Silicon-based micro pulsating heat pipe type thermoelectric energy collecting device

Abstract

The invention discloses a silicon-based micro pulsating heat pipe type thermoelectric energy collecting device which is composed of a micro flat plate pulsating heat pipe, an electric insulation layer and an energy collector formed by a PN structure. The pulsating heat pipe is mainly divided into an evaporation section, a condensation section and a heat insulation section according to the heat flow direction. The electrical insulation layer covers the surface of the silicon substrate on the back of the pulsating heat pipe; pN junctions with different lengths / widths are integrated on the back surface of the insulating layer and have the same heat flow direction as the pulsating heat pipe, and then a potential difference is obtained under the Secret effect. The device is compact in structure, and can meet the requirements of high-heat-flux cooling and energy supply under the conditions of high integration and miniaturization of wireless equipment and wearable devices.

Description

Technical Field

[0001] The invention relates to the technical field of cooling and heat dissipation of microelectronic components and energy saving and environmental protection, and in particular to a silicon-based micro-pulsating heat pipe type thermoelectric energy collection device. Background Art

[0002] With the rapid development of Internet of Things technology, wireless devices and wearable devices are widely used in the field of network data exchange. Generally speaking, the power supply of network nodes mainly relies on traditional lithium batteries, but the difficulty of battery replacement and system maintenance, high cost and environmental pollution have become important bottlenecks restricting the development of the industry. Energy harvesting technology provides a solution for local power supply because it can achieve continuous energy supply. Among them, thermoelectric energy harvesters are used for waste heat recovery due to their advantages such as small size, light weight and green environmental protection, especially low-grade thermal energy has received widespread attention. With the application of MEMS technology, the high integration and miniaturization of wireless devices and wearable devices have continuously increased their requirements for temperature management and energy supply. Therefore, the research and development of both cooling and self-powered technology has become a cutting-edge hot issue in the development of Internet of Things technology.

[0003] Thermoelectric energy harvesting is based on the Secbe effect, using the thermal field at both ends of the material to drive the movement of carriers and form current in the loop to achieve the purpose of output power. The heat pipe thermoelectric energy harvester combines heat pipes and thermoelectric energy harvesting, making full use of the high thermal conductivity of the heat pipe to efficiently transfer the waste heat generated by the system, while the thermoelectric collector uses the temperature difference between the hot and cold ends of the heat pipe to achieve thermoelectric conversion, which has the dual effects of device cooling and waste heat conversion and utilization. Pulsating heat pipes (also known as oscillating heat pipes) not only inherit the characteristics of traditional heat pipes such as simple structure, reliability and zero power consumption, but also have the characteristics of no liquid absorption core, strong environmental adaptability and efficient heat transfer. It is an effective component for solving high heat flux density heat dissipation. Therefore, the combination of pulsating heat pipes and energy harvesters can effectively realize device cooling and convert thermal energy into electrical energy, and provide an effective solution for temperature control and energy supply of integrated chips. Summary of the invention

[0004] The purpose of the present invention is to provide a silicon-based micro-pulsating heat pipe type thermoelectric energy collection device to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned object, the present invention provides a silicon-based micro-pulsating heat pipe type thermoelectric energy collection device, comprising a micro-flat plate type pulsating heat pipe and a thermoelectric energy collector, wherein an electrical insulation layer is provided between the micro-flat plate type pulsating heat pipe and the thermoelectric energy collector;

[0006] The micro flat-plate pulsating heat pipe comprises a semiconductor silicon wafer and a packaging cover plate, wherein the packaging cover plate is fixedly arranged on a side of the semiconductor silicon wafer away from the electrical insulation layer; a micro-groove and a vacuum / filling working medium micro-groove are etched on a side of the semiconductor silicon wafer close to the packaging cover plate, wherein the micro-groove is connected to the vacuum / filling working medium micro-groove; a vacuum / filling working medium hole is arranged on the packaging cover plate, wherein the vacuum / filling working medium hole is arranged corresponding to the vacuum / filling working medium micro-groove, and the vacuum / filling working medium hole is used to fill the micro-groove with liquid working medium;

[0007] The thermoelectric energy collector comprises a protective layer arranged on the electrical insulating layer, a thermopile is arranged on the protective layer, the thermopile is composed of a plurality of PN junctions connected in series through metal leads, and a device insulating layer is arranged on the side of the protective layer and the thermopile away from the electrical insulating layer.

[0008] Preferably, the electrical insulating layer and the device insulating layer are both silicon dioxide layers, and the protective layer is a chrome-plated protective layer.

[0009] Preferably, the electrical insulating layer is deposited on the chrome-plated protective layer by using a PECVD process.

[0010] Preferably, the semiconductor silicon wafer and the packaging cover plate are bonded together by high-voltage electrostatic bonding.

[0011] Preferably, the packaging cover plate is made of glass or silicon wafer.

[0012] Preferably, the micro-grooves include a plurality of parallel horizontal grooves, a U-shaped groove is arranged between two adjacent horizontal grooves, and the plurality of horizontal grooves are connected into a continuous S-shaped groove through the U-shaped groove, and connecting grooves are connected to both ends of the S-shaped groove, and the S-shaped groove and the connecting groove form a closed loop, and the vacuum / filling working fluid micro-grooves are connected to the connecting grooves.

[0013] Preferably, the liquid working fluid is one of environmentally friendly low-boiling-point FC-72, R141b or HFC-7100.

[0014] Preferably, the depth of the micro-grooves is 250 μm to 750 μm.

[0015] Preferably, the volume of the liquid working medium in the vacuum / working medium-filled microchannels accounts for 50% to 60% of the total volume of the loop in the entire micro-flat-plate pulsating heat pipe.

[0016] Preferably, the cross-sectional shape of the micro-channel is one of a triangle, a rectangle or a trapezoid.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] 1. The invention is based on a micro flat plate pulsating heat pipe thermoelectric energy collector. The micro flat plate pulsating heat pipe and the micro thermoelectric energy collector are used as cooling and waste heat recovery devices. It has the advantages of small size and can be directly integrated into semiconductor chips. At the same time, compared with the traditional heat pipe thermoelectric energy collector, the thermoelectric conversion efficiency is higher;

[0019] 2. The mature MEMS process is used in manufacturing, which has the advantages of small size, low cost, batch production, and can be integrated with semiconductor chips;

[0020] 3. Based on the micro-flat pulsating heat pipe thermoelectric energy harvester, a horizontal structure is adopted, that is, the heat flow path is parallel to the chip surface, and the current path is parallel to the chip surface, so that the two ends of the PN pole have a relatively large temperature difference, which can provide a larger thermoelectric conversion output voltage;

[0021] 4. The micro flat-plate pulsating heat pipe thermoelectric energy harvester is a solid-state energy converter with no moving parts, good stability, long service life and low maintenance cost;

[0022] 5. Based on the micro-flat pulsating heat pipe thermoelectric energy harvester, all electrodes are in the same plane, avoiding complex electrical connections;

[0023] 6. Achieve the purpose of cooling and energy collection for the entire system, and master the technology of integrated cooling and self-power supply for wireless devices and wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a schematic diagram of the structure of a silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device in Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of a micro flat-plate pulsating heat pipe in Example 1 of the present invention;

[0027] Figure 3 for Figure 2 Schematic diagram of the cross section at AA;

[0028] Figure 4 This is a schematic diagram of the structure of the packaging cover plate in the micro flat-plate pulsating heat pipe in Example 1 of the present invention;

[0029] Figure 5 It is a cross-sectional schematic diagram of a silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device in Example 1 of the present invention;

[0030] Figure 6 Schematic diagram of the distribution of PN junctions in a planar thin-film thermoelectric energy harvester in Example 1 of the present invention;

[0031] Figure 7 It is a structural cross-sectional view of the micro-channel cross-sectional shape of the micro-flat pulsating heat pipe in Example 2 of the present invention;

[0032] Figure 8 Schematic diagram of the distribution form of the second PN junction of the planar thin-film thermoelectric energy harvester in Example 3 of the present invention;

[0033] In the figure: 1. Semiconductor silicon wafer; 2. Micro-grooves; 3. Vacuuming / filling working fluid micro-grooves; 4. Packaging cover; 5. Vacuuming / filling working fluid holes; 6. Silicon dioxide layer; 7. P pole; 8. N pole; 9. Metal leads; 10. Chrome-plated protective layer. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0035] The present invention provides a silicon-based micro-pulsating heat pipe type thermoelectric energy collection device, comprising a micro-flat plate type pulsating heat pipe and a thermoelectric energy collector, wherein an electrical insulation layer is provided between the micro-flat plate type pulsating heat pipe and the thermoelectric energy collector;

[0036] The micro flat-plate pulsating heat pipe comprises a semiconductor silicon wafer 1 and a packaging cover plate 4, wherein the packaging cover plate 4 is fixedly arranged on a side of the semiconductor silicon wafer 1 away from the electrical insulation layer; a micro-groove 2 and a vacuum / filling working medium micro-groove 3 are etched on a side of the semiconductor silicon wafer 1 close to the packaging cover plate 4, wherein the micro-groove 2 is connected to the vacuum / filling working medium micro-groove 3; a vacuum / filling working medium hole 5 is arranged on the packaging cover plate 4, wherein the vacuum / filling working medium hole 5 is arranged corresponding to the vacuum / filling working medium micro-groove 3, and the vacuum / filling working medium hole 5 is used to fill the micro-groove 2 with liquid working medium;

[0037] The thermoelectric energy collector includes a protective layer arranged on the electrical insulation layer, a thermopile is arranged on the protective layer, and the thermopile is composed of multiple PN junctions connected in series through metal leads 9. A device insulation layer is arranged on the side of the protective layer and the thermopile away from the electrical insulation layer.

[0038] When the present invention is in use, the patent combines the pulsating heat pipe phase change cooling technology and the energy collection technology of the thermoelectric energy collector with the help of MEMS processing technology, and obtains a micro-groove 2 with a rectangular cross-section on the silicon-based surface through plasma etching technology, and then uses electrostatic bonding to integrate the packaging cover plate 4 and the semiconductor silicon wafer 1 etched with the micro-groove 2. Finally, the thin-film planar thermoelectric energy collector is integrated into the bottom of the semiconductor silicon wafer 1 of the micro-flat-plate pulsating heat pipe to form a micro-flat-plate pulsating heat pipe thermoelectric energy collection device.

[0039] The working principle of the silicon-based micro-pulsating heat pipe thermoelectric energy collection device provided by the present invention is as follows: the micro-flat pulsating heat pipe uses the vacuum / filling working medium hole 5 to evacuate the heat pipe and then fill it with part of the working medium. After filling the working medium, the vacuum / filling working medium hole 5 is welded and sealed. Since the equivalent diameter of the micro-groove 2 is very small, a state of random distribution of vapor / liquid plugs will be formed in the channel. The evaporation end of the heat pipe is heated, and then the liquid working medium in this area absorbs heat and changes phase to produce bubbles, which rapidly expand and increase the pressure and push the working medium to flow to the condensation section; the bubbles / vapor plugs in the condensation section cool and shrink or even disappear, and the pressure drops. The pressure difference and pressure fluctuations formed between the heat pipes cause the working medium to oscillate back and forth between the cold and hot sections, realizing heat transfer and achieving a temperature control effect. At the same time, the planar thin film type thermoelectric energy collector connects the P pole 7 and the N pole 8 in series into a thermopile using a metal lead 9, and places its two ends in a high temperature and low temperature state respectively. Driven by thermal excitation, the concentration of holes (electrons) at the high-temperature end of the P (N) pole material is higher than that at the low-temperature end. The holes (electrons) diffuse to the low-temperature end, and the charges accumulate at the low-temperature end, thereby forming a potential difference at one end of the thermopile and achieving the purpose of energy supply.

[0040] The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device provided by the present invention not only inherits the heat dissipation and self-power supply functions of the traditional heat pipe thermoelectric energy harvester, but also has the characteristics of high integration and miniaturization, and can be directly integrated with semiconductor chips with the help of MEMS processing technology. Among them, the micro-flat pulsating heat pipe has the advantages of simple structure and high heat transfer performance due to its unique serpentine structure and no liquid absorption core; at the same time, the flat film type thermoelectric energy harvester integrated on the back of the heat pipe forms an electric potential difference under the action of temperature difference, which has both good temperature control performance and the function of providing power for local energy consumption of the chip.

[0041] According to a further optimized solution, the electrical insulating layer and the device insulating layer are both silicon dioxide layers 6 , and the protective layer is a chrome-plated protective layer 10 .

[0042] According to a further optimized solution, the electrical insulating layer is deposited on the chrome-plated protective layer 10 by using a PECVD process.

[0043] To further optimize the solution, in order to ensure the overall sealing of the micro flat-plate pulsating heat pipe and achieve its excellent heat transfer performance, the semiconductor silicon wafer 1 and the packaging cover plate 4 are bonded together through high-voltage electrostatic bonding.

[0044] According to a further optimization solution, the material of the packaging cover plate 4 is glass or silicon wafer.

[0045] A further optimization scheme is adopted to ensure the normal operation of the micro-flat pulsating heat pipe. The micro-groove 2 includes a plurality of parallel horizontal grooves. A U-shaped groove is arranged between two adjacent horizontal grooves. The plurality of horizontal grooves are connected into a continuous S-shaped groove through the U-shaped groove. Connecting grooves are connected at both ends of the S-shaped groove. The S-shaped groove and the connecting groove form a closed loop. The vacuum / filling working fluid micro-groove 3 is connected to the connecting groove.

[0046] According to the further optimization scheme, the liquid working fluid is one of the environmentally friendly low-boiling-point FC-72, R141b or HFC-7100.

[0047] A further optimization scheme is to process the micro grooves 2 separately, and the depth of the micro grooves 2 is 250 μm to 750 μm.

[0048] To further optimize the solution, in order to ensure that the micro-flat pulsating heat pipe has good heat transfer performance, the liquid working medium filling volume in the vacuum / filled working medium micro-channel 3 accounts for 50% to 60% of the total volume of the entire micro-flat pulsating heat pipe loop.

[0049] According to a further optimization scheme, the cross-sectional shape of the micro-groove 2 is a triangle, a rectangle or a trapezoid.

[0050] The above three structures all have certain chamfers, which can act as the capillary wick of a traditional heat pipe, driving the liquid phase working medium in the condensation section to flow back to the evaporation section under the action of the cross-sectional chamfer, thereby avoiding the "burning dry" phenomenon of the heat pipe.

[0051] Example 1

[0052] like Figures 1 to 5 As shown, the micro flat-plate pulsating heat pipe is formed by bonding a semiconductor silicon wafer 1 and a package cover plate 4. The surface of the semiconductor silicon wafer 1 in contact with the package cover plate 4 is etched with a micro-groove 2 with a rectangular cross section by dry etching process; the package cover plate 4 is processed with a vacuum / filling working medium hole 5; the vacuum / filling working medium hole 5 corresponds to the top position of the vacuum / filling working medium micro-groove 3. FC-72 with a volume fraction of 50% is filled from the vacuum / filling working medium hole 5.

[0053] like Figure 2 and Figure 3As shown, the size of the semiconductor silicon wafer 1 is 55mm×25mm, wherein the longitudinal length of the heat pipe is 40mm and the lateral width is 20mm. The semiconductor silicon wafer 1 is engraved with 12 horizontal grooves with center lines parallel to its boundaries, and 6 U-shaped grooves are formed on both sides. The cross-sectional shape of the micro-groove 2 is rectangular, with a depth of 280μm, a width of 800μm, and an equivalent diameter of the channel cross section of 414.8μm.

[0054] like Figure 1 , Figure 4 , Figure 5 and Figure 6 As shown, the planar thin film thermoelectric energy harvester is composed of a silicon dioxide layer 6, a P pole 7, an N pole 8, a metal lead 9, and a chrome-plated protective layer 10. Figure 1 ,exist Figure 2 On the basis of, a silicon dioxide layer 6 is deposited by PECVD process as an electrical insulating layer, and then a chrome-plated protective layer 10 is attached to the silicon dioxide layer 6, and a thermoelectric energy collector is made on the chrome-plated protective layer 10. First, a layer of aluminum layer with a thickness of 0.3μm is integrated on the chrome-plated protective layer 10, and is formed by a stripping method to serve as the metal lead 9 on the thermoelectric pile; the P-pole 7 thermoelectric material is metal copper, and the N-pole 8 thermoelectric material is metal nickel. The two types of thermoelectric materials, P-pole 7 and N-pole 8, are placed at both ends of the pulsating heat pipe evaporation section and condensation section respectively, and one end is connected to form a thermocouple. Figure 6 Multiple PN junctions are connected in series through metal leads 9 to form a thermopile. Finally, a dense silicon dioxide layer 6 is deposited on the back of the thermoelectric energy collector as a device insulation layer. The final diagram is as follows Figure 1 and Figure 5 shown.

[0055] Example 2

[0056] like Figure 2 and Figure 3 As shown, compared with Example 1, the cross-sectional depth of the micro-channel 2 of the micro-flat pulsating heat pipe is the same as that of Example 1, except that the cross-sectional shape of the micro-channel is as follows: Figure 7 .

[0057] Example 3

[0058] like Figure 5 and Figure 6 As shown, compared with Example 1, the type and size of thermoelectric materials of the planar thin film type thermoelectric energy harvester are the same as those of Example 1, except that the distribution form of the PN junction is as follows: Figure 8 .

[0059] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device, characterized in that: It comprises a micro flat plate type pulsating heat pipe and a thermoelectric energy collector, wherein an electrical insulation layer is provided between the micro flat plate type pulsating heat pipe and the thermoelectric energy collector; The micro flat-plate pulsating heat pipe comprises a semiconductor silicon wafer (1) and a packaging cover plate (4), wherein the packaging cover plate (4) is fixedly arranged on a side of the semiconductor silicon wafer (1) away from the electrical insulation layer; a micro-channel (2) and a vacuum / filling working medium micro-channel (3) are etched on a side of the semiconductor silicon wafer (1) close to the packaging cover plate (4), wherein the micro-channel (2) is connected to the vacuum / filling working medium micro-channel (3); a vacuum / filling working medium hole (5) is arranged on the packaging cover plate (4), wherein the vacuum / filling working medium hole (5) is arranged corresponding to the vacuum / filling working medium micro-channel (3), and the vacuum / filling working medium hole (5) is used to fill the micro-channel (2) with liquid working medium; The thermoelectric energy collector comprises a protective layer arranged on the electrical insulation layer, a thermopile is arranged on the protective layer, the thermopile is composed of a plurality of PN junctions connected in series via metal leads (9), and a device insulation layer is arranged on the side of the protective layer and the thermopile away from the electrical insulation layer.

2. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 1, characterized in that: The electrical insulation layer and the device insulation layer are both silicon dioxide layers (6), and the protective layer is a chrome-plated protective layer (10).

3. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 2, characterized in that: The electrical insulation layer is deposited on the chrome-plated protective layer (10) using a PECVD process.

4. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 1, characterized in that: The semiconductor silicon wafer (1) and the packaging cover plate (4) are bonded together through high-voltage electrostatic bonding.

5. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 4, characterized in that: The material of the packaging cover plate (4) is one of glass or silicon wafer.

6. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 1, characterized in that: The micro-channel (2) comprises a plurality of parallel horizontal channels, a U-shaped channel is arranged between two adjacent horizontal channels, the plurality of horizontal channels are connected to form a continuous S-shaped channel through the U-shaped channel, both ends of the S-shaped channel are connected to connecting channels, the S-shaped channel and the connecting channel form a closed loop, and the vacuum / working medium filling micro-channel (3) is connected to the connecting channel.

7. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 1, characterized in that: The liquid working fluid is one of environmentally friendly low-boiling-point FC-72, R141b or HFC-7100.

8. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to claim 1, characterized in that: The depth of the micro-channel (2) is 250 μm to 750 μm.

9. The silicon-based micro-pulsating heat pipe thermoelectric energy harvesting device according to any one of claims 1 to 8, characterized in that: The volume of liquid working medium filled in the vacuum / working medium filled micro-channel (3) accounts for 50% to 60% of the total volume of the circuit in the entire micro-flat pulsating heat pipe.

10. The silicon-based micro pulsating heat pipe thermoelectric energy harvesting device according to any one of claims 1 to 8, characterized in that: The cross-sectional shape of the micro-channel (2) is one of a triangle, a rectangle or a trapezoid.

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