A two-phase jet cooling radiator for high power density chips

Abstract

The present invention provides a two-phase jet cooling radiator for high-power density chips, belonging to the technical field of chip cooling and heat dissipation. The cooling radiator includes a coolant cavity housing, a jet manifold layer, a jet flow channel plate, and a porous medium layer; a liquid distribution cavity is formed in the coolant cavity housing; a jet cavity is formed in the jet manifold layer, and jet holes are uniformly distributed on the jet cavity; the jet flow channel plates are all installed in the jet cavity, and their jet flow channels are all arranged vertically, and one end of each jet flow channel is connected to the corresponding jet hole; the gaps between the jet flow channel plates in the lower space of the jet cavity are filled with the porous medium layer. The present invention utilizes the influence of the small-aperture porous medium layer on bubble dynamics, improves the critical heat flux density in the heat dissipation process, increases the heat dissipation per unit area, prolongs the working life of the chip, improves the working stability of the chip, and plays an important role in ensuring the stable operation of the chip under the working conditions of high heat flux density and high integration.

Description

Technical Field

[0001] The present invention relates to the technical field of chip cooling and heat dissipation, and particularly relates to a two-phase jet cooling radiator for high-power density chips. Background Art

[0002] With the development of electronic technology, especially integration technology, the size of chips is getting smaller and the power density is getting higher. The heat flux density of high-power chips can reach 1000 W / cm 2 , and too high working temperature of electronic devices will lead to the decline of chip reliability and stability. For some chips, for every 1°C increase in temperature, the performance will decrease by 1-2%, the service life will be reduced, the energy consumption will increase, and even thermal runaway will occur when working at high temperature for a long time. To avoid these problems, it is crucial to research and explore new electronic device heat dissipation technologies. At present, the traditional heat dissipation technologies of electronic devices cannot well meet the heat dissipation requirements. New heat dissipation technologies such as heat pipe heat dissipation, microchannel heat dissipation, spray cooling, jet cooling, and the combined design of related technologies make heat dissipation more efficient.

[0003] Jet technology can produce a very strong heat transfer effect on the jet impact surface. Jet cooling refers to the technology of directly impacting the surface to be cooled by using a high-speed coolant to achieve cooling, mainly by the impact of the fluid or the generation of a phase change to take away heat. Compared with traditional heat dissipation methods, jet cooling technology has the following three significant advantages: First, the heat transfer efficiency is high. Jet cooling realizes direct cooling to reduce the cooling thermal resistance to achieve efficient heat exchange; Second, jet cooling technology is widely applicable to electronic devices with different heat flux densities and different sizes; Third, through the reasonable design and arrangement of jet nozzles, uniform heat dissipation of electronic devices can be better achieved, thermal stress can be reduced, the working reliability of devices can be enhanced, and the service life of electronic devices can be extended.

[0004] At present, the research on jet cooling and heat dissipation focuses on the design of jet nozzle forms, the selection of cooling fluids, the nozzle arrangement forms, the nozzle height and diameter, the surface microstructure design and surface treatment of the contact surface, etc. At the same time, people also pay attention to thermoelectric refrigeration technology to achieve local high-efficiency cooling, apply the excellent thermal conductivity of nanomaterials to improve the cooling effect, study the optimization effect of microscale jet cooling through numerical simulation, and use multiphase flow jet cooling technology to improve the heat transfer capacity.

[0005] The cooling effect of two-phase jet heat dissipation is better than that of single-phase jet heat dissipation, and people optimize the design of traditional jet structures. The team led by Professor Wei Tiwei at Purdue University proposed a chip-level two-phase jet cooling technology. This device directly encapsulates heat dissipation channels inside the chip package, sprays the coolant directly onto the back of the chip, and has a shorter heat dissipation path. Deionized water is used as the coolant. The top of the structure is the coolant inlet, the middle is the coolant outlet, and the bottom is the gas phase outlet. It uses the phase change of liquid boiling to take away heat, forming a multi-layer gas-liquid transport distribution system, achieving a chip cooling performance of 500 W / cm 2 ².

[0006] Although the jet cooling technology of this solution can already achieve a good heat transfer effect, there are still deficiencies. This solution cannot achieve the separated flow of gas and liquid on the heat source surface, which will affect the chip heat dissipation efficiency, and the flow resistance of the cooling working medium also needs to be optimized. At high power densities, once gas is generated on the chip surface, it is easy to coalesce and form large bubbles / columns, blocking the liquid flow path, resulting in an increase in the local flow resistance of the liquid cooling working medium, inducing flow instability, causing the system flow rate to oscillate or even drift, and the coolant flow rate will rapidly decrease (even drop to 0). Once there is an instantaneous lack of liquid on the chip surface, the sudden temperature rise will trigger a burn-out risk. At the same time, due to the extremely low thermal conductivity of gas (generally one order of magnitude lower than that of the liquid phase), the retention / coverage of large bubbles on the chip surface will also increase the heat transfer thermal resistance, causing the chip temperature to rise suddenly instantaneously. It can be seen that accelerating the detachment and removal of bubbles on the chip surface is the inevitable way to improve the chip heat transfer efficiency and thermal management performance. At the same time, the long-term gas-liquid two-phase flow on the heat source surface will also accelerate the corrosion and wear of the chip and porous materials, reduce the service life of the device, and increase the maintenance cost of the work. Therefore, it is necessary to achieve gas-liquid separation to improve reliability and service life. Summary of the Invention

[0007] To solve the problems in the prior art, the present invention proposes a two-phase jet cooling radiator for high-power density chips. The present invention can ensure a small chip operating temperature rise when the chip operating heat flux is about 400 - 1000 W / cm 2 ².

[0008] The technical solution adopted by the present invention is as follows:

[0009] A two-phase jet cooling radiator for high power density chips, comprising a jet manifold layer. A groove is formed at the center position of the jet manifold layer to form a jet cavity, and jet holes are evenly distributed at the bottom of the jet cavity; a plurality of the jet flow channel plates are installed in the jet cavity, and each jet flow channel plate is processed with a number of jet flow channels, and the jet flow channels correspond to the jet holes one by one. The coolant enters the jet flow channels from the jet holes and directly jets the coolant towards the target chip; a porous medium layer is filled in the gap between the jet flow channel plates in the jet cavity, and only half of the jet cavity near the outside is filled. The porous medium layer is in direct contact with the target chip; the porous medium layer is used to absorb the coolant, so that the coolant is evenly distributed on the surface of the target chip, and is also used to limit the nucleation and growth of bubbles, avoiding uneven distribution of the coolant on the surface of the target chip; the pore diameter of the porous medium layer is between 40 and 60 microns, with honeycomb-like pores, and is made by sintering after pressing the dendritic porous medium sintered powder.

[0010] Further, the two-phase jet cooling radiator further comprises a coolant cavity housing. A liquid distribution cavity is formed by digging a groove at the center position of the coolant cavity housing. The coolant cavity housing is provided with a coolant inlet, and the coolant inlet communicates with the outside and the liquid distribution cavity. The coolant enters the liquid distribution cavity from the coolant inlet and enters the jet flow channels through the jet holes; the jet manifold layer is further provided with a gas phase outlet communicating with the space in the jet cavity not filled with the porous medium layer and a liquid phase outlet communicating with the porous medium layer.

[0011] On the other hand, the present invention proposes a chip heat dissipation method based on the above two-phase jet cooling radiator, comprising:

[0012] Placing the target chip on the jet cooling radiator, with the back of the target chip closely attached to the porous medium layer; inputting the coolant from the coolant inlet into the liquid distribution cavity, and entering the jet flow channels through the jet holes. The coolant accelerates in the jet flow channels and directly impacts the back of the target chip, taking away the heat of the target chip through the phase change effect; the impacted coolant infiltrates into the pores of the porous medium layer under the capillary action and is discharged through the liquid phase outlet; the bubbles generated by the phase change of the coolant are restricted in growth by the porous medium layer in the porous medium layer and leave the surface of the target chip as the coolant in the porous medium layer flows. When the bubbles reach the space in the jet cavity not filled with the porous medium layer, the bubbles nucleate and grow and are discharged through the gas phase outlet.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) By directly contacting the heat source surface with the jet coolant, the present invention can dissipate heat with a higher heat flux density, reduce the intermediate links of heat dissipation, improve the heat response speed, lower the heat dissipation resistance, thereby enhancing the heat dissipation efficiency. Meanwhile, by designing a suitable nozzle array, the problem of uneven temperature distribution on the heat source surface is improved, the formation of hot spots is reduced, and energy consumption is saved while achieving efficient heat dissipation.

[0015] (2) The present invention sinters a porous medium with a relatively low porosity on the surface of the heat source. Utilizing the influence of small pore diameters on bubble dynamics, the aggregation of the gas phase is restricted, increasing the difficulty of bubble nucleation, suppressing the growth and coalescence of bubbles on the heat source surface, achieving better gas-liquid two-phase separation, further increasing the critical heat flux density, and reducing the flow instability caused by bubbles, thereby enhancing the stability of the system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the principle of the two-phase jet cooling radiator for high-power density chips of the present invention;

[0017] Figure 2 is a schematic diagram of the structure of the jet flow channel plate in the device of the present invention;

[0018] Figure 3 is a schematic diagram of the assembly of the jet flow channel plate and the jet manifold layer in the device of the present invention;

[0019] Figure 4 is a schematic diagram of the assembly of the two-phase jet cooling radiator of the present invention;

[0020] Figure 5 is a schematic diagram of the assembly of the porous medium layer in the device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention will be further described and explained below in conjunction with specific embodiments. The embodiments are only demonstrations of the present disclosure content and do not delimit the scope of limitation. The technical features of each embodiment of the present invention can be combined correspondingly without conflict.

[0022] It should be noted that in the description of the present application, similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0023] In the description of this application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] When the operating temperature of an electronic device is too high, it will lead to a decrease in the reliability and stability of the chip. To avoid the occurrence of chip overheating problems, it is crucial to research and explore new electronic device heat dissipation technologies. In this regard, the two-phase jet heat dissipation method has significant advantages. This method uses the phase change of liquid boiling to take away heat, and at the same time combines jet impingement to thin the fluid boundary layer, and the synergistic effect is used to achieve efficient cooling of high-power chips.

[0025] The existing jet cooling technology still needs to be optimized in terms of gas-liquid two-phase separation. To achieve better gas-liquid two-phase separation, the present invention proposes a two-phase jet cooling radiator for high-power density chips, which uses gas-liquid separation to enhance the gas removal ability, thereby ensuring that the chip surface is always in a wet state, that is, maintaining an efficient phase change heat transfer ability. Applying the two-phase jet cooling radiator proposed by the present invention can ensure that the chip operates at a normal working temperature when the chip working heat flux is about 400 - 1000 W / cm 2 and the total chip temperature rise does not exceed 40 K.

[0026] To achieve the above functions, the structure of the chip two-phase separation cooling radiator in this embodiment is mainly divided into a coolant cavity housing 1, a jet manifold layer 2, a jet flow channel plate 3, and a porous media layer 4, as shown in the assembly Figure 4 .

[0027] The size of the coolant cavity housing 1 is 35×35×4 mm 3 , and a liquid distribution cavity with a size of 24×24×3 mm 3 is dug at the center position. An O-ring installation groove with a size of 2.3×1.3 mm 2 is left around the cavity for sealing to ensure that the coolant does not leak. The coolant cavity housing 1 is fixedly connected to the jet manifold layer 2 through fastening bolts. In this embodiment, deionized water is used as the coolant.

[0028] The size of the jet manifold layer 2 is the same as that of the coolant cavity housing 1, and a jet cavity with a size of 24×24×3 mm 3 is dug at the center position. There are uniformly distributed jet holes at the top of the jet cavity. The jet holes are a uniformly distributed small hole array of 10×10, and the row and column spacing of the jet holes are equal, which is 2.3 - 2.5 mm, as shown in Figure 5As shown, the evenly distributed jet holes can make the fluid distribution more uniform. The recirculation area flowing through the jet holes is small, reducing the instability of the coolant flow and the noise during the flow process. The aperture of the jet holes is 0.1 - 0.3 mm, and the jet cavity is connected to the liquid distribution cavity through the jet holes.

[0029] There are 20 jet flow channel plates 3, all of which are installed in the jet cavity. Each jet flow channel plate 3 is made by longitudinally machining 5×1 jet flow channels on a metal plate, as Figure 2 shown. All jet flow channels are about 3 mm long, and the flow channel aperture is 0.12 - 0.32 mm. Each jet flow channel corresponds to a jet hole one by one. The assembly of the jet flow channel plate 3 and the jet manifold layer 2 is as Figure 3 shown. The direction of the jet flow channels is vertical and is connected to the liquid distribution cavity through the corresponding jet holes. The jet flow channels can prevent the coolant from directly flowing into the cavity instead of being sprayed onto the back of the chip due to processing accuracy problems. The jet cavity is divided into upper and lower layer spaces. The height of the upper layer is 0.9 - 1.1 mm, and the height of the lower layer is 2 mm. In the upper layer space of the jet cavity, the porous medium layer is filled in the gaps between the jet flow channel plates.

[0030] One side of the coolant cavity housing 1 is provided with a coolant inlet a with a diameter of 0.5 mm to connect to the internal liquid distribution cavity. The coolant inlet a is connected to a hose, and the coolant is introduced into the liquid distribution cavity through the hose at a flow rate of 6 - 15 g / s through the coolant inlet a; one side of the jet manifold layer 2 is provided with two outlets, and there is a height difference between the two outlets. The lower outlet is a gas phase outlet b with a diameter of 0.4 mm, and the upper outlet is a liquid phase outlet c with a diameter of 0.2 mm. The coolant flows into the liquid distribution cavity through the coolant inlet a and is fluidly distributed through the jet holes distributed by the jet manifold layer 2. All jet holes achieve fluid jetting. Among them, the small hole array in contact with the jet flow channel plate 3 guides the coolant to enter the jet flow channel about 3 mm long through the jet holes, and preliminarily distributes and accelerates the inlet fluid before contacting the chip. The coolant enters the lower jet pipeline and is directly sprayed onto the back of the chip for heat dissipation; the hose is inserted into the porous medium layer 4 through the liquid phase outlet c, and the excess coolant is directly discharged from the hose; the exhaust pipe is connected to the inner cavity of the jet hole plate through the gas phase outlet b. After the gas phase generated by the coolant boiling when contacting the chip with higher heat is passed through the porous medium layer and enters the cavity, it is discharged through the exhaust pipe. The working principle diagram of the device is as Figure 1 shown.

[0031] The chip to be cooled is placed at the bottom of the above-mentioned chip jet cooling radiator. The porous medium layer is in close contact with the back of the chip to avoid large gaps forming bubbles and affecting heat dissipation. The bottom of the jet flow channels of the jet flow channel plate 3 is directly in contact with the chip. The coolant directly impacts the heat source surface of the chip through the jet flow channels to take away heat, achieving efficient heat dissipation. The direction of gas discharge is as Figure 4As shown, it is discharged from the cavity between the left and right jet orifice plates through the gas phase outlet b. At the same time, since the porous medium layer 4 has a dense pore structure, the coolant after impacting the chip infiltrates into the pores under capillary action. The porous medium with dense pores has good connectivity, and the spreading and wetting effects of the coolant are good, and it can quickly cover the porous medium layer until it reaches water absorption saturation. Since the porous medium layer is in direct contact with the chip, the porous medium layer can evenly cover the heat source surface of the chip, making the heat distribution on the heat source surface of the chip balanced. Since the water absorption capacity of the porous medium is limited, the excess coolant can be discharged through the coolant liquid phase outlet c to prevent liquid accumulation from affecting the heat dissipation effect. The structural working schematic diagram is as Figure 5 shown.

[0032] In this embodiment, the preparation material of the porous medium layer 4 is copper powder or NU-1500 series MOF material. The MOF material has good water stability, large porosity and specific surface area. During sintering, sacrificial templates such as polymer foam and salt particles are used to fill the jet flow channels to prevent the porous medium from blocking the flow channels during the sintering process. The particle size of the sintered porous medium powder is about 50 microns, the powder shape is selected as dendritic, and the pore-forming agent is selected as paraffin, and then sintering is carried out after pressing into shape.

[0033] The pore diameter of the porous medium layer 4 in this embodiment is between 40 and 60 microns. The sintered porous medium has honeycomb-like pores, and this structure has good water absorption. At the same time, the honeycomb-like pores are more conducive to the discharge of gas; the shape of the sintered porous medium powder is selected as dendritic, and the tree-like structure on the pore wall is conducive to the infiltration of liquid. The pore diameter of the porous medium is small, which increases the energy barrier for bubble nucleation.

[0034] The coolant impacts the chip surface, directly contacts the chip and absorbs the heat generated by the chip. The coolant temperature gradually rises to the boiling point, changes from liquid to gas, and phase change occurs (begins to boil), achieving efficient heat dissipation through latent heat absorption. After the liquid directly impacts the chip surface, it is driven by capillary force and pressure, and the liquid quickly fills along the pore direction and covers the porous medium layer. Since the porous medium fits tightly with the chip, it is difficult to nucleate in the narrow gap and porous voids (there is no additional volume change space in the narrow gap, and the free energy of the surface inside the porous pores increases). The bubbles move with the flow of the liquid. Since there is no additional volume change space in other directions, the bubbles will preferentially be generated and grow in the jet cavity under the porous medium layer, thereby realizing gas-liquid phase separation on the heat source surface. As the bubbles continue to grow, the merged large bubbles will converge to the gas phase outlet through the opening area of the jet channel plate, and leave the chip area from the gas phase outlet, thereby realizing the flow and emptying of the gas, ensuring that the cavity can continuously change phases and generate bubbles. When the liquid continues to jet onto the chip and the porous medium layer is saturated with water, the excess liquid will be discharged from the chip area through the liquid phase outlet. In this way, the flow of gas and liquid phases can be separated in layers without interfering with each other, and the heat dissipation efficiency of the chip will not be affected by the accumulation of bubbles blocking the fluid supply.

[0035] Through this design, the chip surface is continuously and stably wetted by a thin liquid film, while phase change can occur continuously at the place far away from the heat source (top of the porous layer), and nucleation absorption takes away a large amount of heat. It can be seen that the present invention utilizes the influence of the small-pore porous medium layer on the bubble dynamics to increase the critical heat flux density of the heat dissipation process, increase the heat dissipation per unit area, extend the working life of the chip, and improve the working stability of the chip, which plays an important role in ensuring the stable operation of the chip under high heat flux density and high integration working conditions.

[0036] 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 two-phase jet cooling radiator for high power density chips, characterized in that, It includes a jet manifold layer. A groove is formed at the central position of the jet manifold layer to form a jet cavity, and there are uniformly distributed jet holes at the bottom of the jet cavity; multiple jet channel plates are installed in the jet cavity, and each jet channel plate is processed with several jet channels. The jet channels correspond one by one to the jet holes. The coolant enters the jet channels from the jet holes and directly sprays the coolant onto the target chip; a porous medium layer is filled in the gap between the jet channel plates in the jet cavity, and only half of the jet cavity near the outside is filled. The porous medium layer is in direct contact with the target chip. The porous medium layer is used to absorb the coolant to evenly cover the surface of the target chip, and is also used to limit the nucleation and growth of bubbles to avoid uneven distribution of the coolant on the surface of the target chip; the pore diameter of the porous medium layer is between 40 and 60 microns, with honeycomb-like pores, and is made by sintering after being pressed from dendritic porous medium sintered powder. The two-phase jet cooling radiator further includes a coolant cavity housing. A liquid distribution cavity is formed by grooving at the central position of the coolant cavity housing. The coolant cavity housing is provided with a coolant inlet, and the coolant inlet communicates the outside with the liquid distribution cavity. The coolant enters the liquid distribution cavity from the coolant inlet and then enters the jet channels through the jet holes; the jet manifold layer is also provided with a gas phase outlet communicating with the space in the jet cavity not filled with the porous medium layer and a liquid phase outlet communicating with the porous medium layer.

2. The two-phase jet cooling radiator for high power density chips according to claim 1, wherein The coolant inlet is connected with a hose for inputting the coolant; the gas phase outlet is connected with an exhaust pipe, and the exhaust pipe is connected to the lower layer space of the jet cavity through the gas phase outlet for discharging the gas phase generated by the boiling of the coolant; the liquid phase outlet is connected with a hose, and the hose at the liquid phase outlet is inserted into the porous medium layer through the liquid phase outlet for discharging the excess coolant.

3. The two-phase jet cooling radiator for high power density chips according to claim 1, wherein, The jet manifold layer has the same size as the coolant cavity housing, and the jet cavity has the same size as the liquid distribution cavity.

4. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that The side of the jet manifold layer without grooving is closely fixed to the side of the coolant cavity housing with grooving. The coolant cavity housing has an O-ring installation groove around the liquid distribution cavity, and an O-ring is installed in the O-ring installation groove to prevent coolant leakage.

5. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that, The coolant cavity housing and the jet manifold layer are fixedly attached to each other, and the fixing method is by fixing with fastening bolts.

6. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that, The aperture of the jet hole is 0.1 - 0.3 mm.

7. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that, The coolant flow rate in the two-phase jet cooling radiator is 6 - 15 g / s. The average length of the jet channels is 2.9 - 3.1 mm, and the channel aperture is 0.12 - 0.32 mm.

8. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that, The porous medium layer is obtained by sintering after being pressed from porous medium sintered powder. The porous medium sintered powder is copper powder or NU-1500 series MOF material, and the particle size of the porous medium sintered powder is 40 - 60 microns.

9. A chip heat dissipation method for the two-phase jet cooling radiator according to claim 1, characterized in that, The method includes: Placing the target chip on the jet cooling radiator, with the back of the target chip closely attached to the porous medium layer; Inputting the coolant from the coolant inlet into the liquid distribution cavity, and entering the jet channels through the jet holes. The coolant accelerates in the jet channels and directly impacts the back of the target chip, and takes away the heat of the target chip through the phase change effect. After the impact, the coolant infiltrates into the pores of the porous medium layer under capillary action and is discharged through the liquid-phase outlet; the bubbles generated by the phase change of the cooling liquid are restricted from growing within the porous medium layer and leave the surface of the target chip as the coolant flows in the porous medium layer. When the bubbles reach the space in the jet cavity that is not filled with the porous medium layer, the bubbles nucleate and grow and are discharged through the gas-phase outlet.

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