Patent Application
20220392827
The present application relates to the technical field of heat dissipation of semiconductor devices and chips, for example, a heat dissipation structure and a heat dissipation system.
With the development of semiconductor technology, the third-generation semiconductor materials and devices gradually become the “core” supporting the new generation of information technology, energy conservation and emission reduction, and intelligent manufacturing. However, the characteristics of small area and high power of the third-generation semiconductor materials and devices cause the problems of more heating and difficult heat dissipation. Therefore, high power density limits the development and application of third-generation semiconductor devices and chips. Exemplarily, when a gallium nitride (GaN) half-bridge circuit operates at the frequency of 10 MHz and the voltage of 400 V, the heating power density (that is, Joule heat per unit area) of the GaN half-bridge circuit can reach 6,400 W/cm2, close to the heat density of the solar surface. Some graphics processing units (GPUs) have the heating power of nearly 300 W in the size of 815 mm2, and the heating power density of some GPUs reaches 37 W/cm2. The maximum heating power consumption of a central processing unit (CPU) on a chip with the size of 600 mm2 reaches 165 W and the heating power density of the CPU reaches 27.5 W/cm2. It is predicted that the average power density of high power density devices and chips will reach 500 W/cm2, and the local power density in a heat-concentrated area can exceed 1,000 W/cm2, far exceeding the currently widely used upper limit (1.5 W/cm2) of the heat dissipation power density of gas convection and the currently widely used upper limit (120 W/cm2) of the heat dissipation power density of liquid convection.
The highest heat resistant junction temperature of the third-generation semiconductor devices and chips is about 90° C. and can reach about 105° C. in special cases. If there is no efficient heat dissipation system, the operating ambient temperature of the devices and chips can exceed the highest heat resistant junction temperature of the devices and chips, that is, the devices and chips operate in an unstable state, resulting in thermal runaway damage.
The present application provides a heat dissipation structure and a heat dissipation system to improve the heat dissipation efficiency and avoid thermal runaway damage to devices and chips.
An embodiment of the present application provides a heat dissipation structure. The heat dissipation structure includes a heat dissipation channel and a plurality of heat dissipation fins.
The plurality of heat dissipation fins are arranged on at least one side of the heat dissipation channel. Heat dissipation fins arranged on the same side of the heat dissipation channel are arranged along an extension direction of the heat dissipation channel.
The heat dissipation channel and the plurality of heat dissipation fins are each formed as a cavity structure. Each of the plurality of heat dissipation fins includes a first end and a second end arranged opposite to each other. The first end is a closed end, and the second end is an open end. The second end communicates with the heat dissipation channel.
An embodiment of the present application provides a heat dissipation system. The heat dissipation system includes any heat dissipation structure provided by the preceding embodiment.
The heat dissipation system further includes a heat conduction cavity, a transmission channel and a heat exchange medium. The heat conduction cavity communicates with the heat dissipation structure through the transmission channel. The connection end where the transmission channel is connected to the heat dissipation structure is higher than the connection end where the transmission channel is connected to the heat conduction cavity.
The heat exchange medium in the liquid state is stored in the heat conduction cavity. The transmission channel is configured to transmit the heat exchange medium heated and vaporized in the heat conduction cavity to the heat dissipation structure and return the heat exchange medium condensed and liquefied due to a heat exchange at the heat dissipation structure into the heat conduction cavity.
The present application is described below in conjunction with drawings and embodiments. For ease of description, only part, not all, of structures related to the present application are illustrated in the drawings.
With the development of semiconductor technology, in view of the characteristics of small area and high power density of third-generation semiconductor materials and devices, the heat dissipation efficiency of a heat dissipation system urgently needs to be improved to avoid the thermal runaway loss of semiconductor devices.
Heat ultimately needs to be exchanged with the atmosphere to complete a complete heat exchange process. Referring to
In a heat dissipation structure and a heat dissipation system provided by the embodiments of the present application, a heat dissipation channel and heat dissipation fins are each formed as a cavity structure so that the heat dissipation area of the heat dissipation structure with a small volume can be enlarged by 3 to 6 orders of magnitude, thereby increasing the heat dissipation area. That is, the area compensation is used for achieving the matching between the heating power and the heat dissipation power and improving the heat dissipation efficiency.
Technical schemes in the embodiments of the present application will be described in conjunction with drawings in the embodiments of the present application.
Referring to
In the heat dissipation structure provided by the embodiment of the present application, the heat dissipation channel and the heat dissipation fins are each formed as a cavity structure, and the heat exchange can be achieved by using all surface walls of the cavity structure, thereby increasing the heat dissipation area. That is, the heat dissipation area can be increased on a heat dissipation structure with a smaller volume, thereby improving the heat dissipation efficiency and being beneficial to avoiding the thermal runaway damage of devices and chips.
In one embodiment, the cavity structure of the heat dissipation channel 110 and the heat dissipation fins 120 can allow circulation of a heat exchange medium, thereby achieving a heat exchange process.
In one embodiment, the first end of the heat dissipation fin 120 is an end of the heat dissipation fin 120 facing away from the heat dissipation channel 110. Exemplarily, taking the orientation shown in
In one embodiment, the heat dissipation channel 110 and the heat dissipation fins 120 are each formed as a cavity structure so that the contact area between the heat exchange medium and the heat dissipation structure 10 and the contact area between the heat dissipation exchange structure and the atmosphere can be increased, thereby increasing the heat dissipation area and being beneficial to improve the heat dissipation efficiency.
Exemplarily, the heat dissipation structure 10 may be referred to as a “three-dimensional (3D) hollow heat dissipation fin group”. The heat dissipation surface area of the sample to be heat-dissipated (for example, a semiconductor device and chip) is in the order of square centimeters (cm2). For the heat dissipation structure 10, the heat dissipation area can be enlarged by 3 to 6 orders of magnitude in a smaller volume. That is, the heat dissipation area can reach orders of 1 square meter (m2) to 10 square meters (m2).
In one embodiment,
In addition,
In an embodiment, referring to any one of
In this manner, the heat exchange medium in the heat dissipation channel 110 may be dispersed into multiple heat dissipation fins 120. At the same time, the heat exchange medium in the heat dissipation fins 120 may converge into the heat dissipation channel 110. This will be described below in connection with other components of the heat dissipation system.
Exemplarily, when the heat exchange medium is a liquid-vapor phase change material, the gaseous phase change material carrying heat may be dispersed into the plurality of heat dissipation fins 120 through the heat dissipation channel 110. Then, the heat carried by the gaseous phase change material in the heat dissipation fins 120 is finally exchanged with the atmosphere through the inner and outer walls of the heat dissipation fins 120. The heat exchange lowers the temperature of the gaseous phase change material and can condense and recover the liquid phase change material. The distance between the first end of a heat dissipation fin 120 and the horizontal plane is set to be greater than or equal to the distance between the second end of the same heat dissipation fin 120 and the horizontal plane so that the open end of the heat dissipation fin 120 is lower than or equal to the closed end of the heat dissipation fin 120. That is, the open end is horizontal or downward. Thus, the liquid phase change material can flow back from the heat dissipation fins 120 into the heat dissipation channel 110, thereby achieving the circulation of the heat exchange medium.
In one embodiment,
Optional directions of the first direction X and the second direction Y are exemplarily described below in combination with actual spatial orientations.
In an embodiment, referring to
Alternatively, referring to
In other implementations, the included angle between the extension direction of the heat dissipation fins 120 and the horizontal direction may be any angle from 0° to 180°, including 0° and 180°, to ensure that the heat dissipation fins 120 are arranged in such a manner that the open ends are horizontal or downward, that is, as long as the liquid heat exchange medium can flow back to the heat dissipation channel 110.
In one embodiment,
On the basis of the preceding implementations, the embodiments of the present application further provide a heat dissipation system. The heat dissipation system includes any heat dissipation structure provided by the preceding implementations. Therefore, the heat dissipation system has the technical effects of the heat dissipation structure in the preceding implementations. The same content may be understood by referring to the preceding description of the heat dissipation structure and will not be repeated below.
Exemplarily, referring to any one of
In one embodiment, samples 300 to be heat-dissipated are attached to at least part of the sidewall of the heat conduction cavity 210 (taking that samples 300 to be heat-dissipated are attached to the bottom of the heat conduction cavity 210 in
Exemplarily, in
Exemplarily, in the actual product structure, the sample 300 to be heat-dissipated may be a high-power device or chip. In this case, the sidewall of the heat conduction cavity 210 to which the sample 300 to be heat-dissipated is attached may be configured as a heat conduction base 212 with a high thermal conductivity, to use the heat conduction base 212 to assist heat dissipation. The transmission path of heat may include transmitting the heat generated by the sample 300 to be heat-dissipated to the heat exchange medium 230 through the heat conduction base 212. In the heat dissipation system 20, the transmission path of heat is relatively short, and the heat dissipation efficiency is relatively high.
In one embodiment, in the actual product structure, the sample 300 to be heat-dissipated may include a heat conduction base 212 besides a high-power device and chip. The heating surface of the sample 300 to be heat-dissipated is attached to one side of the heat conduction base 212, and another side of the heat conduction base 212 is attached to the bottom of the heat conduction cavity 210. In this case, the transmission path of heat may include transmitting the heat generated by the sample 300 to be heat-dissipated to the heat exchange medium 230 through the heat conduction base 212 and the bottom of the heat conduction cavity 210 sequentially. In the heat dissipation structure 10, the heat conduction cavity 210 may be integrally formed with the same material, and the preparation process is relatively simple and the cost is relatively low.
The heat conduction cavity 210, the transmission channel 220 and the heat exchange medium 230 are exemplarily described below with reference to
In an embodiment, referring to any of
In one embodiment, the heat conduction base 212 is configured to change a point heat source into an equivalent plane heat source to increase the effective heat exchange area, thereby reducing the heat conduction power density.
In an embodiment, the thermal conductivity of the heat conduction base 212 is greater than or equal to 500 W/(m·K).
In this manner, by using the heat conduction base 212 with a high thermal conductivity, the heat of the sample 300 to be heat-dissipated can be rapidly diffused along multiple directions of the heat conduction base 212. Referring to
In an embodiment, referring to
Exemplarily, the thermal conductivity of common materials is shown in Table 1.
In this embodiment, by using diamond or other ultra-high solid heat conduction material as the material of the heat conduction base 212 with a high heat conduction power density, other materials of the heat conduction base 212 with low thermal conductivity can be replaced, thereby improving the thermal conductivity of the heat conduction base 212. The heat inside the sample 300 (for example, a high power density device and chip) to be heat-dissipated can be more easily conducted to the surface of the heat conduction base 212 facing the inside of the heat conduction cavity 210.
On this basis, to achieve matching between the heating power and the heat dissipation power by area compensation, the ratio between the heating area, the heat conduction area and the heat dissipation area may be set.
Exemplarily, referring to
In one embodiment, the heat conduction base 212 is in contact with the heating surface of the sample 300 to be heat-dissipated. By using the material of the large-area solid heat conduction base 212 with an ultra-high thermal conductivity, the area of the heat conduction base 212 is greatly enlarged at the same heating power so that the heat can be rapidly diffused along the plane and side of the heat conduction base 212 shown in
Exemplarily, the area ratio A00 may be in the order of hundreds to tens of thousands, thereby effectively enlarging the heating surface and reducing the heating power density.
Exemplarily, the width of the sample 300 to be heat-dissipated may be 0.1 mm, and the length of the sample 300 to be heat-dissipated may be 0.2 mm; the length and width of the heat conduction base 212 are each 7 mm; and the area ratio A00=2,450.
In other implementations, 500≤A00≤5,000, 900≤A00≤8,000, 5,000≤A00≤80,000 or other optional value ranges may be set according to the actual heat dissipation requirements of the heat dissipation system 20, which is not limited by the embodiments of the present application.
In one embodiment,
In one embodiment, the heat dissipation area of the heat dissipation structure 10 may include the area of the outer wall of a heat dissipation channel and the area of the outer wall of the heat dissipation fins. The heat exchange medium causes a thermal short circuit between the heat conduction base 212 and the heat dissipation structure 10. By setting A01>B01, the heat dissipation rate may be matched with the heating rate by area compensation, thereby achieving a better heat dissipation effect and avoiding thermal runaway damage.
Exemplarily, the average heating power density of high power density devices and chips will reach 500 W/cm2, and the local power density of the heat concentration area may exceed 1,000 W/cm2. The maximum heat dissipation power density of natural gas convection may be 1.5 W/cm2. B01 may be (500/1.5)=333.34 or (1000/1.5)=666.6.
On this basis, by setting the area of the heat dissipation surface in contact with the atmosphere being enlarged by 3 to 6 orders of magnitude, the power density mismatch can be converted into power matching, thereby achieving the heat exchange matching of the system.
In an embodiment, referring to
In this manner, on the one hand, the thickness of the sidewall of the cavity of multiple structures in the heat dissipation system is not too thin, thereby facilitating the overall structural stability of the heat exchange system. On the other hand, the thickness of the sidewall of the cavity is not too thick, thereby ensuring high heat conduction and heat exchange efficiency.
Exemplarily, A11=0.5 mm, and A12=1 mm.
In other implementations, 5 μm≤A11≤5 cm, 8 mm≤A11≤5.8 cm, 5 mm≤A12≤7.5 cm, 8 mm≤A12≤5 cm or other optional ranges may be set, which is not limited by the embodiments of the present application.
In an embodiment, the heat exchange medium 230 may include a heat superconducting phase change material.
In one embodiment, the heat exchange medium 230 is required to connect the heat conduction area of the heat conduction base 212 and the heat dissipation area of the heat dissipation structure 10. The heat exchange medium 230 transmits heat from the heating surface (equivalent to the heat conduction surface of the heat conduction base 212) of the device and the chip to the heat dissipation structure 10. The heat exchange medium 230 is attached to the surface of the heat conduction base 212 of the device and the chip. The heat exchange power density of the heat exchange medium must be of the same order of magnitude as the heating power density of the device and the chip. Moreover, the heat exchange medium 230 must have fast fluidity so that heat can be rapidly transmitted to the heat dissipation structure 10, thereby achieving a thermal short circuit between the heat conduction base 212 and the heat dissipation structure 10.
The gaseous phase heat exchange material has fluidity but insufficient power density. The liquid phase heat exchange material has poor fluidity, and the power density of the liquid phase heat exchange material is not up to the standard. The solid phase material has the power density up to the standard, but does not have fluidity.
In this embodiment, the heat exchange medium 230 is provided as a heat superconducting phase change material which may also be referred to as a “phase change material”, a “liquid-vapor phase change material” or a “liquid phase-vapor phase change heat exchange material” so that the heat exchange medium 230 has the characteristics of power density matching and strong fluidity.
Exemplarily, the heat exchange power density of the liquid phase-vapor phase change heat exchange material may reach 1,000 W/cm2.
In other implementations, other types of heat exchange medium 230 may be selected according to the requirements of the heat dissipation system 20 to ensure that the power density of the heat exchange medium 230 is matched with the heating power density, and that the fluidity thereof is good so that the heat conduction base 212 and the heat dissipation structure 10 can be thermally short-circuited. This is not described repeatedly or limited by the embodiments of the present application.
In an embodiment, the transmission channel 220 is a rigid channel or a flexible channel.
In one embodiment, the heat dissipation structure 10 communicates with the heat conduction base 212 of the device and chip through the transmission channel 220. In this manner, it can be achieved that the effective contact area is enlarged. The transmission path of heat includes a gaseous phase change material→ the inner wall of the heat dissipation structure→ the outer wall of the heat dissipation structure→ atmosphere. As such, the contact area may refer to the contact area between the gaseous phase change material and the inner wall of the heat dissipation structure or may refer to the contact area between the outer wall of the heat dissipation structure and the atmosphere.
Exemplarily, when the transmission channel 220 is a rigid channel, the form of the transmission channel 220 is fixed so that the relative position of the heat conduction cavity 210 and the heat dissipation structure 10 is fixed, thereby being beneficial to enhancing the overall structural stability of the heat dissipation system 20.
Exemplarily, when the transmission channel 220 is a flexible channel, the size and form of the transmission channel 220 may be set according to the spatial positional relationship between the heat dissipation structure 10 and the heat conduction cavity 210, such as the distance, the position and the like, and according to requirements such as the arrangement positional relationship of the device and the chip, thereby increasing the design flexibility of the heat dissipation system 20.
In one embodiment,
In an embodiment,
In one embodiment, the hydrophilic film layer 252 is coated on the heat dissipation surface of the heat conduction base 212, that is, a hydrophilic treatment is performed so that the liquid phase change material can be more easily attached to the surface of the heat conduction base 212 facing the inside of the heat conduction cavity 210. The surface of the heat conduction base 212 is provided with the storage groove 211 in which the heat exchange medium 230 is stored. By performing the water-conducting treatment on the surface of the storage groove 211, the liquid phase change material can conduct to the surface of the heat conduction base 212 of the device and chip more easily. By performing the water-conducting treatment on the inner surface of the heat conduction cavity 210 between the heat conduction base 212 and the groove structure 211, a complete hydrophilic path from the storage groove 211 to the heat conduction base 212 can be formed, thereby enabling the liquid phase change material to transmit from the storage groove 211 to the surface of the heat conduction base 212.
In one embodiment, the hydrophobic treatment is performed on the inner surfaces of the transmission channel 220 and the heat dissipation structure 10 so that the vapor phase change material does not adhere to the inner surfaces of the heat dissipation structure 10 and the transmission channel 220 after condensation, and the vapor phase change material rapidly flows back to the storage groove 211 of the heat conduction cavity 210 along a conducting path and joins the heat exchange cycle again, thereby improving cycle efficiency and further improving heat exchange efficiency.
In an embodiment, the water-conducting film layer 253 includes a fiber structure or a core structure.
In this manner, the water conducting can be achieved through capillary action, and the structure is simple.
In other implementations, other water-conducting film structures may be adopted, as well as any type of hydrophilic film structure and hydrophobic film structure may be adopted, which are not described or limited by the embodiments of the present application.
In one embodiment, in
The heat dissipation process of the heat dissipation system provided by the embodiments of the present application is described below in conjunction with multiple stages of the heat dissipation process of the heat dissipation system.
Exemplarily, the essence of solving the heat dissipation of high power density devices and chips is to solve the problem that the heat dissipation density does not match the heating density in multiple heat dissipation stages. Three stages are taken as an example. In the first stage, heat is conducted from the heating surface of a device or chip to a heat exchange medium through a heat conduction base. In the second stage, the heat exchange medium is in contact with the inner surface of the heat dissipation structure, and the heat is conducted through the inner surface of the heat dissipation structure to the outer surface of the heat dissipation structure. In the third stage, the heat of the outer surface of the heat dissipation structure is exchanged with the convection of the atmosphere, thereby completing a heat exchange cycle.
In the first stage, for solid heat conduction, when the heat transmission path (thickness of the heat conduction base 212) is constant, the equivalent heat dissipation coefficient (h2) of the next stage needs to be set to be equal to or greater than the equivalent heat dissipation coefficient (h1) of the heating/heat transmission/heat conduction of the previous stage: h2≥h1
In the second stage, for the phase change heat exchange, if the effective contact areas are equal, the phase change heat exchange power density (q2″) must be equal to or greater than the heating power density (q1″) of the previous stage: q2″≥q1″.
In the third stage, for convection heat exchange, if the effective heat dissipation areas are not equal, the convection heat dissipation power (q2) needs to be equal to or greater than the power (q1) of the previous stage: q2 q1.
Thus, the embodiments of the present application solve the problem of matching heat exchange power/power density in multiple stages and complete the design of the heat dissipation system 20.
The concepts of power and power density need to be understood. Power is the energy/heat generated or exchanged per unit of time in watts (W). The power density is the power generated or exchanged per unit area in watts per square centimeter (W/cm2).
The operating process of the heat dissipation system 20 is exemplarily described below in conjunction with multiple constituent structures and relative positional relationships of the heat dissipation system 20.
An embodiment of the present application provides a fin-type 3D hollow phase change heat dissipation structure and system. The heat dissipation system 20 includes a heat conduction cavity 210 in which a heat conduction base is located, a heat dissipation structure 10 composed of a fin-type 3D hollow heat dissipation fin and a heat dissipation channel, and a transmission channel 220. A heat superconducting phase change material is stored inside the heat dissipation system 20 as a heat exchange medium 230.
A material with a high thermal conductivity (for example, thermal conductivity≥500 W/(m·K)) such as diamond is used as a heat conduction base 212. The heating surfaces of the high power density devices and chips are attached to the bottom of the heat conduction cavity 210 through the heat conduction base 212.
In one embodiment, the hydrophilic treatment is performed on the heat conduction base 212, and the liquid-vapor phase change material storage groove is located at the bottom of the heat conduction cavity 210. The phase change material can be smoothly and sufficiently coated on the hydrophilic surface through capillary action.
The height of the heat dissipation structure 10 (that is, the fin-type 3D hollow structure) may be higher than the heat conduction base 212. The heat conduction cavity 210 may communicate with the heat dissipation structure 10 through the transmission channel. A flexible transmission channel is provided between the device and chip and the 3D hollow heat dissipation structure to transfer the increased volume of the heat dissipation system to any place and is convenient for the design of the device and the chip. The inner wall of the fin-type 3D hollow structure is coated with a layer of hydrophobic material to reduce the adhesion of the liquid phase change material.
When the heat dissipation system 20 is operating, the device and the chip generate heat with high power density. The heat is transmitted to the phase change material through the heat conduction base 212. With the accumulation of heat, the temperature of the phase change material rises and exceeds the boiling point (phase change temperature). The liquid-vapor phase change heat dissipation material vaporizes and rises, leaving the heat dissipation surface. At the same time, the liquid phase change material is stored in the groove on the side and quickly adsorbed on the heat dissipation surfaces of the device and the chip through the capillary phenomenon and the hydrophilic film, supplementing the vaporized material. The vaporized phase change material passes through the transmission channel (hydrophobic treatment) to the fin-type 3D hollow structure. The vapor phase change material is in contact with the inner surface wall of the 3D hollow heat dissipation fin, and heat is transmitted to the 3D hollow heat dissipation fin through the phase change material. The heat of the phase change material decreases and the temperature drops below the boiling point (phase change temperature). The phase change material changes into a liquid state again. As a result of the hydrophobic treatment performed on the inner wall of the 3D hollow structure and the inclined downward included angle formed between the inner wall of the 3D hollow structure and the horizontal direction, the condensed phase change material passes through the transmission channel and then flows back and adheres to the surface of the heat conduction base or the storage groove of the phase change material. The phase change material is attached to the heat dissipation surface of the heat conduction base again through the capillary phenomenon and the hydrophilic film layer to complete a cycle of the phase change material.
The heat is transmitted from the phase change material to the hollow heat dissipation fin. The heat dissipation fin is hollow inside, the thickness of the surface wall thereof is in an order of 1 mm, and the heat conduction power density thereof is matched with the power density of the phase change material. The heat is transmitted through the inner surface wall of the heat dissipation fin to the outer surface wall of the heat dissipation fin, and the temperature rise of the heat dissipation wall is controlled at about 1° C. The outer surface wall of the 3D hollow heat dissipation fin is in contact with the air (atmosphere) and transmits heat to the atmosphere through heat exchange. Since the heat dissipation area is 3 to 6 orders of magnitude higher than the surface area of the chip, the heating power of the chip matches the heat dissipation power of the atmosphere. The heating heat of the chip is transmitted to the atmosphere to complete a complete heat dissipation cycle.
In the heat dissipation system 20, the phase change medium enables a thermal short circuit to form between the local small-area heat exchange surface with a high heat power density and the non-local large-area heat exchange surface with a low power density. That is, the heating surface and the heat dissipation surface communicate with each other through the phase change medium to form a thermal circuit, thereby improving heat conduction and heat dissipation efficiency. It can also be understood as that a phase change heat exchange material is used as a heat superconducting link to increase the matching area between the hollow heat dissipation fin and the heat dissipation (heat conduction) base of the chip by 4 to 5 orders of magnitude so that the power of the natural gas convection matches the required heat dissipation power.
The heat dissipation system 20 can be applied to heat dissipation of high power density devices and integrated circuit chips of the third-generation semiconductors such as SiC or GaN, solving the heat dissipation problem that the heating power of high power density devices and integrated circuit chips does not match the heat dissipation power thereof and has the advantage of low cost.
Exemplarily, for high power density devices and chips with a heating power density of 500 to 1,000 W/cm2, the temperature rise is ≤33° C. That is, in the case where the ambient temperature is 27° C., the chip temperature is ≤60° C., much lower than the maximum bearable temperature 85° C. of the chip. The heat dissipation requirements of future high power density devices and chip (GaN or SiC) power electronic devices are met, thereby avoiding thermal runaway damage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910853481.3 | Sep 2019 | CN | national |
This is a National Stage Application filed under 35 U. S.C. 371 based on International Patent Application No. PCT/CN2020/095375, filed on Jun. 10, 2020, which claims priority to Chinese Patent Application No. 201910853481.3 filed with the China National Intellectual Property Administration (CNIPA) on Sep. 10, 2019, the contents of which are incorporated herein by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2020/095375 | 6/10/2020 | WO |
