High-precision metal-based two-stage amplification type quartz resonant pressure sensor and assembling method thereof

Abstract

A high-precision metal-based two-stage amplification type quartz resonant pressure sensor and an assembling method thereof, the sensor comprising a pressure sensor shell, the pressure sensor shell and an upper cover plate forming a sensitive chamber; a lower cover plate and the pressure sensor shell forming a PCB mounting chamber; a PCB board being fixed in the PCB mounting chamber; a metal-based two-stage amplification type pressure sensitive structure element being connected to a side surface of the pressure sensor shell; a quartz double-end fixed support tuning fork being connected to the metal-based two-stage amplification type pressure sensitive structure element; a temperature sensor being connected to a surface of the metal-based two-stage amplification type pressure sensitive structure element; the quartz double-end fixed support tuning fork and the temperature sensor being arranged in the sensitive chamber; the quartz double-end fixed support tuning fork being electrically connected to the PCB board; the pressure change introduced by the two-stage metal pressure sensitive structure element composed of the quartz double-end fixed support tuning fork and a metal flexible lever can obtain the pressure information to be measured, and the present application has the characteristics of high precision, high sensitivity, strong anti-interference ability and the like.

Description

Technical Field

[0001] This invention relates to the field of microelectromechanical (MEMS) pressure measurement device technology, specifically to a high-precision metal-based two-stage amplified quartz resonant pressure sensor and its assembly method. Background Technology

[0002] With the development of microelectromechanical systems (MEMS) technology, resonant pressure sensors have been widely used in aerospace, industrial measurement and control, and high-precision instruments due to their advantages such as high resolution, high stability, and strong resistance to electromagnetic interference. These sensors measure pressure by detecting changes in the natural frequency of a resonant element, outputting a frequency signal. They are characterized by good long-term stability and ease of digital processing.

[0003] In existing technologies, quartz resonant pressure sensors typically employ a quartz double-ended fixed tuning fork as the resonant element. A two-stage mechanical structure, consisting of a pressure-sensitive diaphragm, a pressure-transmitting probe, and a flexible metal lever, converts the displacement caused by diaphragm deformation into axial stress acting on the resonant element, thereby causing a change in the resonant frequency and achieving pressure detection. For example, a patent application titled "A High-Precision Double-Ended Fixed Resonant Tuning Fork Pressure Sensor" (Publication No.: CN203376085U) proposes using a micro-lever mechanism to transmit pressure to the resonant tuning fork, achieving pressure measurement by detecting changes in the resonant frequency. However, the aforementioned type of metal-based two-stage amplified quartz resonant pressure sensor typically uses a single-beam structure, meaning only one quartz double-ended fixed tuning fork is placed between the output end and the fixed end of the flexible metal lever. When temperature changes or residual stress is generated during packaging, the single-beam structure is susceptible to common-mode stress, leading to resonant frequency drift and affecting measurement accuracy and long-term stability.

[0004] Therefore, how to improve the ability of the pressure-sensitive structure to suppress temperature changes and residual stress in the packaging while maintaining the high sensitivity of the two-stage amplification structure, and enhance the anti-interference ability of the sensor, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In order to overcome the above-mentioned technical shortcomings, the purpose of this invention is to provide a high-precision metal-based two-stage amplified quartz resonant pressure sensor and its assembly method. The sensor has the performance characteristics of high stability and high precision, and can effectively suppress measurement drift caused by external interference and thermal effects.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: A high-precision metal-based two-stage amplified quartz resonant pressure sensor includes a pressure sensor housing 4, which and an upper cover plate 5 are vacuum-sealed to form a sensitive chamber; a lower cover plate 6 and the pressure sensor housing 4 form a PCB mounting chamber; a PCB board 7 is positioned in the PCB mounting chamber by sintered gold pillars 4f; a metal-based two-stage amplified pressure-sensitive structural element 1 is connected to the side of the pressure sensor housing 4, a quartz double-ended fixed-braced tuning fork 2 is connected to the metal-based two-stage amplified pressure-sensitive structural element 1, a temperature sensor 3 is connected to the surface of the metal-based two-stage amplified pressure-sensitive structural element 1, the quartz double-ended fixed-braced tuning fork 2 and the temperature sensor 3 are disposed in the sensitive chamber, and the quartz double-ended fixed-braced tuning fork 2 and the PCB board 7 are electrically connected.

[0007] The pressure sensor housing 4 is provided with a pressure probe mounting hole 4c on the outside, and a positioning boss 4d is provided on the outside of the pressure probe mounting hole 4c; the pressure sensor housing 4 is provided with a glass sintering hole 4a and a vacuum process hole 4b; a sintered gold pillar 4f is connected in the glass sintering hole 4a, and the sintered gold pillar 4f electrically connects the quartz double-ended fixed tuning fork 2 of the sensitive chamber and the PCB board 7; a flexible lever mounting support 4e is provided under the sensitive chamber.

[0008] The metal-based two-stage amplified pressure-sensitive structural element 1 includes a metal pressure probe structure and a metal flexible lever structure; the metal pressure probe structure is concentric with the pressure probe mounting hole 4c on the pressure sensor housing 4, and the metal pressure probe structure is connected to the positioning boss 4d on the housing; the metal flexible lever structure includes a pressure input end 1a, a flexible hinge 1b located in the middle of the lever, an output end 1c located on one side of the flexible hinge 1b, a fixed reference end 1d rigidly connected to the lever body, a positioning groove 1e, and a positioning hole 1i provided at the pressure input end; the metal flexible lever structure is connected to the flexible lever mounting support 4e.

[0009] The lower cover plate 6 is provided with a lead wire hole 6a.

[0010] The quartz double-ended fixed tuning fork 2 includes connecting parts 2a and 2b at both ends. The lower surfaces of the connecting parts 2a and 2b are connected to the side of the pressure output end 1c of the flexible metal lever and the fixed reference end 1d of the flexible lever. The connecting parts are connected by two symmetrical tuning fork arms 2d. A slit 2c is left between the two tuning fork arms 2d. Electrodes are provided around the surface of the two tuning fork arms 2d. The electrodes are electrically connected to each other for the tuning fork arms 2d to start oscillating. Under the action of the inverse piezoelectric effect, when an alternating voltage is applied, the tuning fork arms 2d are in a preset vibration mode. A detection electrode is provided on the upper surface of the connecting part 2a at one end, and a solder pad is provided on the upper surface of the connecting part 2b at the other end for connection with external circuits. The solder pad is connected to the PCB board 7 through gold wire.

[0011] The temperature sensor 3 is installed close to the quartz double-ended tuning fork 2, and the pins of the temperature sensor 3 are connected to the PCB board 7 through sintered gold pillars 4f.

[0012] The PCB board 7 and the pressure sensor housing 4 are sealed with epoxy resin.

[0013] The assembly method of the high-precision metal-based two-stage amplified quartz resonant pressure sensor includes the following steps: 1) Align the two ends of the quartz double-ended tuning fork 2 with the positioning groove 1e mark on the side of the metal flexible lever, and then fix them to the metal flexible lever with process adhesive. 2) Align the metal flexible lever with the flexible lever mounting support 4e on the shell according to the positioning relationship, and connect the metal flexible lever with the flexible lever mounting support 4e using laser welding process; 3) The pressure probe is concentric with the pressure probe mounting hole 4c and fits against the positioning boss 4d on the pressure sensor housing 4. It is sealed and connected to the pressure sensor housing 4 by welding process; the probe tip of the pressure probe structure is concentric with the positioning hole 1i of the flexible lever and is inserted into the positioning hole 1i. 4) Secure the probe tip to the flexible metal lever using glue injection; 5) Connect the temperature sensor 3 terminals to the sintered gold pillar 4f and the quartz double-ended fixed tuning fork 2 to the sintered gold pillar 4f via gold wire leads; 6) Weld the top cover plate 5 to the pressure sensor housing 4; 7) Evacuate the sensitive chamber through vacuum process hole 4b; seal the process hole by welding. 8) Install PCB board 7, complete lead soldering, and seal the PCB mounting cavity with epoxy resin; 9) The lead wire is led out through the lead wire hole 6a on the lower cover plate 6 and connected to the pressure sensor housing 4 and the lower cover plate 6 by welding.

[0014] Compared with existing technologies, the advantages of this invention are as follows: This invention employs a metal-based two-stage amplification pressure-sensitive structure composed of a metal pressure probe structure and a metal flexible lever structure. This structure amplifies the displacement change caused by the measured pressure step by step and converts it into axial stress changes acting on the quartz double-ended fixed tuning fork, thereby improving the pressure signal transmission efficiency and pressure measurement sensitivity, which is beneficial for achieving high-precision pressure measurement. This invention uses the quartz double-ended fixed tuning fork as the resonant sensitive element and uses a frequency signal as the output, which has the advantages of strong anti-electromagnetic interference capability, stable signal transmission, easy digital processing, and good long-term stability. This invention places the quartz double-ended fixed tuning fork and temperature sensor in the sensitive chamber and vacuum seals the sensitive chamber, providing a relatively stable working environment for the quartz double-ended fixed tuning fork and reducing air damping, etc. The invention minimizes the influence of external factors on the resonance characteristics and facilitates the acquisition of temperature information near the resonant element, thereby enabling temperature compensation and improving measurement stability. The invention separates the sensitive chamber from the PCB mounting chamber and uses sintered gold pillars to achieve electrical connection between the quartz double-ended tuning fork in the sensitive chamber and the PCB board. This ensures the sealing of the sensitive chamber while facilitating stable signal extraction and circuit integration packaging, thus improving the overall reliability of the sensor. Furthermore, the invention improves the assembly positioning accuracy and consistency of key components by incorporating pressure probe mounting holes, positioning bosses, positioning grooves, positioning holes, and flexible lever mounting supports, along with assembly processes such as laser welding, glue injection fixing, and epoxy resin sealing. This reduces the impact of assembly errors on sensor performance, contributing to higher product yield and long-term reliability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an embodiment of the present invention.

[0016] Figure 2 This is an overall exploded view of an embodiment of the present invention.

[0017] Figure 3 This is a cross-sectional view of the shell according to an embodiment of the present invention.

[0018] Figure 4 This is a three-dimensional schematic diagram of a metal-based two-stage amplified pressure-sensitive structural element according to an embodiment of the present invention.

[0019] Figure 5 This is a three-dimensional schematic diagram of a metal flexible lever according to an embodiment of the present invention.

[0020] Figure 6 This is a schematic diagram of the positioning surface of the metal flexible lever and the flexible lever mounting support in an embodiment of the present invention.

[0021] Figure 7 This is a schematic diagram of the lower cover plate according to an embodiment of the present invention.

[0022] Figure 8 This is a three-dimensional schematic diagram of a quartz double-ended fixed tuning fork according to an embodiment of the present invention. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0024] Reference Figure 1-3 A high-precision metal-based two-stage amplified quartz resonant pressure sensor includes a pressure sensor housing 4. The pressure sensor housing 4 is connected from top to bottom to an upper cover plate 5, a PCB board 7, and a lower cover plate 6. The pressure sensor housing 4 and the upper cover plate 5 are vacuum-sealed to form a sensitive chamber. The lower cover plate 6 and the pressure sensor housing 4 form a PCB mounting chamber. The PCB board 7 is positioned in the PCB mounting chamber by sintered gold pillars 4f. A metal-based two-stage amplified pressure-sensitive structural element 1 is connected to the side of the pressure sensor housing 4. A quartz double-ended fixed-braced tuning fork 2 is connected to the metal-based two-stage amplified pressure-sensitive structural element 1. A temperature sensor 3 is connected to the surface of the metal-based two-stage amplified pressure-sensitive structural element 1. The quartz double-ended fixed-braced tuning fork 2 and the temperature sensor 3 are disposed in the sensitive chamber. The quartz double-ended fixed-braced tuning fork 2 and the PCB board 7 are electrically connected. The metal-based two-stage amplified pressure-sensitive structural element 1 senses and amplifies the pressure signal change and transmits it to the quartz double-ended fixed-braced tuning fork 2 to obtain the pressure signal.

[0025] Reference Figure 3 The pressure sensor housing 4 is provided with a pressure probe mounting hole 4c on the outside, and a positioning boss 4d is provided on the outside of the pressure probe mounting hole 4c; the pressure sensor housing 4 is provided with a glass sintering hole 4a and a vacuum process hole 4b; a sintered gold pillar 4f is connected in the glass sintering hole 4a, and the sintered gold pillar 4f electrically connects the quartz double-ended fixed tuning fork 2 of the sensitive chamber and the PCB board 7; a flexible lever mounting support 4e is provided under the sensitive chamber.

[0026] Reference Figure 3-6 The metal-based two-stage amplified pressure-sensitive structural element 1 includes a metal pressure probe structure and a metal flexible lever structure. The metal pressure probe structure is concentric with the pressure probe mounting hole 4c on the pressure sensor housing 4, and the metal pressure probe structure is connected to the positioning boss 4d on the housing. The metal flexible lever structure includes a pressure input end 1a, a flexible hinge 1b located in the middle of the lever, an output end 1c located on one side of the flexible hinge 1b, a fixed reference end 1d rigidly connected to the lever body, a positioning groove 1e, and a positioning hole 1i provided at the pressure input end. The metal flexible lever structure is connected to the flexible lever mounting support 4e. The a surface of the metal flexible lever structure is tightly connected to the d surface of the flexible lever mounting support, the b surface of the metal flexible lever structure is tightly connected to the e surface of the flexible lever mounting support, and the c surface of the metal flexible lever structure is tightly connected to the f surface of the flexible lever mounting support.

[0027] Reference Figure 7 The lower cover plate 6 is provided with lead wire holes 6a for lead wires to be led out of the PCB mounting cavity and for sealing the cavity.

[0028] Reference Figure 8 The quartz double-ended fixed tuning fork 2 includes connecting parts 2a and 2b at both ends. The lower surfaces of the connecting parts 2a and 2b are connected to the side surfaces of the pressure output end 1c of the flexible metal lever and the fixed reference end 1d of the flexible lever, and are aligned with the positioning grooves 1e provided on the side surfaces of the pressure output end 1c and the fixed reference end 1d of the flexible lever. The connecting parts are connected by two symmetrical tuning fork arms 2d, with a slit 2c between the two tuning fork arms 2d. Electrodes are provided around the surface of the two tuning fork arms 2d, and the electrodes are electrically connected to each other for the tuning fork arms 2d to start oscillating. Under the action of the inverse piezoelectric effect, when an alternating voltage is applied, the tuning fork arms 2d are in a preset vibration mode. A detection electrode is provided on the upper surface of the connecting part 2a at one end, and a solder pad connected to an external circuit is provided on the upper surface of the connecting part 2b at the other end. The solder pad is connected to the PCB board 7 through gold wire.

[0029] The temperature sensor 3 is installed close to the quartz double-ended tuning fork 2, and the pins of the temperature sensor 3 are connected to the PCB board 7 through sintered gold pillars 4f.

[0030] The PCB board 7 and the pressure sensor housing 4 are sealed with epoxy resin.

[0031] The assembly method of the high-precision metal-based two-stage amplified quartz resonant pressure sensor includes the following steps: 1) Align the two ends of the quartz double-ended tuning fork 2 with the positioning groove 1e mark on the side of the metal flexible lever, and then fix them to the metal flexible lever with process adhesive. 2) Align the metal flexible lever with the positioning relationship between the positioning surfaces a, b, and c of the metal flexible lever and the positioning surfaces d, e, and f of the flexible lever mounting support 4e on the housing, and connect the metal flexible lever with the flexible lever mounting support 4e using laser welding. 3) The pressure probe is concentric with the pressure probe mounting hole 4c and fits against the positioning boss 4d on the pressure sensor housing 4. It is sealed and connected to the pressure sensor housing 4 by welding process; the probe tip of the pressure probe structure is concentric with the positioning hole 1i of the flexible lever and is inserted into the positioning hole 1i. 4) Secure the probe tip to the flexible metal lever using glue injection; 5) Connect the temperature sensor 3 terminals to the sintered gold pillar 4f and the quartz double-ended fixed tuning fork 2 to the sintered gold pillar 4f via gold wire leads; 6) Weld the top cover plate 5 to the pressure sensor housing 4; 7) Evacuate the sensitive chamber through vacuum process hole 4b; seal the process hole by welding. 8) Install PCB board 7, complete lead soldering, and seal the PCB mounting cavity with epoxy resin; 9) The lead wire is led out through the lead wire hole 6a on the lower cover plate 6 and connected to the pressure sensor housing 4 and the lower cover plate 6 by welding.

[0032] The beneficial effects of this embodiment are as follows: This embodiment adopts a two-stage amplified pressure-sensitive structure composed of a metal pressure probe structure and a metal flexible lever structure. This structure can effectively transmit and amplify the minute displacement caused by external pressure into axial stress changes acting on the quartz double-ended fixed tuning fork, giving the sensor high pressure sensitivity and good frequency output characteristics. The quartz double-ended fixed tuning fork is placed in a vacuum-sealed sensitive chamber, which can effectively reduce the influence of air damping and external environmental disturbances on the resonance characteristics, thus improving the resonance quality factor, frequency output stability, and measurement accuracy. The temperature sensor is arranged close to the quartz double-ended fixed tuning fork, which can more accurately obtain the temperature information of the working area of ​​the resonant element, facilitating subsequent temperature compensation and reducing the impact of temperature changes on the measurement results. At the same time, this embodiment achieves precise positioning of key components through structures such as pressure probe mounting holes, positioning bosses, positioning grooves, positioning holes, and flexible lever mounting supports. Combined with processes such as laser welding, glue injection fixing, gold wire leads, vacuum encapsulation, and epoxy resin sealing, it improves assembly consistency and sealing reliability, reduces the impact of assembly errors and encapsulation stress on sensor performance, and gives the sensor good stability, reliability, and engineering application value.

[0033] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A high-precision metal-based two-stage amplified quartz resonant pressure sensor, comprising a pressure sensor housing (4), characterized in that: The pressure sensor housing (4) and the upper cover plate (5) form a sensitive chamber; the lower cover plate (6) and the pressure sensor housing (4) form a PCB mounting chamber; the PCB board (7) is fixed in the PCB mounting chamber; the side of the pressure sensor housing (4) is connected to a metal-based two-stage amplified pressure sensitive structure element (1), a quartz double-ended fixed-braced tuning fork (2) is connected to the metal-based two-stage amplified pressure sensitive structure element (1), a temperature sensor (3) is connected to the surface of the metal-based two-stage amplified pressure sensitive structure element (1), the quartz double-ended fixed-braced tuning fork (2) and the temperature sensor (3) are set in the sensitive chamber, and the quartz double-ended fixed-braced tuning fork (2) and the PCB board (7) are electrically connected.

2. The pressure sensor according to claim 1, characterized in that: The lower cover plate (6) is provided with lead wire holes (6a).

3. The pressure sensor according to claim 1, characterized in that: The pressure sensor housing (4) is provided with a pressure probe mounting hole (4c) on the outside, and a positioning boss (4d) is provided on the outside of the pressure probe mounting hole (4c); the pressure sensor housing (4) is provided with a glass sintering hole (4a) and a vacuum process hole (4b); a sintered gold pillar (4f) is connected in the glass sintering hole 4a, and the sintered gold pillar (4f) electrically connects the quartz double-ended fixed tuning fork (2) of the sensitive chamber and the PCB board (7); a flexible lever mounting support seat (4e) is provided under the sensitive chamber.

4. The pressure sensor according to claim 3, characterized in that: The metal-based two-stage amplified pressure-sensitive structural element (1) includes a metal pressure probe structure and a metal flexible lever structure; the metal pressure probe structure is concentric with the pressure probe mounting hole (4c) on the pressure sensor housing (4), and the metal pressure probe structure is connected to the positioning boss (4d) on the housing; the metal flexible lever structure includes a pressure input end (1a), a flexible hinge (1b) set in the middle of the lever, an output end (1c) located on one side of the flexible hinge (1b), a fixed reference end (1d) rigidly connected to the lever body, a positioning groove (1e), and a positioning hole (1i) set in the pressure input end; the metal flexible lever structure is connected to the flexible lever mounting support (4e).

5. The pressure sensor according to claim 4, characterized in that: The quartz double-ended fixed tuning fork (2) includes connecting parts (2a, 2b) at both ends. The lower surfaces of the connecting parts (2a, 2b) are connected to the side of the pressure output end (1c) of the metal flexible lever and the fixed reference end (1d) of the flexible lever. The connecting parts are connected by two symmetrical tuning fork arms (2d). A slit (2c) is left between the two tuning fork arms (2d). Electrodes are provided around the surface of the two tuning fork arms (2d). The electrodes are electrically connected to each other for the tuning fork arms (2d) to start oscillating. Under the action of the inverse piezoelectric effect, when an alternating voltage is applied, the tuning fork arms (2d) are in a preset vibration mode. A detection electrode is provided on the upper surface of the connecting part (2a) at one end, and a solder pad is provided on the upper surface of the connecting part (2b) at the other end for connection with the external circuit. The solder pad is connected to the PCB board (7) through a gold wire.

6. The pressure sensor according to claim 4, characterized in that: The temperature sensor (3) is installed close to the quartz double-ended fixed tuning fork (2), and the pins of the temperature sensor (3) are connected to the PCB board (7) through sintered gold pillars (4f).

7. The pressure sensor according to claim 1, characterized in that: The PCB board (7) and the pressure sensor housing (4) are sealed with epoxy resin.

8. An assembly method for a high-precision metal-based two-stage amplified quartz resonant pressure sensor, comprising the following steps: 1) Align the two ends of the quartz double-ended fixed tuning fork (2) with the positioning groove (1e) mark on the side of the metal flexible lever, and then fix them to the metal flexible lever with process glue. 2) Align the metal flexible lever with the flexible lever mounting support (4e) on the shell according to the positioning relationship, and connect the metal flexible lever with the flexible lever mounting support (4e) using laser welding process. 3) The pressure probe is concentric with the pressure probe mounting hole (4c) and fits against the positioning boss (4d) on the pressure sensor housing (4). It is sealed and connected to the pressure sensor housing (4) by welding process; the probe tip of the pressure probe structure is concentric with the positioning hole (1i) of the flexible lever and is inserted into the positioning hole (1i); 4) Secure the probe tip to the flexible metal lever using glue injection; 5) Connect the temperature sensor (3) terminal to the sintered gold pillar (4f) and the quartz double-ended fixed tuning fork (2) to the sintered gold pillar (4f) via gold wire leads. 6) Weld the top cover plate (5) to the pressure sensor housing (4); 7) Evacuate the sensitive chamber through the vacuum process hole (4b); seal the process hole by welding the vacuum process hole. 8) Install the PCB board (7), complete the lead wire soldering, and seal the PCB mounting cavity with epoxy resin; 9) The lead wire is led out through the lead wire hole (6a) on the lower cover plate (6) and connected to the pressure sensor housing (4) and the lower cover plate (6) by welding.

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