A silicon-based micro pulsating heat pipe type thermoelectric energy harvesting device

Abstract

The application discloses a silicon-based micro pulsating heat pipe type thermoelectric energy collection device which is composed of a micro flat plate pulsating heat pipe, an electric insulation layer and a PN structure energy collector; the pulsating heat pipe is mainly divided into an evaporation section, a condensation section and an adiabatic section according to the heat flow direction; the electric insulation layer is covered on the silicon-based surface at the back of the pulsating heat pipe; the PN junctions with different lengths / widths are integrated on the back of the insulation layer and are in the same heat flow direction with the pulsating heat pipe, and then the potential difference is obtained under the Seebeck effect. The application has compact structure and can meet the needs of high heat flow density cooling and energy supply under the conditions of high integration and miniaturization of wireless equipment and wearable devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microelectronic element cooling heat dissipation and energy saving and environmental protection, and particularly relates to a silicon-based micro pulsating heat pipe type thermoelectric energy harvesting device. BACKGROUND

[0002] With the rapid development of Internet of Things technology, wireless devices and wearable devices are widely used in network data exchange field. Generally speaking, the power supply of network nodes mainly depends on traditional lithium batteries, but the problems of difficult battery replacement and system maintenance, high cost and environmental pollution become important bottlenecks restricting the development of the industry. Energy harvesting technology can realize sustainable power supply and provide a solution for local power supply, and thermoelectric energy harvesters are applied to waste heat recovery due to their small size, light weight and green environmental protection, and low-grade heat energy is widely concerned. With the application of MEMS technology, the high integration and miniaturization of wireless devices and wearable devices have continuously improved the requirements for their temperature management and energy supply, and therefore, the research and development of cooling and self-power supply technology have become a front-line hot issue in the development process of Internet of Things technology.

[0003] Thermoelectric energy harvesting is based on the Seebeck effect, which uses the thermal field at both ends of the material to drive the movement of carriers and form an electric current in the loop to achieve the purpose of output power. The heat pipe type thermoelectric energy harvester combines heat pipe and thermoelectric energy harvesting, fully utilizes the high thermal conductivity of heat pipe to efficiently transfer the waste heat generated by the system, and the thermoelectric harvester utilizes the temperature difference between the hot and cold ends of the heat pipe to realize thermoelectric conversion, which has the dual effect of device cooling and waste heat conversion. Pulsating heat pipe (also known as oscillating heat pipe) not only inherits the characteristics of simple structure, reliability and no power consumption of traditional heat pipe, but also has the characteristics of no wick, strong environmental adaptability and high efficient heat transfer, which is an effective element to solve the problem of high heat flux density heat dissipation. Therefore, the combination of pulsating heat pipe and energy harvester can effectively realize device cooling and heat energy conversion to electric energy, which provides an effective solution for temperature control and energy supply of integrated chips. SUMMARY

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

[0005] To achieve the above purpose, the present application provides a silicon-based micro pulsating heat pipe type thermoelectric energy harvesting device, which comprises a micro flat plate type pulsating heat pipe and a thermoelectric energy harvester, and an electrically insulating layer is arranged between the micro flat plate type pulsating heat pipe and the thermoelectric energy harvester.

[0006] The micro flat-plate pulsating heat pipe comprises a semiconductor silicon wafer and a packaging cover plate fixedly arranged on the side of the semiconductor silicon wafer away from the electrically insulating layer; a micro channel and a vacuum / working medium filling micro channel are etched on the side of the semiconductor silicon wafer close to the packaging cover plate, and the micro channel is in communication with the vacuum / working medium filling micro channel; a vacuum / working medium filling hole is arranged on the packaging cover plate, and the vacuum / working medium filling hole is arranged in correspondence with the vacuum / working medium filling micro channel, and the vacuum / working medium filling hole is used for filling liquid working medium into the micro channel;

[0007] The thermoelectric energy collector comprises a protective layer arranged on the electrically insulating layer, and a thermoelectric pile arranged on the protective layer, wherein the thermoelectric pile 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 thermoelectric pile away from the electrically insulating layer.

[0008] Preferably, the electrically insulating layer and the device insulating layer are both silicon dioxide layers, and the protective layer is a chromium plating protective layer.

[0009] Preferably, the electrically insulating layer is deposited on the chromium plating protective layer by a PECVD process.

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

[0011] Preferably, the material of the packaging cover plate is one of glass and silicon wafer.

[0012] Preferably, the micro channel comprises a plurality of parallel horizontal channels, a U-shaped channel is arranged between adjacent two horizontal channels, the plurality of horizontal channels are connected into a continuous S-shaped channel through the U-shaped channels, a connecting channel is connected to both ends of the S-shaped channel, the S-shaped channel and the connecting channel form a closed loop, and the vacuum / working medium filling micro channel is in communication with the connecting channel.

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

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

[0015] Preferably, the filling volume of the liquid working medium in the vacuum / working medium filling micro channel 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 application has the following advantages and technical effects:

[0018] 1. The present application is based on a micro flat plate pulsating heat pipe type thermoelectric energy collector, which uses a micro flat plate pulsating heat pipe and a micro thermoelectric energy collector as a cooling and waste heat recovery device, has the advantages of small size and can be directly integrated into a semiconductor chip, and has higher thermoelectric conversion efficiency compared with traditional heat pipe type thermoelectric energy collectors;

[0019] 2. The process is manufactured by mature MEMS process, and has the advantages of small size, low cost, batch manufacturing, and single chip integration with semiconductor chips;

[0020] 3. The micro flat plate pulsating heat pipe type thermoelectric energy collector adopts a horizontal structure, i.e. 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 type thermoelectric energy collector is a solid-state energy converter, has no movable parts, good stability, long service life and low maintenance cost;

[0022] 5. All electrodes of the micro flat plate pulsating heat pipe type thermoelectric energy collector are in the same plane, avoiding complex electrical connections;

[0023] 6. The purpose of cooling and energy collection of the whole system is achieved, and the technology of integrating cooling and self-energy of wireless devices and wearable devices is mastered. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 It is a structure schematic diagram of the silicon-based micro pulsating heat pipe type thermoelectric energy collection device in embodiment 1 of the present application.

[0026] Figure 2 It is a structure schematic diagram of the micro flat plate type pulsating heat pipe in embodiment 1 of the present application.

[0027] Figure 3 It is a structure schematic diagram of the micro flat plate type pulsating heat pipe in embodiment 1 of the present application. Figure 2 It is a cross-sectional view of A-A in the present application.

[0028] Figure 4 It is a structure schematic diagram of the packaging cover plate in the micro flat plate type pulsating heat pipe in embodiment 1 of the present application.

[0029] Figure 5 Figure 1 is a schematic diagram of the cross section of a silicon-based micro pulsating heat pipe type thermoelectric energy collector device in Embodiment 1 of the present application;

[0030] Figure 6 Figure 2 is a schematic diagram of the distribution of PN junctions in a planar thin film type thermoelectric energy collector in Embodiment 1 of the present application;

[0031] Figure 7 Figure 3 is a schematic diagram of the structure of the cross section of the micro channel of a micro plate type pulsating heat pipe in Embodiment 2 of the present application;

[0032] Figure 8 Figure 4 is a schematic diagram of a second distribution of PN junctions in a planar thin film type thermoelectric energy collector in Embodiment 3 of the present application;

[0033] In the figure: 1, semiconductor silicon wafer; 2, micro channel; 3, vacuum pumping / working medium filling micro channel; 4, encapsulation cover plate; 5, vacuum pumping / working medium hole; 6, silicon dioxide layer; 7, P pole; 8, N pole; 9, metal lead; 10, chromium plating protective layer. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The described embodiments are only some of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] The present application provides a silicon-based micro pulsating heat pipe type thermoelectric energy collector device, comprising a micro plate type pulsating heat pipe and a thermoelectric energy collector, and an electrically insulating layer is arranged between the micro plate type pulsating heat pipe and the thermoelectric energy collector.

[0036] The micro plate type pulsating heat pipe comprises a semiconductor silicon wafer 1 and an encapsulation cover plate 4, and the encapsulation cover plate 4 is fixedly arranged on the side of the semiconductor silicon wafer 1 away from the electrically insulating layer; a micro channel 2 and a vacuum pumping / working medium filling micro channel 3 are etched on the side of the semiconductor silicon wafer 1 close to the encapsulation cover plate 4, and the micro channel 2 is in communication with the vacuum pumping / working medium filling micro channel 3; a vacuum pumping / working medium hole 5 is arranged on the encapsulation cover plate 4, and the vacuum pumping / working medium hole 5 is arranged correspondingly to the vacuum pumping / working medium filling micro channel 3, and the vacuum pumping / working medium hole 5 is used to fill liquid working medium into the micro channel 2;

[0037] The thermoelectric energy collector comprises a protective layer arranged on the electrically insulating layer, and a thermoelectric pile is arranged on the protective layer, the thermoelectric pile is composed of a plurality of PN junctions connected in series through metal leads 9, and a device insulating layer is arranged on the side of the protective layer and the thermoelectric pile away from the electrically insulating layer.

[0038] In use, the application combines the pulsating heat pipe phase change cooling technology and the energy collection technology of thermoelectric energy collector by means of MEMS processing technology, and a rectangular cross-section micro channel 2 is made on a silicon-based surface by plasma etching technology, then the encapsulation cover plate 4 is integrated with the semiconductor silicon wafer 1 etched with the micro channel 2 by means of electrostatic bonding, and finally the thin film planar thermoelectric energy collector is integrated at the bottom of the semiconductor silicon wafer 1 of the micro flat plate type pulsating heat pipe, thereby forming the micro flat plate type pulsating heat pipe type thermoelectric energy collection device.

[0039] The working principle of the silicon-based micro pulsating heat pipe type thermoelectric energy collection device provided by the application is as follows: the micro flat plate type pulsating heat pipe is vacuumized and then filled with part of working medium by means of the vacuumizing / filling working medium hole 5, and the vacuumizing / filling working medium hole 5 is welded and sealed after the working medium is filled, and since the equivalent diameter of the micro channel 2 is very small, the vapor / liquid plug will be randomly and intermittently distributed in the channel. The heat pipe evaporation end is heated, and then the liquid working medium in the region absorbs heat and changes phase to generate bubbles, which expand rapidly, increase in pressure and push the working medium to the condensation section; the bubbles / plug in the condensation section are cooled, shrink and even disappear, and the pressure drops. The pressure difference and pressure fluctuation formed between the heat pipes make the working medium oscillate between the hot and cold sections, thereby realizing heat transfer and achieving temperature control effect. At the same time, the P pole 7 and the N pole 8 of the planar thin film type thermoelectric energy collector are connected in series into a thermoelectric pile by means of the metal lead 9, and the two ends are placed in high-temperature and low-temperature states respectively. Due to thermal excitation driving, the hole (electron) concentration of the P (N) pole material at the high-temperature end is higher than that at the low-temperature end, the holes (electrons) diffuse to the low-temperature end, and the electric charges accumulate at the low-temperature end, thereby forming a potential difference at one end of the thermoelectric pile, and the purpose of energy supply is achieved.

[0040] The silicon-based micro pulsating heat pipe type thermoelectric energy collection device provided by the application not only inherits the heat dissipation and self-energy supply functions of the traditional heat pipe type thermoelectric energy collector, but also has the characteristics of high integration and miniaturization, and can be directly integrated with a semiconductor chip by means of MEMS processing technology. The micro flat plate type pulsating heat pipe has the advantages of simple structure and high heat transfer performance due to its unique serpentine structure and the absence of a wick. At the same time, the planar thin film type thermoelectric energy collector integrated on the back of the heat pipe forms a potential difference under the action of temperature difference, and has good temperature control performance and the function of providing power for local energy consumption of the chip.

[0041] In a further optimization scheme, the electrically insulating layer and the device insulating layer are both silicon dioxide layers 6, and the protective layer is a chromium plating protective layer 10.

[0042] In a further optimization scheme, the electrically insulating layer is deposited on the chromium plating protective layer 10 by PECVD process.

[0043] In a further optimization scheme, in order to ensure the sealing of the micro flat plate type pulsating heat pipe as a whole and realize its excellent heat transfer performance, the semiconductor silicon wafer 1 and the encapsulation cover plate 4 are integrated by means of high-voltage electrostatic bonding.

[0044] Further optimization scheme, the material of the package cover plate 4 is one of glass or silicon wafer.

[0045] Further optimization scheme, to ensure the normal operation of the micro flat pulsating heat pipe, the micro channel 2 includes several parallel horizontal channels, U-shaped channels are arranged between adjacent two horizontal channels, the several horizontal channels are connected into continuous S-shaped channels through the U-shaped channels, the S-shaped channels are connected with the connecting channels, and the S-shaped channels and the connecting channels form a closed loop circuit, and the vacuum / working medium filling channel 3 is in communication with the connecting channels.

[0046] Further optimization scheme, the liquid working medium is one of FC-72, R141b or HFC-7100 with low boiling point and environmental protection.

[0047] Further optimization scheme, to process the micro channel 2 respectively, the depth of the micro channel 2 is 250 μm to 750 μm.

[0048] Further optimization scheme, to ensure that the micro flat pulsating heat pipe has good heat transfer performance, the filling volume of the liquid working medium in the vacuum / working medium filling channel 3 accounts for 50% to 60% of the total volume of the micro flat pulsating heat pipe.

[0049] Further optimization scheme, the cross-sectional shape of the micro channel 2 is one of triangle, rectangle or trapezoid.

[0050] The above three structures are provided with certain chamfers, and the chamfers can act as the function of the traditional heat pipe capillary core, drive the liquid phase working medium in the condensation section to return to the evaporation section under the action of the cross-sectional chamfer, and avoid the 'dry burning' phenomenon of the heat pipe.

[0051] Example 1

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

[0053] As shown in Figure 2 and Figure 3As shown in the figure, the semiconductor silicon wafer 1 is 55mm x 25mm in size, with the heat pipe longitudinal length of 40mm and the transverse width of 20mm. The semiconductor silicon wafer 1 is engraved with 12 horizontal grooves parallel to the boundary, 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 and a width of 800μm, and the equivalent diameter of the channel cross-section is 414.8μm.

[0054] As shown in the figure, Figure 1 , Figure 4 , Figure 5 and Figure 6 , the planar thin film type thermoelectric energy collector is composed of a silicon dioxide layer 6, a P pole 7, an N pole 8, a metal lead 9, and a chromium plating protective layer 10. Referring to Figure 1 , on the basis of Figure 2 , a layer of silicon dioxide layer 6 is deposited as an electrically insulating layer using the PECVD process, and then a layer of chromium plating protective layer 10 is attached on the silicon dioxide layer 6, and the thermoelectric energy collector is made on the chromium plating protective layer 10. First, an aluminum layer with a thickness of 0.3μm is integrated on the chromium plating protective layer 10, which is formed by stripping method, as the metal lead 9 of the thermoelectric pile; the P pole 7 thermoelectric material is metal copper, and the N pole 8 thermoelectric material is metal nickel, and the two types of thermoelectric materials are placed at the evaporation section and the condensation section of the pulsating heat pipe respectively, and the one end is connected to form a thermocouple. As shown in Figure 6 , a plurality of PN junctions are connected in series by the metal lead 9 to form a thermoelectric pile. Finally, a dense layer of silicon dioxide layer 6 is deposited on the back of the thermoelectric energy collector as a device insulating layer. The final figure is shown in Figure 1 and Figure 5 .

[0055] Example 2

[0056] As shown in the figure, Figure 2 and Figure 3 , compared with example 1, the cross-sectional depth of the micro-groove 2 of the micro-plate pulsating heat pipe is the same as that of example 1, and the difference is that the cross-sectional shape of the micro-groove is as shown in Figure 7 .

[0057] Example 3

[0058] As shown in the figure, Figure 5 and Figure 6 , compared with example 1, the types and sizes of thermoelectric materials of the planar thin film type thermoelectric energy collector are the same as those of example 1, and the difference is that the distribution form of the PN junction is as shown in Figure 8 .

[0059] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A silicon-based micro-oscillating heat pipe type thermoelectric energy harvesting device, characterized by, The micro flat plate pulsating heat pipe and the thermoelectric energy collector are provided with an electrically insulating layer therebetween; The micro flat plate pulsating heat pipe comprises a semiconductor silicon wafer (1) and a packaging cover plate (4) fixedly arranged on the side of the semiconductor silicon wafer (1) away from the electrically insulating layer; a micro channel (2) and a vacuum pumping / working medium charging micro channel (3) are etched on the side of the semiconductor silicon wafer (1) close to the packaging cover plate (4), the micro channel (2) is in communication with the vacuum pumping / working medium charging micro channel (3); a vacuum pumping / working medium charging hole (5) is arranged on the packaging cover plate (4) and corresponds to the vacuum pumping / working medium charging micro channel (3), the vacuum pumping / working medium charging hole (5) is used for charging liquid working medium into the micro channel (2); The thermoelectric energy collector comprises a protective layer arranged on the electrically insulating layer, a thermoelectric pile is arranged on the protective layer, the thermoelectric pile is composed of a plurality of PN junctions connected in series through metal leads (9), and a device insulating layer is arranged on the side of the protective layer and the thermoelectric pile away from the electrically insulating layer.

2. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to claim 1, wherein The electrically insulating layer and the device insulating layer are both silicon dioxide layers (6), and the protective layer is a chromium plating protective layer (10).

3. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to claim 2, wherein The electrically insulating layer is deposited on the chromium plating protective layer (10) by PECVD process.

4. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to claim 1, wherein The semiconductor silicon wafer (1) and the packaging cover plate (4) are integrated by high-voltage electrostatic bonding.

5. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to claim 4, wherein The material of the packaging cover plate (4) is one of glass and silicon wafer.

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

7. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to claim 1, wherein The liquid working medium is one of environmentally friendly low-boiling FC-72, R141b or HFC-7100.

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

9. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to any one of claims 1 to 8, wherein The liquid working medium charging volume in the vacuum pumping / working medium charging micro channel (3) accounts for 50-60% of the total volume of the loop in the entire micro flat plate pulsating heat pipe.

10. The silicon-based micro-pulsating heat pipe type thermoelectric energy harvesting device according to any one of claims 1-8, wherein, The cross-sectional shape of the micro channel (2) is one of triangle, rectangle and trapezoid.

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