JP2024010886A - sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor device which suppresses influence of a parasitic capacitance and heat stress.

SOLUTION: A sensor device includes a physical quantity sensor, a conversion circuit for converting a signal detected by the physical quantity sensor into a voltage signal, a first substrate provided with at least a part of the conversion circuit and the physical quantity sensor, and a second substrate electrically connected to the first substrate, wherein a change rate to the temperature or humidity of a parasitic capacitance formed between at least a part of the conversion circuit and the first substrate is smaller than a change rate to the temperature, humidity or pressure of a parasitic capacitance formed between at least the part of the conversion circuit and the second substrate.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a sensor device.

Patent Document 1 states that "parasitic capacitance of wiring connecting a detection circuit and a detection element is reduced, and sensor accuracy is further improved" (abstract).
Patent Document 2 states that "a piezoelectric angular velocity sensor capable of highly accurate angular velocity detection is provided" (abstract).
[Prior art documents]
[Patent document]
[Patent Document 1] JP-A-2007-101533 [Patent Document 2] JP-A-11-325908

In a sensor device, it is preferable to suppress the effects of parasitic capacitance and thermal stress.

In a first aspect of the invention, a sensor device is provided. The sensor device includes a physical quantity sensor, a conversion circuit that converts a signal detected by the physical quantity sensor into a voltage signal, a first substrate provided with at least a portion of the conversion circuit and the physical quantity sensor, and electrically connected to the first substrate. and a second substrate. The rate of change of the parasitic capacitance formed between at least a portion of the conversion circuit and the first substrate with respect to temperature or humidity is the rate of change of the parasitic capacitance formed between at least a portion of the conversion circuit and the second substrate with respect to temperature or humidity. less than the rate of change.

The moisture absorption rate of the first substrate may be lower than the moisture absorption rate of the second substrate.

The first substrate may be made of ceramic.

The second substrate may include an organic material.

The first substrate may be fixed onto the second substrate.

The conversion circuit may include an amplifier circuit and wiring that connects the amplifier circuit and the physical quantity sensor. The amplifier circuit and wiring may be provided on the first substrate.

The conversion circuit may include an amplifier circuit and wiring that connects the amplifier circuit and the physical quantity sensor. At least a portion of the wiring may be provided on the first substrate. The amplifier circuit may be provided on the second substrate.

The coefficient of thermal expansion of the first substrate and the coefficient of thermal expansion of the second substrate may be different.

The sensor device may further include a lead frame that electrically connects the first substrate and the second substrate.

The first substrate may be fixed to the lead frame. The resonant frequency of the first substrate and the lead frame may be higher than the resonant frequency of the physical quantity sensor.

The sensor device may further include a casing to which the first substrate is fixed and which accommodates the first and second substrates, and a connection portion that electrically connects the first and second substrates.

The first substrate may be fixed to the housing using a flexible bonding material.

The resonance frequency of the first substrate and the bonding material may be higher than the resonance frequency of the physical quantity sensor.

Note that the above summary of the invention does not list all the features of the invention. Furthermore, subcombinations of these features may also constitute inventions.

1 is a diagram illustrating an example of a sensor system 200 according to one embodiment of the present invention. 1 is a diagram showing an example of a sensor device 100 according to one embodiment of the present invention. 3 is a diagram of the sensor device 100 shown in FIG. 2 viewed in the Y-axis direction. FIG. 4 is a diagram showing an example of details of the physical quantity sensor 10 shown in FIGS. 2 and 3. FIG. 5 is a diagram showing an example of the aa' cross section of the physical quantity sensor 10 shown in FIG. 4. FIG. It is a figure showing sensor device 300 of a comparative example. 7 is a diagram of the sensor device 300 shown in FIG. 6 viewed in the Y-axis direction. FIG. 1 is a diagram showing an example of a circuit diagram of a sensor device 100. FIG. 5 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T. FIG. 5 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T. FIG. 5 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T. FIG. 5 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T. FIG. 7 is a diagram showing another example of the relationship between the output of the conversion circuit 40-1 and the temperature T. FIG. 7 is a diagram showing another example of a circuit diagram of the sensor device 100. FIG. It is a figure showing another example of sensor device 100 concerning one embodiment of the present invention. 16 is a sectional view taken along line bb' in FIG. 15. FIG. 17 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and time when the sensor device 100 is the example shown in FIGS. 15 and 16. FIG. 17 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and time when the sensor device 100 is the example shown in FIGS. 15 and 16. FIG. 18 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T when the output of the conversion circuit 40-1 is in the state shown in FIG. 17. FIG. 19 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T when the output of the conversion circuit 40-2 is in the state shown in FIG. 18. FIG. 4 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and time when the sensor device 100 is the example shown in FIGS. 2 and 3. FIG. 4 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and time when the sensor device 100 is the example shown in FIGS. 2 and 3. FIG. 22 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T when the output of the conversion circuit 40-1 is in the state shown in FIG. 21. FIG. 23 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T when the output of the conversion circuit 40-2 is in the state shown in FIG. 22. FIG. It is a figure showing another example of sensor device 100 concerning one embodiment of the present invention. 26 is another diagram illustrating the sensor device 100 shown in FIG. 25. FIG.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are essential to the solution of the invention.

FIG. 1 is a diagram illustrating an example of a sensor system 200 according to one embodiment of the present invention. The sensor system 200 of this example includes a sensor device 100, a control section 30, a frequency oscillator 50, an LPF (low pass filter) 52, an AD converter (analog-digital converter) 54, a storage section 70, and an interface section 58. The sensor device 100 includes a physical quantity sensor 10 and a conversion circuit 40.

The physical quantity sensor 10 detects a physical quantity of an object. The physical quantity sensor 10 may be an acceleration sensor or a pressure sensor. The acceleration sensor may be a capacitance type acceleration sensor (described later). The conversion circuit 40 converts the signal detected by the physical quantity sensor 10 into a voltage signal. Conversion circuit 40 may be an analog signal processing circuit.

A frequency oscillator 50 generates a clock signal CK with a period T. The physical quantity sensor 10 detects the physical quantity of the object at a time based on the clock signal CK. The AD converter 54 acquires the signal from the physical quantity sensor 10 at a time based on the clock signal CK. The time based on the clock signal CK is, for example, the time when the clock signal CK rises. Sensor system 200 may be supplied with voltage by power supply hub 130 .

The control unit 30 controls signal processing in the sensor device 100. The control unit 30 may be a so-called CPU (Central Processing Unit). The storage unit 70 may store physical quantity data detected by the physical quantity sensor 10.

The LPF 52 removes high frequency noise in the voltage signal output from the conversion circuit 40. The AD converter 54 converts the analog voltage signal from which high frequency noise has been removed by the LPF 52 into a digital signal at the timing of the clock signal CK. The control unit 30 may transmit a trigger signal to the AD converter 54. The AD converter 54 may start analog-to-digital conversion at the timing of receiving the trigger signal.

Sensor system 200 may include an interface section 58 . The interface unit 58 may receive power supplied by the power feeding hub 130. The interface unit 58 may mediate communication between the power feeding hub 130 and the control unit 30. The interface unit 58 may be connected to the computer 110 and the NTP server 140 via a communication line 150.

FIG. 2 is a diagram showing an example of the sensor device 100 according to one embodiment of the present invention. The sensor device 100 includes a first substrate 20 and a second substrate 22. At least a portion of the conversion circuit 40 (see FIG. 1) and the physical quantity sensor 10 are provided on the first substrate 20. The conversion circuit 40 may include an amplifier circuit 42. In this example, the amplifier circuit 42 is provided on the first substrate 20. The second substrate 22 is electrically connected to the first substrate. The first substrate 20 may be fixed onto the second substrate 22.

The moisture absorption rate of the first substrate 20 may be smaller than the moisture absorption rate of the second substrate 22. The moisture absorption rate of a substrate is defined as the second mass relative to the first mass, where the first mass is the mass of the substrate that has not absorbed moisture, and the second mass is the mass of the substrate whose moisture absorption is saturated. and the first mass.

The coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 may be different. The coefficient of thermal expansion of the substrate may be the coefficient of linear expansion of the substrate. The coefficient of linear expansion of a substrate is defined as the first length, which is the length in one direction in the in-plane direction of the substrate before the temperature rises, and the length in the one direction of the substrate after the temperature rises by a unit temperature (1K). In the case of the second length, it may be the ratio of the difference between the second length and the first length to the first length. The coefficient of thermal expansion of the substrate may be the coefficient of volumetric expansion of the substrate. The coefficient of volumetric expansion of a substrate is defined as the volumetric expansion coefficient of a substrate with respect to the first volume, where the volume of the substrate before the temperature rise is the first volume, and the volume of the substrate after the temperature has increased by a unit temperature (1K) is the second volume. It may be a ratio of the difference between the volume and the first volume.

The first substrate 20 may be made of ceramic. The first substrate 20 may be a so-called ceramic substrate. The first substrate 20 may be formed of at least one of alumina and nonmetal. The first substrate 20 may be made of an inorganic material. The first substrate 20 does not need to contain an organic material.

The second substrate 22 may include an organic material. The organic material is, for example, an epoxy material. The second substrate 22 may be a so-called glass epoxy substrate.

Let the coefficient of thermal expansion of the first substrate 20 be a coefficient of thermal expansion te1, and the coefficient of thermal expansion of the second substrate 22 be a coefficient of thermal expansion te2. Let the coefficient of thermal expansion of the physical quantity sensor 10 be the coefficient of thermal expansion ts. The coefficient of thermal expansion te1 may be smaller than the coefficient of thermal expansion te2. When the physical quantity sensor 10 is a MEMS acceleration sensor, the MEMS acceleration sensor may be formed of Si (silicon) and glass. When the MEMS acceleration sensor is made of Si (silicon) and glass and the second substrate 22 is a glass epoxy substrate, the thermal expansion coefficient ts is smaller than the thermal expansion coefficient te2. Therefore, it is preferable that the coefficient of thermal expansion te1, the coefficient of thermal expansion ts, and the coefficient of thermal expansion te2 have a relationship of ts<te1<te2.

In this specification, technical matters may be explained using orthogonal coordinate axes of the X-axis, Y-axis, and Z-axis. In this specification, a plane parallel to the plate surface of the first substrate 20 is referred to as an XY plane. In this specification, the direction perpendicular to the plate surface of the first substrate 20 is defined as the Z-axis direction. In this specification, a predetermined direction within the XY plane is referred to as the X-axis direction, and a direction perpendicular to the X-axis within the XY plane is referred to as the Y-axis direction. The XY plane may be a horizontal plane. The Z axis may be parallel to the vertical direction.

FIG. 3 is a diagram of the sensor device 100 shown in FIG. 2 viewed in the Y-axis direction. In this example, the physical quantity sensor 10 and the amplifier circuit 42 are provided on the first substrate 20. The sensor device 100 may include a lid part 21. The lid portion 21 may be made of the same material as the first substrate 20. The lid portion 21 may be made of ceramic. The physical quantity sensor 10 and the amplifier circuit 42 may be surrounded by the first substrate 20 and the lid part 21.

FIG. 4 is a diagram showing a detailed example of the physical quantity sensor 10 shown in FIGS. 2 and 3. As shown in FIG. The physical quantity sensor 10 of this example is a capacitive MEMS acceleration sensor. The physical quantity sensor 10 of this example includes a fixed electrode 11, a fixed electrode 12, a movable electrode 13, a fixed frame 14, and an elastic part 15. The movable electrode 13 may be a plate-shaped member.

The physical quantity sensor 10 of this example has two fixed electrodes 11 (fixed electrode 11-1 and fixed electrode 11-2). In this example, the fixed electrode 11-1 is arranged adjacent to one side of the movable electrode 13 in a predetermined direction (X-axis direction in this example), and the fixed electrode 11-2 is a movable electrode in the X-axis direction. They are arranged adjacent to each other on the other side of 13. A gap is provided between the fixed electrode 11 and the movable electrode 13 in the X-axis direction. That is, the fixed electrode 11 and the movable electrode 13 are not in contact with each other.

The physical quantity sensor 10 of this example has two fixed electrodes 12 (fixed electrode 12-1 and fixed electrode 12-2). In this example, the fixed electrode 12-1 is arranged adjacent to one side of the movable electrode 13 in a predetermined direction (Y-axis direction in this example), and the fixed electrode 12-2 is a movable electrode 13 in the Y-axis direction. They are arranged adjacent to each other on the other side of 13. A gap is provided between the fixed electrode 12 and the movable electrode 13 in the Y-axis direction. That is, the fixed electrode 12 and the movable electrode 13 are not in contact with each other.

The fixed frame 14 may be provided so as to surround the fixed electrode 11, the fixed electrode 12, the movable electrode 13, and the elastic part 15 in the XY plane. In this example, the fixed electrode 11 and the fixed electrode 12 are fixed to a fixed frame 14. Fixed electrode 11 and fixed electrode 12 and fixed frame 14 are electrically insulated. In this example, one end of the elastic section 15 is fixed to the fixed frame 14, and the other end of the elastic section 15 is fixed to the movable electrode 13. The one end of the elastic portion 15 and the fixed frame 14 are electrically insulated.

The sensor device 100 (see FIGS. 2 and 3) may include a voltage application section 90. Voltage application section 90 applies a carrier signal to movable electrode 13 through elastic section 15 . The carrier signal may be an alternating current signal with a predetermined frequency f. The frequency f is, for example, 100 kHz.

FIG. 5 is a diagram showing an example of the aa' cross section of the physical quantity sensor 10 shown in FIG. The aa' line is an XZ cross section passing through the fixed frame 14, fixed electrode 11-1, movable electrode 13, and fixed electrode 11-2.

The physical quantity sensor 10 of this example has a fixed electrode 16. The fixed electrode 16 may be arranged adjacent to one side of the movable electrode 13 in the Z-axis direction. Spaces 17 are provided on both sides of the movable electrode 13 in the Z-axis direction. The space 17-1 is provided between the movable electrode 13 and the fixed electrode 16 in the Z-axis direction. The space 17-2 is provided on the opposite side of the space 17-1 with respect to the movable electrode 13 in the Z-axis direction. The movable electrode 13 and the fixed electrode 16 are not in contact with each other.

The movable electrode 13 is displaced by acceleration. The physical quantity sensor 10 of this example detects a change in capacitance between the movable electrode 13 and the fixed electrode 11, the fixed electrode 12, and the fixed electrode 16 due to the displacement of the movable electrode 13. This change in capacitance may be converted into a voltage signal by an amplifier circuit 42 (see FIGS. 2 and 3).

When the physical quantity sensor 10 detects a change in capacitance, a carrier signal may be applied to the movable electrode 13 by the voltage application section 90 (see FIG. 4). The physical quantity sensor 10 of this example detects acceleration by detecting changes in capacitance between the fixed electrodes 11, 12, 16, and the movable electrode 13.

The physical quantity sensor 10 of this example detects the component of acceleration in the X-axis direction by detecting a change in capacitance between the fixed electrode 11 (see FIG. 4) and the movable electrode 13. The physical quantity sensor 10 of this example detects a component of acceleration in the Y-axis direction by detecting a change in capacitance between a fixed electrode 12 (see FIG. 4) and a movable electrode 13. The physical quantity sensor 10 of this example detects a component of acceleration in the Z-axis direction by detecting a change in capacitance between the fixed electrode 16 and the movable electrode 13.

Wiring 92 (see FIG. 4), wiring 93 (see FIG. 4), and wiring 94 are connected to fixed electrode 11 (see FIG. 4), fixed electrode 12 (see FIG. 4), and fixed electrode 16, respectively. In this example, wiring 92-1 and wiring 92-2 are connected to fixed electrode 11-1 and fixed electrode 11-2, respectively, and wiring 93-1 and wiring are connected to fixed electrode 12-1 and fixed electrode 12-2, respectively. 93-2 is connected, and a wiring 94 is connected to the fixed electrode 16.

The sensor device 100 (see FIGS. 2 and 3) may include a plurality of conversion circuits 40. In this example, the sensor device 100 includes three conversion circuits 40 (conversion circuits 40-1 to 40-3). In this example, wiring 92 (see FIG. 4) is connected to conversion circuit 40-1, wiring 93 (see FIG. 4) is connected to conversion circuit 40-2, and wiring 94 is connected to conversion circuit 40-3. There is. In this example, the conversion circuit 40 converts changes in capacitance detected by the physical quantity sensor 10 between the fixed electrodes 11, 12, and 16 and the movable electrode 13 into voltage signals. .

FIG. 6 is a diagram showing a sensor device 300 of a comparative example. FIG. 7 is a diagram of the sensor device 300 shown in FIG. 6 viewed in the Y-axis direction. In the sensor device 300, the amplifier circuit 42 is provided on the second substrate 22. Sensor device 300 differs from sensor device 100 in this respect.

FIG. 8 is a diagram showing an example of a circuit diagram of the sensor device 100. In FIG. 8, a capacitor C1 and a capacitor C2 indicating the capacitance of the physical quantity sensor 10 are shown. The capacitor C1 is, for example, a capacitor formed between the fixed electrode 12-1 and the movable electrode 13 shown in FIG. The capacitor C2 is, for example, a capacitor formed between the fixed electrode 12-2 and the movable electrode 13 shown in FIG. The capacitance of capacitor C1 and capacitor C2 is, for example, 10 pF.

The conversion circuit 40 of this example includes capacitors Ca1 to Ca3, a resistor Ra1, a resistor Ra2, and an amplifier circuit . The conversion circuit in this example is a charge amplifier. The amplifier circuit 42 is, for example, an operational amplifier.

Wiring 92 to wiring 94 connect amplifier circuit 42 and physical quantity sensor 10. In this example, the wiring 92-1 is connected to the capacitor C1, the capacitor Ca1, the resistor Ra1, and the amplifier circuit 42, and the wire 92-2 is connected to the capacitor C2, the capacitor Ca2, the capacitor Ca3, the resistor Ra2, and the amplifier circuit 42. There is. The wiring 93-1 and the wiring 94 are connected to the capacitor C1, the capacitor Ca1, the resistor Ra1, and the amplifier circuit 42, as in FIG. The wiring 93-2 is connected to the capacitor C2, the capacitor Ca2, the capacitor Ca3, the resistor Ra2, and the amplifier circuit 42, as in FIG.

At least a portion of the conversion circuit 40 is provided on the first substrate 20 (see FIGS. 2 and 3). In FIG. 8, the range provided on the first substrate 20 of the sensor device 100 is indicated by a dashed-dotted line frame. In this example, the amplifier circuit 42 and the wiring 92 are provided on the first substrate 20. In this example, the entire sensor device 100 is provided on the first substrate 20.

FIG. 9 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T. Temperature T is the air temperature of the space in which the sensor device 100 is placed. The temperature T0 is, for example, 0°C. In this example, temperatures T1 to T6 are higher than 0°C, and temperatures T1' to T3' are lower than 0°C. The temperatures T1 to T6 are, for example, 10°C to 60°C. Temperature T1' to temperature T3' are, for example, -10°C to -30°C. FIG. 9 shows the results of measuring the relationship between the output of the conversion circuit 40-1 and the temperature T four times.

In FIG. 9, the output indicated by 0 is the reference value of the output of the conversion circuit 40-1. The reference value may be the output at the start of output measurement. The reference value may be a so-called zero point output. The zero point output refers to an output when the physical quantity sensor 10 has no acceleration in the X-axis direction or the Y-axis direction, but has only gravitational acceleration in the Z-axis direction. The outputs indicated by +Vm and -Vm in FIG. 9 are the upper and lower limits, respectively, of allowable output errors. The output of the conversion circuit 40-1 is within the range of -Vm to +Vm over the temperature range from temperature T3' to temperature T6 in all four measurements.

FIG. 10 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T. The output of the conversion circuit 40-2 is within the range of -Vm to +Vm over the temperature range from temperature T3' to temperature T6 in all four measurements. 9 and 10 show the influence of a change in temperature on the parasitic capacitance formed between at least a portion of the conversion circuit 40 provided on the first substrate 20 and the first substrate 20. FIG.

FIG. 11 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T. FIG. 11 is an example in which the conversion circuit 40-1 shown in FIG. 8 is provided on the second substrate 22 (see FIGS. 6 and 7). In the example of FIG. 11, the output of the conversion circuit 40-1 does not fall within the range of -Vm to +Vm over the four measurements. The temperature dependence of the output of the conversion circuit 40-1 is greater than in the example of FIG.

FIG. 12 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T. In the example of FIG. 12 as well, the output of the conversion circuit 40-2 does not fall within the range of -Vm to +Vm over the four measurements. The temperature dependence of the output of the conversion circuit 40-2 is greater than in the example of FIG. FIGS. 11 and 12 show the effect that a change in parasitic capacitance formed between at least a portion of the conversion circuit 40 provided on the second substrate 22 and the second substrate 22 with respect to temperature has on the output of the conversion circuit 40. Showing.

FIG. 13 is a diagram showing another example of the relationship between the output of the conversion circuit 40-1 and the temperature T. FIG. 13 shows a case where the conversion circuit 40-1 is provided on the second substrate 22, and the conversion circuit 40-1 is dry-sealed by a housing housing the sensor system 200 (see FIG. 1). This is an example of a case where the device is hermetically sealed by the casing, and a case where the device is not sealed by the casing. Dry sealing is when dry air is sealed. In FIG. 13, the output of the conversion circuit 40-1 and the temperature T are shown for each of three sensor devices 100 (in the case of dry sealing and airtight sealing) and four sensor devices 100 (in the case of no sealing). relationship is shown.

As shown in FIG. 13, the output of the conversion circuit 40-1 in the case of dry sealing and airtight sealing falls within the range of -Vm to +Vm. A part of the output of the conversion circuit 40-1 in the case of not being sealed may not fall within the range of -Vm to +Vm. From the above, it is understood that by suppressing changes in humidity, fluctuations in the zero point are also suppressed.

As described above, in the sensor device 100, at least a portion of the conversion circuit 40 is provided on the first substrate 20. In the sensor device 300, at least a portion of the conversion circuit 40 is provided on the second substrate 22. The rate of change of the parasitic capacitance formed between the at least part of the conversion circuit 40 and the first substrate 20 with respect to temperature or humidity is determined by the rate of change of the parasitic capacitance formed between the at least part of the conversion circuit 40 and the second substrate 22 Less than the rate of change of parasitic capacitance with temperature or humidity. The at least part of the conversion circuit 40 may refer to the capacitor Ca1, the capacitor Ca2, the capacitor Ca3, the resistor Ra1, the resistor Ra2, and the amplifier circuit 42 of the converter circuit 40. The at least part of the conversion circuit 40 may include the wiring 92, the wiring 93, and the wiring 94 in the case of the conversion circuits 40-1 to 40-3, respectively.

In the non-sealed examples shown in FIGS. 11, 12, and 13, a parasitic capacitance is formed between at least a portion of the conversion circuit 40 and the second substrate 22 due to the second substrate 22 absorbing moisture. is easy to change. Due to the change in the parasitic capacitance, the output of the sensor device 300 tends to change. Since the first substrate 20 is less likely to absorb moisture than the second substrate 22, in the examples shown in FIGS. 9 and 10, the parasitic capacitance formed between at least a portion of the conversion circuit 40 and the first substrate 20 is It is less likely to change than the example shown in FIG. Therefore, the output of the sensor device 100 is less likely to change than the output of the sensor device 300.

FIG. 14 is a diagram showing another example of the sensor device 100 shown in FIG. 8. The wiring 92 connects the amplifier circuit 42 and the physical quantity sensor 10. At least a portion of the wiring 92 may be provided on the first substrate 20. In FIG. 14, the range provided on the first substrate 20 in the sensor device 100 is indicated by a dashed-dotted line frame. In this example, a portion of the wiring 92 is provided on the first substrate 20, and another portion of the wiring 92 is provided on the second substrate 22. In this example, the capacitor C1, the capacitor C2, the capacitor Ca2, the capacitor Ca3, and the resistor Ra2 are provided on the first substrate 20, and the capacitor Ca1, the resistor Ra1, and the amplifier circuit 42 are provided on the second substrate 22.

If the first substrate 20 is a ceramic substrate and the second substrate 22 is a glass epoxy substrate, there is a high probability that the first substrate 20 is more expensive than the second substrate 22. In this example, the capacitor Ca2, the capacitor Ca3, the resistor Ra2, and part of the wiring 92 of the conversion circuit 40 are provided on the first substrate 20. Therefore, the area of the first substrate 20 tends to be smaller than when all of the conversion circuits 40 are provided on the first substrate 20. Therefore, the manufacturing cost of the sensor device 100 tends to be lower than when all of the conversion circuits 40 are provided on the first substrate 20.

FIG. 15 is a diagram showing another example of the sensor device 100 according to one embodiment of the present invention. The sensor device 100 of this example differs from the sensor device 100 shown in FIG. 2 in that it further includes a lead frame 60. The lead frame 60 electrically connects the first substrate 20 and the second substrate 22. The lead frame 60 of this example includes leads 64. The leads 64 electrically connect the first substrate 20 and the second substrate 22.

FIG. 16 is a sectional view taken along line bb' in FIG. 15. The bb' line is an XZ cross section passing through the physical quantity sensor 10, the amplifier circuit 42, the first substrate 20, the lead 64, and the second substrate 22. The lead frame 60 of this example is a so-called J-lead type. In the bb' cross section, the lead 64 has a J-shape.

The first substrate 20 may be fixed to the lead frame 60. The first substrate 20 and the second substrate 22 may be separated from each other. The first substrate 20 and the second substrate 22 may be connected by a lead 64.

FIG. 17 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and time when the sensor device 100 is the example shown in FIGS. 15 and 16. FIG. 18 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and time when the sensor device 100 is the example shown in FIGS. 15 and 16. In this example, the output of conversion circuit 40-1 and the output of conversion circuit 40-2 change periodically.

FIG. 19 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T when the output of the conversion circuit 40-1 is in the state shown in FIG. FIG. 20 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T when the output of the conversion circuit 40-2 is in the state shown in FIG. Temperatures T3' to T6 in FIGS. 19 and 20 are the same as temperatures T3' to T6 in FIGS. 9 to 13. In FIGS. 19 and 20, temperatures T7 and T8 which are higher than temperature T6 are further shown. Temperature T6 and temperature T7 are, for example, 70°C and 80°C.

The coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 may be different. When the first substrate 20 is a ceramic substrate, the coefficient of thermal expansion of the ceramic substrate is, for example, 7.1×10 ⁻⁶ /K. When the second substrate 22 is a glass epoxy substrate, the coefficient of thermal expansion of the glass epoxy substrate is, for example, 1.4×10 ⁻⁵ to 1.5×10 ⁻⁵ /K. The thermal expansion coefficients of the capacitors Cb1 to Cb4 of the sensor device 100 shown in FIG. 14 are, for example, 9×10 ⁻⁶ /K. That is, the thermal expansion coefficients of the capacitors Cb1 to Cb4 and the thermal expansion coefficient of the ceramic substrate may be close to each other.

When the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 are different, when the temperature T of the sensor device 100 changes, the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 are different. A stress may be applied to the first substrate 20 based on the difference between the two. In the case of the sensor device 100 shown in FIG. 14, when the coefficients of thermal expansion of the capacitors Cb1 to Cb4 and the coefficient of thermal expansion of the ceramic substrate are close to each other, and the stress is applied to the first substrate 20, The capacitances of capacitors Cb1 to Cb4 can change depending on the stress.

As described above, in the sensor device 100 of this example, the first substrate 20 is fixed to the lead frame 60. Therefore, even if the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 are different, the difference between the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 This makes it difficult for stress based on this to be applied to the first substrate 20. Therefore, even if the acceleration in the X-axis direction of the sensor device 100 changes periodically as shown in FIG. 17, the acceleration in the X-axis direction and the temperature T of the sensor device 100 as shown in FIG. Hysteresis is more likely to be suppressed in the relationship with Similarly, even if the acceleration in the Y-axis direction of the sensor device 100 changes periodically as shown in FIG. 18, the acceleration in the Y-axis direction and the temperature T of the sensor device 100 as shown in FIG. Hysteresis is more likely to be suppressed in the relationship with

FIG. 21 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and time when the sensor device 100 is the example shown in FIGS. 2 and 3. FIG. 22 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and time when the sensor device 100 is the example shown in FIGS. 2 and 3. In this example, the output of conversion circuit 40-1 and the output of conversion circuit 40-2 change periodically.

FIG. 23 is a diagram showing an example of the relationship between the output of the conversion circuit 40-1 and the temperature T when the output of the conversion circuit 40-1 is in the state shown in FIG. FIG. 24 is a diagram showing an example of the relationship between the output of the conversion circuit 40-2 and the temperature T when the output of the conversion circuit 40-2 is in the state shown in FIG. Temperatures T3' to T8 in FIGS. 23 and 24 are the same as temperatures T3' to T8 in FIGS. 19 and 20.

In the sensor device 100 shown in FIGS. 2 and 3, the first substrate 20 is fixed to the second substrate 22. Therefore, when the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 are different, the stress based on the difference between the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 is The voltage is easily applied to one substrate 20. Therefore, when the output of the conversion circuit 40-1 changes periodically as shown in FIG. 21, hysteresis tends to occur in the relationship between the output of the conversion circuit 40-1 and the temperature T, as shown in FIG. Become. Similarly, when the output of the conversion circuit 40-2 changes periodically as shown in FIG. 22, hysteresis tends to occur in the relationship between the output of the conversion circuit 40-2 and the temperature T, as shown in FIG. Become.

Let the resonant frequency of the first substrate 20 and the lead frame 60 (see FIGS. 15 and 16) be the resonant frequency fr. The resonance frequency fr refers to the resonance frequency when the first substrate 20 and the lead frame 60 are regarded as an integrated vibrating body. When the spring constant of the lead 64 is k and the mass of the first substrate 20 is M, the resonance frequency fr is expressed by the following formula.

When the lead frame 60 includes N leads 64 (N is an integer of 2 or more), the spring constant k of the leads 64 refers to the spring constant when the N leads 64 are considered as one lead 64. . When the lead frame 60 includes N leads 64 (N is an integer of 2 or more), the spring constant k' of each lead 64 is (k/N).

The resonant frequency fr of the first substrate 20 and the lead frame 60 (see FIGS. 15 and 16) may be higher than the resonant frequency of the physical quantity sensor 10. Assuming that the spring constant of the lead 64 is 4×10 ⁷ N/m and the mass of the first substrate 20 is 10 g, the resonance frequency fr is approximately 10 kHz. The resonant frequency of the physical quantity sensor 10 is, for example, 500 to 800 Hz. Therefore, by fixing the first substrate 20 to the lead frame 60, the resonant frequency fr can become ten times or more the resonant frequency of the physical quantity sensor 10. Therefore, in the sensor device 100 of this example, the influence of the resonance frequency fr on the frequency of the physical quantity sensor 10 can be suppressed.

FIG. 25 is a diagram showing another example of the sensor device 100 according to one embodiment of the present invention. The sensor device 100 of this example further includes a housing 80 and a connection section 82. The first substrate 20 is fixed to the casing 80. The connecting portion 82 electrically connects the first substrate 20 and the second substrate 22. The connecting portion 82 is, for example, a lead wire, a flexible board, or the like. The first substrate 20 may be fixed to the housing 80 with a flexible bonding material 83 (described later).

FIG. 26 is another diagram illustrating the sensor device 100 shown in FIG. 25. FIG. 26 is a diagram of the sensor device 100 viewed in the Y-axis direction. In this example, the first substrate 20 and the second substrate 22 are housed in a housing 80. The second board 22 is fixed to the housing 80 by a fixing member 84. In this example, the first substrate 20 and the second substrate 22 are separated from each other. Therefore, even if the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 are different, the difference between the coefficient of thermal expansion of the first substrate 20 and the coefficient of thermal expansion of the second substrate 22 This makes it difficult for stress based on this to be applied to the first substrate 20.

The first substrate 20 may be fixed to the housing 80 with a bonding material 83. In this example, the lower surface of the first substrate 20 and the bottom surface of the casing 80 are connected by a bonding material 83. The bonding material 83 has flexibility. The bonding material 83 may be an insulator. The bonding material 83 is, for example, silicone rubber.

The resonance frequency of the first substrate 20 and the bonding material 83 is defined as a resonance frequency fr'. The resonant frequency fr' refers to the resonant frequency when the first substrate 20 and the bonding material 83 are regarded as an integrated vibrating body.

The resonant frequency fr' may be higher than the resonant frequency of the physical quantity sensor 10. Assuming that the spring constant of the bonding material 83 is 4×10 ⁷ N/m and the total mass of the first substrate 20 and the bonding material 83 is 100 g, the resonance frequency fr' is approximately 100 kHz. Therefore, by fixing the first substrate 20 to the housing 80 with the bonding material 83, the resonant frequency fr' can be 100 times or more the resonant frequency of the physical quantity sensor 10. Therefore, in the sensor device 100 of this example, the influence of the resonance frequency fr' on the frequency of the physical quantity sensor 10 can be suppressed.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the range described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the embodiments described above. It is clear from the claims that such modifications or improvements may be included within the technical scope of the present invention.

The order of execution of each process, such as the operation, procedure, step, and stage in the apparatus, system, program, and method shown in the claims, specification, and drawings, is specifically defined as "before" or "before". It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Even if the claims, specifications, and operational flows in the drawings are explained using "first," "next," etc. for convenience, this does not mean that it is essential to carry out the operations in this order. It's not a thing.

DESCRIPTION OF SYMBOLS 10... Physical quantity sensor, 11... Fixed electrode, 12... Fixed electrode, 13... Movable electrode, 14... Fixed frame, 15... Elastic part, 16... Fixed electrode, 17 . . . Space, 20 . . . First substrate, 21 . . . Lid, 22 . . . Second substrate, 30 . Frequency oscillator, 52 LPF, 54 AD converter, 58 Interface section, 60 Lead frame, 64 Lead, 70 Storage section, 80... - Housing, 82... Connection portion, 83... Bonding material, 84... Fixing member, 90... Voltage application section, 92... Wiring, 93... Wiring, 94... Wiring , 100... Sensor device, 110... Computer, 130... Power feeding hub, 140... NTP server, 150... Communication line, 200... Sensor system, 300... Sensor device

Claims (13)

physical quantity sensor,
a conversion circuit that converts the signal detected by the physical quantity sensor into a voltage signal;
a first substrate provided with at least a portion of the conversion circuit and the physical quantity sensor;
a second substrate electrically connected to the first substrate;
Equipped with
The rate of change of the parasitic capacitance formed between the at least part of the conversion circuit and the first substrate with respect to temperature or humidity is determined by the parasitic capacitance formed between the at least part of the conversion circuit and the second substrate. less than the rate of change of capacitance with temperature or humidity,
sensor device. The sensor device according to claim 1, wherein a moisture absorption rate of the first substrate is lower than a moisture absorption rate of the second substrate. The sensor device according to claim 2, wherein the first substrate is made of ceramic. The sensor device according to claim 2 or 3, wherein the second substrate includes an organic material. The sensor device according to claim 4, wherein the first substrate is fixed on the second substrate. The conversion circuit includes an amplifier circuit and wiring connecting the amplifier circuit and the physical quantity sensor,
The amplifier circuit and the wiring are provided on the first substrate,
The sensor device according to claim 5. The conversion circuit includes an amplifier circuit and wiring connecting the amplifier circuit and the physical quantity sensor,
At least a portion of the wiring is provided on the first substrate,
The amplifier circuit is provided on the second substrate,
The sensor device according to claim 5. The sensor device according to claim 4, wherein the first substrate has a different coefficient of thermal expansion and the second substrate has a different coefficient of thermal expansion. The sensor device according to claim 8, further comprising a lead frame that electrically connects the first substrate and the second substrate. the first substrate is fixed to the lead frame,
a resonance frequency of the first substrate and the lead frame is higher than a resonance frequency of the physical quantity sensor;
The sensor device according to claim 9. a casing to which the first substrate is fixed and accommodates the first substrate and the second substrate;
a connection portion that electrically connects the first substrate and the second substrate;
The sensor device according to claim 8, further comprising: The sensor device according to claim 11, wherein the first substrate is fixed to the casing with a flexible bonding material. The sensor device according to claim 12, wherein a resonance frequency of the first substrate and the bonding material is higher than a resonance frequency of the physical quantity sensor.

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