Thin-film thermopile heat flow sensor with quick response and preparation method of thin-film thermopile heat flow sensor

Abstract

The invention provides a thin film thermopile heat flow sensor with quick response and a preparation method thereof, and belongs to the technical field of sensors. Comprising a first layer of substrate; the second cold junction layer is formed by overlapping L-shaped Cu and the tail part of L-shaped constantan, and the overlapping part of the L-shaped Cu and the tail part of the L-shaped constantan is a cold junction; the third thermal resistance layer covers the second L-shaped Cu layer and the L-shaped constantan layer; the fourth layer is a hot junction layer and is formed by lapping two kinds of metal, namely long-strip-shaped Cu and long-strip-shaped constantan, the lapping part of the long-strip-shaped Cu and the long-strip-shaped constantan is a hot junction, the fourth layer is plated above the third thermal resistance layer, and the port of the fourth layer is connected with the ports of the L-shaped Cu and the L-shaped constantan of the second layer to form a three-dimensional structure. Spatial distribution of cold and hot nodes is changed, a structure that the cold and hot nodes are vertically distributed on the upper and lower surfaces of the thermal resistance layer is formed, the response speed of the thin-film thermopile heat flow sensor can be greatly improved, and meanwhile, the sensitivity is not reduced.

Description

Technical Field

[0001] The invention provides a thin-film thermopile heat flow sensor with rapid response and a preparation method thereof, belonging to the technical field of sensors. Background Art

[0002] Thermal flow control for material processing and process control has become a mature science. Almost all physical systems involve the transfer of heat energy, and the management of heat energy transfer is extremely critical in many engineering applications. In many industrial manufacturing processes, in order to obtain the required material properties and quality control of industrial engineering, strict thermal flow control of the processing process is required. Thermal stress control in ceramic manufacturing, thin film processing and plasma deposition, annealing processes of glass and metals, heat treatment of materials and laser surface treatment all require precise control of heat flow, involving many fields such as aerospace, MEMS technology, and energy management.

[0003] Thermal flow sensors have been widely used in the research of hypersonic flight, combustion and propulsion, and large-scale fire protection testing. In scientific research, thermal flow sensors can be used to measure thermal properties related to the thermal conductivity of materials, providing theoretical and technical support for research. Thermal flow sensors also have many applications in agriculture and energy-saving applications.

[0004] Thermal flow control requires energy to absorb heat from other objects or transfer heat to other objects in a known and controllable way. Therefore, the proper design of dryers, heat exchangers, boilers, condensers and heat pipes becomes particularly important. With the continuous upgrading of electronic products, spacecraft propulsion and power generation equipment, the requirements for thermal flow control are more stringent, and thermal flow sensors can help complete the design of cooling systems.

[0005] Due to principle limitations, the sensitivity and response speed of thin-film thermopile heat flow sensors cannot be achieved at the same time. In order to improve the sensitivity, some people choose to increase the number of thermocouples, but this will obviously increase the size of the device and does not meet the requirements of sensor miniaturization. Choosing a material with a smaller thermal conductivity will increase the response time. In order to increase the response speed, reducing the thickness of the thermal resistance layer and increasing the thermal conductivity will reduce the sensitivity. Summary of the invention

[0006] In response to the above technical problems, the present invention proposes a thin film thermopile heat flow sensor with fast response and a preparation method, which changes the spatial distribution of hot and cold nodes to form a structure in which the hot and cold nodes are vertically distributed on the upper and lower surfaces of the thermal resistance layer, aiming to enable the thermopile to respond quickly without reducing sensitivity.

[0007] The technical solution of the present invention:

[0008] First, the present invention provides a thin film thermopile heat flow sensor with fast response, including a four-layer structure:

[0009] The first layer is a substrate; the material of the first layer substrate is Al2O3 or AlN, a silicon-based substrate, ZrO2, etc.

[0010] The second layer is a cold junction layer, which is formed by overlapping the L-shaped Cu and the L-shaped constantan tail. The overlapping connection part of the L-shaped Cu and the L-shaped constantan tail is the cold junction.

[0011] The third layer is a thermal resistance layer, which covers the L-shaped Cu and L-shaped constantan of the second layer; the material of the third thermal resistance layer is Al2O3, SiO2, Si3N4, etc.

[0012] The fourth layer is also a thermal junction layer, which is formed by overlapping two metals, a long strip of Cu and a long strip of Constantan. The overlapping part of the long strip of Cu and the long strip of Constantan is the thermal junction. The fourth layer is plated on top of the third thermal resistance layer, and the port is connected to the L-shaped Cu and L-shaped Constantan ports of the second layer to form a three-dimensional structure.

[0013] Secondly, the present invention provides a method for preparing a thin film thermopile heat flow sensor with fast response, comprising the following steps:

[0014] Step 1: Surface treatment of substrate:

[0015] The substrate was ultrasonically cleaned with deionized water, and the substrate was ultrasonically cleaned with acetone and alcohol respectively, and dried in a nitrogen atmosphere;

[0016] Step 2: Sputtering the first electrode material of the thermopile Cu on the substrate surface:

[0017] The substrate surface treated in step 1 is subjected to photolithography technology to form a thermopile first electrode pattern on the substrate surface through coating, exposure, and development, and then placed in a vacuum environment, with Cu metal as a target material, argon gas as a sputtering medium, and vacuum coating (including magnetron sputtering, thermal evaporation, electron beam coating, etc.) is used to deposit the thermopile first electrode material Cu on the substrate surface, and the thickness of the thermopile film is 400-600nm, and then acetone is used to strip the photoresist on the substrate surface to obtain an L-shaped Cu pattern;

[0018] Step 3: Sputtering the thermopile second electrode material Constantan on the substrate surface:

[0019] After cleaning the substrate treated in step 2, photolithography technology is used to form a thermopile second electrode pattern on the substrate surface through coating, exposure, and development. The substrate is placed in a vacuum environment, constantan alloy is used as a target, argon gas is introduced as a sputtering medium, and vacuum coating (including magnetron sputtering, thermal evaporation, electron beam coating, etc.) is used to deposit constantan, a thermopile second electrode material, on the substrate surface. The thickness of the thermopile film is 700-900nm. Acetone is then used to strip the photoresist on the substrate surface to obtain an L-shaped second electrode array, and finally a second layer consisting of L-shaped Cu and L-shaped constantan tails is obtained:

[0020] Step 4: Sputter a thermal resistance layer on the second L-shaped Cu and L-shaped Constantan:

[0021] The sample processed in step 3 is cleaned and aligned with the hard mask plate, placed in a vacuum environment, pure Al is used as the target material, oxygen is introduced as the reaction gas, argon is introduced as the sputtering medium, and Al2O3 thin film is deposited by vacuum coating (including magnetron sputtering, thermal evaporation, electron beam coating, etc.); wherein the transparent area of ​​the hard mask plate is the Al2O3 thermal resistance layer area, that is, the area above each alternate row of electrode contacts; finally, the third layer, namely the thermal resistance layer, is obtained;

[0022] Step 5: Sputter the first electrode material of the thermopile Cu on the substrate surface again:

[0023] After cleaning the substrate treated in step 4, a thermopile first electrode pattern is formed on the surface of the substrate by photolithography technology through coating, exposure, and development, and then placed in a vacuum environment, using Cu metal as a target material, introducing argon gas as a sputtering medium, and using vacuum coating (including magnetron sputtering, thermal evaporation, electron beam coating, etc.) technology to deposit the thermopile first electrode material Cu on the surface of the substrate, and the thickness of the thermopile film is 1000-1200nm, and then using acetone to strip the photoresist on the surface of the substrate to obtain a long strip of Cu;

[0024] Step 6: Sputter the thermopile second electrode material Constantan on the substrate surface again:

[0025] After cleaning the substrate treated in step 5, photolithography technology is used to form a thermopile first electrode pattern on the substrate surface through coating, exposure and development. The substrate is placed in a vacuum environment, constantan metal is used as a target, argon gas is introduced as a sputtering medium, and the argon gas flow rate is 80sccm. Vacuum coating (including magnetron sputtering, thermal evaporation, electron beam coating, etc.) is used to deposit constantan, a second electrode material of the thermopile, on the substrate surface. The thickness of the thermopile film is 1100-1300nm. Acetone is then used to strip the photoresist on the substrate surface to obtain a fourth layer of long strips of Cu connected to the tail of the long strips of constantan, and a thin film thermopile is obtained.

[0026] Furthermore, the vacuum environment during magnetron sputtering coating in steps 2 to 6 is better than 1×10 -4Pa.

[0027] Step 7: Use silver paste to connect the 3 cm copper wire thin conductor and the thin film thermopile, and then use a 1 m thick wire to weld the thin wire together to obtain a thin film heat flux sensor.

[0028] The measuring principle of the thin film heat flux sensor provided by the present invention is as follows: the thin film thermopile with fast response is composed of a thermal resistance layer, a substrate and a thermopile layer (i.e., the second layer and the fourth layer). The function of the thermal resistance layer is to form a temperature gradient on its surface and inside. The substrate constructs a stable heat dissipation boundary to accelerate the temperature distribution of the entire temperature field. When the surface of the thermal resistance layer receives a heat flux incident vertically (or conducted, heat convection), after a period of time, the temperature field of the thermal resistance layer reaches a stable state. The incident heat flux is theoretically equal to the heat flux conducted in the thermal resistance layer. Based on the one-dimensional steady-state heat transfer assumption, the heat flux value passing through the thermal resistance layer is calculated by the temperature difference between the two surfaces obtained by the temperature measuring element, thereby obtaining the heat flux to be measured.

[0029] The improvement of the present invention over the prior art is:

[0030] 1. The existing thin film thermopile structure is innovated, and the general horizontal structure is formed into a winding three-dimensional structure through micromachining, which provides a new idea for the design of thin film thermopile sensors.

[0031] 2. The emergence of this structure eliminates horizontal convection heat transfer between the hot node and the cold node, so that equilibrium can be reached more quickly to achieve a fast response time.

[0032] 3. Increasing the number of film layers introduces more interlayer thermal resistance, making the node temperature difference larger. At the same time, the distance between hot and cold nodes is greatly shortened, reducing the time required for the node temperature difference to reach equilibrium and improving the sensor response speed.

[0033] The effects of the present invention relative to the prior art are:

[0034] 1. The prepared sample data show that the response speed of the sensor with this structure has increased by two orders of magnitude compared with the commercial Gordon meter. It can be seen that this structure can be used in scenarios with high frequency and the need to quickly obtain sampling time data.

[0035] 2. For a long time, the sensitivity and fast response of thermopiles cannot be achieved at the same time. The structure provided by the present invention greatly improves the response speed while also slightly improving the sensitivity. The fitting linearity is 0.99924 at 300kW / m 2 The maximum error within the heat flux is only 1.22%. The response time is calibrated by laser, and the results show that the device response time is 2ms with excellent repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1It is a schematic diagram of the structure of a thin film thermopile with fast response of the present invention;

[0037] Figure 2 It is a schematic diagram of the structure of a thin film thermopile with fast response of the present invention;

[0038] Figure 3 It is a front view schematic diagram of a thin film thermopile structure with fast response of the present invention;

[0039] Figure 4 It is a left schematic diagram of a thin film thermopile structure with fast response of the present invention;

[0040] Figure 5 It is a schematic diagram of a local enlarged structure of a thin film thermopile with fast response of the present invention;

[0041] Figure 6 It is a schematic diagram of the structure of each layer of the thin film thermopile with fast response of the present invention;

[0042] Figure 7 It is a schematic diagram of winding Cu and Cu55Ni45 wires of the present invention;

[0043] Figure 8 It is a schematic diagram of the second, third and fourth layer combined structure of the present invention;

[0044] Fig. 9 is a flow chart of the present invention;

[0045] Fig.10 This is the first photolithography pattern (Cu plating) of the present invention;

[0046] Fig.11 It is the second photolithography pattern of the present invention (Cu55Ni45 plating);

[0047] Fig.12 The hard mask pattern of the present invention (plated with Al2O3);

[0048] Fig.13 This is the third photolithography pattern (Cu plating) of the present invention;

[0049] Fig.14 This is the fourth photolithography pattern of the present invention (Cu55Ni45 plating);

[0050] Fig.15 The thermopile output characteristics of the embodiment;

[0051] Fig.16 This is a response time test of an embodiment.

[0052] In the figure, 1-Al2O3, 2-Cu, 3-Cu55Ni45, 4-Al2O3, 5-cold node, 6-hot node. DETAILED DESCRIPTION

[0053] like Figures 1 to 8 As shown, the different materials are marked as: 1-Al2O3, 2-Cu, 3-Cu55Ni45, 4-Al2O3;

[0054] The invention provides a thin film thermopile heat flow sensor with fast response, which consists of four parts:

[0055] The first layer is the substrate, which can be in the shape of square, rectangle, circle, etc. The material can be Al2O3, AlN, Si3N4, etc. Ensure that the substrate is clean and smooth. Al2O3 is selected in this embodiment, which is marked as 1 in the figure.

[0056] The second layer is formed by overlapping the tail of L-shaped Cu and L-shaped Cu55Ni45, and the overlapping connection part of L-shaped Cu and L-shaped Cu55Ni45 tail is the cold node 5. (Completed by the first and second photolithography pattern coating.) Cu55Ni45 is selected in this embodiment.

[0057] The third layer is a thermal resistance layer, made of Al2O3, denoted by 4 in the figure (completed by hard mask pattern plating), covering the L-shaped Cu and L-shaped Cu55Ni45 of the second layer.

[0058] The fourth layer is formed by overlapping two metals, a long strip of Cu and a long strip of Cu55Ni45. The overlapping part of the long strip of Cu and the long strip of Cu55Ni45 is the thermal node 6 (completed by the third and fourth photolithography pattern coating), which is plated on the top of the thermal resistance layer, and the port is connected to the L-shaped Cu and L-shaped Cu55Ni45 ports of the second layer, thereby forming a three-dimensional structure. For details, see Figure 1 .

[0059] The thin film thermopile with fast response provided by the present invention is used to prepare a thin film heat flow sensor, such as Fig. 9 , the specific preparation method is:

[0060] Step 1, surface treatment of the substrate: ultrasonically clean the substrate with deionized water, ultrasonically clean the substrate with acetone, ultrasonically clean the substrate with alcohol, and then dry it in a nitrogen atmosphere;

[0061] Step 2: Sputtering the first electrode material of the thermopile Cu on the substrate surface: Sputtering the substrate surface treated in step 1 by photolithography, such as Fig.10The first photolithography mask shown in the figure is coated, exposed, and developed to form a thermopile first electrode pattern on the substrate surface, and is placed in a vacuum environment. Cu metal is used as a target material, and argon gas is introduced as a sputtering medium. The argon gas flow rate is 80 sccm. The thermopile first electrode material Cu is deposited on the substrate surface by DC magnetron sputtering technology. The sputtering power is 75w, and the thickness of the thermopile film is 600nm. Acetone is then used to strip the photoresist on the substrate surface to obtain an L-shaped Cu pattern.

[0062] Step 3: Sputtering the second electrode material of the thermopile Cu55Ni45 on the substrate surface: After cleaning the substrate processed in step 2, use photolithography technology to select Fig.11 The second photolithography mask shown in the figure is coated, exposed, and developed to form a thermopile second electrode pattern on the substrate surface. It is placed in a vacuum environment, and Cu55Ni45 alloy is used as a target material. Argon gas is introduced as a sputtering medium. The argon gas flow rate is 80sccm. The thermopile second electrode material Cu55Ni45 is deposited on the substrate surface by DC magnetron sputtering technology. The sputtering power is 75w, and the thermopile film thickness is 700nm. Acetone is then used to strip the photoresist on the substrate surface to obtain an L-shaped second electrode array, and finally a second layer consisting of L-shaped Cu connected to the tail of Cu55Ni45 is obtained:

[0063] Step 4: Sputter a thermal resistance layer on the second layer of Cu and Cu55Ni45: Clean the sample treated in step 3 and Fig.12 The hard mask shown is aligned and placed in a vacuum environment. Pure Al is used as the target material. Oxygen is introduced as the reaction gas and argon is introduced as the sputtering medium. The oxygen flow rate is 3.5 sccm and the argon flow rate is 80 sccm. Al2O3 thin film is deposited by DC magnetron sputtering. The transparent area of ​​the hard mask is the Al2O3 thermal resistance layer area, that is, the area above each row of electrode contacts. Finally, the third layer, namely the thermal resistance layer, is obtained.

[0064] Step 5: Sputter the first electrode material of the thermopile Cu on the substrate surface again: After cleaning the substrate processed in step 4, use photolithography technology to select Fig.13 The third photolithography mask shown in the figure is coated, exposed, and developed to form a thermopile first electrode pattern on the substrate surface. It is placed in a vacuum environment, with Cu metal as the target material, and argon gas is introduced as the sputtering medium. The argon gas flow rate is 80 sccm. The thermopile first electrode material Cu is deposited on the substrate surface by DC magnetron sputtering technology. The sputtering power is 75w, and the thickness of the thermopile film is 1000nm. Then, acetone is used to strip the photoresist on the substrate surface to obtain a long strip of Cu.

[0065] Step 6: Sputter the second electrode material of the thermopile Cu55Ni45 on the substrate surface again: After cleaning the substrate treated in step 5, use photolithography technology to select Fig.14 The fourth photolithography mask shown in the figure is coated, exposed, and developed to form a thermopile first electrode pattern on the substrate surface, and is placed in a vacuum environment. Cu55Ni45 metal is used as a target material, and argon gas is introduced as a sputtering medium. The argon gas flow rate is 80sccm. The thermopile second electrode material Cu55Ni45 is deposited on the substrate surface by DC magnetron sputtering technology. The sputtering power is 75w, and the thermopile film thickness is 1100nm. Acetone is then used to strip the photoresist on the substrate surface to obtain a fourth layer in which a long strip of Cu is connected to the tail of Cu55Ni45.

[0066] Step 7, connecting wires: Use silver paste to connect a 3 cm copper wire to the thermopile electrode disk on the substrate processed in step 7, and finally weld the 1 m thick wire and the thin wire together to obtain a thin film heat flux sensor.

[0067] The vacuum environment during magnetron sputtering coating in the above steps 2, 3, 4, 5, and 6 is better than 1x10 -4 Pa.

[0068] Conduct infrared thermal radiation test on the prepared samples:

[0069] The thermal radiation calibration system used in this embodiment consists of a quartz lamp array, a power control system, a data acquisition system, and a water cooling system. A certain number of quartz lamp arrays can provide a large area of ​​uniform heat flow. The heat flux density is controlled by adjusting the power of the quartz lamp array. The water cooling system uses a water pump to circulate cooling water to remove excess heat from the system to maintain the steady state of the system. The output signal of the sensor is collected by the data acquisition system. The system can provide 0~500kW / m 2 Heat flux density, control accuracy 1kW / m 2 Before the test begins, the sensor under test needs to be left to reach thermal equilibrium with the room temperature. During the test, the packaged sensor and the standard sensor are fixed in the same position to keep the test conditions of the two sensors consistent to avoid uncertainty in comparative calibration.

[0070] First, use a standard Gordon meter (sensitivity 0.0228mV / kW·m -2) The heat flux of the quartz lamp heating platform is calibrated, and a standard Gordon meter is placed 5 cm below the quartz lamp array. The upper surface of the Gordon meter is parallel to the quartz lamp array. The power control system controls the power of the quartz lamp array to 5kW, 10kW, 15kW, 20kW, 25kW and then decreases gradually. After collecting the potential signal output by the Gordon meter, the heat flux density at this position can be calculated. Then the heat flux sensor is calibrated, and the heat flux sensor is placed in the same position, and its output potential is tested under the same power conditions. The Vt curve trends of the two are consistent. When the power of the quartz lamp array increases, the output potentials of the Gordon meter and the heat flux sensor both increase rapidly and reach stability. In comparison, the heat flux sensor has a higher output signal. Fig.15 The curve of the device output voltage changing with heat flux density shows that when different heat flux densities are applied to the platform through quartz lamp radiation heating, the output voltage of the heat flux sensor increases with the increase of heat flux density, showing a good linear relationship. The sensitivity of the sensor is 0.03784mV / (kW / m 2 ), the fitting linearity is 0.99924.

[0071] Laser response test:

[0072] The laser calibration system includes a laser power control system, a data acquisition system, a focusing system and a laser source. The laser source is composed of an adjustable fiber laser with a wavelength of 1080nm and a laser frequency of 1000H. Z The laser power is adjusted by setting the output percentage in the computer. The heat flux sensor is fixed on an adjustable bracket. The spot diameter on the sensor's sensitive surface can be changed by adjusting the bracket position where the focusing mirror is installed. In order to avoid asymmetric temperature distribution and reduction of output signal caused by the deviation of the laser focus position, the spot must completely cover the sensor's thermal sensitive area. The thermal sensitive area of ​​the heat flux sensor is 12×11mm 2 , so the spot diameter is selected to be 6mm. Under this setting, the heat flux density on the sensor surface changes with the change of laser power. Finally, the test data of the sensor is collected by the data acquisition system. Before the measurement begins, the sensor under test is allowed to reach thermal equilibrium with the laboratory environment. The device response time is tested, such as Fig.16 After the laser is turned on, the output voltage reaches its peak value after 2ms, so the sensor response time is 2ms. This indicator is much better than the reported thin film thermopile heat flow sensor, as shown in Table 1.

[0073] Table 1 Reported response time of thin film thermopile heat flow sensor

[0074]

[0075] The structure of this embodiment is composed of 150 pairs of thermocouples. When a heat flow is applied to the structure, the hot junction exposed to the outside first contacts the heat flow and then heats up. The heat flow continues to transfer downward along the thermal resistance layer, and the cold junction also begins to heat up. After a period of time, the temperature field of the thermal resistance layer reaches a stable state. The incident heat flow is theoretically equal to the heat flow conducted in the thermal resistance layer. Due to the temperature difference between the cold junction and the hot junction, the Seebeck effect outputs a voltage difference. According to Fourier's law:

[0076]

[0077] q is the heat flux density, in W / m2; λ is the thermal conductivity of the thermal resistance layer, in W / (m·K); ΔT / ΔX is the temperature gradient in the direction perpendicular to the isothermal surface; T1 is the surface temperature of the hot node, in °C; T2 is the surface temperature of the cold node, in °C; dx is the thickness of the thermal resistance layer, in mm. The heat flux value can be calculated.

Claims

1. A thin film thermopile heat flow sensor with fast response, characterized in that: It includes four layers: The first layer is the substrate; The second layer is a cold junction layer, which is formed by overlapping the L-shaped Cu and the L-shaped constantan tail. The overlapping connection part of the L-shaped Cu and the L-shaped constantan tail is a cold junction. The third layer is a thermal resistance layer, covering the L-shaped Cu and L-shaped Constantan of the second layer; The fourth layer is the thermal junction layer, which is formed by overlapping two metals, a long strip of Cu and a long strip of Constantan. The overlapping part of the long strip of Cu and the long strip of Constantan is the thermal junction. The fourth layer is plated on top of the third thermal resistance layer, and the port is connected to the L-shaped Cu and L-shaped Constantan ports of the second layer to form a three-dimensional structure.

2. A thin film thermopile heat flow sensor with fast response according to claim 1, characterized in that: The material of the first substrate is Al2O3, AlN, silicon-based substrate or ZrO2.

3. The thin film thermopile heat flow sensor with fast response according to claim 1, characterized in that: The material of the third thermal resistance layer is Al2O3, SiO2 or Si3N4.

4. A method for preparing a thin film thermopile heat flow sensor with fast response according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Surface treatment of substrate: The substrate was ultrasonically cleaned with deionized water, and the substrate was ultrasonically cleaned with acetone and alcohol respectively, and dried in a nitrogen atmosphere; Step 2: Sputtering the first electrode material of the thermopile Cu on the substrate surface: The substrate surface treated in step 1 is subjected to photolithography technology to form a thermopile first electrode pattern on the substrate surface through coating, exposure, and development, and then placed in a vacuum environment, using Cu metal as a target material, introducing argon gas as a sputtering medium, and using vacuum coating to deposit the thermopile first electrode material Cu on the substrate surface, with the thermopile film thickness being 400-600nm, and then using acetone to strip the photoresist on the substrate surface to obtain an L-shaped Cu pattern; Step 3: Sputtering the thermopile second electrode material Constantan on the substrate surface: After cleaning the substrate treated in step 2, photolithography technology is used to form a thermopile second electrode pattern on the substrate surface through coating, exposure, and development. The substrate is placed in a vacuum environment, constantan alloy is used as a target, argon gas is introduced as a sputtering medium, and vacuum coating technology is used to deposit constantan, a thermopile second electrode material, on the substrate surface. The thickness of the thermopile film is 700-900nm. Acetone is then used to strip the photoresist on the substrate surface to obtain an L-shaped second electrode array, and finally a second layer consisting of L-shaped Cu and L-shaped constantan tail is obtained: Step 4: Sputter a thermal resistance layer on the second L-shaped Cu and L-shaped Constantan: The sample processed in step 3 is cleaned and aligned with the hard mask plate, placed in a vacuum environment, pure Al is used as the target material, oxygen is introduced as the reaction gas, argon is introduced as the sputtering medium, and Al2O3 thin film is deposited by vacuum coating; wherein the transparent area of ​​the hard mask plate is the Al2O3 thermal resistance layer area, that is, the area above each alternate row of electrode contacts; finally, the third layer, namely the thermal resistance layer, is obtained; Step 5: Sputter the first electrode material of the thermopile Cu on the substrate surface again: After cleaning the substrate treated in step 4, a thermopile first electrode pattern is formed on the surface of the substrate by photolithography technology through coating, exposure, and development, and then placed in a vacuum environment, using Cu metal as a target material, introducing argon gas as a sputtering medium, and using vacuum coating to deposit the thermopile first electrode material Cu on the surface of the substrate, with the thickness of the thermopile film being 1000-1200nm, and then using acetone to strip the photoresist on the surface of the substrate to obtain a long strip of Cu; Step 6: Sputter the thermopile second electrode material Constantan on the substrate surface again: After cleaning the substrate treated in step 5, a first thermopile electrode pattern is formed on the surface of the substrate by photolithography technology through coating, exposure, and development, and then placed in a vacuum environment, constantan metal is used as a target, argon gas is introduced as a sputtering medium, and constantan, a second electrode material of the thermopile, is deposited on the surface of the substrate by vacuum coating, and the thickness of the thermopile film is 1100-1300nm, and then acetone is used to strip the photoresist on the surface of the substrate to obtain a fourth layer of long strips of Cu connected to the tail of the long strips of constantan, and a thin film thermopile is obtained; Step 7: Connect the thin film thermopile to the thermal wire: A 3 cm copper wire thin conductor was connected to the thin film thermopile using silver paste, and then a 1 m thick wire was used to weld the thin wire together to obtain a thin film heat flux sensor.

5. The method for preparing a thin film thermopile heat flow sensor with fast response according to claim 4, characterized in that: The vacuum environment during magnetron sputtering coating in steps 2 to 6 is better than 1×10 -4 Below Pa.

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