JP4511208B2 - 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, for example, in the pressure sensor module that monitors the air pressure in the tire, since the centrifugal force generated by the rotation of the tire is applied to the pressure sensor module, this centrifugal force increases when the mass of the pressure sensor module is large, There is still a problem that the pressure sensor module is unfixed inside the tire and causes a failure, and further weight reduction is required.

  The present invention has been devised in view of the above problems, and its object is to reduce the weight of a pressure sensor module that is miniaturized by integrating a resonator connected to an oscillation circuit that oscillates a reference signal with a pressure sensor. An object of the present invention is to provide an integrated pressure sensor module.

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 pressure sensor module comprising comprising a modulation circuit for outputting to the outside by modulating the electrical signal from said second oscillation circuit in said converted signal et, the, the and the pressure sensing SAW element a reference SAW element through the reflector while being arranged in a row Rutotomoni, is shared as a reflector of the surface acoustic wave device of both of said reflectors are arranged on both sides, The entire reflector is formed in a region where the concave portion is formed on the lower surface of the sensor substrate .

  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 surface acoustic wave element for pressure detection and the surface acoustic wave element for reference share a reflector located between them, the surface acoustic wave element for pressure detection is referred to Therefore, the area of the sensor substrate on which the surface acoustic wave element is formed can be further reduced, and the pressure sensor module can be further reduced in weight. As a result, even when the pressure sensor module is used for the purpose of monitoring the air pressure in the tire, for example, the centrifugal force generated by the rotation of the tire can be reduced, so that the pressure sensor module can be fixed inside the tire. It is possible to reduce detachment failure.

  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. A pressure sensor module 10 shown in FIG. 1 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 is composed of, for example, a surface acoustic wave element composed of a piezoelectric body and an interdigital transducer 2a. The interdigital transducer 2a is electrically connected to a connection pad of the support substrate 6. The electrode pads 7 to be joined through the material are connected. A pair of reflectors 2 b for reflecting the surface acoustic wave generated in the region where the pressure detecting surface acoustic wave element 2 is formed are arranged on both sides of the pressure detecting surface acoustic wave element 2.

  Similarly, the surface acoustic wave element 3 for reference is also composed of a surface acoustic wave element composed of a piezoelectric body and an interdigital transducer 3a. In the interdigital transducer 3a, a conductive bonding material is connected to a connection pad of the support substrate 6. The electrode pads 7 to be joined are connected. A pair of reflectors 3 b for reflecting the surface acoustic wave generated in the region where the reference surface acoustic wave element 3 is formed are disposed on both sides of the reference surface acoustic wave element 3.

  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 that of the sensor substrate 1, that is, crystal, lithium niobate, lithium tantalate, etc. Piezoelectric material 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., for example, to a thickness of about 2000 mm. By forming a pattern, interdigital transducers 2a and 3a and reflectors 2b and 3b are formed.

  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.

  And the characteristic point in the pressure sensor module 10 of the present invention is that the surface acoustic wave element for pressure detection 2 and the surface acoustic wave element for reference 3 are arranged in a line through a reflector 2b (3b), This reflector 2b (3b) is shared as a reflector for both surface acoustic wave elements 2 and 3.

  According to the pressure sensor module 10 of the present invention, the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 share the reflector 2b (3b) positioned therebetween, so that the pressure detection The area of the sensor substrate 1 on which the surface acoustic wave element 2 for reference and the surface acoustic wave element 3 for reference are formed can be further reduced, and the pressure sensor module 10 can be further reduced in weight. As a result, even when the pressure sensor module 10 is used for the purpose of monitoring the air pressure in the tire, for example, the centrifugal force generated by the rotation of the tire can be further reduced. It is possible to reduce the failure of the fixing failure.

  FIG. 1 shows an example in which the shared reflector 2b (3b) is formed so as to extend inside and outside the formation region of the recess 5, but the entire reflector 2b (3b) is used as the recess. 5 may be formed in the formation region of 5 or outside the formation region of the recess 5. From the viewpoint of easily deforming the region where the surface acoustic wave element 2 for pressure detection is formed when pressure from the outside is applied to the pressure sensor module 10 and increasing the sensitivity of the pressure sensor module 10, a shared reflection is used. It is preferable to form the entire vessel 2b (3b) in the formation region of the recess 5.

  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 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 become so.

  In addition, when using conductor materials, such as solder, as such a sealing material 4, if this is connected to the ground terminal on the lower surface of the support substrate 6, the sealing material 4 is used when the sensor element 20 is used. Since it is held at the ground potential, 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.

  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 for pressure detection 2 and the surface acoustic wave element for reference 3 are designed to have the same resonance frequency. By comparing two electric signals based on the frequency with a comparator and generating a conversion signal, a pressure fluctuation from the outside applied from above the sensor substrate 1 is detected.

  At this time, since the pressure detecting surface acoustic wave element 2 and the reference surface acoustic wave element 3 are formed on the same sensor substrate 1, the temperature dependence of the resonance frequency is determined by both surface acoustic wave elements. When the two electrical signals based on the resonance frequency are compared by the comparator, the signal is canceled and the conversion signal compared by the comparator is temperature-corrected.

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.

  As shown in the perspective view of the sensor element in FIG. 4, the electrode pad 7 is shared by the interdigital transducer 2a of the surface acoustic wave element 2 for pressure detection and the interdigital transducer 3a of the surface acoustic wave element 3 for reference. Also good. In this case, since the number of electrode pads is reduced by one, the process can be simplified.

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 perspective view of the sensor element in the other Example 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

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 pressure sensor module comprising and a modulation circuit for outputting to the outside the electrical signal is modulated from the second oscillator circuit in the converted signal from the comparator,
The pressure sensing SAW element and the and the reference SAW element are arranged in a row through the reflector between the Rutotomoni, surface acoustic wave both of said reflectors are arranged on both sides A pressure sensor module , which is shared as a reflector of an element , and the entire reflector is formed in a region where the concave portion is formed on the lower surface of the sensor substrate .   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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