Two-phase jet cooling radiator for high-power density chip

Abstract

The invention provides a two-phase jet flow cooling radiator for a high-power-density chip, and belongs to the technical field of chip cooling and heat dissipation. The cooling radiator comprises a cooling liquid cavity shell, a jet manifold layer, a jet runner plate and a porous medium layer; a liquid distribution cavity is formed in the cooling liquid cavity shell; a jet flow cavity is formed in the jet flow manifold layer, and jet flow holes are evenly distributed in the jet flow cavity. The jet flow runner plates are installed in the jet flow cavity, jet flow runners of the jet flow runner plates are vertically arranged, and one end of each jet flow runner is connected with the corresponding jet flow hole; gaps among the jet flow channel plates in the lower space of the jet flow cavity are filled with the porous medium layer. The influence of the small-aperture porous dielectric layer on bubble dynamics is utilized, the critical heat flux in the heat dissipation process is improved, the heat dissipating capacity per unit area is improved, the working life of the chip is prolonged, the working stability of the chip is improved, and the method plays an important role in ensuring that the chip stably works under the working conditions of high heat flux and high integration level.

Description

Technical Field

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

[0002] With the development of electronic technology, especially integrated technology, the size of chips is getting smaller and smaller, and the power density is getting higher and higher. The heat flux density of high-power chips can reach 1000 W / cm 2 , the operating temperature of electronic equipment is too high, which will lead to the decrease of chip reliability and stability. For some chips, the performance will decrease by 1-2% for every 1°C increase in temperature, the service life will be reduced, the energy consumption will increase, and long-term operation in a high temperature state may even cause thermal runaway. In order to avoid these problems, it is very important to study and explore new electronic heat dissipation technologies. At present, traditional electronic equipment heat dissipation technologies cannot meet the heat dissipation needs well. New heat dissipation technologies such as heat pipe heat dissipation, microchannel heat dissipation, spray cooling, jet cooling and related technologies can make heat dissipation more efficient.

[0003] Jet technology can produce a strong heat exchange effect on the jet impact surface. Jet cooling refers to the technology of using high-speed coolant to directly impact the cooled surface to achieve cooling. It mainly takes away heat through the impact of the fluid or the generation of phase change. Compared with traditional heat dissipation methods, jet cooling technology has the following three significant advantages: First, the heat exchange efficiency is high. The jet 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 the jet nozzle, it can better achieve uniform heat dissipation of electronic devices, reduce thermal stress, enhance the working reliability of devices, and extend the service life of electronic devices.

[0004] At present, the research on jet cooling and heat dissipation focuses on the design of jet nozzle form, the selection of coolant, the nozzle layout, nozzle height and diameter, surface microstructure design and surface treatment of the contact surface, etc. At the same time, people are also paying attention to the thermoelectric refrigeration technology to achieve local efficient cooling, the application of the excellent thermal conductivity of nanomaterials to improve the cooling effect, the optimization effect of micro-scale jet cooling through numerical simulation, and the use of multiphase jet cooling technology to improve heat transfer capacity.

[0005] The effect of two-phase jet cooling is better than that of single-phase jet cooling, and people have optimized the design of traditional jet structures. The team of Professor Wei Tiwei of Purdue University proposed a chip-level two-phase jet cooling technology. The device directly encapsulates the heat dissipation channel inside the chip package and sprays the coolant directly onto the back of the chip. The heat dissipation path is shorter and 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. The phase change of liquid boiling is used to remove heat, forming a multi-layer gas-liquid transport distribution system, achieving 500 W / cm 2 Chip cooling performance.

[0006] Although the jet cooling technology of this solution can achieve a good heat exchange effect, there are still some shortcomings. This solution cannot realize the separation flow of gas and liquid phases on the heat source surface, which will affect the heat dissipation efficiency of the chip. The flow resistance of the cooling medium also needs to be optimized. Under high power density, once the gas is generated on the chip surface, it is easy to gather and form large bubbles / columns, blocking the liquid flow path, resulting in an increase in the local flow resistance of the liquid cooling medium, inducing flow instability, causing the system flow to oscillate or even drift, and the coolant flow rate will drop rapidly (even to 0). Once there is a momentary lack of liquid on the chip surface, the temperature rises suddenly, which will cause the risk of burning. At the same time, due to the extremely low thermal conductivity of the gas (generally one order of magnitude lower than the liquid phase), large bubbles staying / covering the chip surface will also increase the heat transfer resistance, causing the chip temperature to rise suddenly in an instant. It can be seen that accelerating the detachment and removal of bubbles on the chip surface is an inevitable way to improve the chip's heat transfer efficiency and thermal management performance. At the same time, long-term gas-liquid two-phase flow on the heat source surface will accelerate the corrosion and wear of chips 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 phase separation to improve reliability and working life. Summary of the invention

[0007] In order 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 cool the chip with a working heat flux of 400-1000 W / cm 2 The chip operating temperature rise is kept small when the temperature is around 0.

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

[0009] A two-phase jet cooling radiator for high power density chips comprises a jet manifold layer, a groove is dug at the center of the jet manifold layer to form a jet cavity, and the bottom of the jet cavity is provided with uniformly distributed jet holes; a plurality of jet flow channel plates are installed in the jet cavity, each jet flow channel plate is processed with a plurality of jet flow channels, the jet flow channels correspond to the jet holes one by one, and the coolant enters the jet flow channel from the jet holes and directly sprays the coolant to the target chip; a porous medium layer is filled in the gap between the jet flow channel plates in the jet cavity, and only the half of the jet cavity close to the outside is filled, and 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 to avoid uneven distribution of the coolant on the surface of the target chip; the porous medium layer has a pore size between 40 and 60 microns, has honeycomb pores, and is made by pressing and sintering dendritic porous medium sintering powder.

[0010] Furthermore, the two-phase jet cooling radiator also includes a cooling liquid cavity shell, a groove is dug at the center position of the cooling liquid cavity shell to form a liquid distribution cavity, the cooling liquid cavity shell is provided with a cooling liquid inlet, the cooling liquid inlet is connected to the outside and the liquid distribution cavity, and the cooling liquid enters the liquid distribution cavity from the cooling liquid inlet and enters the jet channel through the jet hole; the jet manifold layer is also provided with a gas phase outlet connected to the space in the jet cavity that is not filled by the porous medium layer and a liquid phase outlet connected to 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] The target chip is placed on the jet cooling radiator, with the back of the target chip close to the porous medium layer; the coolant is input into the liquid distribution cavity from the coolant inlet, and enters the jet flow channel through the jet hole, and the coolant is accelerated in the jet flow channel and directly impacts the back of the target chip, and takes away the heat of the target chip through the phase change effect; the coolant after the impact is immersed in 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 to grow in the porous medium layer, and leave the surface of the target chip with the flow of the coolant in the porous medium layer, and 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.

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

[0014] (1) The present invention can achieve heat dissipation with higher heat flux density by directly contacting the heat source surface with the jet coolant, which can reduce the intermediate links of heat dissipation, improve the thermal response speed, reduce the heat dissipation thermal resistance, and thus improve the heat dissipation efficiency. At the same time, a suitable nozzle array is designed to improve the problem of uneven temperature distribution on the heat source surface, reduce the formation of hot spots, and achieve efficient heat dissipation while saving energy.

[0015] (2) The present invention sintered a porous medium with low porosity on the surface of the heat source, and utilized the influence of small pore size on bubble dynamics to limit the aggregation of the gas phase and increase the difficulty of bubble nucleation, thereby inhibiting the growth and merging of bubbles on the surface of the heat source, better separating the gas-liquid two phases, further improving 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 It 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 It is a schematic diagram of the structure of the jet channel plate in the device of the present invention;

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

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

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

[0021] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[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, and 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 "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] The high operating temperature of electronic equipment will lead to the decrease of chip reliability and stability. In order to avoid the problem of chip overheating, it is crucial to explore new electronic device heat dissipation technology. In this regard, the two-phase jet heat dissipation method has significant advantages. This method uses the phase change of liquid boiling to remove heat, and combines the jet impact to thin the fluid boundary layer, and the synergistic effect can 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. In order 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 efficient phase change heat transfer ability. The two-phase jet cooling radiator proposed by the present invention can be used in chips with a working heat flux of 400-1000 W / cm 2 The chip is kept at normal operating temperature and the total temperature rise of the chip does not exceed 40 K.

[0026] To achieve the above functions, the structure of the chip two-phase separation cooling radiator of this embodiment is mainly divided into a cooling liquid cavity shell 1, a jet manifold layer 2, a jet channel plate 3 and a porous medium layer 4, see the assembly Figure 4 .

[0027] The size of the cooling liquid chamber housing 1 is 35×35×4 mm 3 , the center is dug with 24×24×3 mm 3 The liquid distribution cavity has a 2.3×1.3 mm 2 The O-ring installation groove is used for sealing to ensure that the coolant does not leak. The coolant cavity housing 1 is fixedly connected to the jet manifold layer 2 by 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 chamber shell 1, with a 24×24×3 mm hole dug in the center. 3 The jet cavity has uniformly distributed jet holes on the top of the jet cavity. The jet holes are a 10×10 uniformly distributed small hole array. The spacing between the rows and columns of the jet holes is equal, which is 2.3-2.5 mm. Figure 5As shown, the uniformly distributed jet holes can make the fluid distribution more uniform, the reflow area flowing through the jet holes is smaller, the instability of the coolant flow is reduced, and the noise of the flow process is reduced. The aperture of the jet hole is 0.1-0.3 mm, and the jet cavity is connected to the liquid distribution cavity through the jet hole.

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

[0030] A coolant inlet a with a diameter of 0.5 mm is left on one side of the coolant cavity shell 1 to connect to the internal liquid distribution cavity. The coolant inlet a is connected to a hose, and the coolant passes from the hose through the coolant inlet a at a flow rate of 6-15 g / s into the liquid distribution cavity; two outlets are left on one side of the jet manifold layer 2, and there is a height difference between the two outlets, wherein the outlet located at the bottom is a gas phase outlet b with a diameter of 0.4 mm, and the outlet located at the top 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 the fluid is distributed through the jet holes distributed in the jet manifold layer 2. All jet holes realize fluid jetting, wherein the small hole array in contact with the jet channel plate 3 guides the coolant through the jet holes into the jet channel about 3 mm long, and the inlet fluid is preliminarily distributed and accelerated before contacting the chip. The coolant enters the jet pipe below 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 cavity in the jet orifice plate through the gas phase outlet b, and the coolant contacts the chip with higher heat and the boiling gas generated passes through the porous medium layer into the cavity and is discharged through the exhaust pipe. The working principle diagram of the device is as follows: Figure 1 shown.

[0031] The chip to be cooled is placed at the bottom of the chip jet cooling radiator, and the porous medium layer is in close contact with the back of the chip to avoid the gap from being too large to form bubbles that affect heat dissipation. The bottom of the jet channel of the jet channel plate 3 is directly in contact with the chip, and the coolant directly impacts the heat source surface of the chip through the jet channel to take away the heat, achieving efficient heat dissipation. The direction of gas discharge is as follows: Figure 4As shown, the air is discharged from the cavity in the middle of the jet orifice plates on the left and right sides through the gas phase outlet b. At the same time, since the porous medium layer 4 is a dense pore structure, the coolant that impacts the chip penetrates into the pores under the capillary action. The porous medium with dense pores has good connectivity, and the coolant spreads and infiltrates well, and 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 chip heat source surface, so that the heat distribution on the chip heat source surface is balanced. Since the porous medium has limited water absorption capacity, 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 diagram is shown in 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. MOF material has good water stability, large porosity and specific surface area. During sintering, sacrificial templates such as polymer foam, salt particles and other materials are used to fill the jet flow channel to prevent the porous medium from blocking the flow channel during the sintering process. The particle size of the porous medium sintering powder is about 50 microns, the powder shape is dendritic, and the pore-forming agent is paraffin. Sintering is performed after pressing and molding.

[0033] The pore size of the porous medium layer 4 of this embodiment is between 40 and 60 microns. The porous medium after sintering has honeycomb pores, which have good water absorption and are easier for gas to be discharged. The shape of the porous medium sintered powder is selected to be dendritic, and the pore wall has a tree-like structure that is easy for liquid to penetrate. The pore size 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 dug at the center of the jet manifold layer to form a jet cavity, and the bottom of the jet cavity has uniformly distributed jet holes; a plurality of jet channel plates are installed in the jet cavity, each jet channel plate is processed with a plurality of jet channels, and the jet channels correspond to the jet holes one by one, and the coolant enters the jet channel from the jet holes and directly sprays the coolant to the target chip; a porous medium layer is filled in the gap between the jet channel plates in the jet cavity, and only the half of the jet cavity close to the outside is filled, and 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 to avoid uneven distribution of the coolant on the surface of the target chip; the porous medium layer has a pore size between 40 and 60 microns, has honeycomb pores, and is made by pressing and sintering dendritic porous medium sintering powder.

2. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that: The two-phase jet cooling radiator also includes a cooling liquid cavity shell, a groove is dug at the center of the cooling liquid cavity shell to form a liquid distribution cavity, the cooling liquid cavity shell is provided with a cooling liquid inlet, the cooling liquid inlet is connected to the outside and the liquid distribution cavity, and the cooling liquid enters the liquid distribution cavity from the cooling liquid inlet and enters the jet channel through the jet hole; the jet manifold layer is also provided with a gas phase outlet connected to the space in the jet cavity that is not filled by the porous medium layer and a liquid phase outlet connected to the porous medium layer.

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

4. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that: The jet manifold layer has the same size as the outer shell of the cooling liquid cavity, and the jet cavity has the same size as the liquid distribution cavity.

5. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that: The ungrooved side of the jet manifold layer is tightly fixed to the grooved side of the coolant cavity shell. The coolant cavity shell 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.

6. The two-phase jet cooling radiator for high power density chips according to claim 1, characterized in that: The cooling liquid cavity shell and the jet manifold layer are fixed to each other by fastening bolts.

7. 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.

8. 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 jet flow channels are 2.9-3.1 mm long, and the flow channel aperture is 0.12-0.32 mm.

9. 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 pressing and molding porous medium sintered powder and then sintering. The porous medium sintered powder is copper powder or NU-1500 series MOF material. The particle size of the porous medium sintered powder is 40-60 microns.

10. A chip heat dissipation method based on the two-phase jet cooling radiator according to claim 2, characterized in that: The method comprises: Placing the target chip on the jet cooling radiator, with the back of the target chip close to the porous medium layer; The coolant is input into the liquid distribution cavity from the coolant inlet and enters the jet flow channel through the jet hole. The coolant is accelerated in the jet flow channel and directly impacts the back of the target chip, taking away the heat of the target chip through phase change. The coolant after impact penetrates into the pores of the porous medium layer under the action of capillary action and is discharged through the liquid phase outlet; the bubbles generated by the phase change of the coolant are restricted by the porous medium layer in the growth and leave the surface of the target chip with the flow of coolant 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, grow and are discharged through the gas phase outlet.

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