A miniature transient thin-film heat flux sensor

Abstract

The present application relates to the technical field of thin film heat flow sensor, disclose a kind of micro transient thin film heat flow sensor, the present application will be set up in the upper high thermal conductivity cover layer and the lower high thermal conductivity cover layer respectively in the upper surface and the lower surface of micro transient thin film heat flow sensor, when measuring the heat flux density of the non-uniform temperature field of the surface temperature of the wall surface to be measured simultaneously measuring the surface temperature of the wall surface to be measured, utilize the high thermal conductivity of the upper and lower two layers of high thermal conductivity cover layer, promote the heat of sensor upper and lower two sides to spread quickly and evenly, to ensure that the temperature field of the two sides of sensor is even, avoid the local hot spot or local cold spot possibly existing in non-uniform temperature field to generate interference to measurement, improve the measurement accuracy and reliability of sensor in complex thermal environment, reduce overall measurement error.

Description

Technical Field

[0001] This invention relates to the field of thin-film heat flow sensor technology, and discloses a miniature transient thin-film heat flow sensor. Background Technology

[0002] The miniature transient thin-film heat flux sensor is a thin-film sensor utilizing a thermopile structure to measure the heat flux density of a solid surface and simultaneously measure its temperature. The thermopile is an array of multiple thermocouples connected in series, each thermocouple consisting of a junction made of two different materials. By amplifying the signal from a single thermocouple, the thermopile can generate a higher thermoelectric potential, improving sensitivity. The core working mechanism of the miniature transient thin-film heat flux sensor is based on the Seebeck effect, indirectly measuring heat flux by converting a temperature gradient into an electrical signal. In thin-film form, this sensor uses micro / nano fabrication techniques to prepare functional layer films, thus ensuring high response speed and low thermal mass, making it suitable for transient heat flux measurements in hypersonic wind tunnels, spacecraft thermal protection, or high-temperature environments.

[0003] Existing miniature transient thin-film heat flux sensors are calibrated based on a uniform temperature field before use. However, in practical applications, miniature transient thin-film heat flux sensors often measure non-uniform temperature fields, resulting in large measurement errors. Summary of the Invention

[0004] The purpose of this invention is to provide a miniature transient thin-film heat flow sensor that is suitable for measuring non-uniform temperature fields and reduces measurement errors caused by non-uniform temperature fields.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A miniature transient thin-film heat flux sensor, comprising, from top to bottom, the following:

[0007] High thermal conductivity top coating;

[0008] A first thermal resistance layer is bonded to the upper high thermal conductivity covering layer, and the first thermal resistance layer is provided with a heat-sensing part that is in thermal contact with the upper high thermal conductivity covering layer.

[0009] A first thermopile layer, the first thermopile layer including a first temperature measuring strip and a plurality of first current measuring strips, the first temperature measuring strip and the first current measuring strips being disposed on the lower surface of the first thermal resistance layer;

[0010] A second thermal resistance layer is bonded to the lower surface of the first thermal resistance layer and covers the first thermopile layer; the second thermal resistance layer has a plurality of through holes, and the through holes are filled with conductors;

[0011] The second thermopile layer includes a second temperature measurement strip and a plurality of second current measurement strips;

[0012] A third thermal resistance layer is provided, wherein the upper surface of the third thermal resistance layer is provided with the second thermopile layer, and the third thermal resistance layer is bonded to the lower surface of the second thermal resistance layer; the third thermal resistance layer is also provided with a cold end sensing part;

[0013] A lower high thermal conductivity cover layer is bonded to the lower surface of the third thermal resistance layer and in thermal contact with the cold end sensing part.

[0014] Wherein, one end of the first temperature measuring strip is electrically connected to one end of the second temperature measuring strip through a conductor in a through hole to form a temperature measuring thermocouple; the hot end node of the temperature measuring thermocouple is in thermal contact with the cold end sensing part, and the temperature of the lower high thermal conductivity covering layer is sensed through the cold end sensing part; the cold end of the temperature measuring thermocouple is provided with a temperature measuring terminal.

[0015] The first flow measurement strip is connected in series with the second flow measurement strip alternately in the positive direction through a conductor in the through hole to form a flow measurement thermopile. The flow measurement hot end node of the flow measurement thermopile senses the temperature of the upper high thermal conductivity covering layer through the hot end sensing part, and the flow measurement cold end node of the flow measurement thermopile senses the temperature of the lower high thermal conductivity covering layer through the cold end sensing part; and the flow measurement strips at both ends of the flow measurement thermopile are respectively provided with flow measurement terminals.

[0016] Furthermore, the upper high thermal conductivity cover layer and the lower high thermal conductivity cover layer are copper foils.

[0017] Furthermore, one side of the copper foil is provided with several serrated protrusions, which are in thermal contact with the hot end sensing part or the cold end sensing part.

[0018] Furthermore, the first thermal resistance layer, the second thermal resistance layer, and the third thermal resistance layer are all polyimide films.

[0019] Furthermore, the hot end sensing part includes a first through hole and a first thermally conductive metal; the first through hole is disposed on the first thermal resistance layer; the first thermally conductive metal is filled in the first through hole, one side of the first thermally conductive metal is in thermal contact with the upper high thermal conductivity cover layer, and the other side of the first thermally conductive metal is in thermal contact with the current measuring hot end node of the current measuring thermopile.

[0020] Furthermore, the cold-end sensing part includes a second via and a second thermally conductive metal; the second via is disposed on the third thermal resistance layer; the second thermally conductive metal is filled in the second via, one side of the second thermally conductive metal is in thermal contact with the lower high thermal conductivity cover layer, and the other side of the second thermally conductive metal is in thermal contact with the temperature measuring hot end node of the temperature measuring thermocouple or the current measuring cold end node of the current measuring thermopile.

[0021] Furthermore, the thickness of the first thermal resistance layer is determined by the following formula:

[0022] ;

[0023] in: This is the initial temperature of the first thermal resistance layer; The heating temperature applied to the surface where the first thermal resistance layer and the upper high thermal conductivity cover layer are in thermal contact; To allow for the designed transient response time after heating begins At that time, the interior of the first thermal resistance layer is in position The local temperature at the location; The thickness of the first thermal resistance layer, The design transient response time of the first thermal resistance layer. denoted as the thermal diffusivity of the first thermal resistance layer.

[0024] Furthermore, the number of current-measuring thermocouples in the current-measuring thermopile is determined by the following formula:

[0025] ;

[0026] in: Design signal-to-noise ratio for miniature transient thin-film heat flow sensors N The number of current-measuring thermocouples in the current-measuring thermopile. The Seebeck coefficient of a single current-measuring thermocouple in a current-measuring thermopile. The temperature difference between the upper and lower high thermal conductivity capping layers of the miniature transient thin-film heat flux sensor. Boltzmann's constant, At room temperature To measure the resistance of a single current-measuring thermocouple in a current-measuring thermopile, Design measurement bandwidth for a miniature transient thin-film heat flux sensor.

[0027] Furthermore, it also includes: a fourth thermal resistance layer, which is bonded to the third thermal resistance layer, and the lower surface of the fourth thermal resistance layer is flush with the lower surface of the lower high thermal conductivity cover layer.

[0028] Furthermore, the miniature transient thin-film heat flow sensor is fabricated using a flexible printed circuit board process.

[0029] Compared with the prior art, the beneficial effects of this invention are:

[0030] This invention places an upper high thermal conductivity covering layer and a lower high thermal conductivity covering layer on the upper and lower surfaces of a miniature transient thin-film heat flux sensor, respectively. When measuring the surface temperature of the wall to be measured and simultaneously measuring the heat flux density of the non-uniform temperature field on the surface of the wall, the high thermal conductivity of the two high thermal conductivity covering layers promotes the rapid and uniform diffusion of heat on both sides of the sensor, thereby ensuring a uniform temperature field on both sides of the sensor. This avoids interference from local hot spots or cold spots that may exist in the non-uniform temperature field, improves the measurement accuracy and reliability of the sensor in complex thermal environments, and reduces the overall measurement error. Attached Figure Description

[0031] Figure 1 This is an exploded view of the micro transient thin-film heat flow sensor structure in the embodiment;

[0032] Figure 2 This is a schematic diagram of the structure of the first thermal resistance layer in the embodiment;

[0033] Figure 3 This is a schematic diagram of the structure of the first thermopile layer in the embodiment;

[0034] Figure 4 This is a schematic diagram of the structure of the second thermal resistance layer in the embodiment;

[0035] Figure 5 This is a schematic diagram of the structure of the second thermopile layer in the embodiment;

[0036] Figure 6 This is a schematic diagram of the structure of the third thermal resistance layer in the embodiment;

[0037] Figure 7 This is a schematic diagram of the structure of the lower high thermal conductivity overlay layer in the embodiment;

[0038] Figure 8 This is a side view of the miniature transient thin-film heat flow sensor in the embodiment;

[0039] Figure 9 This is used in the embodiment to describe the internal location of the first thermal resistance layer. A Cartesian coordinate system at the location;

[0040] Among them, 1-upper high thermal conductivity cover layer, 2-first thermal resistance layer, 21-first via, 3-first thermopile layer, 31-first temperature measuring strip, 32-first flow measuring strip, 4-second thermal resistance layer, 41-through hole, 5-second thermopile layer, 51-second temperature measuring strip, 52-second flow measuring strip, 6-third thermal resistance layer, 61-second via, 7-lower high thermal conductivity cover layer, 8-fourth thermal resistance layer, 9-temperature measuring terminal, 10-flow measuring terminal, 11-heat flow and temperature sensing part, 12-connection part, 13-serrated protrusion. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0042] See Figures 1 to 8 The present invention provides a miniature transient thin-film heat flux sensor, comprising, from top to bottom, the following:

[0043] Upper high thermal conductivity cover layer 1;

[0044] The first thermal resistance layer 2 is bonded to the upper high thermal conductivity covering layer 1, and the first thermal resistance layer 2 is provided with a heat-sensing part that is in thermal contact with the upper high thermal conductivity covering layer 1.

[0045] The first thermopile layer 3 includes a first temperature measuring strip 31 and a plurality of first flow measuring strips 32, wherein the first temperature measuring strip 31 and the first flow measuring strips 32 are disposed on the lower surface of the first thermal resistance layer 2.

[0046] The second thermal resistance layer 4 is bonded to the lower surface of the first thermal resistance layer 2 and covers the first thermopile layer 3; the second thermal resistance layer 4 is provided with a plurality of through holes 41, and the through holes 41 are filled with conductors.

[0047] The second thermopile layer 5 includes a second temperature measuring strip 51 and a plurality of second flow measuring strips 52;

[0048] The third thermal resistance layer 6 has the second thermopile layer 5 on its upper surface and is bonded to the lower surface of the second thermal resistance layer 4; the third thermal resistance layer 6 also has a cold end sensing part.

[0049] A lower high thermal conductivity cover layer 7 is bonded to the lower surface of the third thermal resistance layer 6 and is in thermal contact with the cold end sensing part.

[0050] Wherein, one end of the first temperature measuring strip 31 is electrically connected to one end of the second temperature measuring strip 51 through a conductor in the through hole 41 to form a temperature measuring thermocouple; the temperature measuring hot end node of the temperature measuring thermocouple is in thermal contact with the cold end sensing part, and the temperature of the lower high thermal conductivity covering layer 7 is sensed through the cold end sensing part; the temperature measuring cold end of the temperature measuring thermocouple is provided with a temperature measuring terminal 9.

[0051] The first flow measurement strip 32 is connected in series with the second flow measurement strip 52 alternately in the positive direction through the conductor in the through hole 41 to form a flow measurement thermopile. The flow measurement hot end node of the flow measurement thermopile senses the temperature of the upper high thermal conductivity covering layer 1 through the hot end sensing part, and the flow measurement cold end node of the flow measurement thermopile senses the temperature of the lower high thermal conductivity covering layer 7 through the cold end sensing part; and the flow measurement strips at both ends of the flow measurement thermopile are respectively provided with flow measurement terminals 10.

[0052] This invention places an upper high thermal conductivity covering layer 1 and a lower high thermal conductivity covering layer 7 on the upper and lower surfaces of a miniature transient thin-film heat flux sensor, respectively. When measuring the surface temperature of the wall to be measured and simultaneously measuring the heat flux density of the non-uniform temperature field on the surface of the wall to be measured, the high thermal conductivity of the upper and lower high thermal conductivity covering layers promotes the rapid and uniform diffusion of heat on both sides of the sensor, thereby ensuring a uniform temperature field on both sides of the sensor. This avoids interference from local hot spots or cold spots that may exist in the non-uniform temperature field, reduces measurement errors caused by lateral heat flux interference, improves the measurement accuracy and reliability of the sensor in complex thermal environments, and reduces the overall measurement error.

[0053] Example

[0054] See Figures 1 to 8 This embodiment further elaborates on the structure of the miniature transient thin-film heat flow sensor. The miniature transient thin-film heat flow sensor consists of a multi-layer structure, stacked together using a flexible printed circuit board manufacturing process. Specifically, the miniature transient thin-film heat flow sensor, from top to bottom, includes an upper high thermal conductivity cover layer 1, a first thermal resistance layer 2, a first thermopile layer 3, a second thermal resistance layer 4, a second thermopile layer 5, a third thermal resistance layer 6, a lower high thermal conductivity cover layer 7, and a fourth thermal resistance layer 8. The upper high thermal conductivity cover layer 1 is an upper copper layer; the first thermal resistance layer 2, the second thermal resistance layer 4, the third thermal resistance layer 6, and the fourth thermal resistance layer 8 are respectively made of a first polyimide film, a second polyimide film, a third polyimide film, and a fourth polyimide film; and the lower high thermal conductivity cover layer 7 is a lower copper layer.

[0055] See Figure 1 , Figure 2 , Figure 4 and Figure 6The lower surface of the first thermal resistance layer 2, i.e., the first polyimide film, is electroplated with a first thermopile layer 3. The first thermopile layer 3 includes a first temperature measuring strip 31 and several first current measuring strips 32, both of which are made of copper. The upper surface of the third polyimide film is electroplated with a second thermopile layer 5. The second thermopile layer 5 includes a second temperature measuring strip 51 and several second current measuring strips 52, both of which are made of constantan. The second thermal resistance layer 4, i.e., the second polyimide film, has several through holes 41, and each through hole 41 is filled with conductive copper.

[0056] See Figures 1 to 6 After the first thermal resistance layer 2, the second thermal resistance layer 4, and the third thermal resistance layer 6 are stacked and pasted from top to bottom, one end of the first temperature measuring strip 31 in the upper layer is electrically connected to one end of the second temperature measuring strip 51 in the lower layer through a conductor copper to form a temperature measuring thermocouple for measuring temperature. The connection between the first temperature measuring strip 31 and the second temperature measuring strip 51 is the hot junction of the temperature measuring thermocouple, and the free ends of the first temperature measuring strip 31 and the second temperature measuring strip 51 are the cold junctions of the temperature measuring thermocouple, and are connected to a temperature measuring terminal 9. The temperature measuring terminal 9 is used to directly output the temperature signal of the solid wall surface being measured. Simultaneously, the upper first current-measuring strip 32 is connected in series alternately with the lower second current-measuring strip 52 via a conductor copper, forming a current-measuring thermopile for measuring heat flow, thereby increasing the total thermoelectric potential output. For example, the upper first current-measuring strip 32 is electrically connected to the lower first second current-measuring strip 52 via a conductor copper, then the lower first second current-measuring strip 52 is electrically connected to the upper second first current-measuring strip 32 via a conductor copper, and then the upper second first current-measuring strip 32 is electrically connected to the lower... The second flow measurement strip 52 is electrically connected, and so on, until all the first flow measurement strips 32 and second flow measurement strips 52 are connected in series. Each first flow measurement strip 32 and its adjacent second flow measurement strip 52 are electrically connected to form a flow measurement thermocouple. Several flow measurement thermocouples are connected in forward direction to form a flow measurement thermopile for measuring heat flux. A flow measurement terminal 10 is provided on each of the flow measurement strips at both ends of the flow measurement thermopile. The flow measurement terminal 10 is used to output a thermoelectric potential signal proportional to the transient heat flux density. It should be noted that each flow measurement thermocouple has a flow measurement hot end node and a flow measurement cold end node.

[0057] Further, see Figure 2The first thermal resistance layer 2 is provided with several hot-end sensing parts, that is, several first through holes 21 are provided on the first polyimide film. Each first through hole 21 corresponds to a hot-end node of the current-measuring thermopile, and each first through hole 21 is filled with copper. The upper high thermal conductivity cover layer 1, which is attached to the upper surface of the first polyimide film, is provided with several serrated protrusions 13. The serrated protrusions 13 make thermal contact with all the hot-end nodes of the current-measuring thermopile through the copper in the first through holes 21, so that all the hot-end nodes of the current-measuring thermopile are concentrated close to the upper surface of the sensor. When the sensor is working, all the hot-end nodes of the current-measuring thermopile sense the temperature of the fluid flowing through the wall of the solid being measured through the hot-end sensing parts and the upper high thermal conductivity cover layer 1.

[0058] Further, see Figure 6 The third thermal resistance layer 6 has several cold-end sensing sections, that is, several second vias 61 are provided on the third polyimide film. Each second via 61 corresponds to a current-measuring cold-end node of the current-measuring thermopile, and each second via 61 is filled with copper. See also Figure 7 The lower high thermal conductivity cover layer 7, adhered to the lower surface of the third polyimide film, also has several serrated protrusions 13. These serrated protrusions 13 make thermal contact with all the cold-end nodes of the current-measuring thermopile through copper in the second through-hole 61, concentrating all the cold-end nodes close to the lower surface of the sensor. Simultaneously, the serrated protrusions 13 make thermal contact with the hot-end nodes of the temperature-measuring thermocouple through copper in the second through-hole 61. When the sensor is applied, the lower high thermal conductivity cover layer 7 is in close contact with the wall surface of the solid being measured. All the cold-end nodes of the current-measuring thermopile sense the temperature of the solid wall surface through the cold-end sensing part and the lower high thermal conductivity cover layer 7. At the same time, the hot-end nodes of the temperature-measuring thermocouple sense the temperature of the solid wall surface through the cold-end sensing part and the lower high thermal conductivity cover layer 7. It should be noted that the lower high thermal conductivity cover layer 7 has the same structure as the upper high thermal conductivity cover layer 1.

[0059] In this embodiment, both the upper high thermal conductivity cover layer 1 and the lower high thermal conductivity cover layer 7 are processed into a sawtooth structure. The sawtooth protrusions 13 are in thermal contact with the hot end node or cold end node of the current-measuring thermopile through the conductor copper to improve the thermal conductivity. Moreover, the sawtooth recesses are filled with adhesive to enhance the bonding strength between the upper high thermal conductivity cover layer 1 and the first thermal resistance layer 2 and the bonding strength between the lower high thermal conductivity cover layer 7 and the third thermal resistance layer 6.

[0060] In this embodiment, a first via 21 is formed on the first thermal resistance layer 2, and a second via 61 is formed on the first thermal resistance layer 2. The positions of the first via 21 and the second via 61 are staggered, so that all the hot-end nodes of the flow measurement thermopile are concentrated close to the upper surface of the sensor to sense the high temperature of the fluid flowing through the solid wall being measured, and all the cold-end nodes of the flow measurement thermopile are concentrated close to the lower surface of the sensor to sense the low temperature of the solid wall being measured, thereby forming a large temperature difference driving thermoelectric potential.

[0061] In this embodiment, the thickness of the first thermal resistance layer 2 is determined by the following formula:

[0062] ;

[0063] in: The initial temperature of the first thermal resistance layer 2; The heating temperature applied to the surface in thermal contact between the first thermal resistance layer 2 and the upper high thermal conductivity cover layer 1; To allow for the designed transient response time after heating begins At that time, the interior of the first thermal resistance layer 2 is in position The local temperature at the location; The term is dimensionless temperature, when hour, The value is 0.95; The thickness of the first thermal resistance layer 2; The design transient response time of the first thermal resistance layer 2; The thermal diffusivity of the first thermal resistance layer 2; 0~ The integer. In calculating the thickness of the first thermal resistance layer 2. hour, The value is taken as room temperature, and any temperature value is arbitrarily assigned within the design operating temperature range of the miniature transient thin-film heat flux sensor. And must meet This embodiment considers the initial temperature of the first thermal resistance layer 2, the heating temperature applied to the surface of the first thermal resistance layer 2 in thermal contact with the upper high thermal conductivity cover layer 1, the designed transient response time, and the thermal diffusivity to achieve accurate calculation of the thickness of the first thermal resistance layer 2. This ensures that the miniature transient thin-film heat flow sensor can respond quickly and accurately to changes in fluid temperature, thereby achieving high-precision heat flow measurement. It should be noted that the thickness calculation method for the third thermal resistance layer 6 is the same as that for the first thermal resistance layer 2.

[0064] It should be noted that, Figure 9 The description of the interior of the first thermal resistance layer 2 is given. A Cartesian coordinate system is used to define the position. The Y-axis of this system is established on the lower surface of the first thermal resistance layer 2, i.e., the plane in contact with the first thermopile layer 3. The X-axis is established along the thickness direction of the first thermal resistance layer 2, pointing towards the upper high thermal conductivity covering layer 1. The origin of the coordinate system is located at the edge of the first thermal resistance layer 2. Furthermore, The initial temperature of the first thermal resistance layer 2 is set. When calculating the thickness of the first thermal resistance layer 2, the lower surface of the first thermal resistance layer 2 is set to maintain the initial temperature. That is, when hour, The temperature of the upper surface of the first thermal resistance layer 2 is set to That is, when hour, .

[0065] In this embodiment, the number of current-measuring thermocouples in the current-measuring thermopile is determined by the following formula:

[0066] ;

[0067] in: Design signal-to-noise ratio for miniature transient thin-film heat flow sensors; N The number of current-measuring thermocouples in the current-measuring thermopile; The Seebeck coefficient of a single current-measuring thermocouple in a current-measuring thermopile; The temperature difference between the upper high thermal conductivity coating layer 1 and the lower high thermal conductivity coating layer 7 of the miniature transient thin-film heat flux sensor; is the Boltzmann constant, with a value of 1.38 × 10⁻⁶. -23 J / K; The value is 300K, which is the room temperature. The resistance of a single current-measuring thermocouple in a current-measuring thermopile; This embodiment considers the design signal-to-noise ratio, design measurement bandwidth, Seebeck coefficient of a single flow-measuring thermocouple in the flow-measuring thermopile, temperature difference between the upper high thermal conductivity layer 1 and the lower high thermal conductivity layer 7, and room temperature to accurately calculate the number of flow-measuring thermocouples in the flow-measuring thermopile, thereby improving the measurement accuracy of the miniature transient thin-film heat flow sensor.

[0068] It should be noted that the first temperature measuring strip 31 and the first flow measuring strip 32 are copper strips, while the second temperature measuring strip 51 and the second flow measuring strip 52 are constantan strips.

[0069] Furthermore, a fourth thermal resistance layer 8 is also attached to the lower surface of the third thermal resistance layer 6, and the fourth thermal resistance layer 8 is flush with the lower high thermal conductivity cover layer 7, so that the lower surface of the micro transient thin film heat flow sensor is flat and can be firmly attached to the solid wall surface to be measured by adhesive.

[0070] It should be noted that, see Figure 8In the miniature transient thin-film heat flux sensor, the portion with the upper high thermal conductivity covering layer 1 and the lower high thermal conductivity covering layer 7 is defined as the heat flux and temperature sensing part 11, and the remaining portion is the wiring part 12. The temperature-sensing hot-end node of the temperature-sensing thermocouple, all flow-sensing hot-end nodes of the flow-sensing thermopile, and all flow-sensing cold-end nodes are located in the heat flux and temperature sensing part 11. The flow-sensing terminal 10 and the temperature-sensing terminal 9 are located in the wiring part 12. When applying the sensor, the flow-sensing terminal 10 and the temperature-sensing terminal 9 are respectively led out to an external data acquisition system via leads to achieve synchronous high-precision measurement of the heat flux density and wall temperature of the solid surface being measured. Furthermore, since one of the temperature-sensing terminals 9 is located on the third thermal resistance layer 6, before applying the sensor, holes must be drilled in the first thermal resistance layer 2 and the second thermal resistance layer 4 to expose the temperature-sensing terminal 9 on the third thermal resistance layer 6 for wiring. It should be noted that... Figure 8 The side view of the miniature transient thin-film heat flow sensor shown only shows the heat flow and temperature sensing part 11 and the wiring part 12. Therefore, the first thermopile layer 3 and the second thermopile layer 5 are omitted.

[0071] This invention uses flexible printed circuit board processing technology to fabricate a miniature transient thin-film heat flow sensor, which gives the miniature transient thin-film heat flow sensor a certain degree of flexibility and makes it suitable for thermal measurement on non-flat surfaces.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniature transient thin-film heat flux sensor, characterized in that, Including those stacked from top to bottom: High thermal conductivity overlay (1); The first thermal resistance layer (2) is bonded to the upper high thermal conductivity covering layer (1), and the first thermal resistance layer (2) is provided with a heat-sensing part that is in thermal contact with the upper high thermal conductivity covering layer (1). The first thermopile layer (3) includes a first temperature measuring strip (31) and a plurality of first flow measuring strips (32), wherein the first temperature measuring strip (31) and the first flow measuring strips (32) are disposed on the lower surface of the first thermal resistance layer (2); The second thermal resistance layer (4) is bonded to the lower surface of the first thermal resistance layer (2) and covers the first thermopile layer (3); the second thermal resistance layer (4) is provided with a plurality of through holes (41), and the through holes (41) are filled with conductors; The second thermopile (5) includes a second temperature measuring strip (51) and a plurality of second flow measuring strips (52); The third thermal resistance layer (6) has the second thermopile layer (5) on its upper surface and is bonded to the lower surface of the second thermal resistance layer (4); the third thermal resistance layer (6) also has a cold end sensing part. A lower high thermal conductivity cover layer (7) is bonded to the lower surface of the third thermal resistance layer (6) and in thermal contact with the cold end sensing part; Wherein, one end of the first temperature measuring strip (31) is electrically connected to one end of the second temperature measuring strip (51) through a conductor in the through hole (41) to form a temperature measuring thermocouple; the hot end node of the temperature measuring thermocouple is in thermal contact with the cold end sensing part, and the temperature of the lower high thermal conductivity covering layer (7) is sensed through the cold end sensing part; the cold end of the temperature measuring thermocouple is provided with a temperature measuring terminal (9). The first flow measurement strip (32) is connected in series with the second flow measurement strip (52) alternately in the positive direction through the conductor in the through hole (41) to form a flow measurement thermopile. The flow measurement hot end node of the flow measurement thermopile senses the temperature of the upper high thermal conductivity covering layer (1) through the hot end sensing part, and the flow measurement cold end node of the flow measurement thermopile senses the temperature of the lower high thermal conductivity covering layer (7) through the cold end sensing part; and the flow measurement strips at both ends of the flow measurement thermopile are respectively provided with flow measurement terminals (10). The upper high thermal conductivity covering layer (1) and the lower high thermal conductivity covering layer (7) are copper foils; one side of the copper foil is provided with a plurality of serrated protrusions (13), and the serrated protrusions (13) are in thermal contact with the hot end sensing part or the cold end sensing part. The thickness of the first thermal resistance layer (2) is determined by the following formula: ； in: The initial temperature of the first thermal resistance layer (2); The heating temperature applied to the surface in thermal contact between the first thermal resistance layer (2) and the upper high thermal conductivity covering layer (1); To allow for the designed transient response time after heating begins At that time, the interior of the first thermal resistance layer (2) is in position The local temperature at the location; The thickness of the first thermal resistance layer (2) is denoted as . The design transient response time of the first thermal resistance layer (2); is the thermal diffusivity of the first thermal resistance layer (2).

2. The miniature transient thin-film heat flux sensor according to claim 1, characterized in that, The first thermal resistance layer (2), the second thermal resistance layer (4) and the third thermal resistance layer (6) are all polyimide films, the first temperature measuring strip (31) and the first current measuring strip (32) are copper strips, and the second temperature measuring strip (51) and the second current measuring strip (52) are constantan strips.

3. The miniature transient thin-film heat flux sensor according to claim 2, characterized in that, The hot end sensing part includes a first through hole (21) and a first thermally conductive metal; the first through hole (21) is disposed on the first thermal resistance layer (2); the first thermally conductive metal is filled in the first through hole (21), one side of the first thermally conductive metal is in thermal contact with the upper high thermal conductivity cover layer (1), and the other side of the first thermally conductive metal is in thermal contact with the current measuring hot end node of the current measuring thermopile.

4. The miniature transient thin-film heat flux sensor according to claim 3, characterized in that, The cold-end sensing part includes a second via (61) and a second thermally conductive metal; the second via (61) is disposed on the third thermal resistance layer (6); the second thermally conductive metal is filled in the second via (61), one side of the second thermally conductive metal is in thermal contact with the lower high thermal conductivity cover layer (7), and the other side of the second thermally conductive metal is in thermal contact with the temperature measuring hot end node of the temperature measuring thermocouple or the current measuring cold end node of the current measuring thermopile.

5. The miniature transient thin-film heat flux sensor according to claim 4, characterized in that, The number of current-measuring thermocouples in the current-measuring thermopile is determined by the following formula: ； in: Design signal-to-noise ratio for miniature transient thin-film heat flow sensors N The number of current-measuring thermocouples in the current-measuring thermopile. The Seebeck coefficient of a single current-measuring thermocouple in a current-measuring thermopile. The temperature difference between the upper high thermal conductivity capping layer (1) and the lower high thermal conductivity capping layer (7) of the miniature transient thin-film heat flux sensor. Boltzmann's constant, At room temperature To measure the resistance of a single current-measuring thermocouple in a current-measuring thermopile, Design measurement bandwidth for a miniature transient thin-film heat flux sensor.

6. The miniature transient thin-film heat flux sensor according to claim 1, characterized in that, Also includes: The fourth thermal resistance layer (8) is bonded to the third thermal resistance layer (6), and the lower surface of the fourth thermal resistance layer (8) is flush with the lower surface of the lower high thermal conductivity cover layer (7).

7. The miniature transient thin-film heat flux sensor according to any one of claims 1-6, characterized in that, The miniature transient thin-film heat flow sensor is manufactured using a flexible printed circuit board process.

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