Thin-film resistor thermal flow sensor with double-sided asymmetric integrated structure

Abstract

The utility model discloses a double-sided asymmetric integrated structure thin film resistor thermal flow sensor, and belongs to the technical field of flow sensors. The utility model aims to solve the problems that an existing resistance thermal flow sensor is composed of a plurality of discrete devices, and the medium flow measurement accuracy is low. The thin-film resistance thermal type flow sensor is of a multi-layer structure and comprises a ceramic substrate substrate layer, a top-layer temperature sensitive thin film layer, a top-layer glass sealing passivation layer, top-layer electrode slurry, top-layer glass slurry, a top-layer lead, a bottom-layer temperature sensitive thin film layer, a bottom-layer glass sealing passivation layer, bottom-layer electrode slurry, bottom-layer glass slurry and a bottom-layer lead. The film sensitive grids with different resistance values are manufactured on the front surface and the back surface of the ceramic substrate, the front temperature sensitive unit and the back temperature sensitive unit work independently at the same time, the sensitive grid with small resistance value at the top layer of the front surface measures the speed, the sensitive grid with large resistance value at the bottom layer of the back surface measures the temperature, and the sensor can be widely applied to high-reliability and high-precision medium flow measurement in automobiles and industries.

Description

Technical Field

[0001] The utility model belongs to the technical field of flow sensors, and in particular relates to a thin film resistance thermal flow sensor with a double-sided asymmetric integrated structure. Background Art

[0002] There are many ways to test flow, the most common ones are: differential pressure type, float type, turbine type, electromagnetic type and thermal type. Thermal flowmeters are made based on the principle of convection exchange between heated objects and fluids. Resistive thermal flow sensors are one of the main types of thermal flowmeters. They have the characteristics of small size, fast response speed, good stability and acid and corrosion resistance. The measurement principle of existing resistance thermal flow sensors is: two thermistors are added to the measuring pipeline, one as a temperature measuring resistor for measuring the temperature of the measured medium, and the other as a speed measuring resistor for measuring the speed of the measured medium. Heat is provided to the speed measuring resistor at a constant power to heat it to a temperature higher than the ambient temperature. According to the principle of heat conduction, the flow of the medium takes away part of the heat on the surface of the speed measuring resistor. The greater the flow rate, the smaller the temperature difference between the two thermistors. Measuring the temperature difference between the two thermistors that changes with the medium flow rate can reflect the medium flow rate. However, the existing resistive thermal flow sensor structure consists of two discrete resistor devices, and the product has problems such as inconvenience in use and poor reliability. In addition, since the nominal resistance of the temperature measuring thermistor is small, its sensitivity to medium temperature measurement is low. According to the principle that the flow measurement value is related to the temperature difference between the two thermistors, the existing flow meter has the problem of low flow measurement accuracy and complex structure caused by discrete devices. Utility Model Content

[0003] The purpose of the utility model is to solve the problem that the existing resistance thermal flow sensor is composed of multiple discrete components and has low medium flow measurement accuracy, and to provide a double-sided asymmetric integrated structure thin film resistance thermal flow sensor.

[0004] This utility model proposes a double-sided asymmetric processing technology for the base layer 1 of a ceramic substrate. The process utilizes a double-sided micromachining process for the ceramic substrate. Temperature-sensitive resistor film sensitive gates of varying resistance values ​​are fabricated on the front and back sides of the ceramic substrate. The small-resistance sensitive gate acts as a speed-measuring resistor, while the large-resistance sensitive gate acts as a temperature-measuring resistor. This single-chip device achieves flow measurement and improves measurement reliability. Simultaneously, increasing the resistance of the temperature-measuring resistor increases temperature measurement sensitivity, thereby enhancing flow measurement accuracy.

[0005] A double-sided asymmetric integrated structure thin film resistance thermal flow sensor has a multi-layer structure, including a ceramic substrate substrate layer 1, a top temperature sensitive thin film layer 2, a top glass sealing passivation layer 3, a top electrode paste 4, a top glass paste 5, two top leads 6, a bottom temperature sensitive thin film layer 7, a bottom glass sealing passivation layer 8, a bottom electrode paste 9, a bottom glass paste 10 and two bottom leads 11;

[0006] The top temperature-sensitive film layer 2 and the bottom temperature-sensitive film layer 7 are respectively placed on the front and back surfaces of the ceramic substrate layer 1; the top temperature-sensitive film layer 2 has a top temperature-sensitive metal line pattern 12 on its surface away from the ceramic substrate layer 1; and the bottom temperature-sensitive film layer 7 has a bottom temperature-sensitive metal line pattern 13 on its surface away from the ceramic substrate layer 1.

[0007] The top temperature-sensitive metal line pattern 12 includes a top temperature-sensitive portion 12-1 and two top lead pads 12-2; the bottom temperature-sensitive metal line pattern 13 includes a bottom temperature-sensitive portion 13-1 and two bottom lead pads 13-2; the top electrode paste 4 covers the top temperature-sensitive portion 12-1, and forms a top glass sealing passivation layer 3 on the top temperature-sensitive portion 12-1; the bottom electrode paste 9 covers the bottom temperature-sensitive portion 13-1, and forms a bottom glass sealing passivation layer 8 on the bottom temperature-sensitive portion 13-1;

[0008] The two top leads 6 are welded to the two top lead pads 12-2 through the top electrode paste 4, and the top glass paste 5 is provided on the welding points to protect the welding points;

[0009] The two bottom leads 11 are welded to the two bottom lead pads 13 - 2 through the bottom electrode paste 9 , and bottom glass paste 10 is provided on the welding points to protect the welding points.

[0010] Principle of this utility model:

[0011] When the double-sided asymmetric integrated thin-film resistive thermal flow sensor developed by the utility model is in operation, the front sensitive resistor grid is a speed-measuring resistor used to measure the speed of the measured medium, and the back sensitive resistor grid is a temperature-measuring resistor used to measure the temperature of the measured medium. The flow meter is placed in the pipeline, and the speed-measuring resistor is placed facing the direction of the medium flow. A constant power is applied to the heater to heat the speed-measuring resistor. When the medium is stationary, the surface temperature difference △t between the speed-measuring resistor and the temperature-measuring resistor is maximum. As the medium flows, the surface temperature difference between the two resistors decreases. The greater the medium flow rate, the smaller the temperature difference between the two resistors. The temperature-measuring and speed-measuring resistors are connected to two Wheatstone bridges respectively. When the medium flows through the device, the different temperatures on the front and back sides cause the front and back sensitive resistor grids of the device to exhibit different resistance values, thereby making each bridge unbalanced. The medium flow rate is reflected by detecting the voltage difference between the bridges.

[0012] The double-sided asymmetric integrated structure thin film resistance thermal flow sensor developed by the utility model has a multi-layer structure, the first layer is a top glass sealing passivation layer 3, the second layer is a top temperature sensitive thin film layer 2, the third layer is a ceramic substrate substrate layer 1, the fourth layer is a bottom temperature sensitive thin film layer 7, and the bottom layer is a bottom glass sealing passivation layer 8; a specific double-sided polished ceramic substrate is selected as the substrate material, and during the manufacturing process, a sputtering method is used to deposit sensitive films on the front and back sides of the ceramic substrate, and photolithography and fine etching plane processing technology are used to process sensitive grids with different resistance values ​​on the front and back sensitive films respectively. The sensitive grid with a small resistance value measures the speed, and the sensitive grid with a large resistance value measures the temperature, thereby improving the flow measurement accuracy. The positive and negative sensitive resistance grids are adjusted to the expected resistance value by laser resistance adjustment method, and the glass sealing process is used to passivate and protect the positive and negative sensitive grid patterns of the ceramic substrate. Finally, the single device is manufactured through chip separation, lead welding and solder joint glass protection.

[0013] Advantages of this utility model:

[0014] 1. This utility model is a double-sided asymmetric integrated structure thin film resistance thermal flow sensor. By using the double-sided micromachining process of a ceramic substrate, thin film sensitive grids with different resistance values ​​are made on the front and back sides of the ceramic substrate. The two temperature sensitive units on the front and back sides work simultaneously and independently. The sensitive grid with a small resistance on the top side of the front side measures the speed, while the sensitive grid with a large resistance on the bottom side of the back side measures the temperature, thereby achieving accurate measurement of the medium flow.

[0015] 2. This utility model adopts an integrated monolithic integrated design. The positive and negative thin film temperature sensitive units are located on the same chip. The product is small in size and easy to install and use. It solves the problem of large size and low accuracy of thermal medium flow meters composed of multiple discrete devices.

[0016] 3. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor of the utility model has the advantages of small size, reliable operation and high measurement accuracy, and can be widely used in high-reliability and high-precision medium flow measurement in the automotive and industrial fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of a thin film resistance thermal flow sensor with a double-sided asymmetric integrated structure according to the present invention;

[0018] Figure 2 This is a discrete schematic diagram of a double-sided asymmetric integrated structure thin film resistance thermal flow sensor of the utility model;

[0019] Figure 3 A sensitive grid pattern of the top temperature sensitive thin film layer on the front side of the ceramic substrate layer;

[0020] Figure 4It is a sensitive grid pattern of the bottom temperature sensitive thin film layer on the reverse side of the ceramic substrate substrate layer. DETAILED DESCRIPTION

[0021] Specific embodiment 1: This embodiment is a double-sided asymmetric integrated structure thin film resistance thermal flow sensor, which is a multi-layer structure, including a ceramic substrate substrate layer 1, a top temperature sensitive thin film layer 2, a top glass sealing passivation layer 3, a top electrode paste 4, a top glass paste 5, two top leads 6, a bottom temperature sensitive thin film layer 7, a bottom glass sealing passivation layer 8, a bottom electrode paste 9, a bottom glass paste 10 and two bottom leads 11;

[0022] The top temperature-sensitive film layer 2 and the bottom temperature-sensitive film layer 7 are respectively placed on the front and back surfaces of the ceramic substrate layer 1; the top temperature-sensitive film layer 2 has a top temperature-sensitive metal line pattern 12 on its surface away from the ceramic substrate layer 1; and the bottom temperature-sensitive film layer 7 has a bottom temperature-sensitive metal line pattern 13 on its surface away from the ceramic substrate layer 1.

[0023] The top temperature-sensitive metal line pattern 12 includes a top temperature-sensitive portion 12-1 and two top lead pads 12-2; the bottom temperature-sensitive metal line pattern 13 includes a bottom temperature-sensitive portion 13-1 and two bottom lead pads 13-2; the top electrode paste 4 covers the top temperature-sensitive portion 12-1, and forms a top glass sealing passivation layer 3 on the top temperature-sensitive portion 12-1; the bottom electrode paste 9 covers the bottom temperature-sensitive portion 13-1, and forms a bottom glass sealing passivation layer 8 on the bottom temperature-sensitive portion 13-1;

[0024] The two top leads 6 are welded to the two top lead pads 12-2 through the top electrode paste 4, and the top glass paste 5 is provided on the welding points to protect the welding points;

[0025] The two bottom leads 11 are welded to the two bottom lead pads 13 - 2 through the bottom electrode paste 9 , and bottom glass paste 10 is provided on the welding points to protect the welding points.

[0026] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the ceramic substrate substrate layer 1 is made of AlN ceramic, SiC ceramic, Si3N4 ceramic or Al2O3 ceramic. The other steps are the same as those in specific embodiment 1.

[0027] Specific Embodiment 3: This embodiment differs from either Specific Embodiment 1 or 2 in that the top-layer temperature-sensitive metal line pattern 12 and the bottom-layer temperature-sensitive metal line pattern 13 are connected to two top-layer lead pads 12-2 and two bottom-layer lead pads 13-2, respectively, via the top-layer electrode paste 4 and bottom-layer electrode paste 9 applied to the surfaces, connecting to two top-layer leads 6 and two bottom-layer leads 11, thereby enabling signal transmission between the positive and negative temperature-sensitive units. Other steps are the same as Specific Embodiment 1 or 2.

[0028] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that metal films are deposited on the front and back surfaces of a ceramic substrate 1 by sputtering to form a top temperature-sensitive thin film layer 2 and a bottom temperature-sensitive thin film layer 7. The remaining steps are the same as those of specific embodiments 1 to 3.

[0029] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the thickness of the top temperature-sensitive film layer 2 is 1.2 μm to 1.4 μm, and the thickness of the bottom temperature-sensitive film layer 7 is 1.2 μm to 1.4 μm. The other steps are the same as specific embodiments 1 to 4.

[0030] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the metal film is a platinum film or a copper film. The other steps are the same as those of specific embodiments 1 to 5.

[0031] Specific Embodiment 7: This embodiment differs from Specific Embodiments 1 to 6 in that a top temperature-sensing portion 12-1 and two top lead pads 12-2 are fabricated on the top temperature-sensing metal line pattern 12 using micromachining methods using photolithography and dry etching; a bottom temperature-sensing portion 13-1 and two bottom lead pads 13-2 are fabricated on the bottom temperature-sensing metal line pattern 13; and the resistance values ​​of the sensitive gates of the top temperature-sensing metal line pattern 12 and the bottom temperature-sensing metal line pattern 13 are different. The other steps are the same as Specific Embodiments 1 to 6.

[0032] Specific Embodiment 8: This embodiment differs from Specific Embodiments 1 to 7 in that the top temperature-sensing portion 12-1 has a line width of 20 μm to 30 μm and a resistance of 20 Ω to 100 Ω, and is a speed-measuring resistor. The bottom temperature-sensing portion 13-1 has a line width of 6 μm to 15 μm and a resistance of 100 Ω to 1000 Ω, and is a temperature-measuring resistor. Other steps are the same as Specific Embodiments 1 to 7.

[0033] Specific Embodiment 9: This embodiment differs from Specific Embodiments 1 to 8 in that a ceramic substrate substrate layer 1 is fabricated using a micromachining process; and the two top leads 6 and two bottom leads 11 are made of platinum or silver. The remaining steps are the same as Specific Embodiments 1 to 8.

[0034] Specific embodiment 10: The difference between this embodiment and specific embodiments 1 to 9 is that the material of the top electrode paste 4 and the bottom electrode paste 9 is platinum paste or silver palladium paste; the sintering temperature of the top glass paste 5 and the bottom glass paste 10 is 700℃~1000℃; the thermal expansion coefficient is 3~9×10 -6 / °C. The other steps are the same as those in the first to ninth embodiments.

[0035] The following examples are used to verify the beneficial effects of the present invention:

[0036] Example 1: Combination Figures 1 to 4 This embodiment describes a double-sided asymmetric integrated thin film resistance thermal flow sensor having a multi-layer structure, including a ceramic substrate layer 1, a top temperature-sensitive thin film layer 2, a top glass sealing passivation layer 3, a top electrode paste 4, a top glass paste 5, two top leads 6, a bottom temperature-sensitive thin film layer 7, a bottom glass sealing passivation layer 8, a bottom electrode paste 9, a bottom glass paste 10, and two bottom leads 11.

[0037] The top temperature-sensitive film layer 2 and the bottom temperature-sensitive film layer 7 are respectively placed on the front and back surfaces of the ceramic substrate layer 1; the top temperature-sensitive film layer 2 has a top temperature-sensitive metal line pattern 12 on its surface away from the ceramic substrate layer 1; and the bottom temperature-sensitive film layer 7 has a bottom temperature-sensitive metal line pattern 13 on its surface away from the ceramic substrate layer 1.

[0038] The top temperature-sensitive metal line pattern 12 includes a top temperature-sensitive portion 12-1 and two top lead pads 12-2; the bottom temperature-sensitive metal line pattern 13 includes a bottom temperature-sensitive portion 13-1 and two bottom lead pads 13-2; the top electrode paste 4 covers the top temperature-sensitive portion 12-1, and forms a top glass sealing passivation layer 3 on the top temperature-sensitive portion 12-1; the bottom electrode paste 9 covers the bottom temperature-sensitive portion 13-1, and forms a bottom glass sealing passivation layer 8 on the bottom temperature-sensitive portion 13-1;

[0039] The two top leads 6 are welded to the two top lead pads 12-2 through the top electrode paste 4, and the top glass paste 5 is provided on the welding points to protect the welding points;

[0040] The two bottom leads 11 are welded to the two bottom lead pads 13-2 through the bottom electrode paste 9, and the bottom glass paste 10 is provided on the welding points to protect the welding points;

[0041] The material of the ceramic substrate layer 1 is Al2O3 ceramic;

[0042] The top temperature-sensitive metal line pattern 12 and the bottom temperature-sensitive metal line pattern 13 are connected to the two top leads 6 and the two bottom leads 11 through the two top lead pads 12-2 and the two bottom lead pads 13-2, respectively, via the top electrode paste 4 and the bottom electrode paste 9 coated on the surface, to achieve signal transmission between the positive and negative temperature sensitive units;

[0043] Depositing metal thin films on the front and back surfaces of the ceramic substrate layer 1 by sputtering to form a top temperature sensitive thin film layer 2 and a bottom temperature sensitive thin film layer 7;

[0044] The thickness of the top temperature-sensitive film layer 2 is 1.3 μm; the thickness of the bottom temperature-sensitive film layer 7 is 1.3 μm;

[0045] The metal film is a platinum film, and the raw material used is a high-purity platinum target;

[0046] A top temperature-sensing portion 12-1 and two top lead pads 12-2 are fabricated on the top temperature-sensing metal line pattern 12 using photolithography and ion beam etching. A bottom temperature-sensing portion 13-1 and two bottom lead pads 13-2 are fabricated on the bottom temperature-sensing metal line pattern 13. The resistance values ​​of the sensitive gates of the top temperature-sensing metal line pattern 12 and the bottom temperature-sensing metal line pattern 13 are different.

[0047] The top temperature sensing portion 12-1 has a line width of 30 μm and a resistance of 20 Ω, and is a speed measuring resistor; the bottom temperature sensing portion 13-1 has a line width of 15 μm and a resistance of 100 Ω, and is a temperature measuring resistor;

[0048] The ceramic substrate layer 1 is prepared by micromachining technology; the two top leads 6 and the two bottom leads 11 are made of platinum;

[0049] The material of the top electrode slurry 4 and the bottom electrode slurry 9 is platinum slurry;

[0050] The sintering temperature of the top glass paste 5 and the bottom glass paste 10 is 1000°C; the thermal expansion coefficient is 7.2×10 -6 / ℃.

[0051] The air medium flow rate was tested using a double-sided asymmetric integrated structure thin film resistance thermal flow sensor prepared in Example 1, with an accuracy of ±1% FS, while the accuracy of the existing flow sensor made using two discrete devices was only ±3% FS. It can be seen that the double-sided asymmetric integrated structure thin film resistance thermal flow sensor prepared in Example 1 can achieve accurate measurement of medium flow.

[0052] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of this patent.

Claims

1. A double-sided asymmetric integrated structure thin film resistance thermal flow sensor, characterized in that The thin film resistance thermal flow sensor has a multi-layer structure, comprising a ceramic substrate layer (1), a top temperature sensitive thin film layer (2), a top glass sealing passivation layer (3), a top electrode paste (4), a top glass paste (5), two top leads (6), a bottom temperature sensitive thin film layer (7), a bottom glass sealing passivation layer (8), a bottom electrode paste (9), a bottom glass paste (10) and two bottom leads (11); The top temperature-sensitive film layer (2) and the bottom temperature-sensitive film layer (7) are respectively placed on the front and back surfaces of the ceramic substrate substrate layer (1); the top temperature-sensitive film layer (2) contains a top temperature-sensitive metal line pattern (12) on its surface away from the ceramic substrate substrate layer (1); and the bottom temperature-sensitive film layer (7) contains a bottom temperature-sensitive metal line pattern (13) on its surface away from the ceramic substrate substrate layer (1); The top temperature-sensitive metal line pattern (12) includes a top temperature-sensitive portion (12-1) and two top lead pads (12-2); the bottom temperature-sensitive metal line pattern (13) includes a bottom temperature-sensitive portion (13-1) and two bottom lead pads (13-2); the top electrode paste (4) covers the top temperature-sensitive portion (12-1), and forms a top glass sealing passivation layer (3) on the top temperature-sensitive portion (12-1); the bottom electrode paste (9) covers the bottom temperature-sensitive portion (13-1), and forms a bottom glass sealing passivation layer (8) on the bottom temperature-sensitive portion (13-1); The two top-layer leads (6) are welded to the two top-layer lead pads (12-2) through the top-layer electrode paste (4), and a top-layer glass paste (5) is provided on the welding points to protect the welding points; The two bottom leads (11) are welded on two bottom lead pads (13-2) through bottom electrode paste (9), and bottom glass paste (10) is provided on the welding points to protect the welding points.

2. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that The ceramic substrate layer (1) is AlN ceramic, SiC ceramic, Si3N4 ceramic or Al2O3 ceramic.

3. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that The top temperature-sensitive metal line pattern (12) and the bottom temperature-sensitive metal line pattern (13) are connected to two top leads (6) and two bottom leads (11) respectively through two top lead pads (12-2) and two bottom lead pads (13-2), via the top electrode paste (4) and the bottom electrode paste (9) coated on the surface, thereby realizing signal transmission of the positive and negative temperature-sensitive units.

4. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that Metal films are deposited on the front and back surfaces of a ceramic substrate layer (1) by sputtering to form a top temperature-sensitive film layer (2) and a bottom temperature-sensitive film layer (7).

5. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 4, characterized in that The thickness of the top temperature-sensitive film layer (2) is 1.2 μm to 1.4 μm; the thickness of the bottom temperature-sensitive film layer (7) is 1.2 μm to 1.4 μm.

6. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 4, characterized in that The metal film is a platinum film or a copper film.

7. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that A top temperature-sensitive portion (12-1) and two top lead pads (12-2) are processed on a top temperature-sensitive metal line pattern (12) using a micromachining method of photolithography and dry etching; a bottom temperature-sensitive portion (13-1) and two bottom lead pads (13-2) are processed on a bottom temperature-sensitive metal line pattern (13); the resistance values ​​of the sensitive gates of the top temperature-sensitive metal line pattern (12) and the bottom temperature-sensitive metal line pattern (13) are different.

8. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that The line width of the top temperature sensing part (12-1) is 20μm to 30μm, and the resistance is 20Ω to 100Ω, which is a speed measuring resistor; the line width of the bottom temperature sensing part (13-1) is 6μm to 15μm, and the resistance is 100Ω to 1000Ω, which is a temperature measuring resistor.

9. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that A ceramic substrate layer (1) is prepared by adopting a micromachining process; the two top-layer leads (6) and the two bottom-layer leads (11) are made of platinum or silver.

10. The double-sided asymmetric integrated structure thin film resistance thermal flow sensor according to claim 1, characterized in that The material of the top electrode paste (4) and the bottom electrode paste (9) is platinum paste or silver palladium paste; the sintering temperature of the top glass paste (5) and the bottom glass paste (10) is 700°C to 1000°C; the thermal expansion coefficient is (3 to 9)×10 -6 / ℃.

Images