JP2014112110A - Surface acoustic wave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave sensor which measures or monitors transmission rate, relative permittivity, viscosity coefficient or the like of a desired medium on the basis of propagation characteristics of a surface acoustic wave on a piezoelectric substrate, while significantly reducing or eliminating errors to be caused by electrical coupling between the medium to be measured and an electrode.SOLUTION: A surface acoustic wave sensor is formed on a piezoelectric substrate, includes a plurality of seal members for sealing each of electrodes which perform energy conversion between an electric signal and a surface acoustic wave, and detects presence or characteristics of a medium in a reaction field, as propagation characteristics of the surface acoustic wave in the reaction field surrounded by the electrodes on the piezoelectric substrate. The surface acoustic wave sensor includes a plurality of cover members which are covered by each of the seal members, prevent electrical coupling between the electrodes and the medium, and are roughened.

Description

  The present invention relates to a surface acoustic wave sensor that realizes measurement and monitoring of conductivity, relative permittivity, viscosity, and the like of a desired medium based on the propagation characteristics of surface acoustic waves on a piezoelectric substrate.

  A surface acoustic wave sensor that measures the conductivity, relative permittivity, viscosity, etc. of a medium such as a liquid based on the propagation characteristics on the piezoelectric substrate with respect to the surface acoustic wave, the wavelength of the surface acoustic wave is the wavelength of the electromagnetic wave. Because it is as short as 1 / 1,000,000, it can be reduced in size and weight, and it can be made unadjustable in conjunction with application to a medium harmful to the human body and is high without human intervention. Due to its high accuracy, it is being adopted as a sensor in various fields.

FIG. 9 is a diagram illustrating a configuration example of a conventional surface acoustic wave sensor.
In the figure, two interdigital transducers (IDT: Interdigital Transducer) (hereinafter referred to as “IDT”) 82-1 and 82-2 are formed on the piezoelectric substrate 81 so as to face each other. Between 82-2, a reaction field 83 in which the liquid to be measured contacts or drops is arranged. Rectangular wall bodies 84-1 and 84-2 are individually joined around IDTs 82-1 and 82-2 on the piezoelectric substrate 81, and a plate is placed on top of these wall bodies 84-1 and 84-2. Glass 85-1 and 85-2 are joined together. The output of an excitation circuit (not shown) is connected to the IDT 82-1 through a pair of bonding wires 86-11 and 86-12. The IDT 82-2 is connected to an input of a sense circuit (not shown) through a pair of bonding wires 86-21 and 86-22. The main body of the surface acoustic wave sensor configured as described above is fixed to the top of a predetermined pedestal member 87, and the ends of the top are bonded wires 86-11, 86-12, 86-21, 86-22. Is coated with a resin 88 that protects against short circuit and contact with the liquid described above.

  In such a surface acoustic wave sensor, the IDT 82-1 is excited by a high frequency signal of 50 MHz to 250 MHz provided by the excitation circuit, and converts the high frequency signal into a surface acoustic wave. The surface acoustic wave propagates near the surface of the piezoelectric substrate 81 and reaches the IDT 82-2 via the reaction field 83. The IDT 82-2 converts the surface acoustic wave that has arrived in this way into an electric signal and delivers it to the sense circuit described above.

The level or phase of the surface acoustic wave reaching the IDT 82-2 varies depending on the conductivity, relative dielectric constant, viscosity, etc. of the liquid that contacts or drops the reaction field 83 as a measurement target.
Therefore, the sense circuit indirectly detects the electrical characteristics of the liquid to be measured, or the components and properties of the liquid, based on the electrical signal given by the conversion of such surface acoustic waves. be able to.

  The IDTs 82-1 and 82-2 are sealed on the piezoelectric substrate 81 by “wall body 84-1 and glass 85-1” and “wall body 84-2 and glass 85-2”, respectively. Accordingly, these IDTs 82-1 and 82-2 can operate as transducers that perform electro-acoustic conversion without directly contacting the liquid to be measured.

  In addition, as a conventional example related to the present invention, for example, as disclosed in Patent Document 1, “each arithmetic expression indicating a correlation between a characteristic value signal corresponding to each surface acoustic wave device and a characteristic value of a liquid” When selecting the storage device that stores the liquid and the characteristic value of the liquid, the calculation equation suitable for detecting the characteristic value of the liquid is selected from a plurality of arithmetic expressions or tables stored in the storage device. And a microcomputer for calculating the characteristic value by inputting the characteristic value signal from the surface acoustic wave device having the selected arithmetic expression, thereby ensuring a wide measurement range, and accurately measuring the liquid within the measurement range. There is a “liquid characteristic value measuring apparatus using a surface acoustic wave device” characterized in that it can measure characteristic values.

JP 2003-139746 A

  By the way, in the above-described conventional example, as shown in FIG. 10A, the liquid to be measured contacts or drops not only on the reaction field 83 but also on the tops of the glasses 85-1 and 85-2. In the state, as shown by broken lines with arrows in FIG. 10 (a), IDTs 82-1 and 82-2 are electrostatically tightly coupled through glass 85-1, liquid and glass 85-2. To do. Moreover, the relative dielectric constant of such a liquid is generally about “80”, which is significantly larger than the relative dielectric constant of air (≈1.0).

  In such a state, most of the high-frequency signals supplied from the drive circuit described above to the IDT 82-1 are not converted into surface acoustic waves, but via the electrostatic coupling path formed by the electrostatic coupling. It is transmitted to IDT 82-2. Hereinafter, the high-frequency signal directly transmitted to the IDT 82-2 in this way is referred to as “direct wave”.

  Therefore, in the conventional example, when the amount of the liquid to be measured is larger than the ideal amount shown in FIG. 10B, a direct wave is generated, and the electric signal passed from the IDT 82-2 to the sense circuit by the direct wave is generated. Since the signal-to-noise ratio is reduced, the measurement accuracy is likely to be reduced.

Further, such direct waves are more likely to occur as the distance between the IDTs 82-1 and 82-2 on the piezoelectric substrate 81 is shorter, and the characteristics of the propagation path of the direct waves are not determined as listed below.
(1) The position of the liquid intervening in the propagation path of the direct wave is not determined in the process of replacing the liquid and often fluctuates irregularly.

(2) Since the shape of the liquid is not constant, the path through which the liquid is injected into the reaction field 83 or discharged from the reaction field 83 is not determined.
(3) The amount of liquid injected into the reaction field 83 and the amount of liquid discharged from the reaction field 83 are not necessarily constant.

  An object of the present invention is to provide a surface acoustic wave sensor that can significantly reduce or avoid errors caused by electrical coupling between a measurement target medium and an electrode.

In the first aspect of the present invention, the surface acoustic wave is present between the plurality of electrodes and the reaction field over a distance in which a minimum distance between the plurality of electrodes and the medium is limited. Additional propagation paths that can be propagated are individually formed. The plurality of sealing members seals additional propagation paths formed between the reaction waves for each of the plurality of electrodes.
That is, the electrostatic coupling between the plurality of electrodes and the medium in the reaction field becomes rough because the distance between the electrodes and the medium is wide over the length of the additional propagation path described above.

According to the present invention, compared to the conventional example, the level of the direct wave is suppressed to a low level without significantly changing the configuration, and the decrease in measurement accuracy due to the direct wave is greatly suppressed.
Therefore, according to the present invention, in addition to the price-performance ratio, a measurement system and a monitoring system with high accuracy and reliability are realized, and the possibility of expanding the application field of the surface acoustic wave sensor is enhanced.

It is a figure which shows 1st embodiment of this invention. It is a figure which shows 2nd embodiment of this invention. It is a figure which shows 3rd embodiment of this invention. It is a figure which shows 4th embodiment of this invention. It is a figure which shows 5th embodiment of this invention.

It is a figure which shows 6th embodiment of this invention. It is a figure which shows 7th embodiment of this invention. It is a figure which shows 8th embodiment of this invention. It is a figure which shows the structural example of the conventional surface acoustic wave sensor. It is a figure explaining the subject of a prior art example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the embodiments listed below, the same components as those in the conventional example shown in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted.

[First embodiment]
FIG. 1 is a diagram showing a first embodiment of the present invention.
In the figure, the difference from the conventional example shown in FIG. 9 is that the resin 88 is coated over the entire top of the glass 85-1, 85-2.
In this embodiment, since the liquid is blocked by the resin 88, as shown by the broken line portion and the shaded portion in FIG. 1, the liquid does not directly contact or drop the top of the glass 85-1, 85-2. .

Further, the distance between the IDTs 82-1 and 82-2 and the liquid is larger than that of the conventional example because a layer of the resin 88 is interposed between the IDTs 82-1 and 82-2 and the glasses 85-1 and 85-2.
Furthermore, the relative dielectric constant of such a resin 88 is generally less than “10”, which is significantly smaller than the relative dielectric constant (≈80) of the liquid.

  In other words, an electrostatic coupling path can theoretically be formed between the tops of the glasses 85-1 and 85-2 via the resin 88, but the coupling degree of the electrostatic coupling path is formed in the conventional example. The degree of coupling of the electrostatic coupling path is significantly smaller, and the level of the direct wave generated is suppressed to be significantly lower than that of the conventional example.

  Therefore, according to the present embodiment, as compared with the conventional example, the direct wave described above can be obtained by a minor change in the configuration in which the region coated with the resin 88 is expanded to the entire top of the glass 85-1, 85-2. The decrease in measurement accuracy due to the is greatly suppressed.

[Second Embodiment]
FIG. 2 is a diagram showing a second embodiment of the present invention.
In the present embodiment, the resin 88 is coated on the tops of the glasses 85-1 and 85-2 in a form different from the embodiment shown in FIG.

(1) It coats in the area | region (henceforth a "specific area | region") of the predetermined | prescribed width close | similar to the reaction field 83 among the top parts of glass 85-1, 85-2.
(2) The thickness of the resin coated on the specific region is set to a thickness sufficient as a weir to avoid overflow of the liquid from the reaction wave 83 to the tops of the glasses 85-1 and 85-2.

  In the present embodiment, the resin 88 is not coated over the entire tops of the glasses 85-1 and 85-2, but, similar to the first embodiment described above, the tops of these glasses 85-1 and 85-2. It is avoided that the liquid is in direct contact with or dripping.

  The distance between the IDTs 82-1 and 82-2 and the liquid is such that the resin 88 functions as the weir even when the amount of the liquid is large. It becomes larger than the same distance in.

  Therefore, according to the present embodiment, the measurement accuracy caused by the direct wave is greatly reduced by the minor change in the configuration that enlarges the area on the top of the glass 85-1, 85-2 coated with the resin 88. Be suppressed.

  In the present embodiment, the central portion of the top of the glasses 85-1 and 85-2 is not coated with the resin 88. Therefore, the visual confirmation of the state of the IDTs 82-1 and 82-2 sealed under these glasses 85-1 and 85-2 is possible as in the conventional example.

[Third embodiment]
FIG. 3 is a diagram showing a third embodiment of the present invention.
The difference between the present embodiment and the first embodiment described above is that glasses 31-1, 31-2 are provided instead of the glasses 85-1, 85-2, and these glasses 31- The top of 1 and 31-2 is that the resin 88 is not coated. Moreover, the thickness of the glass 31-1, 31-2 is the thickness t of the glass 85-1, 85-2 shown in FIG. 1 and the top of these glasses 85-1, 85-2 in the first embodiment. It is set to be equal to or greater than the sum (= t + T) of the thickness T of the resin 88 that has been coated.

  That is, even if an electrostatic coupling path is formed between the IDTs 82-1 and 82-2 via the glass 31-1, the liquid, and the glass 31-2, the coupling degree of the electrostatic coupling path is the same as that of the conventional example. The degree of coupling of the formed electrostatic coupling path is much smaller, and the level of the direct wave generated is also significantly lower than that of the conventional example.

  Therefore, according to the present embodiment, the measurement accuracy is reduced due to the direct wave due to a minor change in the configuration in which the thick glasses 31-1, 31-2 are provided instead of the glasses 85-1, 85-2. Is greatly suppressed.

[Fourth embodiment]
FIG. 4 is a diagram showing a fourth embodiment of the present invention.
The difference between the present embodiment and the first embodiment described above is that the wall bodies 41-1 and 41-2 are provided instead of the wall bodies 84-1 and 84-2, and the glass 85 is provided. -1 and 85-2 are not coated with the resin 88. Further, the heights of the wall bodies 41-1 and 41-2 are coated on the height h of the wall bodies 84-1 and 84-2 and the tops of the glasses 85-1 and 85-2 in the embodiment shown in FIG. It is set to be equal to or larger than the sum (= h + T) of the thickness T of the resin 88 made.

  That is, in this embodiment, the liquid can directly contact or drop on the tops of the glasses 85-1 and 85-2. The distance between the liquid and the IDTs 82-1 and 82-2 is the same as that described above. It is set longer than the distance in one embodiment. Furthermore, the relative dielectric constant of each space between the IDTs 31-1 and 31-2 and the glasses 85-1 and 85-2 is generally much smaller (≈1) than the relative dielectric constant of the resin 88. .

  That is, between the IDTs 31-1 and 31-2, an electrostatic coupling path in which a liquid is interposed is formed as listed in (1) to (5) below. The coupling degree of the electrostatic coupling path is In the conventional example, the coupling degree of the electrostatic coupling path formed via the liquid between the tops of the glasses 85-1 and 85-2 is significantly smaller than that of the conventional example, and the level of the direct wave generated is significantly lower than that of the conventional example. It can be suppressed.

(1) Space formed between IDT 82-1 and the bottom of glass 85-1.
(2) Between the bottom and top of glass 85-1, which is a dielectric
(3) A liquid that contacts the tops of both glass 85-1 and glass 85-2 and functions as a dielectric.
(4) Between the top and bottom of glass 85-2, which is a dielectric
(5) Space formed between the bottom of glass 85-2 and IDT 82-2

  Therefore, according to the present embodiment, the wall bodies 41-1 and 41-2 having different sizes are subjected to the measurement due to the direct wave by changing the minor configuration applied instead of the wall bodies 84-1 and 84-2. The loss of accuracy is greatly suppressed.

[Fifth embodiment]
FIG. 5 is a diagram showing a fifth embodiment of the present invention.
In the figure, the difference in configuration from the conventional example shown in FIG. 9 is as follows.
(1) Conductive films (hereinafter referred to as “conductive films”) 51-1 and 51-2 are formed over the entire top portions of the glasses 85-1 and 85-2, and these conductive films 51-1 and 51 are formed. -2 is grounded.
(2) The resin 88 is coated after the conductive films 51-1 and 51-2 are formed.

  In the present embodiment, even if a liquid overflows from the reaction field 83, the liquid does not contact the tops of the glasses 85-1, 85-2, but contacts the grounded conductive films 51-1, 51-2. The electrostatic coupling between the IDTs 82-1 and 82-2 and the liquid is blocked by the conductive films 51-1 and 51-2.

  Therefore, according to the present embodiment, compared with the conventional example, the minor configuration change in which the conductive films 51-1 and 51-2 grounded are formed on the entire top portions of the glasses 85-1 and 85-2. Thus, a decrease in measurement accuracy due to the direct wave described above is greatly suppressed.

  In the present embodiment, when the glass 85-1 and 85-2 are bonded to the tops of the wall bodies 84-1 and 84-2 through a photosensitive resin, the exposure of the resin is excluded. The formation of the conductive films 51-1 and 51-2 as a factor is performed after such an exposure process.

[Sixth embodiment]
FIG. 6 is a diagram showing a sixth embodiment of the present invention.
In the figure, the difference from the conventional example shown in FIG. 9 is that glasses 61-1 and 61-2 are provided instead of the glasses 85-1 and 85-2, and these glasses 61-1 and 61-2 are provided. Is configured in any of the following forms.
(1) Constructed as hydrophobic glass.
(2) A hydrophobic coating is applied to both the top and bottom, or only the entire top.

In the present embodiment, since the liquid dropped on the glasses 61-1 and 61-2 is repelled by the hydrophobicity, it is excluded without staying at the tops of these glasses 61-1 and 61-2.
Therefore, according to the present embodiment, the measurement caused by the direct wave described above can be performed by changing the minor configuration in which the hydrophobic glasses 61-1 and 61-2 are provided instead of the glasses 85-1 and 85-2. The loss of accuracy is greatly suppressed.

In the present embodiment, the glasses 61-1 and 61-2 are attached by being joined to the tops of the wall bodies 84-1 and 84-2 having the same height as the conventional example.
However, the glasses 61-1 and 61-2 may be combined with any of the first to fifth embodiments described above, and the liquid stays at the top of these glasses 61-1 and 61-2 quickly. For example, it may be attached in a state of being inclined in the direction of the reaction field 83.

  In the present embodiment, the reaction field 83 may be subjected to hydrophilic processing or covered with a hydrophilic film or material for the purpose of limiting overflow of the liquid from the reaction field 83.

[Seventh embodiment]
FIG. 7 is a diagram showing a seventh embodiment of the present invention.
In the figure, the difference in configuration from the first embodiment shown in FIG. 1 is as follows.
(1) The distance between the reaction field 83 on the piezoelectric substrate 81 and the IDTs 82-1 and 82-2 is set larger by a predetermined value δ.

(2) The propagation path of the surface acoustic wave between the reaction field 83 on the piezoelectric substrate 81 and the IDTs 82-1 and 82-2 is formed longer by the predetermined value δ. In the following, of these propagation paths, two sections extending between the reaction field 83 and the IDTs 82-1 and 82-2 will be referred to as “additional propagation paths” and denoted by reference numerals “71− “1” and “71-2” are attached.
(3) These additional propagation paths 71-1 and 71-2 are sealed together with the nearest IDTs 82-1 and 82-2, respectively.

In the present embodiment, the electrostatic coupling between the IDTs 82-1 and 82-2 and the liquid in the reaction field 83 is such that the distance between these IDTs 82-1 and 82-2 and the liquid is widened over the above δ. It becomes rough.
Therefore, according to the present embodiment, the minor propagation change in which the additional propagation paths 71-1 and 71-2 are added between the reaction field 83 on the piezoelectric substrate 81 and the IDTs 82-1 and 82-2. Therefore, a decrease in measurement accuracy due to the direct wave described above is greatly suppressed.
Although this embodiment is configured by improving the first embodiment, it may be configured as a combination with any of the second to sixth embodiments described above.

[Eighth embodiment]
FIG. 8 is a diagram showing an eighth embodiment of the present invention.
In the figure, the difference in configuration from the sixth embodiment shown in FIG. 6 is as follows.
(1) Instead of the glasses 61-1 and 61-2, a single glass 72 is disposed.
(2) Such a glass 72 forms a gap 73 through which the liquid described above flows between the reaction field 83.
(3) Between the top and bottom of the glass 72, an inlet 74a that guides the liquid flowing into the gap 74 and an outlet 74b that guides the liquid flowing out of the gap 74 to the outside are formed.

In the present embodiment, the liquid to be measured is introduced onto the reaction field 83 through the inlet 74a and the gap 73, and is discharged to the outside through the outlet 73b from the gap 73.
Moreover, since the reaction field 83 is covered with such glass 72, the liquid does not drop directly.

Therefore, according to the present embodiment, restrictions on the form and path of liquid supply are alleviated, and the increase in electrostatic coupling described above due to the fact that there is no limit on the thickness of the liquid on the reaction field is alleviated. .
In the present embodiment, it is avoided that the liquid is directly dropped on the reaction field 83 by the single glass 72 provided in place of the glasses 61-1 and 61-2.

However, the present embodiment is not limited to such a configuration, and the glass 72 may be configured as follows, for example.
(1) Glasses 61-1 and 61-2 are configured as separate glasses and supported by wall bodies 84-1 and 84-2 (built between wall bodies 84-1 and 84-2). The
(2) It is integrally formed with the resin 88 and other members.

In each of the embodiments described above, the present invention is applied to a surface acoustic wave sensor that realizes detection of the presence or absence of a medium such as a liquid in the reaction field 83 or a component of the medium.
However, the present invention is not limited to such a medium, but can be applied to, for example, a sensor adapted to gas, smoke, or the like as a medium to replace the liquid, or a biosensor that realizes measurement of an antigen-antibody reaction in the body. is there.

  Further, in each of the above-described embodiments, the IDTs 82-1 and 82-2 are not limited to interdigital electrodes as long as they can perform energy conversion between a desired high-frequency signal (electric signal) and a surface acoustic wave. The electrode may have any shape, structure and size.

  Further, in each of the above-described embodiments, the present invention is applied to a transversal surface acoustic wave sensor. However, the present invention can be similarly applied to SAW resonance type or ladder type sensors.

  Further, the present invention is not limited to the above-described embodiments, and various configurations can be made within the scope of the present invention, and any improvement may be applied to all or some of the components.

  Hereinafter, the inventions disclosed in the present application will be organized and listed in a format according to the descriptions in the “Claims” and “Means for Solving the Problems” columns.

[Claim 1] A plurality of sealing members individually sealing a plurality of electrodes formed on a piezoelectric substrate and performing energy conversion between an electric signal and a surface acoustic wave. A surface acoustic wave sensor that detects the presence or absence of a medium in the reaction field as a propagation characteristic of the surface acoustic wave in the reaction field surrounded by the electrodes,
A surface acoustic wave sensor comprising: a plurality of covering members that are individually mounted on the plurality of sealing members, and prevent or roughen electrical coupling between the plurality of electrodes and the medium.
In the surface acoustic wave sensor having such a configuration, the plurality of covering members are individually mounted on the plurality of sealing members to prevent or roughen the electrical coupling between the plurality of electrodes and the medium. .

  That is, an electrostatic coupling path is theoretically formed between a plurality of sealing members via a plurality of covering members and a medium interposed between these covering members. The coupling degree of the path is significantly smaller than the coupling degree of the electrostatic coupling path formed through only the medium without such a covering member.

  Therefore, compared to the conventional example, the level of the direct wave is suppressed to a low level, and a decrease in measurement accuracy due to the direct wave is greatly suppressed.

[Claim 2] In the surface acoustic wave sensor according to claim 1,
The plurality of covering members are:
A surface acoustic wave sensor characterized by limiting a minimum distance between the plurality of electrodes and the medium.
In the surface acoustic wave sensor having such a configuration, the plurality of covering members limit a minimum distance between the plurality of electrodes and the medium.

  That is, an electrostatic coupling path is theoretically formed between a plurality of sealing members via a plurality of covering members and a medium interposed between these covering members. The coupling degree of the path is significantly smaller than the coupling degree of the electrostatic coupling path formed through only the medium without such a covering member.

  Therefore, compared to the conventional example, the level of the direct wave is suppressed to a low level, and a decrease in measurement accuracy due to the direct wave is greatly suppressed.

[Claim 3] In the surface acoustic wave sensor according to claim 1,
The plurality of covering members are:
A surface acoustic wave sensor, wherein the surface acoustic wave sensor is provided so as to protrude from end portions of the top portions of the plurality of sealing members, and prevents the medium from adhering to or dropping from the top portions.

  In the surface acoustic wave sensor having such a configuration, the plurality of covering members are provided so as to protrude from end portions of the top portions of the plurality of sealing members, and prevent the medium from adhering to or dropping from the top portions.

That is, even when the amount of the medium is large, the degree of electrostatic coupling between the plurality of sealing members can be kept small when the medium is blocked by the plurality of covering members.
Accordingly, the level of the direct wave generated due to such electrostatic coupling is suppressed to be lower than that of the conventional column, and the decrease in measurement accuracy is greatly suppressed.

[Claim 4] In the surface acoustic wave sensor according to claim 1,
The tops of the plurality of covering members are
A surface acoustic wave sensor characterized by being a conductor that encloses the tops of the plurality of sealing members and can be grounded.
In the surface acoustic wave sensor having such a configuration, the top portions of the plurality of covering members are conductors that enclose the top portions of the plurality of sealing members and can be grounded.

  That is, since the medium is blocked by the conductor, the medium does not contact the tops of the plurality of sealing members.

  Therefore, in the state where these conductors are grounded, the electrostatic coupling path through the medium is not formed between the tops of the sealing members described above, and the direct connection is made via such an electrostatic coupling path. A reduction in measurement accuracy due to the generation of waves is avoided.

[Claim 5] In the surface acoustic wave sensor according to claim 4,
The conductor is
A surface acoustic wave sensor formed on top of the plurality of sealing members.
In the surface acoustic wave sensor having such a configuration, the conductor is formed on top of the plurality of sealing members.

  That is, since the medium is blocked by the conductor, the medium does not contact the tops of the plurality of sealing members.

Therefore, in the state where these conductors are grounded, the electrostatic coupling path through the medium is not formed between the tops of the sealing members described above, and the direct connection is made via such an electrostatic coupling path. A reduction in measurement accuracy due to the generation of waves is avoided.

[Claim 6] A plurality of electrodes formed on the piezoelectric substrate and formed on a plurality of electrode piezoelectric substrates that perform energy conversion between the electric signal and the surface acoustic wave, and perform energy conversion between the electric signal and the surface acoustic wave. As a propagation characteristic of the surface acoustic wave in the reaction field surrounded by the plurality of electrodes on the piezoelectric substrate, the presence or absence of the medium in the reaction field or the characteristic A surface acoustic wave sensor for detecting
The main component of the medium is water,
The tops of the plurality of sealing members are
A surface acoustic wave sensor formed of a hydrophobic member or subjected to hydrophobic processing.

  In the surface acoustic wave sensor having such a configuration, the main component of the medium is water. The tops of the plurality of sealing members are formed of a hydrophobic member or are subjected to hydrophobic processing.

That is, since the medium dropped on the tops of the plurality of sealing members is repelled by the hydrophobicity, it is excluded without staying at the tops of these sealing members.
Therefore, a decrease in measurement accuracy due to the direct wave described above is greatly suppressed.
[Claim 7] In the surface acoustic wave sensor according to claim 6,
A surface acoustic wave sensor comprising a hydrophilic encapsulating member encapsulating the reaction field and having hydrophilicity.

  The surface acoustic wave sensor having such a configuration includes a hydrophilic encapsulating member that encapsulates the reaction field and has hydrophilicity.

That is, even if the amount of the medium is large, the possibility of spilling from the reaction field onto the surfaces of the plurality of sealing members is reduced.
Therefore, the possibility that the measurement accuracy decreases due to the direct wave described above is reduced.
[Claim 8] A plurality of electrodes formed on the piezoelectric substrate and formed on a plurality of electrode piezoelectric substrates that perform energy conversion between the electrical signal and the surface acoustic wave, and perform energy conversion between the electrical signal and the surface acoustic wave. As a propagation characteristic of the surface acoustic wave in the reaction field surrounded by the plurality of electrodes on the piezoelectric substrate, the presence or absence of the medium in the reaction field or the characteristic A surface acoustic wave sensor for detecting
The tops of the plurality of sealing members are
A surface acoustic wave sensor, wherein the surface acoustic wave sensor is formed with a thickness that limits a minimum distance between the plurality of electrodes and the medium.

  In the surface acoustic wave sensor having such a configuration, the tops of the plurality of sealing members are formed with a thickness that limits a minimum distance between the plurality of electrodes and the medium.

That is, even if an electrostatic coupling path is formed between the tops of a plurality of sealing members via a medium, the degree of coupling of the electrostatic coupling paths is the same as when these sealing members are thin. Significantly smaller than the degree of coupling.
Therefore, the possibility that the measurement accuracy decreases due to the direct wave described above is reduced.

[Claim 9] A plurality of electrodes formed on a piezoelectric substrate and formed on a plurality of electrode piezoelectric substrates that perform energy conversion between an electric signal and a surface acoustic wave, and perform energy conversion between the electric signal and the surface acoustic wave. As a propagation characteristic of the surface acoustic wave in the reaction field surrounded by the plurality of electrodes on the piezoelectric substrate, the presence or absence of the medium in the reaction field or the characteristic A surface acoustic wave sensor for detecting
The ends of the plurality of sealing members bonded to the piezoelectric substrate are
A surface acoustic wave sensor, characterized in that the minimum distance between the plurality of electrodes and the medium is limited.

  In the surface acoustic wave sensor having such a configuration, the end portions of the plurality of sealing members bonded to the piezoelectric substrate are formed with dimensions that limit the minimum distance between the plurality of electrodes and the medium. Is done.

That is, an electrostatic coupling path can be formed between the tops of the plurality of sealing members via a medium, but an electrostatic coupling path formed via a plurality of sealing members and the medium between the plurality of electrodes. The degree of coupling becomes smaller as the minimum distance is longer.
Therefore, the possibility that the measurement accuracy decreases due to the direct wave described above is reduced.

[Claim 10] A plurality of electrodes formed on the piezoelectric substrate and formed on a plurality of electrode piezoelectric substrates that perform energy conversion between the electrical signal and the surface acoustic wave, and perform energy conversion between the electrical signal and the surface acoustic wave. As a propagation characteristic of the surface acoustic wave in the reaction field surrounded by the plurality of electrodes on the piezoelectric substrate, the presence or absence of the medium in the reaction field or the characteristic A surface acoustic wave sensor for detecting
Between the plurality of electrodes and the reaction field,
An additional propagation path through which the surface acoustic wave can propagate over a distance in which a minimum distance between the plurality of electrodes and the medium is limited is formed,
The plurality of sealing members are:
A surface acoustic wave sensor, wherein an additional propagation path formed between the plurality of electrodes and the reaction wave is sealed together.

  In the surface acoustic wave sensor having such a configuration, the surface elasticity is extended between the plurality of electrodes and the reaction field over a distance in which a minimum distance between the plurality of electrodes and the medium is limited. Additional propagation paths through which waves can propagate are formed individually. The plurality of sealing members seals additional propagation paths formed between the reaction waves for each of the plurality of electrodes.

That is, the electrostatic coupling between the plurality of electrodes and the medium in the reaction field becomes rough because the distance between the electrodes and the medium is wide over the length of the additional propagation path described above.
Therefore, the possibility that the measurement accuracy decreases due to the direct wave described above is reduced.

[Claim 11] In the surface acoustic wave sensor according to any one of claims 1 to 10,
A surface acoustic wave sensor comprising a gap forming member that covers the reaction field and forms a gap through which the medium flows between the reaction field and the reaction field.

  That is, the thickness of the layer of the medium positioned as a measurement target on the reaction field is limited by the size and shape of the gap, and the formation member prevents the medium from dropping directly on the reaction field. .

  Therefore, flexible adaptation to various supply paths and supply methods of the medium is possible, and the increase in the electrostatic coupling described above due to the fact that the thickness of the medium on the reaction field is not limited is mitigated.

31, 61, 72, 85 Glass 41, 84 Wall body 51 Conductive film 71 Additional propagation path 73 Gap 74a Inlet 74b Outlet 81 Piezoelectric substrate 82 Interdigital electrode 83 Reaction field 86 Bonding wire 87 Base member 88 Resin

Claims (1)

A plurality of sealing members for individually sealing a plurality of electrodes formed on the piezoelectric substrate and performing energy conversion between an electric signal and a surface acoustic wave, and surrounded by the plurality of electrodes on the piezoelectric substrate; As a surface acoustic wave propagation characteristic in the reaction field, a surface acoustic wave sensor for detecting presence or absence of a medium in the reaction field or a characteristic,
Between the plurality of electrodes and the reaction field,
An additional propagation path through which the surface acoustic wave can propagate over a distance in which a minimum distance between the plurality of electrodes and the medium is limited is formed,
The plurality of sealing members are:
A surface acoustic wave sensor, wherein an additional propagation path formed between the plurality of electrodes and the reaction wave is sealed together.