Pressure sensor element, pressure sensor module and signal correction method thereof

Abstract

The present invention relates to a pressure sensor element that detects changes in electrostatic capacitance between electrodes. The pressure sensor element (1) comprises an electrically insulating substrate (10), a base electrode layer (20), a spacer (30, 31), a protective electrode layer (30A), and a diaphragm (40). A sensing electrode (S) serving as a sensing electrode portion and monitoring electrodes (M1 to M4) serving as a monitoring electrode portion are arranged on the diaphragm (40) in a manner facing the substrate (10). When the monitoring electrodes (M1 to M4) are mounted on a circuit substrate, they detect stress and strain generated in the spacer (30, 31). With such a structure, high measurement accuracy can be achieved even after mounting on a circuit substrate.

Description

Technical Field

[0001] The present invention relates to a pressure sensor element for measuring air pressure, water pressure, or the like, and a pressure sensor module using the same. Furthermore, the present invention relates to a signal calibration method for the pressure sensor module. Background Art

[0002] Pressure sensors can be manufactured using MEMS (micro-electromechanical systems) technology, which leverages semiconductor manufacturing techniques. This allows for the creation of ultra-small sensors, for example, measuring approximately 0.5 mm to 2 mm square. A typical pressure sensor has a capacitor structure with two electrodes and measures pressure by detecting changes in capacitance due to changes in ambient pressure.

[0003] Figure 10 This is a cross-sectional view showing an example of a conventional pressure sensor element. This pressure sensor element includes a conductive substrate 91 functioning as a base electrode, a diaphragm 95 functioning as a sensing electrode, and a spacer that maintains a gap G between the two. The spacer includes a protective electrode layer 93 and electrical insulating layers 92 and 94 disposed above and below.

[0004] When measuring the electrostatic capacitance between the substrate 91 and the diaphragm 95, a positive voltage or a negative voltage is applied between the base terminal TB and the sensing terminal TS at a fixed period, the generated charge is extracted and A / D (analog / digital) conversion is performed, and then the linearity and temperature characteristics are corrected through digital calculations to convert it into an appropriate pressure value.

[0005] In Patent Document 1 listed below, a substantially C-shaped reference capacitor electrode 6 is disposed outside a circular main capacitor electrode 5 , and an insulating spacer 3 b is provided between the two to suppress deformation of the reference capacitor electrode 6 .

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 9-61273 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Figure 10 The pressure sensor element shown above is typically manufactured and shipped from the factory. It is then mounted on a circuit board on the product assembly line using soldering techniques such as reflow soldering. Heat is applied during mounting, inducing stress and strain in the package and sensor body. As a result, the pressure sensor output may shift by, for example, approximately 100 Pa relative to the initial value, causing measurement errors.

[0011] The present invention aims to provide a pressure sensor element capable of achieving high measurement accuracy even after being mounted on a circuit board, and a pressure sensor module using the same. Furthermore, the present invention provides a signal correction method for a pressure sensor module capable of achieving high measurement accuracy even after being mounted on a circuit board.

[0012] Solutions for solving problems

[0013] One embodiment of the present invention is a pressure sensor element for detecting a change in electrostatic capacitance between electrodes, comprising:

[0014] base electrode portion;

[0015] a sensing electrode portion, which together with the base electrode portion constitutes a sensing capacitor and is deformable in response to a pressure difference in the surrounding area;

[0016] a spacer portion that maintains a gap between the base electrode portion and the sensor electrode portion; and

[0017] The monitor electrode portion, together with the base electrode portion, constitutes a monitor capacitor and detects stress and strain generated in the spacer portion.

[0018] Another aspect of the present invention is a pressure sensor module including the above-mentioned pressure sensor element and an integrated circuit for processing an output signal from the pressure sensor element, wherein:

[0019] The integrated circuit includes:

[0020] a switching circuit for switching between a sensing signal of the sensing electrode portion and a monitoring signal of the monitoring electrode portion;

[0021] an A / D converter that converts an output signal from the switching circuit into a digital signal;

[0022] a digital signal processing unit that performs signal processing on the digital signal; and

[0023] A memory or a register, wherein the memory or the register is used to store the digital value of the monitoring signal.

[0024] Another embodiment of the present invention is a signal calibration method for the pressure sensor module, comprising the following steps:

[0025] Before mounting the pressure sensor module on a circuit board, measuring the electrostatic capacitance of the monitoring capacitor and storing it in a memory or a register as an initial capacitance value;

[0026] After the pressure sensor module is mounted on a circuit board, the electrostatic capacitance of the monitoring capacitor is measured and stored as a mounted capacitance value in a memory or a register;

[0027] calculating a strain correction factor based on the initial capacitance value and the installed capacitance value; and

[0028] The electrostatic capacitance of the sensor capacitor is measured, and the electrostatic capacitance is corrected using the strain correction coefficient and then converted into a pressure value.

[0029] Effects of the Invention

[0030] According to the present invention, high measurement accuracy can be achieved even after mounting on a circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 (A) is a plan view showing an example of a pressure sensor element according to Embodiment 1 of the present invention. Figure 1 (B) is a cross-sectional view thereof.

[0032] Figure 2 yes Figure 1 The equivalent circuit diagram of the pressure sensor element is shown.

[0033] Figure 3 is a circuit diagram showing the electrical connection between the pressure sensor element and the integrated circuit.

[0034] Figure 4 This is a block diagram showing an example of an integrated circuit.

[0035] Figure 5 This is a flowchart showing an example of an operation sequence of an integrated circuit in the manufacturing stage.

[0036] Figure 6 This is a flowchart showing an example of an operation sequence of an integrated circuit after being mounted on a circuit board.

[0037] Figure 7 This is a plan view showing an example of a pressure sensor element 1 according to a second embodiment of the present invention.

[0038] Figure 8 This is a plan view showing an example of a pressure sensor element 1 according to a third embodiment of the present invention.

[0039] Figure 9 This is a plan view showing an example of a pressure sensor element 1 according to a fourth embodiment of the present invention.

[0040] Figure 10 This is a cross-sectional view showing an example of a conventional pressure sensor element. DETAILED DESCRIPTION

[0041] One embodiment of the present invention is a pressure sensor element for detecting a change in electrostatic capacitance between electrodes, comprising:

[0042] base electrode portion;

[0043] a sensing electrode portion, which together with the base electrode portion constitutes a sensing capacitor and is deformable in response to a pressure difference in the surrounding area;

[0044] a spacer portion that maintains a gap between the base electrode portion and the sensor electrode portion; and

[0045] The monitor electrode portion, together with the base electrode portion, constitutes a monitor capacitor and detects stress and strain generated in the spacer portion.

[0046] With this structure, the monitoring electrode section can detect stress and strain applied to the spacer. Therefore, even if the capacitance of the sensing capacitor fluctuates due to thermal stress, such as soldering, when the pressure sensor element is mounted on the circuit board, the capacitance of the sensing capacitor can be adjusted to an appropriate value by taking into account the change in capacitance before and after mounting. As a result, highly accurate pressure measurements can be made even in the final product.

[0047] Preferably, the sensing electrode portion includes sensing electrodes having a rectangular or oval planar shape.

[0048] The monitoring electrode unit includes a first monitoring electrode, a second monitoring electrode, a third monitoring electrode, and a fourth monitoring electrode, respectively arranged on left and right outer sides and upper and lower outer sides relative to the sensor electrode.

[0049] With this configuration, the first, second, third, and fourth monitoring electrodes can independently detect stress and strain generated on the left and right sides and the top and bottom sides of the sensor electrode, thereby more accurately detecting the stress and strain state.

[0050] Preferably, the sensing electrode portion has a rectangular or oval planar shape.

[0051] The monitor electrode unit includes a first monitor electrode and a second monitor electrode, respectively arranged on the left and right outer sides or the upper and lower outer sides relative to the sensor electrode.

[0052] With this configuration, the first and second monitoring electrodes can independently detect stress and strain generated on the left and right sides or the top and bottom sides of the sensor electrode. Therefore, the stress and strain state can be more accurately detected with a simplified configuration.

[0053] Preferably, the monitoring gap included in the monitoring capacitor and the sensing gap included in the sensing capacitor are isolated from the fluid perspective.

[0054] According to this configuration, it is possible to reduce the mutual influence between the capacitance measurement of the monitoring capacitor and the capacitance measurement of the sensing capacitor.

[0055] Another aspect of the present invention is a pressure sensor module including the above-mentioned pressure sensor element and an integrated circuit for processing an output signal from the pressure sensor element, wherein:

[0056] The integrated circuit includes:

[0057] a switching circuit for switching between a sensing signal of the sensing electrode portion and a monitoring signal of the monitoring electrode portion;

[0058] an A / D converter that converts an output signal from the switching circuit into a digital signal;

[0059] a digital signal processing unit that performs signal processing on the digital signal; and

[0060] A memory or a register, wherein the memory or the register is used to store the digital value of the monitoring signal.

[0061] This structure allows high measurement accuracy even after mounting on a circuit board. Furthermore, since signal processing can be performed within the module, the load on the external host can be reduced.

[0062] Another embodiment of the present invention is a signal calibration method for the pressure sensor module, comprising the following steps:

[0063] Before mounting the pressure sensor module on a circuit board, measuring the electrostatic capacitance of the monitoring capacitor and storing it in a memory or a register as an initial capacitance value;

[0064] After the pressure sensor module is mounted on a circuit board, the electrostatic capacitance of the monitoring capacitor is measured and stored as a mounted capacitance value in a memory or a register;

[0065] calculating a strain correction factor based on the initial capacitance value and the installed capacitance value; and

[0066] The electrostatic capacitance of the sensor capacitor is measured, and the electrostatic capacitance is corrected using the strain correction coefficient and then converted into a pressure value.

[0067] This structure calculates the strain correction coefficient based on the initial capacitance value before and after mounting on the circuit board. This allows for high measurement accuracy even after mounting on the circuit board. Furthermore, since signal processing can be performed within the module, the load on the external host computer is reduced.

[0068] (Implementation 1)

[0069] Figure 1 (A) is a plan view of an example of the pressure sensor element 1 according to the first embodiment of the present invention. Figure 1 (B) is a cross-sectional view thereof.

[0070] The pressure sensor element 1 includes an electrically insulating substrate 10 , a base electrode layer 20 , spacer portions 30 and 31 , a guard electrode layer 30A, a membrane plate 40 , and the like.

[0071] The substrate 10 is formed of an electrically insulating material such as silicon oxide. A base electrode layer 20 is provided on one principal surface of the substrate 10. The base electrode layer 20 functions as a base electrode portion, which is a common electrode for the element 1. The base electrode layer 20 is formed of a conductive material such as polycrystalline Si, amorphous Si, or single-crystalline Si (a material with low resistivity). Alternatively, the substrate 10 can be formed of a conductive material to function as the base electrode portion. In this case, the base electrode layer 20 is unnecessary.

[0072] The diaphragm 40 is formed from an electrically insulating material such as silicon oxide or single-crystal silicon. The sensor electrode S and monitor electrodes M1-M4 are provided on the bottom surface of the diaphragm 40, facing the substrate 10. A sensing terminal TS, a base terminal TB, a guard terminal TG, and monitoring terminals TM1-TM4 are provided on the top surface of the diaphragm 40. The sensor terminal TS is electrically connected to the sensor electrode S, the base terminal TB is electrically connected to the top surface of the base electrode layer 20, the guard terminal TG is electrically connected to the guard electrode layer 30A, and the monitor terminals TM1-TM4 are electrically connected to the monitor electrodes M1-M4, respectively.

[0073] The sensor electrode S has, for example, a rectangular planar shape. It serves as a sensing electrode portion, forming a sensor capacitor together with the upper surface of the base electrode layer 20. The inter-electrode capacitance Cs is expressed as Cs = ε × S / d, using the dielectric constant ε of the gap G, the electrode area S, and the inter-electrode distance d. When the diaphragm 40 elastically deforms in response to the pressure difference between the gap G and the external pressure, the inter-electrode distance d changes due to the displacement of the sensor electrode S, and the capacitance Cs also changes accordingly. This change in capacitance Cs is detected by an external circuit via the sensor terminal TS.

[0074] The spacers 30 and 31 are formed of an electrically insulating material such as silicon oxide and are provided to maintain the gap G between the sensor electrode S and the substrate 10 and the gaps G1 to G4 between the monitor electrodes M1 to M4 and the substrate 10. Figure 1 Only gaps G2 and G4 are shown in (B). Spacer 30 is provided along the periphery of substrate 10 to hermetically seal gap G and gaps G1 to G4. Spacer 31 is provided along the periphery of sensor electrode S to hermetically seal gap G and gaps G1 to G4. Gap G and gaps G1 to G4 are externally sealed spaces and are isolated (non-connected) from a fluid perspective. For example, they are filled with an inert gas to maintain a constant pressure. Alternatively, a dielectric material may be enclosed.

[0075] The protective electrode layer 30A is provided within the spacer 30. Specifically, the protective electrode layer 30A is provided along the periphery of the substrate 10 and is electrically insulated from the base electrode layer 20 and the diaphragm 40 by the spacer 30. The presence of the spacer 30 between the base electrode layer 20 and the diaphragm 40 generates parasitic capacitance that is unrelated to pressure changes. However, this parasitic capacitance can be eliminated by electrically grounding the protective electrode layer 30A via the guard terminal TG.

[0076] Monitor electrodes M1-M4 have, for example, a rectangular planar shape. Monitor electrodes M1-M4 serve as monitor electrode portions, forming a monitor capacitor together with substrate 10. The widths of gaps G1-G4 are smaller than the width of gap G, for example, by a ratio of 1 / 4 to 1 / 10. Therefore, even when diaphragm 40 elastically deforms in response to a pressure differential between the external environment and gap G, monitor electrodes M1-M4 do not displace. Gaps G1-G4 can also be filled with a dielectric having a different dielectric constant than gap G, such as a solid polymer, to further suppress deformation of monitor electrodes M1-M4.

[0077] On the other hand, when pressure sensor element 1 is mounted on a circuit board using soldering methods such as reflow soldering, thermal stress and strain may occur in spacers 30 and 31, causing slight fluctuations in inter-electrode distance d. In this case, the capacitances Cd1 to Cd4 of the monitor capacitors corresponding to monitor electrodes M1 to M4 change in accordance with the stress and strain distribution, enabling detection of the stress and strain generated in spacer 31. Changes in capacitances Cd1 to Cd4 are detected by external circuitry via monitor terminals TM1 to TM4, respectively.

[0078] Figure 2 yes Figure 1 The equivalent circuit diagram of the pressure sensor element 1 is shown. Figure 3 This is a circuit diagram showing the electrical connection between the pressure sensor element 1 and the integrated circuit 50. A sensing capacitor with capacitance Cs exists between the base terminal TB and the sense terminal TS. Monitoring capacitors with capacitances Cd1 to Cd4 exist between the base terminal TB and the monitoring terminals TM1 to TM4, respectively. A parasitic capacitance Cbg exists between the base terminal TB and the guard terminal TG. A parasitic capacitance Csg exists between the sense terminal TS and the guard terminal TG.

[0079] like Figure 3 As shown, switching circuits SW0 to SW4 and a CDC circuit 51 (CDC is the abbreviation of Capacitance to Digital Convertor) are provided in the integrated circuit 50. The switching circuits SW0 to SW4 operate as a multiplexer that selects one output signal from a plurality of input signals at a predetermined timing. Specifically, a) when SW0 is turned on and SW1 to 4 are turned off, the electrostatic capacitance Cs can be detected. b) when SW1 is turned on and SW0 and SW2 to 4 are turned off, the electrostatic capacitance Cd1 can be detected. c) when SW2 is turned on and SW0 to 1 and SW3 to 4 are turned off, the electrostatic capacitance Cd2 can be detected. d) when SW3 is turned on and SW0 to 2 and SW4 are turned off, the electrostatic capacitance Cd3 can be detected. e) when SW4 is turned on and SW0 to 3 are turned off, the electrostatic capacitance Cd4 can be detected.

[0080] The CDC circuit 51 includes an A / D converter that converts analog signals into digital signals. The CDC circuit 51 converts the capacitance selected by the switch circuits SW0 to SW4 into a digital signal. Although not shown, a pulse generator that supplies a rectangular wave voltage to the capacitance and an amplifier that amplifies the charge generated by the capacitance are provided between the switch circuits SW0 to SW4 and the CDC circuit 51.

[0081] Figure 4: This is a block diagram showing an example of an integrated circuit 50. The integrated circuit 50 is formed, for example, by an ASIC, FPGA, PLD, or CPLD, and includes the aforementioned CDC circuit 51, a digital filter 52, a temperature sensor 53, a digital correction unit 54, a register 55, a FIFO buffer 56, and a digital I / F (interface) 57. These components can be implemented using a combination of a CPU, a GPU, or other arithmetic processor, an EEPROM, a RAM, or other memory, software, and hardware.

[0082] The digital filter 52 filters the digital signal from the CDC circuit 51, removes high-frequency noise components, and outputs a low-frequency signal. The temperature sensor 53 includes a PN junction diode, a thermistor, etc., and measures the temperature near the pressure sensor element 1 and outputs it as a digital value.

[0083] The digital correction unit 54 uses the digital temperature value from the temperature sensor 53 and the correction coefficient stored in the internal memory to correct the digital pressure value output from the digital filter 52, performing temperature correction and linearity correction. The register 55 stores various digital data. The FIFO buffer 56 temporarily stores digital data and adjusts the timing of input and output. The digital I / F 57 communicates with an external host and transmits and receives various digital data.

[0084] The pressure sensor module includes the pressure sensor element 1 and the integrated circuit 50 .

[0085] Figure 5 This flowchart shows an example of the operating sequence of integrated circuit 50 during the manufacturing phase. For example, this sequence can be programmed into a state machine (a digital circuit that automatically controls the operating process) within an ASIC to automatically execute the operation. Here, the initial values ​​of the electrostatic capacitances Cd1 to Cd4 of the monitor capacitors corresponding to monitor electrodes M1 to M4 are measured.

[0086] First, in step P1, SW1 of the switch circuit is turned on, SW0 and SW2-4 are turned off, and the initial capacitance Cdi1 is measured. Next, in step P2, SW2 of the switch circuit is turned on, SW0-1 and SW3-4 are turned off, and the initial capacitance Cdi2 is measured.

[0087] Next, in step P3, SW3 of the switch circuit is turned on, SW0-2 and SW4 are turned off, and the initial capacitance Cdi3 is measured. Next, in step P4, SW4 of the switch circuit is turned on, SW0-3 are turned off, and the initial capacitance Cdi4 is measured.

[0088] Next, in step P5, the measured initial capacitances Cdi1 to Cdi4 are stored in a nonvolatile memory or register, such as an EEPROM, of the integrated circuit 50. At this stage, the pressure sensor module is ready for shipment.

[0089] Figure 6 This flowchart shows an example of the operation sequence of integrated circuit 50 after it is mounted on a circuit board. For example, this sequence can be automatically executed by programming a state machine within the ASIC. This sequence can be initiated when integrated circuit 50 is powered on or by receiving a control command from an external host. Data correction is performed here using initial capacitances Cdi1 to Cdi4 measured during the manufacturing phase.

[0090] First, in step S1, SW1 of the switch circuit is turned on, SW0 and SW2-4 are turned off, and the capacitance Cd1 after mounting is measured and stored in a memory or register. Next, in step S2, SW2 of the switch circuit is turned on, SW0-1 and SW3-4 are turned off, and the capacitance Cd2 after mounting is measured and stored in a memory or register.

[0091] Next, in step S3, the switch circuit SW3 is turned on, SW0-2 and SW4 are turned off, and the capacitance Cd3 after mounting is measured and stored in a memory or register. Next, in step S4, the switch circuit SW4 is turned on, SW0-3 are turned off, and the capacitance Cd4 after mounting is measured and stored in a memory or register.

[0092] Next, in step S5, the initial capacitances Cdi1 to Cdi4 stored in the memory or register of the integrated circuit 50 in step P5 are read out. Next, in step S6, the strain correction coefficient is calculated based on the initial capacitances Cdi1 to Cdi4 and the capacitances Cd1 to Cd4 after mounting measured in steps S1 to S4.

[0093] Next, in step S7, the obtained strain correction coefficient is stored in the digital correction unit 54. Next, in step S8, digital correction is started.

[0094] Next, in step S9 , SW0 of the switch circuit is turned on, and SW1 to SW4 are turned off, and the current capacitance Cs is measured. The capacitance Cs is converted into pressure corrected using the strain correction coefficient.

[0095] As an example, the specific method for calculating the strain correction coefficient is described. First, the difference ΔCdn = Cdn - Cdin (n = 1, 2, 3, 4) is calculated. Next, the change in capacitance in the X and Y directions is calculated based on the difference between the capacitances Cd1 and Cd3, which are arranged facing each other across the sensor electrode S, and the difference between the capacitances Cd2 and Cd4. Next, using the capacitor-related formula: C = ε × S / d, the displacements dx and dy in the X and Y directions of the gaps G1 to G4 are calculated, and the following pressure change P is derived. offset In addition, α is the strain constant related to the X direction, and β is the strain constant related to the Y direction.

[0096] P offset =α×d×+β×dy…(1)

[0097] All capacitance values ​​are stored as digitized data in the memory or register of the integrated circuit. In addition, the temperature value from the temperature sensor 53 can also be digitized and used as temperature data. In addition, the temperature characteristics and linearity are combined with the correction coefficients obtained in advance before the manufacturing stage to perform polynomial operations to obtain the following final output p (L, T). In addition, a ij is the temperature / linearity correction coefficient, f(L) is a function of linearity, and f(T) is a function of temperature.

[0098] p(L, T) = ∑[a ij ·f(L)·f(T)]…(2)

[0099] In order to take stress-strain correction into account, the pressure variation P obtained in the previous process is subtracted from equation (2). offset , get the final pressure value P final .

[0100] P final =p(L, T)-P offset …(3)

[0101] These correction calculations can be Figure 4 The digital correction unit 54 in the embodiment is executed in synchronization with the internal clock.

[0102] (Implementation Method 2)

[0103] Figure 7 FIG. 1 is a top view showing an example of a pressure sensor element 1 according to a second embodiment of the present invention. Figure 1 Compared with the structure of the sensor electrode S, the sensor electrode S has a long round (or elliptical) planar shape, and the monitoring electrodes M1 to M4 also have a long round planar shape. Figure 1In such a structure, the monitor electrodes M1 to M4 can also detect stress and strain applied to the spacer.

[0104] (Implementation 3)

[0105] Figure 8 1 is a top view showing an example of a pressure sensor element 1 according to a third embodiment of the present invention. Figure 1 Compared with the structure of , the monitoring electrodes M2 and M4 arranged on the left and right outer sides (short sides) relative to the sensor electrode S are omitted, and only the two monitoring electrodes M1 and M3 are arranged on the upper and lower outer sides (long sides) relative to the sensor electrode S. Other mechanical and electrical structures are the same as Figure 1 In such a structure, the monitoring electrodes M1 and M3 can also detect the stress and strain applied to the spacer.

[0106] (Implementation 4)

[0107] Figure 9 FIG. 1 is a top view showing an example of a pressure sensor element 1 according to a fourth embodiment of the present invention. Figure 1 Compared with the structure of , the monitoring electrodes M1 and M3 arranged on the upper and lower outer sides (long sides) relative to the sensor electrode S are omitted, and only the two monitoring electrodes M2 and M4 are arranged on the left and right outer sides (short sides) relative to the sensor electrode S. Other mechanical and electrical structures are the same as Figure 1 In such a structure, the monitoring electrodes M2 and M4 can also detect the stress and strain applied to the spacer.

[0108] In the above embodiments, the case where four or two monitor electrodes are arranged around the sensor electrode has been described. However, one, three, or five monitor electrodes may also be arranged.

[0109] Furthermore, in the above embodiments, the sensor electrodes and the monitor electrodes are described as having rectangular or oval planar shapes. However, they may also be polygonal shapes such as triangles, pentagons, and hexagons.

[0110] Although the present invention has been fully described with reference to the accompanying drawings and in conjunction with the preferred embodiments thereof, various modifications and variations will be apparent to those skilled in the art. It should be understood that such modifications and variations are intended to be within the scope of the present invention as long as they do not depart from the scope of the present invention as defined by the appended claims.

[0111] Industrial applicability

[0112] Since high measurement accuracy can be achieved even after mounting on a circuit board, the present invention is extremely useful industrially.

[0113] Description of Reference Numerals

[0114] 1: Pressure sensor element; 10: Substrate; 20: Base electrode layer; 30, 31: Spacer; 30A: Guard electrode layer; 40: Diaphragm; 50: Integrated circuit; 51: CDC circuit; 52: Digital filter; 53: Temperature sensor; 54: Digital correction unit; 55: Register; 56: FIFO buffer; 57: Digital I / F; G: Gap; M1 to M4: Monitoring electrodes; S: Sensing electrode; SW0 to SW4: Switch circuit; TS: Sensing terminal; TB: Base terminal; TG: Guard terminal; TM1 to TM4: Monitoring terminals.

Claims

1. A pressure sensor element for detecting a change in electrostatic capacitance between electrodes, the pressure sensor element comprising: base electrode portion; a sensing electrode portion, which together with the base electrode portion constitutes a sensing capacitor and is deformable in response to a pressure difference in the surrounding area; a spacer portion that maintains a gap between the base electrode portion and the sensor electrode portion; and The monitoring electrode portion, which together with the base electrode portion constitutes a monitoring capacitor, detects stress and strain generated in the gap portion. in, The monitoring electrode portion includes a plurality of monitoring electrodes respectively arranged on the left and right outer sides and / or the upper and lower outer sides relative to the sensing electrode portion. The plurality of monitoring electrodes are electrically connected to different monitoring terminals respectively. A monitoring gap included in the monitoring capacitor is isolated from a sensing gap included in the sensing capacitor from a fluidic perspective.

2. The pressure sensor element according to claim 1, wherein The sensing electrode portion includes a sensing electrode having a rectangular or oval planar shape, The monitoring electrode unit includes a first monitoring electrode, a second monitoring electrode, a third monitoring electrode, and a fourth monitoring electrode, respectively arranged on left and right outer sides and upper and lower outer sides relative to the sensor electrode.

3. The pressure sensor element according to claim 1, wherein The sensing electrode portion has a rectangular or oval planar shape, The monitor electrode unit includes a first monitor electrode and a second monitor electrode, respectively arranged on the left and right outer sides or the upper and lower outer sides relative to the sensor electrode.

4. A pressure sensor module comprising the pressure sensor element according to any one of claims 1 to 3 and an integrated circuit for processing an output signal from the pressure sensor element, wherein: The integrated circuit includes: a switching circuit for switching between a sensing signal of the sensing electrode portion and a monitoring signal of the monitoring electrode portion; an A / D converter that converts an output signal from the switching circuit into a digital signal; a digital signal processing unit that performs signal processing on the digital signal; and A memory or a register, wherein the memory or the register is used to store the digital value of the monitoring signal.

5. A signal calibration method for a pressure sensor module, comprising the steps of: Before mounting the pressure sensor module on a circuit board, measuring the electrostatic capacitance of the monitoring capacitor and storing it in a memory or a register as an initial capacitance value; After the pressure sensor module is mounted on a circuit board, the electrostatic capacitance of the monitoring capacitor is measured and stored as a mounted capacitance value in a memory or a register; calculating a strain correction factor based on the initial capacitance value and the installed capacitance value; as well as The electrostatic capacitance of the sensor capacitor is measured, and the electrostatic capacitance is corrected using the strain correction coefficient and then converted into a pressure value.

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