CN216246574U

CN216246574U - MEMS (micro-electromechanical systems) thermal mass flow meter with large range ratio

Info

Publication number: CN216246574U
Application number: CN202122859635.5U
Authority: CN
Inventors: 胡国庆; 田伟; 卢笛
Original assignee: Qingdao Xinsheng Micro Nano Electronic Technology Co ltd
Current assignee: Qingdao Xinsheng Micro Nano Electronic Technology Co ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-04-08
Anticipated expiration: 2031-11-22

Abstract

The utility model discloses an MEMS (micro electro mechanical system) thermal mass flow meter with a large range ratio, which comprises an air passage seat provided with a flow passage, wherein the flow passage comprises a main flow passage and a sub-flow passage, an air inlet and an air outlet are arranged on the main flow passage, a Venturi tube structure is arranged on the main flow passage, a packaging plate is arranged on the sub-flow passage, an MEMS flow chip is packaged on the packaging plate, and the packaging plate is respectively connected with at least two main circuit boards with different voltage amplification factors. According to the MEMS thermal mass flow meter, the main circuit boards with different voltage amplification factors are arranged, so that when the flow to be measured is small, the signals of the MEMS flow chip can be processed through the main circuit board with the large amplification factor; when the flow to be measured is large, the signals of the MEMS flow chip are processed through the main circuit board with small amplification factor, so that the problem that the prior art cannot give consideration to large and small flows is solved, and large-range ratio and high-precision measurement is realized.

Description

MEMS (micro-electromechanical systems) thermal mass flow meter with large range ratio

Technical Field

The utility model relates to the technical field of flow measurement, in particular to an MEMS (micro-electromechanical systems) thermal mass flowmeter with a large range ratio.

Background

Accurate measurement of flow is a fundamental requirement for industrial production and scientific research. The flow sensors are of various types, and among them, the thermal mass flow meter manufactured based on the MEMS flow chip is widely used due to its advantages of simple structure, small size, high precision, fast response, low power consumption, and the like.

The MEMS flow chip mainly comprises a heater and thermosensitive elements symmetrically distributed on the upper and lower parts of the heater. The heater provides certain power to enable the surface temperature of the chip to be higher than the ambient temperature, when no air flow exists, the surface temperature is normally distributed by taking the heater as the center, and the upstream thermosensitive element and the downstream thermosensitive element have the same electric signal; when air flow exists, the surface temperature distribution is deviated due to the heat transferred by the gas molecules, the electric signals of the upstream and downstream thermosensitive elements are different, and the gas flow can be calculated by acquiring the difference by using a rear-end signal processing circuit.

The thermal mass flowmeter based on the MEMS flow chip is particularly suitable for measuring micro flow. Referring to fig. 1, when the flow rate to be measured is small, the diameter of the flow channel 2 is small, and the flow rate passing through the MEMS flow chip 3 is within the sensitive range, so that high-precision measurement can be achieved. When the flow to be measured is large, the flow directly passing through the MEMS flow chip 3 exceeds the sensitive range. Therefore, when the flow rate to be measured is large, the prior art often adopts a flow-splitting gas path structure, please refer to fig. 2, a main flow path 204 and a sub-flow path 203 are arranged in the gas path seat 1, and a venturi tube structure 205 is arranged on the main flow path 204, so as to ensure that only a small amount of flow rate enters the sub-flow path 203 and passes through the MEMS flow chip 3 when the flow rate to be measured is large, and realize high-precision measurement of the large flow rate under the condition of a fixed flow-splitting ratio. However, it is difficult to ensure the measurement accuracy of a small flow rate with this structure.

In summary, the conventional MEMS thermal mass flow meter cannot achieve both large and small flow rates during measurement, that is, cannot achieve large-range ratio and high-precision measurement.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problems, the utility model provides an MEMS thermal mass flow meter with a large range ratio, which aims to solve the problem that the existing MEMS thermal mass flow meter cannot give consideration to both large flow and small flow, and realize large range ratio and high-precision measurement.

In order to achieve the purpose, the technical scheme of the utility model is as follows:

the utility model provides a MEMS hot type mass flow meter of wide-range ratio, includes the gas circuit seat that is equipped with the runner, the runner includes sprue and subchannel, set up air inlet and gas outlet on the sprue, be equipped with the venturi structure on the sprue, set up the encapsulation board on the subchannel, the last MEMS flow chip that is packaged with of encapsulation board, the encapsulation board is connected with two at least main circuit boards that voltage amplification is different respectively.

In the above scheme, the main circuit board includes a first main circuit board and a second main circuit board.

In the above scheme, the MEMS flow chip includes a substrate, a heater disposed above the substrate, an upstream sensing element and a downstream sensing element, where the upstream sensing element and the downstream sensing element are located at two sides of the heater.

In a further technical scheme, a heater, an upstream sensitive element and a downstream sensitive element are arranged on the MEMS flow chip, and one side of the upstream sensitive element and one side of the downstream sensitive element face the flow channel.

In the above scheme, the MEMS flow chip is fixed on the package board by an SMT chip mounting method, and is electrically connected to the package board by a bonding method.

In the above scheme, the package board is electrically connected to the first main circuit board and the second main circuit board respectively in a plug-in or wire-arranging manner.

In the above scheme, the cross-sectional shape of the flow channel is circular or polygonal.

In the above scheme, the cross-sectional shape of the main runner is circular, and the cross-sectional shape of the sub-runners is rectangular.

Through the technical scheme, the MEMS thermal mass flow meter with the large range ratio has the following beneficial effects:

according to the utility model, the main circuit boards with different voltage amplification factors are arranged on the MEMS flow chip, so that when the flow to be detected is small, the signals of the MEMS flow chip can be acquired through the main circuit board with the larger amplification factor; when the flow to be measured is large, the main circuit board with small amplification factor is used for collecting signals of the MEMS flow chip, so that the problem that the prior art cannot give consideration to large and small flows is solved, and large-range ratio and high-precision measurement is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.

FIG. 1 is a schematic diagram of a prior art MEMS mass flow meter for small scale measurements;

FIG. 2 is a schematic diagram of a prior art MEMS mass flow meter for wide range measurements;

FIG. 3 is a schematic structural diagram of a large range ratio MEMS thermal mass flow meter disclosed in an embodiment of the present invention;

fig. 4 is a schematic cross-sectional structure diagram of a MEMS flow chip according to an embodiment of the present invention.

FIG. 5 is a schematic diagram (no air flow) of a MEMS flow chip employed in an embodiment of the present invention;

FIG. 6 is a schematic diagram of a MEMS flow chip (with air flow) employed in an embodiment of the present invention;

in the figure, 1, an air channel seat; 2. a flow channel; 201. an air inlet; 202. an air outlet; 203. a shunt channel; 204. a main flow channel; 205. a venturi structure; 3. an MEMS flow chip; 401. a first main circuit board; 402. a package board; 403. a second main circuit board; 31. a substrate; 32. a heater; 33. an upstream sensing element; 34. a downstream sensing element.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The utility model provides an MEMS thermal mass flow meter with a large range ratio, which comprises an air channel seat 1 provided with a flow channel 2, wherein the flow channel 2 comprises a main flow channel 204 and a sub-flow channel 203, the main flow channel 204 is provided with an air inlet 201 and an air outlet 202, the main flow channel 204 is provided with a Venturi tube structure 205, the sub-flow channel 203 is provided with a packaging plate 402, an MEMS flow chip is packaged on the packaging plate 402, and the packaging plate 402 is respectively connected with a first main circuit board 401 and a second main circuit board 403.

It should be noted that the first main circuit board 401 and the second main circuit board 403 use different voltage amplification factors, where the amplification factor of the first main circuit board 401 is smaller, and the amplification factor of the second main circuit board 403 is larger. The amplification factor is determined according to the measuring range of the MEMS mass flowmeter, and the signal of the MEMS flow chip is ensured not to exceed the circuit reference voltage after being amplified.

Specifically, the air path seat 1 is made of an airtight hard material, and the cross section of the flow channel 2 is circular or polygonal; in the embodiment of the present invention, the material of the air path seat 1 is an aluminum alloy, the cross-sectional shapes of the air inlet 201, the air outlet 202 and the main flow channel 204 are circular, and the cross-sectional shape of the sub-flow channel 203 is rectangular.

It should be noted that the venturi structure 205 functions to generate a pressure difference between the side of the main flow passage 204 close to the air inlet 201 and the side close to the air outlet 202, so as to allow a part of the air flow to pass through the sub-flow passage 203.

Specifically, as shown in fig. 4, the MEMS flow chip 3 includes a substrate 31, a heater 32 disposed above the substrate 31, an upstream sensor 33 and a downstream sensor 34, where the upstream sensor 33 and the downstream sensor 34 are located at two sides of the heater 32. The core unit of the MEMS thermal mass flowmeter is an MEMS flow chip 3, and the working principle is as follows: the heater 32 provides a certain power to make the surface temperature of the chip higher than the ambient temperature, when there is no air flow, the surface temperature is normally distributed around the heater 32, the upstream heat sensitive element 33 and the downstream sensitive element 34 have the same electrical signal (fig. 5); when there is air flow, the surface temperature distribution is deviated by the heat transferred by the gas molecules, the difference is generated between the electric signals of the upstream thermosensitive element 33 and the downstream thermosensitive element 34 (fig. 6), and the back end signal processing circuit is used for acquiring the difference to calculate the gas flow. Due to the small size, the MEMS flow chip 3 is particularly suitable for the measurement of minute flows.

The MEMS flow chip 3 is manufactured by adopting an MEMS process: the substrate 31 is a common semiconductor substrate including but not limited to one of a silicon substrate, a germanium substrate, an SOI substrate, and a GeOI substrate; the heater 32 is made of one of P-type polysilicon, N-type polysilicon and metal; the upstream sensor 33 and the downstream sensor 34 can be thermistors or thermopiles; the material of the thermistor is metal with positive/negative temperature coefficients, and the material of the thermopile is a combination of P-type polycrystalline silicon/N-type polycrystalline silicon, or a combination of P-type polycrystalline silicon/metal, or a combination of N-type polycrystalline silicon/metal.

The side (i.e., the sensitive surface) of the MEMS flow chip 3 on which the heater 32 and the upstream and downstream

sensitive elements

33 and 34 are provided faces the flow channel.

The MEMS flow chip 3 is fixed on the package board 402 by an SMT patch method, and is electrically connected to the package board 402 by a bonding method. The package board 402 is electrically connected to the first main circuit board 401 and the second main circuit board 403 by plugging or wire arrangement, respectively.

It should be noted that the packaging board 402 is used to extract the electrical signals of the MEMS flow chip 3 and transmit the electrical signals to the first main circuit board 401 and the second main circuit board 403 for processing.

It should be noted that, according to the size of the measurement range, a third main circuit board or a fourth and fifth main circuit board having a voltage amplification factor different from that of the first main circuit board 401 and the second main circuit board 403 may be further provided.

The working principle of the MEMS thermal mass flowmeter provided by the utility model is as follows: when the flow to be detected is small, the electrical signal of the MEMS flow chip 3 is weak, and the package board 402 transmits the weak signal to the second main circuit board 403 with a large amplification factor for processing, so as to realize high-precision detection of the weak signal; when the flow to be measured is large, the electrical signal of the MEMS flow chip 3 is relatively strong, and the packaging board 402 transmits the strong signal to the first main circuit board 401 with a small amplification factor for processing, so as to ensure that the signal does not exceed the circuit reference voltage. Therefore, the utility model is beneficial to solving the problem that the prior art can not give consideration to both large and small flows, and realizes large-range ratio and high-precision measurement.

Therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the utility model. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The utility model provides a MEMS hot type mass flow meter of wide-range ratio, is including the gas circuit seat that is equipped with the runner, the runner includes sprue and subchannel, set up air inlet and gas outlet on the sprue, its characterized in that, be equipped with the venturi structure on the sprue, set up the encapsulation board on the subchannel, the last MEMS flow chip that is packaged with of encapsulation board, the encapsulation board is connected with two at least main circuit boards that the voltage amplification factor is different respectively.

2. The wide range ratio MEMS thermal mass flow meter of claim 1 wherein the main circuit board comprises a first main circuit board and a second main circuit board.

3. The large-range-ratio MEMS thermal mass flow meter according to claim 1, wherein the MEMS flow chip comprises a substrate, a heater disposed above the substrate, an upstream sensing element and a downstream sensing element, the upstream sensing element and the downstream sensing element being located on both sides of the heater.

4. The MEMS thermal mass flow meter with the large range ratio as claimed in claim 3, wherein the side of the MEMS flow chip on which the heater and the upstream sensing element and the downstream sensing element are arranged faces the flow channel.

5. The MEMS thermal mass flow meter with large range ratio as claimed in claim 1, wherein the MEMS flow chip is fixed on the package board by SMT chip mounting method and electrically connected with the package board by bonding method.

6. The MEMS thermal mass flow meter with large range ratio of claim 1, wherein the package plate is electrically connected to the first main circuit board and the second main circuit board respectively by plugging or wire arranging.

7. The wide range ratio MEMS thermal mass flow meter of claim 1, wherein the cross-sectional shape of the flow channel is circular or polygonal.

8. The large-range-ratio MEMS thermal mass flow meter according to claim 1, wherein the cross-sectional shape of the main flow channel is circular, and the cross-sectional shape of the sub flow channel is rectangular.