore, packaging and heat dissipation technology for strong overcurrent conditions has become a key factor in improving overcurrent capability.

[0005] In recent years, academia and industry have discovered that phase change materials have a huge heat storage capacity during the phase change process, which provides a new research direction for using phase change materials in power device packaging to improve its overcurrent capacity. Due to the instability of liquid phase change materials after vaporization, most current research focuses on the application of solid phase change materials. A common method is to fill the solid phase change material in a metal shell and attach the metal shell to the top of the power chip. When the chip is running at overcurrent, the heat is introduced into the solid phase change material through the metal shell, thereby cooling the chip and improving its stability under strong overcurrent conditions.

[0006] In view of the above analysis, the technical problems that need to be solved urgently in the prior art are:

[0007] (1) The metal shell filled with phase change material is only attached to one side of the power chip, and the heat transfer to the phase change material is single, resulting in uneven heating of the phase change material, slow heat conduction rate, slow overall temperature rise, and phase change heat absorption cannot be completed in time, limiting its application in short-term (less than 1 second) overcurrent conditions. In addition, the cooling effect during overcurrent is only 20-30°C, and the overcurrent capacity is limited;

[0008] (2) The coefficient of thermal expansion (CTE) of the metal shell filled with phase change material and the power chip are different. When the metal shell and the power chip are thermally deformed under temperature changes, the problem of loose adhesion may occur, which in turn affects the subsequent heat conduction and limits the long-term reliability of the device.

[0009] (3) The latent heat of melting of solid phase change materials suitable for phase change heat dissipation is usually 20-60 J / g, while the latent heat of vaporization of liquid phase change materials can reach 120-200 J / g. In comparison, liquid phase change materials have higher heat storage potential, but their application still faces technical challenges such as stability. Summary of the invention

[0010] In view of the problems existing in the prior art, the present invention provides a strong overcurrent power device packaging structure filled with phase change material.

[0011] The present invention is implemented as follows: a packaging structure for a strong overcurrent power device filled with phase change material, characterized in that the packaging structure for a strong overcurrent power device filled with phase change material includes a bottom shell, a top shell, a SiC MOSFET chip, a chip substrate, a device pin, an insulator and a phase change liquid, wherein the device pin is welded to a side plate of the shell through an insulator, the bottom shell and the top shell are welded to form a device shell through a sealing gasket, and the inside of the device is filled with a phase change liquid to immerse the SiC MOSFET chip and all bonding wires.

[0012] Further, the device housing includes a top housing and a bottom housing, and the bottom housing includes a housing bottom plate and a housing side plate.

[0013] Furthermore, the device pins include external pins and internal end platforms, the external pins are used to connect to external circuits, the internal end platforms are used to connect various levels of the chip, the external pins include gate pins, source pins and drain pins, and the internal end platforms include gate pin end platforms, source pin end platforms and drain pin end platforms.

[0014] Furthermore, the insulator includes a gate insulator, a source insulator and a drain insulator, the external pins are welded together with the insulators and fixed on the side panels of the shell, the external pins extend into the device through the insulators and are connected to the internal end platform, and the internal end platform is fixed by the external pins.

[0015] Furthermore, the SiC MOSFET chip includes a chip gate, a chip left source, a chip right source and a chip drain, the chip drain is welded to the chip substrate through a chip solder layer, the chip gate and the gate pin end platform are bonded through a first bonding wire, the chip left source and the source pin end platform are bonded through a second bonding wire, and the chip right source and the source pin end platform are bonded through a third bonding wire.

[0016] Furthermore, the chip substrate includes a conductive metal substrate and an insulating substrate, the insulating substrate is welded together with the bottom shell, the conductive metal substrate is welded to the upper layer of the insulating substrate, the chip drain of the SiC MOSFET chip is welded to the conductive metal substrate through a solder layer, and the conductive metal substrate is bonded to the drain pin end platform through a fourth bonding wire and a fifth bonding wire.

[0017] Furthermore, the device is filled with a phase change liquid, which occupies most of the volume inside the device and immerses the SiCMOSFET chip and all bonding wires. The air is exhausted from the device, leaving a small amount of inert gas filling space.

[0018] Furthermore, the output current path of the device is connected from the drain pin to the drain pin end platform, the drain pin end platform is connected to the conductive metal substrate through the fourth bonding wire and the fifth bonding wire, the conductive metal substrate conducts the current into the chip drain through the chip solder layer, the output current is respectively derived from the left source and the right source of the chip, and is conducted to the source pin end platform through the second bonding wire and the third bonding wire, and finally output from the source pin.

[0019] Furthermore, in the packaging structure of the strong overcurrent power device filled with phase change material, when the device is in overcurrent operation, the output current increases, and the structures in the output current path heat up, among which the temperature rise of the SiC MOSFET chip is the most significant; when the temperature exceeds the boiling point of the phase change liquid, the phase change liquid begins to vaporize and absorb heat, suppressing the temperature rise rate and reducing the temperature rise, thereby enhancing the overcurrent capacity and overcurrent duration of the device; after the overcurrent ends, the vaporized phase change gas is cooled and re-liquefied into a phase change liquid, ensuring normal steady-state operation of the device when it is not in overcurrent.

[0020] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0021] First, the packaging structure of the strong overcurrent power device filled with phase change material described in the present invention forms a containing space through the airtight packaging of the top shell and the bottom shell, which contains and supports the SiC MOSFET chip that bears the overcurrent heat generation and the phase change liquid for overcurrent heat dissipation. The SiC MOSFET chip realizes external input and internal output through the device pins, and the device pins realize airtight packaging through the insulator and the shell side plate.

[0022] Phase change liquids not only dissipate heat during overcurrent, but also play a role in environmental isolation and electrical insulation, and have the characteristics of functional reuse, thereby improving the practicality of power devices. By hermetically sealing the phase change material inside the power device, the space occupied by the power device is reduced, and its convenience of use in a strong overcurrent environment is enhanced, making it suitable for a variety of applications.

[0023] The phase change liquid is directly hermetically sealed inside the device, so that the phase change material is in direct contact with the chip, shortening the heat conduction distance, increasing the heat conduction path, and accelerating the heat conduction rate, making it applicable to a variety of short-term and long-term flow occasions.

[0024] Phase change materials show a huge equivalent heat capacity through the phase change process from liquid to gas, which is more than 20 times that of silicone materials, thereby increasing the heat capacity of the entire device. When the phase change occurs, the phase change material has an extremely high thermal conductivity, which increases the heat dissipation area of ​​the chip and reduces the heat flux density inside the power device, making its thermal resistance 20% lower than that of traditional power devices. After adopting the packaging structure filled with phase change liquid, the junction temperature fluctuation of the power device during strong overcurrent operation is reduced by 40%-50% compared with traditional power devices, the overcurrent capacity is increased by 2-3 times, and the overcurrent duration is extended by 5-10 times, thereby significantly enhancing the overcurrent capacity of the power semiconductor chip and improving its reliability under strong overcurrent conditions.

[0025] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0026] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0027] In engineering applications, in order to solve the overcurrent problem, there is a solution of connecting multiple chips in parallel. However, this method will significantly increase costs and lead to waste of resources. For example, to increase the overcurrent capacity of ordinary devices by 3 times, 3 chips need to be connected in parallel, which increases the chip cost to 3 times the original. The application of the present invention can achieve the equivalent of 3 times the overcurrent through 1 device, and only needs to increase the design and manufacturing costs of phase change materials and device structures. Comprehensively calculated, the total cost of the present invention is estimated to be about 1 / 2 of the solution of connecting 3 chips in parallel, which greatly reduces the cost while achieving significant performance improvement.

[0028] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0029] At present, the research on using phase change materials to reduce the junction temperature of power semiconductor devices at home and abroad mainly focuses on the application of solid phase change materials, while the research on liquid phase change materials has hardly been involved. Although liquid phase change materials have been widely used in the cooling of data center servers and large electronic equipment to improve the power usage efficiency (PUE, Power Usage Effectiveness) of data centers, there has been no research on introducing them into the field of power semiconductor device packaging. The present invention sees the huge potential of liquid phase change materials and pioneeringly applies them to the packaging of power semiconductor devices, so that the phase change liquid directly contacts the chip, thereby achieving efficient heat dissipation. This technology fills the technical gap in this field at home and abroad and has important innovative significance.

[0030] (3) The technical solution of the present invention solves the technical problems that people have been eager to solve but have never been able to solve successfully:

[0031] In recent years, academia and industry have conducted in-depth explorations around advanced packaging and heat dissipation technologies, focusing on how to improve the current flow capacity of power semiconductor devices under steady-state and quasi-steady-state conditions. In various existing solutions, the heat storage / heat dissipation structure is usually at a certain distance from the chip. Studies have shown that the closer the heat storage / heat dissipation structure is to the chip, the faster its response rate to the chip temperature rise, and the more timely the effect of suppressing the chip temperature rise. However, since the heat storage / heat dissipation structure is far away from the chip in traditional solutions, the response speed is often not enough to effectively suppress the increase in the junction temperature of the chip under overcurrent conditions. In these cases, the chip temperature may have risen to the damage threshold before the heat dissipation system reacts, making effective protection impossible.

[0032] The present invention uses phase change liquid as the main heat storage structure, and through innovative design, the phase change liquid is in direct contact with the chip. Since the heat conduction path is the shortest, the phase change liquid can respond to the chip overcurrent temperature rise at the fastest speed, and it is the design with the fastest reaction rate among all solutions. This design effectively solves the response lag problem caused by the traditional heat dissipation / heat storage structure being too far away from the chip, and provides the chip with efficient junction temperature suppression capability under millisecond-level overcurrent conditions. This breakthrough solution significantly improves the reliability and stability of power semiconductor devices under extreme working conditions.

[0033] (4) The technical solution of the present invention overcomes technical prejudice:

[0034] The traditional view is that due to the instability of liquid phase change materials after vaporization, the structural design of liquid phase change materials is relatively complex and difficult to apply to power semiconductor devices, and it is believed that solid phase change materials have a wider application prospect in the field of heat dissipation. However, the present invention innovatively replaces the silicone layer structure in traditional power semiconductor devices with liquid phase change materials, and hermetically seals it inside the device. Through minor structural changes, the application of liquid phase change materials in power semiconductor devices is realized, which not only simplifies the design, but also reduces the space occupied by the device.

[0035] When the chip is overcurrent, the liquid phase change material vaporizes. Due to its extremely large latent heat of phase change, the vaporization mass is small relative to the total amount of liquid. Even in the current overcurrent scenario, it will not cause excessive pressure on the internal cavity. After the overcurrent ends, as the overall temperature decreases, the phase change gas will re-liquefy and return to a steady state. This process ensures that power semiconductor devices can operate stably for a long time under multiple overcurrent conditions.

[0036] The technical solution of the present invention breaks through the traditional technical prejudice that liquid phase change materials are difficult to apply to power semiconductor devices, fully taps the potential of liquid phase change materials in efficient heat dissipation and heat storage, and provides a new solution for the design and application of power semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of an external structure provided by an embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of the internal structure provided by an embodiment of the present invention;

[0039] Figure 3 is an exploded diagram of the internal structure provided by an embodiment of the present invention;

[0040] Figure 4 is a schematic diagram of the output current direction and path provided by an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of the overcurrent junction temperature suppression effect of solid-state phase change provided by an embodiment of the present invention;

[0042] Figure 6 The liquid phase change overcurrent junction temperature suppression effect provided by the embodiment of the present invention;

[0043] Figure 7 This is a 100ms overcurrent chip junction temperature comparison diagram provided by an embodiment of the present invention;

[0044] Figure 8 This is a comparison diagram of the junction temperature of a 200ms overcurrent chip provided by an embodiment of the present invention;

[0045] Fig. 9 This is a comparison diagram of the junction temperature of a 2s overcurrent chip provided by an embodiment of the present invention;

[0046] Fig.10 This is a comparison diagram of the junction temperature of a 5s overcurrent chip provided by an embodiment of the present invention;

[0047] Fig.11 It is a waveform diagram of an overcurrent test experiment provided by an embodiment of the present invention;

[0048] Fig.12 It is a comparative diagram of the cooling effect of the junction temperature of the solid phase change structure device provided by the embodiment of the present invention and the liquid phase change structure device of the present invention under the same overcurrent time;

[0049] Fig.13 This is a comparison diagram of the reduction of overcurrent junction temperature of power semiconductor devices in different cooling methods provided by an embodiment of the present invention (air cooling, solid phase change cooling, liquid cooling, liquid phase change cooling);

[0050] In the figure: 1. top shell; 2. gate pin; 3. drain pin; 4. source pin; 5. gate insulator; 6. drain insulator; 7. source insulator; 8. sealing gasket; 9. bottom shell; 10. gate pin end platform; 11. drain pin end platform; 12. source pin end platform; 13. second bonding wire; 14. third bonding wire; 15. fourth bonding wire; 16. fifth bonding wire; 17. first bonding wire; 18. chip solder layer; 19. chip substrate; 20. chip gate; 21. chip drain; 22. chip right source; 23. chip left source; 24. SiC MOSFET chip; 25. insulating substrate; 26. shell side panel; 27. device shell; 28. conductive metal substrate; 29. ​​device pin. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] like Figure 1 , Figure 2 As shown, an embodiment of the present invention provides a strong overcurrent power device packaging structure filled with phase change material, including a device housing 27, a chip substrate 19, a device pin 29, a first bonding wire 17, a second bonding wire 13, a third bonding wire 14, a fourth bonding wire 15, a fifth bonding wire 16 and a phase change liquid airtight package.

[0053] like Figure 2As shown, the chip substrate 19 includes an insulating substrate 25 and a conductive metal substrate 28. The conductive metal substrate provides a connection platform for the chip drain 21. The insulating substrate 25 is welded to the lower layer of the conductive metal substrate 28. The insulating substrate 25 and the conductive metal substrate 28 are welded together in the cavity of the bottom shell 9 in the device shell 27. The insulating substrate 25 insulates the SiC MOSFET chip 24 from the device shell 27.

[0054] like Figure 2 As shown, the first bonding wire 17 is bonded to connect the chip gate 20 and the source pin end platform 12, and the external driving signal is transmitted through the gate pin 2 to the source pin end platform 12, and then transmitted to the chip gate 20 through the first bonding wire 17, thereby controlling the SiCMOSFET chip 24 to be turned on and off.

[0055] like Figure 2 As shown, the second bonding wire 13 connects the left side source 23 of the chip and the source pin end platform 12, and the third bonding wire 14 connects the side source 22 of the chip and the source pin end platform 12. The second bonding wire 13 and the third bonding wire 14 provide a current path for the chip source and source pin.

[0056] like Figure 2 As shown, the fourth bonding wire 15 and the fifth bonding wire 16 connect the drain pin end platform 11 and the conductive metal substrate 29, and the conductive metal substrate 29 and the SiC MOSFET chip 24 are welded together through the chip solder layer 18. The fourth bonding wire 15, the fifth bonding wire 16, the conductive metal substrate 29 and the chip solder layer 18 provide a current path for the chip drain 21 and the source pin.

[0057] like Figure 4 As shown, when the device is turned on, the device output current path is from the drain pin 3 to the drain pin end platform 11, through the fourth bonding wire 15 and the fifth bonding wire 16 to the conductive metal substrate 29, the conductive metal substrate 29 conducts the current to the chip drain 21 through the chip solder layer 18, and then conducts the current from the chip right side source 22 and the chip left side source 23 through the fourth bonding wire 15 and the fifth bonding wire 16 to the source pin end platform 12, and finally outputs the current to the outside of the device through the source pin 4.

[0058] like Figure 1 , Figure 2 and Figure 3 As shown, the device housing 27 is composed of a top housing 1 and a bottom housing 9. The insulator is welded to the housing side plate 26 by silver-copper solder to form an airtight package. Figure 2The remaining space of the bottom shell 9 is filled with phase change liquid to immerse the chip and all bonding wires, replacing the silicone layer in conventional power devices to isolate the environment and electrically insulate the inside of the device. Then, in an inert gas environment, the top shell 1 and the bottom shell 9 are crimped together with a sealing gasket to form an airtight seal at the connection to prevent the phase change liquid from evaporating due to the high temperature of welding.

[0059] like Figure 4 As shown, when the power device is running under strong overcurrent, the output current increases, causing the heat generated by each structure in the output current path to increase rapidly and rise in temperature. The area with the fastest temperature rise rate is the connection between the right source 22 and the left source 23 of the chip and the fourth bonding wire 15 and the fifth bonding wire 16. When the temperature of these connections exceeds the boiling point of the phase change liquid, the phase change liquid begins to vaporize near this area, and the bubbles generated float the phase change gas from the release surface of the phase change liquid and mix with the inert gas. The phase change liquid absorbs a large amount of heat during the phase change by virtue of its huge phase change latent heat, effectively suppressing the temperature rise and temperature rise rate of the SiC MOSFET chip, thereby resisting the thermal shock caused by strong overcurrent and avoiding thermal instability inside the device. When the output current returns to normal, the heat generated by each structure in the output current path decreases, the temperature gradually decreases, and the phase change gas in the device housing 27 liquefies into a phase change liquid, ensuring that the power device is not affected under normal steady-state operation.

[0060] The strong overcurrent power device packaging structure of the present invention realizes the conduction and shutdown of the device through a series of current paths. When the device is turned on, the current flows from the drain pin 3 into the drain pin end platform 11, and then is introduced into the conductive metal substrate 29 through the fourth bonding wire 15 and the fifth bonding wire 16. The conductive metal substrate 29 conducts the current to the chip drain 21 of the SiC MOSFET chip 24 through the chip solder layer 18. The current continues to be conducted from the chip drain 21 to the source area of ​​the chip, that is, the right source 22 and the left source 23, and returns to the source pin end platform 12 through the fourth bonding wire 15 and the fifth bonding wire 16, and finally outputs the current to the outside through the source pin 4, completing the current conduction path.

[0061] The first bonding wire 17 of the device is used to transmit the gate control signal. The external drive signal is transmitted to the source pin end platform 12 through the gate pin 2, and then transmitted to the chip gate 20 through the first bonding wire 17, thereby controlling the switching state of the SiC MOSFET chip 24 and realizing the conduction and shutdown of the chip. The electrical connection between the gate and the source of the chip enables the control signal to flow between the source pin end platform 12 and the chip gate, affecting the conduction characteristics of the chip.

[0062] The second bonding wire 13 and the third bonding wire 14 respectively connect the left source 23 and the right source 22 of the chip to the source pin terminal platform 12. These bonding wires provide a current path so that the current from the chip source can be introduced into the source pin terminal platform 12 through these bonding wires and finally transmitted to the external device. The function of the bonding wires 13 and 14 is to ensure the current conduction path between the chip source and the external current system to ensure that the system can operate normally.

[0063] The present invention also uses phase change materials for thermal management to avoid overheating of the device due to excessive heat generated by long-term operation. The chip substrate 19 uses a conductive metal substrate 28 to connect the bottom of the device housing 27 to the cavity of the housing 9 to form an effective heat conduction path. The conductive metal substrate 29 is connected to the chip solder layer 18 to achieve heat conduction from the chip to the housing. At the same time, the phase change material helps to improve the heat dissipation efficiency and reduce the negative impact of excessive temperature on the device performance, thereby extending the service life of the device and improving its reliability.

[0064] The specific working principle of the present invention is described in detail:

[0065] 1. Overall structure of the device and signal input

[0066] The strong overcurrent power device packaging structure of the present invention uses the chip substrate 19 as the core component, and uses the combination of the insulating substrate 25 and the conductive metal substrate 28 to ensure the electrical insulation and stable connection between the SiC MOSFET chip 24 and the device housing 27. The driving signal is input through the gate pin 2, and is transmitted to the chip gate 20 through the source pin end platform 12 and the first bonding wire 17 to control the conduction and shutdown of the SiC MOSFET chip 24, thereby realizing precise control of the current.

[0067] 2. Current path between source and pin

[0068] When the device is in the on state, the left source 23 and the right source 22 of the chip are connected to the source pin terminal platform 12 through the second bonding wire 13 and the third bonding wire 14 respectively, forming a stable current path. This path provides a low impedance channel for power flow, ensuring that the device can withstand large current loads while reducing energy loss.

[0069] 3. Current path between drain and pin

[0070] The current of the drain pin 3 passes through the drain pin end platform 11, and is transferred to the conductive metal substrate 29 via the fourth bonding wire 15 and the fifth bonding wire 16, and then is transferred to the chip drain 21 through the chip solder layer 18. This path significantly improves the conduction efficiency of the drain current by optimizing the conductive performance and structural design of the conductive metal substrate 29.

[0071] 4. Thermal management function of phase change liquid hermetic packaging

[0072] The present invention introduces phase change liquid packaging technology into device packaging. Phase change materials can quickly absorb the heat generated by the chip under the action of large current, and transfer the heat to the housing 27 through the airtight packaging structure, thereby achieving rapid heat dissipation. This design effectively alleviates the overheating problem of the SiC MOSFET chip 24 when running at high power, prolongs the device life and improves working stability.

[0073] 5. Integrity and efficiency of current conduction path

[0074] When the device is turned on, the drain current enters from the drain pin 3, passes through the drain pin end platform 11 to the conductive metal substrate 29, and then passes through the chip solder layer 18 to the chip drain 21, and is conducted from the left source 23 and the right source 22 of the chip to the source pin end platform 12 through the second bonding wire 13 and the third bonding wire 14 respectively, and finally output to the outside through the source pin 4. This design reduces the on-resistance and improves the current conduction efficiency through multi-path optimization.

[0075] 6. Mechanical and electrical reliability of packaging structure

[0076] The structural design of the chip substrate 19 and the device housing 27 enhances the mechanical strength of the package. The layout of multiple bonding wires (the first to fifth bonding wires) allows the current to be shunted and conducted under heavy load, effectively reducing the current density of a single wire and avoiding connection failure caused by overheating. At the same time, the hermetic packaging design isolates the influence of the external environment and prevents device performance degradation caused by humidity or impurities.

[0077] In summary, the present invention achieves efficient heat dissipation and stable operation of strong overcurrent power devices through efficient current path design, multi-bond wire shunt structure, phase change liquid thermal management technology, and reliable airtight packaging process, providing a reliable solution for high-power application scenarios.

[0078] The most direct application field of the present invention is the new energy industry and the new power system, which is also the original intention of the design of the present invention. Power electronic equipment is widely used in all aspects of the new energy industry and the new power system. From power generation, transmission to distribution, all aspects have certain requirements for the overcurrent capacity of power semiconductor devices, which are all application fields of the present invention. Among them, the new energy industry can be specifically photovoltaic inverters, wind power converters, bidirectional converters of energy storage systems, modular multilevel converters, distributed renewable energy, etc., and the new power system can be specifically high-voltage direct current transmission, smart grids, direct current distribution networks, power electronic transformers, etc. The related products involved include IGBT power modules (inverters, rectifiers), SiCMOSFET modules (wind power, photovoltaic inverters), STATCOM (static VAR compensation device), FACTS equipment (flexible AC transmission system), energy storage power conversion system (PCS), etc.

[0079] At the same time, in other fields, the present invention also has many application scenarios, such as electric vehicles, rail transit, data centers, etc., among which they can be specifically motor control units (MCU), electric vehicle fast charging and on-board charging systems (OBC); railway traction rectifiers, traction motor control modules; data center power conversion modules, SiC power modules for power converters.

[0080] The photovoltaic inverter is used for specific description. The strong overcurrent power device using the structure of the invention can play the following key roles.

[0081] 1. Function:

[0082] 1. Improve impact resistance

[0083] Photovoltaic inverters will encounter various overcurrent shocks during operation, such as current shocks at the start-up moment, high-power load switching, or external faults (such as power grid faults). The strong overcurrent power device using the structure of the invention can withstand large instantaneous currents, avoid damage to the device due to overload, and ensure the stability and operational reliability of the equipment.

[0084] 2. Improve system efficiency

[0085] By reducing the number of parallel chips, the strong overcurrent power device using the structure of the invention can reduce the power loss of the inverter and improve the overall efficiency. This is particularly important for the long-term operation of the photovoltaic system, because a small increase in efficiency will bring significant energy benefits.

[0086] 3. Reduce failure rate and extend service life

[0087] The power module of the photovoltaic inverter is its core component, and traditional power devices are prone to thermal instability and shortened life under overcurrent conditions. The strong overcurrent power device with the structure of the invention can effectively suppress junction temperature fluctuations, significantly increase device life, and reduce maintenance frequency.

[0088] 4. Support high power density design

[0089] Modern photovoltaic inverters tend to be lightweight and miniaturized. The strong overcurrent power device of the invention reduces the heat dissipation structure and the number of modules, so that the inverter can achieve higher output power density with a smaller volume.

[0090] 2. Related application cases:

[0091] 1. High power photovoltaic inverter

[0092] Background: 1MW photovoltaic inverters need to have a high overcurrent tolerance to cope with high current density operating environments. Traditional inverters meet this requirement by connecting multiple power modules in parallel, but this increases costs and reduces efficiency.

[0093] Solution: Replace traditional power devices with strong overcurrent SiC MOSFET devices using the structure of the invention, and achieve up to 2.5 times the overcurrent tolerance without increasing the number of devices.

[0094] Results: Through phase change cooling packaging technology, the power module maintains stable operation under high current impact conditions, and the overall reliability and conversion efficiency of the inverter are improved by about 10%.

[0095] 2. Household photovoltaic system (5kW-20kW inverter)

[0096] Background: Inverters for household photovoltaic systems need to adapt to environments with frequent load switching and large grid-connected fluctuations. Overcurrent shocks place high demands on power modules, but due to cost and volume limitations, traditional methods are difficult to balance performance and cost.

[0097] Solution: Use a strong overcurrent device that applies the structure of the invention to design a small inverter, optimize heat dissipation and packaging design, and simplify the inverter structure.

[0098] Result: A single module can handle more than 2 times the overcurrent, avoiding additional heat dissipation and parallel design, reducing the overall cost of the inverter by 15%-20% and reducing the volume by about 30%.

[0099] 3. Distributed photovoltaic power station

[0100] Background: Distributed photovoltaic power stations need to face unstable loads and environmental conditions. Inverters may face large current shocks under fault conditions and need to have high reliability and strong overcurrent capability.

[0101] Solution: Use the strong overcurrent power device of the invention to improve the overcurrent protection capability of the inverter, while reducing the spare modules and system redundancy design.

[0102] Results: The inverter reliability was significantly improved, the operating life was extended by more than 5 years, and the overall system maintenance cost was reduced by more than 20%.

[0103] 3. Economic Benefits:

[0104] 1. Reduce system costs

[0105] Through the application of the invention, the number of power modules in the inverter can be reduced, and the cost of devices and heat dissipation systems can be reduced. For example, under the same power requirement, the number of inverter modules using the strong overcurrent device of the invention structure is reduced by about 30%, and the total cost is reduced by 15%-25%.

[0106] 2. Improve energy efficiency

[0107] The high overcurrent power device of the invention structure can operate stably at a higher current density, significantly reducing energy waste caused by efficiency loss. Taking a 100MW photovoltaic power station as an example, a 1% increase in inverter efficiency will bring an additional 1MW of power generation revenue. Based on about 1,500 hours of power generation per year, the annual power generation revenue will increase by about 1 million yuan.

[0108] 3. Extend service life and reduce maintenance costs

[0109] The thermal stability and junction temperature suppression capability of the high overcurrent device of the invention structure can significantly extend the operating life of the inverter and reduce the frequency of maintenance and replacement. For example, a traditional power module may need to be replaced twice in 10 years, while the life of the high overcurrent device can reach more than 20 years, thus saving equipment and maintenance costs.

[0110] 4. Promote system miniaturization and modular design

[0111] The high power density design reduces the size and weight of the inverter, making it easier to transport and install. For household and distributed photovoltaic applications, the miniaturized design can significantly reduce installation and operation and maintenance costs.

[0112] 5. Support the promotion of new energy

[0113] The application of the high overcurrent device of the inventive structure reduces the initial investment and operation and maintenance costs of the photovoltaic system, improves the economic efficiency of renewable energy power generation, and promotes the popularization and market expansion of photovoltaic power generation.

[0114] Figure (1) is a diagram of the overcurrent junction temperature suppression effect of solid-state phase change materials in a 2018 Chongqing University paper. It can be seen that the solid-state phase change material suppresses the junction temperature rise of power semiconductor devices to about 20°C. After that, some major research teams continued to conduct some related research, and the junction temperature suppression effect of solid-state phase change materials did not exceed 30°C.

[0115] The present invention has been verified by some experiments. Figure 1 The device shown compares the chip junction temperature of ordinary cooling without phase change liquid (base) and phase change cooling filled with phase change liquid (liquid). Figures (2) to (6) are the experimental results. Figure (2) is a comparison of the chip junction temperature rise of phase change cooling and air cooling under 1.7 times overcurrent for 2 seconds. It can be seen that liquid phase change cooling and phase change air cooling have a better effect on suppressing the chip overcurrent junction temperature rise. At the same time, the temperature rise curve is similar to the solid phase change temperature rise curve in the major paper, indicating that the solid phase change and liquid phase change have similar effects on suppressing the junction temperature rise, and the liquid phase change material has a better effect on reducing the temperature rise than the solid phase change material due to its larger phase change latent heat. In Figures (3) to (6), different Vds represent different overcurrent sizes. The larger the Vds, the larger the overcurrent multiple, and the higher the corresponding chip temperature rise. Temperature T is the chip junction temperature at the end of the overcurrent, and the initial chip junction temperature is 25°C. Over-current tests were carried out for 100ms, 200ms, 2s and 5s respectively.

[0116] Table 1 Average and maximum temperature drop under different overcurrent time

[0117]

[0118] From the perspective of the maximum cooling effect, under 5-second overcurrent conditions, phase change cooling technology can effectively suppress the junction temperature rise of the chip, with a maximum drop of up to 100°C, which fully demonstrates that phase change liquid has a significant inhibitory effect on the control of the junction temperature of power semiconductor devices. The experimental results verify the huge heat storage potential of phase change liquid refrigeration, and its cooling effect far exceeds the traditional air cooling, liquid cooling and solid-state phase change cooling methods. It has a breakthrough significance in suppressing the junction temperature rise of power semiconductor devices under overcurrent conditions, thereby greatly improving the extreme overcurrent capacity of power semiconductor devices.

[0119] From the perspective of the average cooling effect, as the overcurrent time increases, the suppression of the chip junction temperature rise by phase change cooling gradually increases. This is because under the experimental conditions within 5 seconds, the mass of the phase change liquid that absorbs heat and vaporizes when the power semiconductor device is overcurrent is still small compared to the total amount of liquid in the shell, and the maximum consumption of the phase change liquid during the 5-second overcurrent period is about 50% of the total amount. The average cooling effect of 30°C to 70°C shows that the cooling effect of the present invention under different overcurrent conditions shows extremely high stability, which further proves the steady-state reliability of the invention and its applicability in various applications.

[0120] Figure (7) shows the oscilloscope waveform of the laboratory-made SiC MOSFET device in the overcurrent test experiment using the strong overcurrent power device packaging structure filled with phase change material of the present invention. It can be seen from the figure that the packaging structure can enable the SiC MOSFET device to operate stably for 10 seconds under 2 times overcurrent conditions without overheating. This verifies that the device is fully capable of withstanding the second-level 2 times overcurrent impact.

[0121] It should be pointed out that Figure (7) is not an overcurrent test under extreme conditions, indicating that the performance potential of the device has room for further exploration. In addition, the packaging structure can achieve the best overcurrent capacity of the power semiconductor device by adjusting the size design or selecting phase change liquids with different boiling points. Although these adjustments involve changes in specific parameters, they do not change the core structural design of the invention, so similar structural designs still fall within the scope of protection of the present invention.

[0122] It is speculated based on the existing data that the packaging structure is fully capable of achieving 2.5 times the overcurrent and stable operation for 10 seconds, further proving the excellent performance and adaptability of the present invention in improving the overcurrent capacity of power semiconductor devices.

[0123] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A packaging structure for a high-current power device filled with phase change material, characterized in that: It includes a bottom shell, a top shell, a SiC MOSFET chip, a chip substrate, device pins, insulators and phase change liquid. The device pins are welded to the shell side plate through the insulators. The bottom shell and the top shell are welded through a sealing gasket to form a device shell. The phase change liquid is filled inside the device to immerse the SiC MOSFET chip and all bonding wires.

2. The high overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The device housing comprises a top housing and a bottom housing, and the bottom housing comprises a housing bottom plate and a housing side plate.

3. The high overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The device pins include external pins and internal end platforms, the external pins are used to connect external circuits, the internal end platforms are used to connect various levels of the chip, the external pins include gate pins, source pins and drain pins, and the internal end platforms include gate pin end platforms, source pin end platforms and drain pin end platforms.

4. The strong overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The insulator includes a gate insulator, a source insulator and a drain insulator. The external pins are welded to the insulators and fixed on the side plates of the shell. The external pins extend into the device through the insulators and are connected to the internal terminal platform. The internal terminal platform is fixed by the external pins.

5. The strong overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The SiCMOSFET chip includes a chip gate, a chip left source, a chip right source and a chip drain. The chip drain is welded to a chip substrate through a chip solder layer. The chip gate and the gate pin end platform are bonded through a first bonding wire. The chip left source and the source pin end platform are bonded through a second bonding wire. The chip right source and the source pin end platform are bonded through a third bonding wire.

6. The high overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The chip substrate comprises a conductive metal substrate and an insulating substrate, the insulating substrate is welded together with the bottom shell, the conductive metal substrate is welded to the upper layer of the insulating substrate, the chip drain of the SiC MOSFET chip is welded to the conductive metal substrate through a solder layer, and the conductive metal substrate is bonded to the drain pin end platform through a fourth bonding wire and a fifth bonding wire.

7. The high overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The device is filled with a phase change liquid, which occupies most of the volume inside the device and immerses the SiC MOSFET chip and all bonding wires. The air is exhausted from the device, leaving a small amount of inert gas filling space.

8. The strong overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The output current path of the device is connected from the drain pin to the drain pin end platform, the drain pin end platform is connected to the conductive metal substrate through the fourth bonding wire and the fifth bonding wire, the conductive metal substrate guides the current into the chip drain through the chip solder layer, the output current is respectively derived from the left source and the right source of the chip, and is guided to the source pin end platform through the second bonding wire and the third bonding wire, and finally output from the source pin.

9. The strong overcurrent power device packaging structure filled with phase change material as claimed in claim 1, characterized in that: The packaging structure of the strong overcurrent power device filled with phase change material increases the output current when the device is in overcurrent operation, and the temperature of each structure in the output current path rises, among which the temperature rise of the SiC MOSFET chip is the most significant; when the temperature exceeds the boiling point of the phase change liquid, the phase change liquid begins to vaporize and absorb heat, suppressing the temperature rise rate and reducing the temperature rise, thereby enhancing the overcurrent capacity and overcurrent duration of the device; after the overcurrent ends, the vaporized phase change gas is cooled and re-liquefied into a phase change liquid, ensuring the normal steady-state operation of the device when it is not in overcurrent.

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