JP4511216B2 - Pressure sensor module - Google Patents

Description

  The present invention relates to a pressure sensor module that detects a change in pressure and transmits a predetermined electrical signal.

  2. Description of the Related Art Conventionally, pressure sensor modules that detect pressure fluctuations such as gas and liquid and transmit pressure fluctuation data to the outside have been used.

  As such a pressure sensor module, one having a pressure sensor and an oscillation circuit and transmitting pressure fluctuation data detected by the pressure sensor to the outside is known (for example, see Patent Document 1).

In such a conventional pressure sensor module, a capacitance type sensor element (for example, see Patent Document 2) made of a ceramic package is used as the pressure sensor, and the pressure sensor is obtained by applying pressure to the pressure sensor. A transmission signal generated by modulating pressure fluctuation data and an electrical signal as a reference signal that oscillates based on the resonance frequency of a resonator composed of a surface acoustic wave element is output from an antenna. It is used as a device for monitoring.
JP 2003-303388 A JP 2003-315190 A

  However, since the pressure sensor module described above includes a pressure sensor made of a ceramic package and a resonator made of a surface acoustic wave element connected to an oscillation circuit that oscillates a reference signal. Since such a conventional pressure sensor module has a large number of parts to be mounted, it has been difficult to reduce the weight and size of the module.

  In order to solve such problems, the applicant of Japanese Patent Application No. 2003-431559 has a piezoelectric substrate and an interdigital transducer in a recess formation region on a sensor substrate having a recess formed on one main surface. The surface acoustic wave element for pressure detection including the sensor element provided with the surface acoustic wave element for reference including the piezoelectric body and the interdigital transducer outside the formation region of the recess, and the resonance frequency of the surface acoustic wave element for pressure detection A first oscillation circuit that oscillates an electrical signal of a predetermined frequency based on the first oscillation circuit, a second oscillation circuit that oscillates an electrical signal of a predetermined frequency based on the resonance frequency of the surface acoustic wave element for reference, and a first oscillation circuit And an electric signal from the second oscillation circuit to generate a converted signal, and a comparator that outputs the converted signal and a comparator Proposed a pressure sensor module comprising a modulation circuit for outputting an electrical signal from the converted signal and a second oscillator circuit to the outside modulation.

  According to this pressure sensor module, the surface acoustic wave element for reference is provided on the same sensor substrate as the surface acoustic wave element for pressure detection, and an electric signal that oscillates based on the resonance frequency of the surface acoustic wave element for reference is generated. Since it is used to generate a conversion signal in comparison with an electric signal that oscillates based on the resonance frequency of the surface acoustic wave element for pressure detection, it is also used as a reference signal to be modulated with this conversion signal. The number of points is reduced, and the pressure sensor module can be reduced in weight and size.

  However, in this pressure sensor module, since the surface acoustic wave element for reference is provided on the same sensor substrate as the surface acoustic wave element for pressure detection, for example, the surface acoustic wave element for reference and the surface acoustic wave element for pressure detection When the sensor substrate is miniaturized by placing them close to each other, the leakage traveling wave that could not be reflected by the reflectors is the traveling wave of the surface acoustic wave element for reference or the surface acoustic wave element for pressure detection. There was a risk that interference could make accurate pressure measurement difficult.

  The present invention has been devised in view of the above-described problems, and the object of the present invention is to reduce the size of the pressure sensor module by integrating the resonator connected to the oscillation circuit that oscillates the reference signal with the pressure sensor. Provides a pressure sensor module that can suppress interference with the surface acoustic wave element for reference or the surface acoustic wave element for pressure detection provided on the same sensor substrate as the leakage traveling wave, and can perform accurate pressure measurement There is to do.

The pressure sensor module of the present invention, the lower surface of the sensor substrate recess in the upper surface is formed, the recess forming region directly below the recess, piezoelectric and pressure sensing SAW element including a interdigital transducer but outside formation region of the recess, and the sensor element the reference SAW element including a piezoelectric body and interdigital transducers are provided respectively with a predetermined frequency based on a resonance frequency of said pressure sensing SAW element A first oscillation circuit that oscillates an electrical signal; a second oscillation circuit that oscillates an electrical signal having a predetermined frequency based on a resonance frequency of the surface acoustic wave element for reference; and an electrical signal from the first oscillation circuit and the with second by comparing the electrical signal from the oscillation circuit for generating a conversion signal, a comparator for outputting the converted signal, said comparator A modulation circuit for outputting to the outside by modulating the electrical signal from said second oscillation circuit in said converted signal et, the pressure sensor module comprising equipped with a resonant frequency of the pressure sensing SAW element fr _2, the anti-resonance frequency is fa _2, fr ₃ the resonance frequency of the reference SAW element, when the anti-resonance frequency is fa _3, fa 2 <fr ₃ or _fa 3 <fr ₂ become as In addition, each frequency is different.

  In the pressure sensor module of the present invention, the first oscillation circuit, the second oscillation circuit, the comparator, and the modulation circuit are integrated on a single IC chip in the above configuration. And the sensor element are mounted on a common support substrate.

  According to the pressure sensor module of the present invention, since the resonance frequency of the surface acoustic wave element for pressure detection is different from the resonance frequency of the surface acoustic wave element for reference, the surface acoustic wave element for pressure detection and the surface acoustic wave for reference Even when the wave element is formed on the same sensor substrate, the leakage traveling wave does not interfere with the traveling wave of the surface acoustic wave element for reference or the surface acoustic wave element for pressure detection. Can be done.

  According to the pressure sensor module of the present invention, in the above configuration, the first oscillation circuit, the second oscillation circuit, the comparator, and the modulation circuit are integrated on a single IC chip. When the element is mounted on a common support substrate, the pressure sensor module can be further reduced in weight and size by mounting the IC chip and the sensor element on the common support substrate. .

  Hereinafter, a pressure sensor module of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a pressure sensor module 10 according to an embodiment of the present invention, and FIG. 2 is a perspective view of a sensor element 20 used in the pressure sensor module 10 of FIG. The pressure sensor module 10 mainly includes a sensor element 20, a support substrate 6, a sealing material 4, an IC chip 12, and an antenna 13.

  The sensor substrate 1 constituting the sensor element 20 has a concave portion 5 on its upper surface, and a pressure detecting surface acoustic wave element 2 is provided in the concave portion 5 formation region immediately below the concave portion 5 on its lower surface. A surface acoustic wave element 3 for reference is provided outside the formation region 5.

Note that the surface acoustic wave element 2 for pressure detection is provided in the concave portion 5 formation region immediately below the concave portion 5, as will be described later, when pressure is applied to the pressure sensor module 10 from the outside. This is to make it easier to deform the region where the surface wave element 2 is formed, and the greater the deformation, the higher the sensitivity of the pressure sensor module 10 .

  As a material for such a sensor substrate 1, it can be formed integrally with the surface acoustic wave element 2 for pressure detection, and deforms relatively easily when subjected to external pressure (pressure from above in FIG. 1). Preferred are single crystal piezoelectric materials such as quartz, lithium niobate, lithium tantalate, and lithium tetraborate.

  The surface acoustic wave element 2 for pressure detection includes, for example, a surface acoustic wave element including a piezoelectric body, an interdigital transducer 2a, and a pair of reflectors 2b disposed on both sides thereof. The electrode pad 7 bonded to the connection pad of the support substrate 6 through the conductive bonding material is connected.

  Similarly, the surface acoustic wave element 3 for reference is also composed of a surface acoustic wave element composed of a piezoelectric body, an interdigital transducer 3a, and a pair of reflectors 3b arranged on both sides thereof. An electrode pad 7 bonded to the connection pad of the substrate 6 via a conductive bonding material is connected.

  As a material of the piezoelectric body constituting the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3, for example, the same material as the sensor substrate 1, that is, quartz, lithium niobate, lithium tantalate A piezoelectric material such as lithium tetraborate is used, and a metal material such as aluminum or gold is applied to the surface of the piezoelectric body using a well-known thin film forming technique such as sputtering or vapor deposition, photolithography technique, etc. Interdigital transducers 2a and 3a and reflectors 2b and 3b are formed by forming a pattern with a thickness of about 2000 mm.

  Normally, a part of the surface of the sensor substrate 1 is used as the piezoelectric body constituting the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3.

  The lower surface of the sensor substrate 1 has an annular shape surrounding the interdigital transducers 2a and 3a and the reflectors 2b and 3b constituting the surface acoustic wave element 2 for pressure detection and the surface acoustic wave element 3 for reference. The joining conductor 8 is provided. The joining conductor 8 is made of the same metal material as the interdigital transducer 2a and the like, and its surface is subjected to Ni plating, Au plating or the like, and a sealing material 4 described later is joined thereto. Note that the bonding conductor 8 is formed on the lower surface of the sensor substrate 1 by employing the same formation method as that of the interdigital transducer 2a described above, for example, a thin film formation technique, a photolithography technique, or the like.

  On the other hand, the support substrate 6 is required to have mechanical properties such as sufficient strength and being difficult to be deformed even when subjected to external pressure. For example, a multilayer circuit substrate using a glass-ceramic material or a ceramic material, etc. Are preferably used.

  On the upper surface of the support substrate 6, a connection pad (not shown) that is electrically connected to the electrode pad 7 on the lower surface of the sensor substrate 1 via a conductive bonding material, and a bonding conductor on the lower surface of the sensor substrate 1. An annular bonding conductor 9 that is bonded to the bonding conductor 8 via the sealing material 4 is provided at a portion that faces 8.

  A plurality of terminal electrodes (not shown) are formed on the lower surface of the support substrate 6, and these terminal electrodes are used for wiring patterns, via-hole conductors, etc. (not shown) of the support substrate 6 and the sensor substrate 1. The surface acoustic wave element 2 for pressure detection, the surface acoustic wave element 3 for reference and the like on the lower surface of the sensor substrate 1 are electrically connected.

  Such a support substrate 6 is formed by, for example, a conventionally known green sheet laminating method, specifically, laminating a plurality of green sheets obtained by printing and applying a wiring pattern or a conductor paste to be a via hole conductor in a predetermined pattern. -It is manufactured by pressure bonding and firing these together.

  An annular sealing material 4 is interposed between the sensor substrate 1 and the support substrate 3 so as to surround the surface acoustic wave element 2 for pressure detection.

  The sealing material 4 is made of, for example, a conductor material such as solder or Au—Ni alloy, and the sealing material 4 is bonded to the bonding conductors 8 and 9 of both substrates (sensor substrate 1 and support substrate 6). By doing so, the above-described surface acoustic wave device 2 for pressure detection, the surface acoustic wave device 3 for reference, and the like are hermetically sealed in a sealing region surrounded by the sensor substrate 1, the support substrate 6, and the sealing material 4. It is supposed to be.

  The inside of such a sealing region is usually filled with an inert gas such as nitrogen gas or argon gas, thereby effectively preventing oxidative corrosion of an interdigital transducer or the like disposed in the sealing region. It has come to be.

  In the case where a conductive material such as solder is used as the sealing material 4, if the conductive material is connected to the ground terminal on the lower surface of the support substrate 6, the sealing material 4 is set to the ground potential when the sensor element 20 is used. Therefore, the shielding effect by the sealing material 4 can be expected, and unnecessary noise from the outside can be well blocked by the sealing material 4.

  Further, as the conductive bonding material for connecting the electrode pad 7 of the sensor substrate 1 and the connection pad of the support substrate 6, for example, solder, conductive resin, or the like is used. The terminal electrode on the lower surface of the support substrate 6 is connected to an IC chip 12, an amplifier 15 and an antenna 13 in which a first oscillation circuit, a second oscillation circuit, a comparator and a conversion circuit, which will be described later, are integrated. A resin 14 is molded so as to cover the surface.

As described above, the first oscillation circuit, the second oscillation circuit, the comparator, and the modulation circuit are integrated on the single IC chip 12 , and the IC chip 12 and the sensor element are mounted on the common support substrate 6. By doing so, the pressure sensor module 10 can be reduced in weight and size.

  In the pressure sensor module 10 of the present invention, the resonance frequency of the surface acoustic wave element 2 for pressure detection on the sensor substrate 1 and the resonance frequency of the surface acoustic wave element 3 for reference are different from each other. Has been. This is also important.

  According to the pressure sensor module 10 of the present invention, the resonance frequency of the surface acoustic wave element 2 for pressure detection on the sensor substrate 1 is different from the resonance frequency of the surface acoustic wave element 3 for reference. Even if the surface acoustic wave element 2 and the reference surface acoustic wave element 3 are formed on the same substrate and are reduced in size, the leakage traveling wave and the traveling wave of the reference surface acoustic wave element 3 or the pressure detecting surface acoustic wave element 2 are reduced. Does not interfere with each other, so that pressure measurement can be performed accurately.

In the pressure sensor module 10 of the present invention, the resonance frequency of the surface acoustic wave element 2 for pressure detection is fr ₂ , the antiresonance frequency is fa ₂ , the resonance frequency of the reference surface acoustic wave element 3 is fr ₃ , and antiresonance. When the frequency is fa ₃ ,
fa ₂ <fr ₃ (1)
Or
fa ₃ <fr ₂ (2)
It is preferable to set the respective frequencies so that

The piezoelectric bodies such as the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 have a resonance frequency (fr) which is a frequency at which the insertion loss is minimized, as shown in FIG. And an anti-resonance frequency (fa) which is a frequency at which the insertion loss is maximum, and has a relationship of fr <fa. Therefore, the expressions (1) and (2) are obtained by the frequency band (fr ₂ to fa ₂ ) from the resonance frequency fr ₂ to the anti-resonance frequency fa ₂ of the surface acoustic wave element 2 for pressure detection, and the surface acoustic wave element for reference. 3 of the resonance frequency from fr ₃ so that the frequency band up to the anti-resonant frequency fa ₃ and _(fr 3 ~fa ₃₎ do not overlap, meaning that it is preferable to set each of the resonance frequency and anti-resonance frequency ing.

Note that the resonance frequency fr ₂ and anti-resonance frequency fa _{2 of the} surface acoustic wave element 2 for pressure detection, and the resonance frequency fr ₃ and anti-resonance frequency fa _{3 of} the reference surface acoustic wave element 3 are expressed by the following equation (1) or When the expression (2) is not satisfied, that is, the frequency band (fr ₂ to fa ₂ ) from the resonance frequency fr ₂ to the anti-resonance frequency fa ₂ of the surface acoustic wave element 2 for pressure detection, and the surface acoustic wave element 3 for reference If the frequency band (fr _{3 to} fa ₃ ) from fr ₃ to the anti-resonance frequency fa ₃ overlaps, the leakage traveling wave of the surface acoustic wave element 2 for pressure detection has a frequency of fr _{3 to} fa ₃ . Spurious appears in the band, or the leakage traveling wave of the surface acoustic wave element 3 for reference appears as spurious in the frequency band fr _{2 to} fa ₂ , and the surface acoustic wave element 2 for pressure detection or the reference The resonance characteristics of the surface acoustic wave element 3 may be disturbed, making accurate pressure measurement difficult. Therefore, when the resonance frequency of the surface acoustic wave element 2 for pressure detection is fr ₂ , the anti-resonance frequency is fa ₂ , the resonance frequency of the reference surface acoustic wave element 3 is fr ₃ , and the anti-resonance frequency is fa ₃ , Each frequency is preferably set so that ₂ <fr ₃ or fa ₃ <fr ₂ .

Also, in FIG. 4, the horizontal axis represents the frequency (the unit MHz), a vertical axis represents insertion loss (in dB), a dotted line an example of resonance characteristics of the pressure sensing SAW element 2, see elastic An example of the resonance characteristics of the surface acoustic wave element 3 is indicated by a solid line. FIG. 4 shows the resonance characteristics of the reference surface acoustic wave device 3 having a resonance frequency (fr ₃ ) of 314.68 MHz and an anti-resonance frequency (fa ₃ ) of 314.82 MHz. In this case, the resonance frequency fr ₂ of the pressure detecting surface acoustic wave element 2 may be set to be higher than the anti-resonance frequency (fa ₃ = 314.82 MHz) of the reference surface acoustic wave element 3. For example, a quartz substrate (ST cut quartz, surface wave velocity V = 3110 m / s, normalized film thickness (H / λ) = 2% H: electrode film thickness of metal material (μm) λ: wavelength (μm) ) Is used, the specific element design of the surface acoustic wave element for pressure detection 2 and the surface acoustic wave element for reference 3 is such that the resonance frequency of the surface acoustic wave element for pressure detection 2 is fr ₂ > 314.82 MHz. The wavelength λ ₂ <9.879 μm of the surface acoustic wave element 2 for pressure detection and the electrode finger width P ₂ of the interdigital transducer 2a <2.470 μm. When the resonant frequency of the reference surface acoustic wave element 3 is fr ₃ = 314.68 MHz, the wavelength of the reference surface acoustic wave element 3 λ ₃ = 9.883 μm, the electrode finger width P ₂ of the interdigital transducer 2b = 2. 471 μm. In the above example, the case of fa ₃ <fr ₂ has been described. Similarly, in the case of fa ₂ <fr ₃ , the frequency band from the resonance frequency fr ₂ to the anti-resonance frequency of the surface acoustic wave element 2 for pressure detection is equal to fa _2. (Fr _{2 to} fa ₂ ) and the resonant frequency of the reference surface acoustic wave element 3 may be set so that the frequency band (fr _{3 to} fa ₃ ) from fr ₃ to the antiresonant frequency fa ₃ does not overlap. .

  FIG. 5 shows the frequency-temperature characteristics of the surface acoustic wave element when a quartz substrate is used as the sensor substrate 1. In FIG. 5, the horizontal axis represents temperature (unit: ° C.), and the vertical axis represents frequency change rate (unit: ppm). When a single crystal piezoelectric material whose frequency temperature characteristic represented by a quartz substrate as shown in this figure has a quadratic curve is used, the resonance frequency of the surface acoustic wave element 2 for pressure detection and the surface acoustic wave element 3 for reference is used. When the difference (fr) increases, the difference between the apex temperature of the frequency temperature characteristic of the surface acoustic wave element 2 for pressure detection and the apex temperature of the frequency temperature characteristic of the reference surface acoustic wave element 3 increases, and accurate pressure measurement is difficult. Therefore, it is not preferable.

  In general, a single crystal piezoelectric material having a peak temperature has a peak due to the relationship between the cut angle of the single crystal piezoelectric material and the normalized film thickness (H / λ) of the electrode film thickness of the metal material forming the interdigital transducer or the like. The temperature is determined. Here, H is the electrode film thickness (μm) of the metal material, and λ is the wavelength (μm). However, when the resonant frequencies of the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 are made different as in the present invention, the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 have λ. Therefore, if the electrode film thickness of the metal material is the same, the normalized film thickness (H / λ) is different, and the apex temperature of the frequency temperature characteristic is also different. From this relationship, when the resonance frequency difference between the resonance frequency of the surface acoustic wave element 2 for pressure detection and the surface acoustic wave element 3 for reference increases, the difference in the normalized film thickness also increases. As a result, the peak of both frequency temperature characteristics The temperature difference also increases.

Therefore, when forming the surface acoustic wave element 2 for pressure detection and the surface acoustic wave element 3 for reference in the pressure sensor module 10 of the present invention, the anti-resonance frequency is changed from the resonance frequency fr ₂ of the surface acoustic wave element 2 for pressure detection. the frequency band up to _{fa 2 (fr 2 ~fa 2)} , overlapping the frequency band of the resonance frequency of the reference SAW element 3 fr ₃ to antiresonance frequency fa _{3 (fr 3} ~fa ₃₎ is In order to set each resonance frequency and anti-resonance frequency so that there is no single crystal piezoelectric material whose frequency temperature characteristic shows a quadratic curve, such as a quartz substrate, the surface acoustic wave element 2 for pressure detection and the reference For example, the surface temperature wave element 3 is formed so that the apex temperature difference is within a range of ± 5 ° C. so that the apex temperature difference does not deviate greatly.

  Here, if the apex temperature difference is larger than ± 5 ° C., the frequency temperature change between the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 becomes a measurement error at the time of pressure measurement, which is not preferable. Therefore, when the apex temperature difference exceeds ± 5 ° C, the metal film etching technique such as plasma etching is applied to the electrode film thickness H of the metal material so that both normalized film thicknesses (H / λ) are the same. The reference surface acoustic wave element 3 and the pressure surface acoustic wave element 2 may be made to have the same normalized film thickness (H / λ) by etching using the same.

  Note that the surface acoustic wave element for pressure detection 2 and the surface acoustic wave element for reference 3 are not necessarily arranged adjacent to each other from the viewpoint of preventing interference between the traveling wave and the leakage traveling wave. That is, the positions of both may be shifted with respect to the traveling direction of the traveling wave, but from the viewpoint of miniaturization, they may be arranged adjacently in series as shown in FIGS. preferable.

  Next, a circuit configuration of the pressure sensor module according to the present embodiment will be described.

  As shown in FIG. 3, the surface acoustic wave element 2 for pressure detection is connected to a first oscillation circuit that oscillates an electric signal of a predetermined frequency based on the resonance frequency, and this oscillated electric signal is supplied to a comparator. Output. Since the surface acoustic wave element 2 for pressure detection according to the present embodiment is formed in a region immediately below the recess 5 of the sensor substrate 1 (hereinafter referred to as a thin portion), an external pressure is applied from above the sensor substrate 1. Then, the surface acoustic wave element 2 for pressure detection is deformed together with the thin portion according to the strength of the pressure, and the pressure fluctuation is detected by changing the resonance frequency.

As shown in FIG. 3, the surface acoustic wave element for reference 3 is connected to a second oscillation circuit that oscillates an electric signal having a predetermined frequency based on the resonance frequency, and this oscillated electric signal is also supplied to a comparator. Output. The reference surface acoustic wave element 3 is for comparing an output signal based on the resonance frequency with an output signal based on the resonance frequency of the surface acoustic wave element for sensors constituting the surface acoustic wave element 2 for pressure detection. Since the reference surface acoustic wave element 3 is provided outside the region where the recess 5 is formed, that is, in the thick portion of the sensor substrate 1, even if external pressure is applied from above the sensor substrate 1. Almost no deformation occurs, and an electric signal having a predetermined frequency can be oscillated through the second oscillation circuit regardless of whether or not pressure is applied.

  In the pressure sensor module of the present embodiment, the surface acoustic wave element 2 for pressure detection and the surface acoustic wave element 3 for reference are arranged on the same sensor substrate 1, and therefore the temperature dependence of the resonance frequency is both When the two electric signals based on the resonance frequency of the surface acoustic wave element are compared by the comparator, the signal is canceled, and the conversion signal compared by the comparator is temperature-corrected. At this time, the two electric signals based on the resonance frequencies of both surface acoustic wave elements are compared by a comparator to generate a converted signal, thereby detecting an external pressure fluctuation applied from above the sensor substrate 1. It has become. That is, the pressure fluctuation is detected by comparing the resonance frequency difference in the element design (initial) of both surface acoustic wave elements with the resonance frequency difference of both due to pressure fluctuation.

Then, the conversion signal generated by comparing with a comparator, as shown in FIG. 3, the electrical signal from the second oscillating circuits described above is modulated by the modulation circuit, resulting pressure variation data, by an amplifier or the like It is amplified and output to the outside from the antenna 13. Thus, the pressure sensor module 10 of this embodiment functions as a pressure sensor module that transmits pressure fluctuation data that detects pressure fluctuations such as gas and liquid. become.

As described above, according to the pressure sensor module 10 of the present embodiment, the reference surface acoustic wave element 3 is provided on the same sensor substrate 1 as the pressure detecting surface acoustic wave element 2, and the reference surface acoustic wave element 3 is provided. The electrical signal oscillated based on the resonance frequency of the pressure is used to generate a converted signal by comparing with the electrical signal oscillated based on the resonant frequency of the surface acoustic wave element 2 for pressure detection, and is modulated by the converted signal. that since also used as signal, fewer parts to be mounted is, it becomes possible to reduce the weight and miniaturization of the pressure sensor module 10.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change and improvement are possible in the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the sealing material 4 is formed using a conductor material such as solder. Instead, the sealing material 4 is sealed using a resin material having excellent sealing properties such as an epoxy resin. The material 4 may be formed. In this case, it is not necessary to provide the bonding conductors 8 and 9 on the lower surface of the sensor substrate 1 or the upper surface of the support substrate 3. Further, when the sealing material 4 is formed of a resin material, a predetermined amount of conductive filler such as metal fine particles is added therein to impart conductivity to the sealing material 4, and this is used as a ground terminal on the lower surface of the support substrate. As in the above-described embodiment, the sealing material 4 can function as a shield material, and the surface acoustic wave element 2 for pressure detection in the sealing region can be externally connected. It is possible to operate stably without being affected by noise from the.

It is sectional drawing of the pressure sensor module concerning one Embodiment of this invention. It is a perspective view of the sensor element used for the pressure sensor module of FIG. It is a figure explaining the circuit structure of the pressure sensor module concerning one Embodiment of this invention. It is a frequency characteristic figure which shows the resonance characteristic of the surface acoustic wave element for a reference and the surface acoustic wave element for pressure detection at the time of using a quartz substrate as a sensor element used for the pressure sensor module of the present invention. It is a frequency temperature characteristic figure which shows the temperature characteristic at the time of using a quartz substrate as a sensor element used for the pressure sensor module of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sensor substrate 2 ... Surface acoustic wave element for pressure detection 2a ... Interdigital transducer of surface acoustic wave element for pressure detection 2b ... Reflector of surface acoustic wave element for pressure detection 3 ... Surface acoustic wave element for reference 3a ... Interdigital transducer for surface acoustic wave element for reference 3b ... Reflector for surface acoustic wave element for reference 4 ... Sealing material 5 ... Recess 6 ... Support Substrate 7 ... Electrode pad 8,9 ... Conducting conductor 10 ... Pressure sensor module 12 ... IC chip 13 ... Antenna 14 ... Resin 15 ... Amplifier fr ₂ ... Pressure Resonant frequency of surface acoustic wave element for detection fa ₂ ... Anti-resonant frequency of surface acoustic wave element for pressure detection fr ₃ ... Resonant frequency of surface acoustic wave element for reference fa ₃ ... Surface acoustic wave element for reference Anti-community Frequency

Claims (2)

Of the lower surface of the sensor substrate recess in the upper surface is formed, the recess forming region directly below the recess, the pressure detecting surface acoustic wave element including a piezoelectric body and interdigital transducers formed outside the region of the recess to a sensor element for reference SAW element including a piezoelectric body and interdigital transducers are provided respectively,
A first oscillation circuit that oscillates an electric signal having a predetermined frequency based on a resonance frequency of the surface acoustic wave element for pressure detection;
A second oscillation circuit that oscillates an electric signal having a predetermined frequency based on a resonance frequency of the surface acoustic wave element for reference;
A comparator for generating a converted signal by comparing the electrical signal from the first oscillator circuit and the electrical signal from the second oscillator circuit, and outputting the converted signal;
A modulation circuit for outputting to the outside by modulating the electrical signal from said second oscillation circuit in the converted signal from the comparator, the pressure sensor module comprising comprise,
When the resonance frequency of the pressure detecting surface acoustic wave element is fr ₂ , the anti-resonance frequency is fa ₂ , the resonance frequency of the reference surface acoustic wave element is fr ₃ , and the anti-resonance frequency is fa ₃ , fa ₂ Each pressure sensor module is characterized in that each frequency is different so that <fr ₃ or fa ₃ <fr ₂ .   The first oscillation circuit, the second oscillation circuit, the comparator, and the modulation circuit are integrated on a single IC chip, and the IC chip and the sensor element are mounted on a common support substrate. The pressure sensor module according to claim 1.

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