Flow sensor, manufacturing method thereof and gas mass flow controller

Abstract

The invention discloses a flow sensor, a manufacturing method thereof and a gas mass flow controller. The flow sensor comprises a capillary tube and a micron-sized thin-film resistor located on the outer surface of the capillary tube. The capillary comprises a capillary horizontal section and a capillary vertical section; the thin-film resistor comprises an upstream thin-film resistor and a downstream thin-film resistor, the upstream thin-film resistor and the downstream thin-film resistor are wound on the horizontal section of the capillary tube in a mirror symmetry mode, and the winding mode of the thin-film resistor is any one of an annular single-wire mode, an annular double-wire mode and a horizontal single-wire mode. The thin-film resistor disclosed by the invention has a micron-sized line width, so that resistors manufactured on the same capillary tube are denser and have thinner thickness and more effective area contact, the heat transfer efficiency of gas is remarkably improved, and the sensitivity and response time of the sensor are favorably improved; in addition, the preparation method is simple, a complex winding process is avoided, the controllability is high, and the consistency is good.

Description

Technical Field

[0001] The present invention relates to the technical field of flow detection, and in particular to a flow sensor and a manufacturing method thereof, and a gas mass flow controller. Background Art

[0002] Flow measurement and control are basic requirements for industrial production and scientific research. As a device that can directly set and control gas flow, the gas mass flow controller plays an important role in many fields such as semiconductors and integrated circuits, vacuum coating, medical treatment, and environmental protection. As one of the core components of the gas mass flow controller, the flow sensor achieves accurate measurement of gas flow by detecting changes in physical parameters such as heat and pressure caused by gas flow. Among them, the thermal flow sensor uses the principle of heat transfer temperature difference calorimetry to make a set of thermistor wires upstream and downstream of the capillary, and connects two precision resistors to form a bridge structure. When working, the bridge is heated. If there is airflow passing through, the temperature of the thermistor wires upstream and downstream will be different, and the bridge outputs a voltage signal proportional to the gas mass flow rate. However, this flow sensor structure inevitably has the following problems:

[0003] First, to avoid short circuits, the surface of the thermistor wire is usually coated with insulating paint, and its wire width is often not less than 15μm, resulting in a limit on the number of resistance wires wound on a unit length of the capillary;

[0004] Second, thermistor wire is usually a columnar structure. When winding, only the adjacent surfaces are in contact with the capillary tube to achieve heat exchange, resulting in low heat transfer efficiency.

[0005] Third, the process of winding thermistor wire is complicated and the consistency between products is poor.

[0006] The above content is only used to assist in understanding the technical solution of this application and does not constitute a denial of the prior art. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a flow sensor and a manufacturing method thereof, and a gas mass flow controller, which achieve the purpose of improving sensitivity and consistency by manufacturing micron-level thin film resistors on the capillary.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A flow sensor comprises a capillary and a micrometer-level thin film resistor located on the outer surface of the capillary; the capillary comprises a horizontal capillary section and a vertical capillary section; the thin film resistor comprises an upstream thin film resistor and a downstream thin film resistor, the upstream thin film resistor and the downstream thin film resistor are wound on the horizontal capillary section in a mirror-symmetrical manner, and the winding method of the thin film resistor adopts any one of an annular single-wire type, an annular double-wire type or a horizontal single-wire type.

[0010] In the above solution, the capillary is made of heat-conducting material.

[0011] In the above solution, the cross-sectional shape of the capillary is circular or polygonal.

[0012] In the above solution, the capillary horizontal section and the capillary vertical section are an integrally formed structure, which is formed by bending.

[0013] In the above scheme, the thin film resistor is made of metal or non-metal conductive paste and is manufactured on the horizontal section of the capillary by spray printing, dipping, injection molding or pad printing technology.

[0014] In a further technical solution, the printing technology includes electrofluid printing, piezoelectric printing or thick film printing technology.

[0015] A method for manufacturing the flow sensor as described above comprises the following steps:

[0016] S1. Prepare equipment and materials;

[0017] The equipment is a printing, dipping, injection molding or pad printing equipment; the material includes a capillary, a metal or non-metallic conductive paste;

[0018] S2, fixing the capillary on a bracket of the device that can rotate axially;

[0019] S3. Use the setting program to make preset patterns in the upstream and downstream of the horizontal section of the capillary.

[0020] The present invention also discloses a gas mass flow controller, comprising the flow sensor as described above.

[0021] Specifically, the two ends of the capillary of the flow sensor are respectively connected to the upstream and downstream of the main channel as branch channels, and a diversion structure for diverting part of the gas in the main channel to the capillary is provided at the position of the flow sensor in the main channel; a proportional control valve is also provided on the main channel, and the flow sensor is connected to the proportional control valve through a circuit function unit.

[0022] In the above solution, the circuit functional unit includes a signal processing unit, an analog-to-digital conversion unit and a control unit.

[0023] Through the above technical solution, the flow sensor and its manufacturing method, and the gas mass flow controller provided by the present invention have the following beneficial effects:

[0024] The present invention prepares a micron-sized thin film resistor on a capillary to replace the thermistor wire wound in the sensing scheme. On the one hand, the reduction in the resistor line width makes the resistors made on the same capillary more dense, and the reduction in the resistor thickness significantly increases the heat transfer efficiency of the gas, which is beneficial to improving the sensitivity and response time of the sensor; on the other hand, the preparation method is relatively simple, avoiding a complicated winding process, and has strong controllability and good consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0026] Figure 1 It is a schematic diagram of the structure of the flow sensor disclosed in the embodiment of the present invention;

[0027] Figure 2 The annular single-wire resistor layout of the flow sensor disclosed in the embodiment of the present invention;

[0028] Figure 3 The annular two-wire resistor layout of the flow sensor disclosed in the embodiment of the present invention;

[0029] Figure 4 A horizontal single-line resistor layout of a flow sensor disclosed in an embodiment of the present invention;

[0030] Figure 5 The following are steps for manufacturing the flow sensor disclosed in the embodiment of the present invention;

[0031] Figure 6 The present invention is a schematic diagram of the structure of a gas mass flow controller disclosed in an embodiment of the present invention.

[0032] In the figure, 1, capillary; 101, horizontal section of capillary; 102, vertical section of capillary; 2, thin film resistor; 201, upstream thin film resistor; 201a, one terminal of upstream thin film resistor; 201b, the other terminal of upstream thin film resistor; 202, downstream thin film resistor; 3, main channel; 301, air inlet; 302, shunt structure; 303, air outlet; 4, proportional control valve; 5, circuit function unit; 501, signal processing unit; 502, analog-to-digital conversion unit; 503, control unit; S1~S4, each manufacturing step. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] The present invention provides a flow sensor, see Figure 1, including a capillary 1 and a micrometer-sized thin film resistor 2 located on the outer surface thereof. The capillary 1 includes a capillary horizontal section 101 and a capillary vertical section 102, for gas to flow along the indicated direction; the thin film resistor 2 includes an upstream thin film resistor 201 and a downstream thin film resistor 202, and the upstream thin film resistor 201 and the downstream thin film resistor 202 are wound on the capillary horizontal section 101 in a mirror-symmetrical manner.

[0035] Thin film resistors 2 can be arranged in a variety of different resistor layouts, including but not limited to ring single-wire, ring double-wire, and horizontal single-wire. Figure 2 In the ring-shaped single-line resistor layout, one terminal 201a of the upstream thin-film resistor and the other terminal 201b of the upstream thin-film resistor are respectively located at two ends of the upstream thin-film resistor and at two axial sides of the capillary 1. Figure 3 In the annular two-wire resistor layout, one terminal 201a of the upstream thin film resistor and the other terminal 201b of the upstream thin film resistor are located at one end of the upstream thin film resistor and at one axial side of the capillary 1. Figure 4 In the horizontal single-line resistor layout, one terminal 201 a of the upstream thin-film resistor and another terminal 201 b of the upstream thin-film resistor are located at one end of the upstream thin-film resistor and at both sides of the axial direction of the capillary 1 .

[0036] Specifically, the capillary 1 is made of airtight hard heat-conducting material, including but not limited to 316 stainless steel, 304 stainless steel, etc. The cross-sectional shape of the capillary 1 is circular or polygonal. The capillary horizontal section 101 and the capillary vertical section 102 are an integrally formed structure, formed by bending. In an embodiment of the present invention, the material of the capillary 1 is 316 stainless steel, and the cross-sectional shape is circular.

[0037] Specifically, the thin film resistor 2 is made of metal or non-metal conductive paste and is manufactured on the capillary horizontal section 101 by inkjet printing, dipping, injection molding or pad printing technology; in an embodiment of the present invention, the thin film resistor 2 is made of gold material and is manufactured by inkjet printing technology.

[0038] Furthermore, the printing technology for manufacturing the thin film resistor 2 includes but is not limited to electrofluidic printing, piezoelectric printing or thick film printing technology.

[0039] As described above, the embodiment of the present invention prepares a micron-sized thin film resistor 2 on the capillary 1 through inkjet printing technology. On the one hand, the reduction in the resistor line width makes the resistors produced on the same capillary 1 more dense, and the reduction in the resistor thickness significantly increases the heat transfer efficiency of the gas, which is beneficial to improving the sensitivity and response time of the sensor; on the other hand, the preparation method is relatively simple, avoiding the complicated winding process, and has strong controllability and good consistency.

[0040] The present invention also provides a method for manufacturing a flow sensor, such as Figure 5 As shown, the following steps are included:

[0041] S1. Prepare printing equipment and materials;

[0042] Specifically, the printing device is an electro-fluid printing device, a piezoelectric printing device or a thick film printing device; the materials include a capillary 1 and a gold paste;

[0043] S2, fixing the capillary 1 on an axially rotatable support of the device;

[0044] S3 . Use a setting program to create a preset pattern upstream and downstream of the capillary horizontal section 101 .

[0045] Through the above method, the flow sensor according to the embodiment of the present invention is formed. It can be understood that the above only describes a method of forming the flow sensor according to the embodiment of the present invention, and the present invention can also manufacture the flow sensor through other different implementation methods.

[0046] The present invention also provides a gas mass flow controller, comprising the flow sensor as described above.

[0047] See also Figure 6 The two ends of the capillary 1 of the flow sensor are respectively connected to the upstream and downstream of the main channel 3 as branch channels. A shunt structure 302 for shunting part of the gas in the main channel 3 to the capillary 1 is provided at the position of the flow sensor in the main channel 3; a proportional control valve 4 is also provided on the main channel 3, and the flow sensor is connected to the proportional control valve 4 through a circuit function unit 5.

[0048] The two ends of the main channel 3 are an air inlet 301 and an air outlet 303 respectively. The main channel 3 is made of the same or different hard heat-conducting material as the capillary 1, including but not limited to 316 stainless steel, 304 stainless steel, aluminum alloy, etc.

[0049] Specifically, the circuit functional unit 5 includes but is not limited to a signal processing unit 501 , an analog-to-digital conversion unit 502 and a control unit 503 .

[0050] The signal processing unit 501 is used to amplify, filter and process the output signal of the flow sensor; the digital-to-analog conversion unit 502 is used to convert the analog signal transmitted by the signal processing unit 501 into a digital signal; the control unit 503 is used to control and adjust the opening of the proportional control valve 4 according to the output voltage of the flow sensor.

[0051] The upstream thin film resistor 201 and the downstream thin film resistor 202 of the flow sensor are externally connected to two precision resistors to form a bridge structure, and the bridge structure is signal-connected to the signal processing unit 501 .

[0052] Since the gas mass flow controller adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0053] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0054] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flow sensor, characterized in that: It includes a capillary and a micron-sized thin film resistor located on the outer surface of the capillary; the capillary includes a horizontal capillary section and a vertical capillary section; the thin film resistor includes an upstream thin film resistor and a downstream thin film resistor, and the upstream thin film resistor and the downstream thin film resistor are wound on the horizontal capillary section in a mirror-symmetrical manner, and the winding method of the thin film resistor adopts any one of an annular single-wire type, an annular double-wire type or a horizontal single-wire type.

2. A flow sensor according to claim 1, characterized in that: The capillary is made of heat-conducting material.

3. A flow sensor according to claim 1, characterized in that: The cross-sectional shape of the capillary is circular or polygonal.

4. A flow sensor according to claim 1, characterized in that: The capillary horizontal section and the capillary vertical section are an integrally formed structure, which are formed by bending.

5. A flow sensor according to claim 1, characterized in that: The thin film resistor is made of metal or non-metal conductive paste and is manufactured on the horizontal section of the capillary by spray printing, dipping, injection molding or pad printing technology.

6. A flow sensor according to claim 5, characterized in that: The printing technology includes electrofluidic printing, piezoelectric printing or thick film printing technology.

7. A method for manufacturing a flow sensor according to any one of claims 1 to 6, characterized in that: The steps include: S1. Prepare equipment and materials; The equipment is a printing, dipping, injection molding or pad printing equipment; the material includes a capillary, a metal or non-metallic conductive paste; S2, fixing the capillary on a bracket of the device that can rotate axially; S3. Use the setting program to make preset patterns in the upstream and downstream of the horizontal section of the capillary.

8. A gas mass flow controller, characterized in that: It comprises a flow sensor as described in any one of claims 1 to 6.

9. The gas mass flow controller according to claim 8, characterized in that: The two ends of the capillary of the flow sensor are respectively connected to the upstream and downstream of the main channel as branch channels. A diversion structure for diverting part of the gas in the main channel to the capillary is provided at the position of the flow sensor in the main channel; a proportional control valve is also provided on the main channel, and the flow sensor is connected to the proportional control valve through a circuit function unit.

10. The gas mass flow controller according to claim 8, characterized in that: The circuit functional unit includes a signal processing unit, an analog-to-digital conversion unit and a control unit.

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