HK1147608A - Surface acoustic wave element and equipment for measuring characteristics of liquid material - Google Patents

Description

Surface acoustic wave element and liquid material characteristic measuring device

Technical Field

The present invention relates to a surface acoustic wave device (element) having a sealing electrode provided on a piezoelectric substrate and a liquid material property measuring apparatus (device) including such a surface acoustic wave device.

Background

In general, a surface acoustic wave device includes a piezoelectric substrate, and input and output electrodes including comb-tooth electrode fingers provided on the piezoelectric substrate. When an electric signal is input to an input electrode of the surface acoustic wave device, an electric field is generated between the electrode fingers, and a surface acoustic wave is excited due to a piezoelectric effect and propagates on the piezoelectric substrate. A surface acoustic wave sensor for detecting various substances and measuring characteristics thereof, which includes a surface acoustic wave device using a shear horizontal surface acoustic wave (SH-SAW) among the aforementioned excited surface acoustic waves, has been studied. The shear horizontal surface acoustic wave moves in a direction perpendicular to the propagation direction of the surface acoustic wave (japanese patent No. 3481298).

The operation of surface acoustic wave sensors makes use of the fact that: when the area of the piezoelectric substrate where the liquid material to be measured is located is electrically disconnected, the output signal output from the output electrode has different characteristics than when the same area of the piezoelectric substrate is electrically short-circuited. More specifically, the output signal generated when the area of the piezoelectric substrate is open-circuited is affected by both the electrical interaction and the mechanical interaction, whereas the output signal generated when the area of the piezoelectric substrate is short-circuited is affected only by the mechanical interaction. Thus, the physical properties of the liquid material, such as dielectric constant, conductivity, etc., can be determined by counteracting mechanical interactions, and then extracting the electrical interactions from the output signal.

For measuring physical properties of a liquid material using a surface acoustic wave sensor, there is an example in which the surface acoustic wave sensor is immersed in the liquid material. In this application, the electrode of the surface acoustic wave device of the surface acoustic wave sensor is sealed by the sealing member to prevent the electrode from being short-circuited by the liquid material.

If the seal member is provided on the propagation path of the surface acoustic wave, since the thickness of the seal member in the propagation direction is determined by the propagation characteristics of the surface acoustic wave, the seal member must be formed very accurately. In addition, after a certain period of time, the seal for sealing the electrodes may peel off from the piezoelectric substrate, with the result that liquid material may enter a gap between the peeled seal and the piezoelectric substrate, thereby causing short-circuiting of the electrodes.

Disclosure of Invention

The present invention has been made in view of the above problems. An object of the present invention is to provide a surface acoustic wave device which prevents an electrode from being short-circuited even when the surface acoustic wave device is immersed in a liquid material. It is a further object of the present invention to provide a liquid material property measuring apparatus including such a surface acoustic wave device for measuring a physical property of a liquid material.

The present invention provides a surface acoustic wave device having an electrode provided on a piezoelectric substrate, the surface acoustic wave device including: a sealing member having a peripheral wall (peripheral wall) provided on the piezoelectric substrate so as to surround the electrode and a top plate (top plate) covering the peripheral wall. Further, a seal reinforcement is provided on the piezoelectric substrate, faces the liquid material applied on the piezoelectric substrate, and extends parallel to a portion of the peripheral wall.

According to the present invention, the seal reinforcement prevents the liquid material from coming into contact with the peripheral wall, prevents the peripheral wall from peeling off from the piezoelectric substrate, and prevents the liquid material from being applied to the input electrode and the output electrode.

Another aspect of the present invention provides a surface acoustic wave device having an electrode provided on a piezoelectric substrate, the surface acoustic wave device including: a sealing member having a peripheral wall provided on the piezoelectric substrate so as to surround the electrode, a first wall provided on the piezoelectric substrate so as to face the liquid material applied on the piezoelectric substrate and extending parallel to a part of the peripheral wall, and a top plate covering the peripheral wall and the first wall.

The first wall and the peripheral wall collectively form a double protection wall that prevents the liquid material from coming into contact with the peripheral wall, prevents the peripheral wall from peeling off from the piezoelectric substrate, and prevents the liquid material from being applied to the input electrode and the output electrode. Further, a seal reinforcement may be provided which fills in a space between the first wall and a wall portion of the peripheral wall facing the first wall.

The peripheral wall is made of a photosensitive resin. Therefore, the peripheral wall can have a desired thickness in the propagation direction of the surface acoustic wave, thereby preventing the propagation characteristics of the surface acoustic wave from deteriorating.

Still another aspect of the present invention provides a liquid material property measurement apparatus including the surface acoustic wave device described above, wherein the electrodes include an input electrode and an output electrode, both of which are sealed by the sealing member, and wherein the liquid material property measurement apparatus determines a physical property of the liquid material applied on a transmission path provided between the input electrode and the output electrode. The surface acoustic wave device includes: a first surface acoustic wave device having a first propagation path disposed between a first input electrode and a first output electrode; and a second surface acoustic wave device having a second propagation path disposed between the second input electrode and the second output electrode and having different amplitude and phase characteristics from the first propagation path. Accordingly, the surface acoustic wave device can determine the physical properties of the liquid material applied to the first propagation path and the second propagation path. The first input electrode and the second input electrode may be composed of the same electrode.

According to the present invention, the seal reinforcement prevents the liquid material from coming into contact with the peripheral wall, prevents the peripheral wall from peeling off from the piezoelectric substrate, and also prevents the liquid material from being applied to the electrode.

The peripheral wall and the first wall facing the liquid material and extending parallel to a part of the peripheral wall jointly constitute a double protection wall that prevents the liquid material from coming into contact with the peripheral wall, prevents the peripheral wall from peeling off from the piezoelectric substrate, and prevents the liquid material from being applied to the electrodes. Furthermore, the effect of the seal reinforcement filling the space between the first wall and the wall portion of the peripheral wall facing the first wall is to reliably prevent liquid material from being applied to the electrode.

The peripheral wall is made of a photosensitive resin, thereby making it possible to have a desired thickness in the propagation direction of the surface acoustic wave and to prevent the propagation characteristics of the surface acoustic wave from deteriorating.

In the liquid material property measurement apparatus including the surface acoustic wave device described above, the electrodes include an input electrode and an output electrode, which are both sealed by the sealing member. The liquid material property measurement device determines a physical property of the liquid material applied to a transmission path provided between the input electrode and the output electrode.

Drawings

Fig. 1 is a plan view of a liquid material property measurement apparatus according to a first embodiment of the present invention;

FIG. 2A is a partial end view taken along line IIA-IIA of FIG. 1;

FIG. 2B is a partial enlarged view of FIG. 2A;

FIG. 3 is a plan view of a liquid material property measurement apparatus according to a second embodiment of the present invention;

FIG. 4A is a partial end view taken along line IVA-IVA of FIG. 3;

FIG. 4B is a partial enlarged view of FIG. 4A;

FIG. 5 is a plan view of a liquid material property measurement apparatus according to a third embodiment of the present invention;

FIG. 6A is a partial end view taken along line VIA-VIA of FIG. 5;

FIG. 6B is a partial enlarged view of FIG. 6A;

FIG. 7 is a plan view of a liquid material property measurement apparatus according to a fourth embodiment of the present invention; while

Fig. 8 is a plan view of a liquid material property measurement apparatus according to a fifth embodiment of the present invention.

Detailed Description

A first embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a plan view of a liquid material property measurement apparatus 50 according to a first embodiment of the present invention. Fig. 2A is a partial end view taken along line IIA-IIA of fig. 1, and fig. 2B is a partial enlarged view of fig. 2A.

As shown in fig. 1, the liquid material property measurement apparatus 50 includes a first surface acoustic wave device 10 and a second surface acoustic wave device 20. The first surface acoustic wave device 10 has an input electrode 12 and an output electrode 14, and a first propagation path 16 is arranged between the input electrode 12 and the output electrode 14. The second surface acoustic wave device 20 has an input electrode 22 and an output electrode 24, and a second propagation path 26 is arranged between the input electrode 22 and the output electrode 24.

The input electrodes 12 and 22 include comb-teeth electrodes for exciting surface acoustic waves in accordance with an electric signal input from an oscillator (not shown). The output electrodes 14 and 24 comprise comb-shaped electrodes for receiving surface acoustic waves excited and propagated by the input electrodes 12 and 22.

The input electrode 12 and the input electrode 22 are sealed by a sealing material 30a, and the output electrode 14 and the output electrode 24 are sealed by a sealing material 30 b. The sealing members 30a, 30b serve to prevent the test object 52 in the form of a liquid material from being applied to the comb-teeth electrodes when the physical properties thereof are measured.

The seal 30a includes a peripheral wall 32a and a top plate 34 a. The peripheral wall 32a is provided on the piezoelectric substrate 54 around the input electrodes 12, 22. The top plate 34a is bonded to the upper end of the peripheral wall 32a by an adhesive 36 in such a manner as to cover the peripheral wall 32 a. The top plate 34a is coupled to the upper end of the peripheral wall 32a substantially in parallel with the piezoelectric substrate 54. The top plate 34a extends from the input electrodes 12, 22 toward the first and second propagation paths 16, 26, defining a gap 38a between an end 35a of the top plate 34a and the piezoelectric substrate 54. The gap 38a is filled with a sealing reinforcement 40a, which sealing reinforcement 40a acts on a wall portion 42a of the peripheral wall 32a facing the object 52 applied on the piezoelectric substrate 54. Like the seal 30a, the seal 30b also includes a peripheral wall 32b and a top plate 34 b. The gap 38b defined between the end portion 35b and the piezoelectric substrate 54 is filled with a seal reinforcement 40b, and the seal reinforcement 40b acts on the wall portion 42b of the peripheral wall 32 b. The seal reinforcements 40a, 40b are provided on a piezoelectric substrate 54 facing the object 52 applied on the first and second propagation paths 16, 26.

The first propagation path 16 and the second propagation path 26 include metal films 56, 58, respectively, evaporated on the piezoelectric substrate 54. The metal films 56, 58 are electrically shorted. Since the metal film 56 of the first propagation path 16 is partially peeled, the piezoelectric substrate 54 is exposed in the open region 60. Since the open area 60 is electrically disconnected, the first propagation path 16 serves as an open propagation path. The residual band of the metal film 56 is electrically short-circuited. The second propagation path 26 is integrally constituted by the metal film 58, and thus functions as a short-circuit propagation path for electrical short-circuiting. To improve the accuracy of the measurement of the physical properties of the object 52, the metal films 56, 58 are grounded. The metal films 56, 58 may be made of any material and are not limited to a particular material, but the metal films 56, 58 are preferably made of gold that is chemically stable with respect to the object 52. A side wall 62 is provided on the piezoelectric substrate 54 along the sides of the first and second propagation paths 16 and 26. The sidewalls 62 extend from the input electrodes 12, 22 and extend toward the output electrodes 14, 24. The piezoelectric substrate 54 is not limited to any particular material. The piezoelectric substrate 54 may be in the form of a single substrate made of a piezoelectric material, or may be a substrate in which: comprising a glass substrate on which a thin film of piezoelectric material is provided.

The first surface acoustic wave device 10 and the second surface acoustic wave device 20 are arranged in parallel with each other on a piezoelectric substrate 54, and the piezoelectric substrate 54 is mounted on a printed circuit board 64 by die bonding. Pads 66 provided on the printed circuit board 64 are connected to the input electrodes 12, 22 and the output electrodes 14, 24 by bonding wires 68. A peripheral wall 70 is provided at the outer edge of the printed circuit board 64. The peripheral walls 32a, 32b, the side wall 62 and the outer peripheral wall 70 collectively define a recess 72 therebetween, the recess 72 being filled with a protective resin 74.

A method of manufacturing the liquid material property measurement device 50 according to the first embodiment is described below.

First, the input electrodes 12, 22, the output electrodes 14, 24, the first propagation path 16, and the second propagation path 26 are formed on the piezoelectric substrate 54 by photolithography. A peripheral wall 32a is formed around the input electrodes 12, 22, a peripheral wall 32b is formed around the output electrodes 14, 24, and side walls 62 are formed along the sides of the first and second propagation paths 16, 26, all of which are formed of photosensitive resin (SU-8: photosensitive epoxy resin manufactured by Kayaku Microchem corporation) used in photolithography.

Then, an adhesive is applied on the surface of the top plates 34a, 34b including the glass substrate. The top plate 34a coated with the adhesive is bonded to the upper end of the peripheral wall 32a, and similarly the top plate 34b is bonded to the upper end of the peripheral wall 32 b.

The piezoelectric substrate 54 on which the input electrodes 12 and the like are formed is connected to the printed circuit board 64 by die bonding. The pads 66 on the printed circuit board 64 are connected to the input electrodes 12, 22 and the output electrodes 14, 24 by bonding wires 68. Subsequently, a peripheral wall 70 is formed at the outer edge of the printed circuit board 64 using a thermosetting resin. Thereafter, the gaps 38a, 38b formed by the top plates 34a, 34b and the piezoelectric substrate 54 are filled with a thixotropic underfill agent (serving as the seal reinforcements 40a, 40 b). Since thixotropic underfill agent is used as the sealing reinforcement 40a, 40b, the sealing reinforcement 40a, 40b fills the gap 38a, 38b by capillary action. As a result, since the object 52 is prevented from coming into contact with the peripheral walls 32a, 32b, the peripheral walls 32a, 32b are prevented from peeling off from the piezoelectric substrate 54, thereby preventing the object 52 from being applied to the input electrodes 12, 22 and the output electrodes 14, 24. Then, the recesses 72 formed between the peripheral walls 32a, 32b, the side walls 62, and the peripheral wall 70 are filled with a protective resin 74. Thus, the liquid material property measurement device 50 is prepared.

The liquid material property measurement device 50 measures a physical property of the object 52 as follows. The liquid material property measurement apparatus 50 is immersed in the object 52, and an oscillator (not shown) inputs the same signal to the input electrodes 12, 22. The input electrode 12 excites a surface acoustic wave based on the input signal, which propagates along a first propagation path 16 and is received by the output electrode 14. Similarly, the input electrode 22 excites a surface acoustic wave based on the input signal, which propagates along the second propagation path 26 and is received by the output electrode 24. The amplitude ratio and the phase difference of the output signals are detected by generating the output signals from the surface acoustic waves received by the output electrodes 14, 24. The physical characteristics of the object 52 are measured from the detected amplitude ratio and the detected phase difference.

As described above, the liquid material property measurement apparatus 50 according to the first embodiment includes: a first surface acoustic wave device 10 having a first propagation path 16 arranged between an input electrode 12 and an output electrode 14; and a second surface acoustic wave device 20 having a second propagation path 26 disposed between the input electrode 22 and the output electrode 24, wherein the second propagation path 26 has an amplitude and a phase different from the first propagation path 16. The liquid material property measurement device 50 determines physical properties of an object 52 applied to the first and second travel paths 16, 26.

In the liquid material property measurement apparatus 50, the input electrodes 12, 22 are surrounded by the sealing member 30a, the sealing member 30a being defined by the peripheral wall 32a of the photosensitive resin disposed on the piezoelectric substrate 54 and the top plate 34a covering the peripheral wall 32 a. The seal stiffener 40a is disposed on the piezoelectric substrate 54 facing the object 52 applied on the piezoelectric substrate 54 such that the seal stiffener 40a extends parallel to the wall 42 a. The output electrodes 14, 24 are surrounded by a sealing member 30b, and the sealing member 30b is defined by a peripheral wall 32b of photosensitive resin disposed on the piezoelectric substrate 54 and a top plate 34b covering the peripheral wall 32 b. The seal stiffener 40b is disposed on the piezoelectric substrate 54 facing the object 52 applied on the piezoelectric substrate 54 such that the seal stiffener 40b extends parallel to the wall 42 b. The first and second surface acoustic wave devices 10 and 20 prevent the object 52 applied on the piezoelectric substrate 54 from coming into contact with the peripheral walls 32a and 32b, prevent the peripheral walls 32a and 32b from being peeled off from the piezoelectric substrate 54, and prevent the piezoelectric substrate 54 from being applied to the input electrodes 12 and 22 and the output electrodes 14 and 24.

A liquid material characteristic measurement apparatus 50A according to a second embodiment of the present invention will be described below. Fig. 3 is a plan view of a liquid material property measurement apparatus 50A according to a second embodiment of the present invention. Fig. 4A is a partial end view taken along line IVA-IVA of fig. 1, and fig. 4B is a partial enlarged view of fig. 4A. Parts of the second embodiment that are identical to parts of the first embodiment are designated with the same reference numerals and these features will not be described in detail below.

The liquid material property measurement device 50A differs from the liquid material property measurement device 50 in that: the first walls 80a, 80b are added to the sealing members 30Aa, 30Ab, and the peripheral walls 32a, 32b are not coated with the sealing reinforcements 40a, 40 b. In the liquid material property measurement apparatus 50A, the first walls 80A, 80b made of photosensitive resin are arranged on the piezoelectric substrate 54 facing the object 52 applied on the piezoelectric substrate 54. Further, seal 30Aa is constructed from first wall 80a, wall 42a and top plate 34a, and seal 30Ab is constructed from first wall 80b, wall 42b and top plate 34 b. Wall 42a and first wall 80a facing wall 42a, and wall 42b and first wall 80b facing wall 42b, respectively, form a dual protective wall for protecting object 52. Further, the first and second propagation paths 16, 26 are surrounded by the first walls 80a, 80b and the side wall 62. A top plate 34a, one side of which is coated with an adhesive 36, is bonded to the peripheral wall 32a and the respective upper ends of the first walls 80 a. And, a top plate 34b, one side of which is coated with an adhesive 36, is bonded to the peripheral wall 32b and the respective upper ends of the first walls 80 b. The top plate 34a, the peripheral wall 32a, the piezoelectric substrate 54, and the first wall 80a collectively define an enclosed space 82a, while the top plate 34b, the peripheral wall 32b, the piezoelectric substrate 54, and the first wall 80b collectively define another enclosed space 82 b. The connections formed by the bonding wires 68 between the input electrodes 12, 22, the output electrodes 14, 24, and the printed circuit board 64, the outer peripheral wall 70 disposed on the printed circuit board 64, and the protective resin 74 are the same as those in the first embodiment, and therefore, detailed description of these features will not be given below.

In the liquid material property measurement apparatus 50A, the input electrodes 12, 22 are surrounded by a seal 30Aa, the seal 30Aa including: a peripheral wall 32a of photosensitive resin disposed on the piezoelectric substrate 54; a first wall 80a facing the object 52 applied on the piezoelectric substrate 54 and extending parallel to a part of the peripheral wall 32 a; and a top plate 34a covering the peripheral wall 32a and the first wall 80 a. The output electrodes 14, 24 are surrounded by a seal 30Ab, which seal 30Ab includes: a peripheral wall 32a of photosensitive resin disposed on the piezoelectric substrate 54; a first wall 80b facing the object 52 applied on the piezoelectric substrate 54 and extending parallel to a part of the peripheral wall 32 a; and a top plate 34b covering the peripheral wall 32b and the first wall 80 b.

In the liquid material property measurement apparatus 50A, the double protection wall prevents the object 52 from being applied to the input electrodes 12, 22 and the output electrodes 14, 24. Even if the first walls 80a, 80b are peeled off from the piezoelectric substrate 54, thereby causing the object 52 to enter the closed spaces 82a, 82b, a considerable period of time is required until the peripheral walls 32a, 32b are peeled off from the piezoelectric substrate 54 due to the object 52 entering the closed spaces 82a, 82 b. Thus, the normal period of time may be maintained during which the liquid material property measurement device 50A may be used.

The liquid material property measurement device 50A measures the physical property of the object 52 in the same manner as the first embodiment. Therefore, the measurement of the physical properties of the object 52 by the liquid material property measurement device 50A will not be described in detail below.

A liquid material characteristic measurement apparatus 50B according to a third embodiment of the present invention will be described below. Fig. 5 is a plan view of a liquid material property measurement apparatus 50B according to a third embodiment of the present invention. Fig. 6A is a partial end view taken along line VIA-VIA of fig. 5, and fig. 6B is a partial enlarged view of fig. 6A. Parts of the third embodiment that are identical to the parts of the first and second embodiments are denoted by the same reference numerals and these features will not be described in detail below.

The liquid material property measurement device 50B differs from the liquid material property measurement device 50 in that: first walls 80a, 80b are added to the sealing members 30Ba, 30 Bb. In the liquid material property measurement apparatus 50B, the first walls 80a, 80B made of photosensitive resin are arranged on the piezoelectric substrate 54 facing the object 52 applied on the piezoelectric substrate 54. The sealing member 30Ba is constructed by the first wall 80a, the wall 42a, and the ceiling 34a, and the sealing member 30Bb is constructed by the first wall 80b, the wall 42b, and the ceiling 34 b. Further, the first and second propagation paths 16, 26 are surrounded by the first walls 80a, 80b and the side wall 62. A top plate 34a, one side of which is coated with an adhesive 36, is bonded to the peripheral wall 32a and the respective upper ends of the first walls 80 a. A top plate 34b, one side of which is coated with an adhesive 36, is bonded to the peripheral wall 32b and the respective upper ends of the first walls 80 b. The top plate 34a, the peripheral wall 32a, the piezoelectric substrate 54, and the first wall 80a collectively define an enclosed space 82a, while the top plate 34b, the peripheral wall 32b, the piezoelectric substrate 54, and the first wall 80b collectively define another enclosed space 82 b. The enclosed spaces 82a and 82b are filled with sealing reinforcements 84a, 84b, respectively, comprising thixotropic underfill agents, to more reliably prevent the application of the object 52 to the input electrodes 12, 22 and the output electrodes 14, 24.

The connections formed by the bonding wires 68 between the input electrodes 12, 22, the output electrodes 14, 24 and the printed circuit board 64, the outer peripheral wall 70 disposed on the printed circuit board 64, and the protective resin 74 are the same as those in the first embodiment, and therefore, a detailed description of these features will not be given below. The liquid material property measurement device 50B measures the physical property of the object 52 in the same manner as the first embodiment. Therefore, the measurement of the physical properties of the object 52 by the liquid material property measurement device 50B will not be described in detail below.

A liquid material characteristic measurement apparatus 50C according to a fourth embodiment of the present invention will be described below. Fig. 7 is a plan view of a liquid material property measurement apparatus 50C according to a fourth embodiment of the present invention. In the first to third embodiments described above, the first surface acoustic wave device 10 and the second surface acoustic wave device 20 include the respective input electrodes 12 and the respective output electrodes 14. However, the liquid material property measurement apparatus 50C has a single input electrode. Other parts of the fourth embodiment that are identical to those of the first embodiment are denoted by the same reference numerals and these features will not be described in detail below.

The liquid material property measurement device 50C includes: a surface acoustic wave device having an input electrode 112 and output electrodes 114, 124; a first transmission path 116 provided as an open transmission path between the input electrode 112 and the output electrode 114; and a second transmission path 126 provided as a short-circuit transmission path between the input electrode 112 and the output electrode 124.

The input electrode 112 is sealed by a sealing member 130a, the output electrode 114 is sealed by a sealing member 130b, and the output electrode 124 is sealed by a sealing member 130c, for preventing the object 52 from being applied to the comb-teeth electrodes when measuring the physical properties of the object 52.

The seal 130a includes a peripheral wall 132a and a top plate 134 a. The peripheral wall 132a is provided on the piezoelectric substrate 54 in a manner surrounding the input electrode 112. The top plate 134a is bonded to the upper end of the peripheral wall 132a by an adhesive 136. The top plate 134a is coupled to the upper end of the peripheral wall 132a substantially in parallel with the piezoelectric substrate 54. The top plate 134a extends toward the output electrodes 114, 124, defining a gap 138a between one end of the top plate 134a and the piezoelectric substrate 54. The gap 138a is filled with a sealing reinforcement 140a, which is applied to the surface of the peripheral wall 132a facing the object 52 applied to the piezoelectric substrate 54. Similar to the seal 130a, the seal 130b also includes a peripheral wall 132b and a top plate 134 b. The gap 138b is filled with a seal reinforcement 140b applied to the peripheral wall 132 b. Similar to the seal 130a, the seal 130c also includes a peripheral wall 132c and a top plate 134 c. The gap 138c is filled with a seal reinforcement 140c applied to the peripheral wall 132 c.

The connections formed by the bonding wires 68 between the input electrodes 112, the output electrodes 114, 124 and the printed circuit board 64, the outer peripheral wall 70 disposed on the printed circuit board 64, and the protective resin 74 are the same as those in the first embodiment, and therefore, a detailed description of these features will not be given below.

The liquid material property measurement device 50C measures the physical property of the object 52 as follows. The liquid material property measurement device 50C is immersed in the object 52, and an oscillator (not shown) inputs an electric signal to the input electrode 112. Based on the input signal, the same surface acoustic wave is excited from both sides of the input electrode 112, one of which propagates on the first propagation path 116 and is received by the output electrode 114, and the other of which propagates on the second propagation path 126 and is received by the output electrode 124.

An output signal is generated from the surface acoustic waves received by the output electrodes 114, 124, whereby the amplitude ratio and the phase difference of the output signal are detected. The physical characteristics of the object 52 are measured from the detected amplitude ratio and the detected phase difference.

The liquid material characteristic measurement apparatus 50C is similar in structure to the liquid material characteristic measurement apparatus 50 according to the first embodiment, except that the liquid material characteristic measurement apparatus 50C has only a single input electrode. However, it should be understood that the liquid material property measurement device 50C may be configured similarly to the liquid material property measurement device 50A according to the second embodiment, except for having a single input electrode. Further, the liquid material property measurement device 50C may be configured similarly to the structure of the liquid material property measurement device 50B according to the third embodiment, except that there is a single input electrode.

A liquid material property measurement apparatus 50D according to a fifth embodiment of the present invention will be described below. Fig. 8 is a plan view of a liquid material property measurement apparatus 50D according to a fifth embodiment of the present invention. In the first embodiment described above, the liquid material characteristic measurement apparatus 50 includes the first surface acoustic wave device 10 and the second surface acoustic wave device 20. However, the liquid material property measurement apparatus 50D further includes a second surface acoustic wave device 20D. Other parts of the fifth embodiment that are identical to those of the first embodiment are designated with the same reference numerals and these features will not be described in detail below.

In the liquid material characteristic measurement apparatus 50D, the input electrode 22 is surrounded by the sealing member 30Da, and the sealing member 30Da includes a peripheral wall 32a of photosensitive resin disposed on the piezoelectric substrate 54 and a top plate 34a covering the peripheral wall 32 a. The seal reinforcement 40a is disposed between the object 52 and a wall portion 42a of the peripheral wall 32a, the wall portion 42a facing the object 52 applied on the piezoelectric substrate 54. The output electrode 24 is surrounded by a sealing member 30Db, which sealing member 30Db includes a peripheral wall 32b of photosensitive resin disposed on the piezoelectric substrate 54 and a top plate 34b covering the peripheral wall 32 b. The seal reinforcement 40b is disposed between the object 52 and a wall portion 42b of the peripheral wall 32b, the wall portion 42b facing the object 52 applied on the piezoelectric substrate 54. The second surface acoustic wave device 20D prevents the object 52 from coming into contact with the peripheral walls 32a, 32b, prevents the peripheral walls 32a, 32b from peeling off from the piezoelectric substrate 54, and prevents the piezoelectric substrate 54 from being applied to the input electrode 22 and the output electrode 24. The connections formed by the bonding wires 68 between the input electrodes 12, the output electrodes 24, and the printed circuit board 64, the outer peripheral wall 70 disposed on the printed circuit board 64, and the protective resin 74 are the same as those in the first embodiment, and therefore, a detailed description of these features will not be given below.

The liquid material property measurement device 50D measures the physical property of the object 52 as follows. The liquid material property measurement device 50D is immersed in the object 52, and an oscillator (not shown) inputs an electric signal to the input electrode 22. The surface acoustic wave is excited from the input electrode 22, propagates on the second propagation path 26, and is received by the output electrode 24. An output signal is generated from the surface acoustic wave received by the output electrode 24, and the amplitude ratio and the phase difference of the output signal and the electric signal from the oscillator are detected. The density, viscosity, and fixation quantity (immobilized quality) of the object 52, which are physical characteristics of the object 52, are measured from the detected amplitude ratio and the detected phase difference.

The liquid material property measurement device 50D may be configured to include a double protection wall by: similarly to the first embodiment, a first wall of photosensitive resin formed between the wall 42a of the peripheral wall 32a and the object 52 applied on the piezoelectric substrate 54, and a second wall of photosensitive resin formed between the wall 42b of the peripheral wall 32b and the object 52 applied on the piezoelectric substrate 54 are provided. The liquid material property measurement device 50D may also be configured similarly to the third embodiment by filling the closed space defined by the top plate 34a, the peripheral wall 32a, the piezoelectric substrate 54, and the first wall, and the closed space defined by the top plate 34b, the peripheral wall 32b, the piezoelectric substrate 54, and the first wall with the sealing reinforcement.

The physical properties of the object measured by the liquid material property measurement device 50 are not limited to the relative permittivity, conductivity, and density as described above. For example, the liquid material property measurement device 50 may also measure the viscosity of the object to be measured.

The object to be measured is not limited to any particular substance, but may contain at least one liquid. The object to be measured may comprise a pure liquid or a mixed liquid. The present invention is particularly effective in measuring physical properties of alcohols (e.g., methanol, ethanol, etc.). Even if the object to be measured contains an antigen, an antibody, bacteria, and the like, the physical properties of the object can be measured.

If the object to be measured contains charged bacteria, the percentage of these bacteria can be measured by measuring the electrical conductivity of the object. If the object to be tested contains charged bacteria of different polarities, the predominant type of bacteria in the object can be identified by measuring the conductivity of the object. If bacteria are applied on the propagation path of the applied object, the increase or decrease of the applied bacteria can be detected by measuring the density and viscosity of the object.

In addition, in the case where protein is adsorbed on the surface of the metal film, a change in mass or a change in viscosity can be detected. More specifically, the amount of adsorption of the protein and the type of the adsorbed protein can be detected by measuring the amplitude and phase of the surface acoustic wave propagating on the metal film.

If the surface of the metal film is fixed with an antibody and an antigen solution is applied to the surface of the metal film, a mass change and a viscosity change can be detected by binding the antigen and the antibody. More specifically, the amount of applied antigen can be detected by measuring the amplitude and phase of a surface acoustic wave propagating on the metal film. It is therefore apparent that if an antibody is immobilized on the surface of the metal film and an antigen solution is applied to the surface of the metal film, the amount of the applied antibody can be detected.

The present invention is not limited to the above-described embodiments, but various structures may be adopted without departing from the scope of the present invention.

Claims (7)

1. A surface acoustic wave device having an electrode provided on a piezoelectric substrate (54), the surface acoustic wave device comprising:

a seal member having a peripheral wall (32a, 32b) provided on the piezoelectric substrate (54) so as to surround the electrodes and a top plate (34a, 34b) covering the peripheral wall (32a, 32 b); and

a seal stiffener (40a, 40b) provided on the piezoelectric substrate (54), facing the liquid material applied on the piezoelectric substrate (54), and extending parallel to a portion of the peripheral wall (32a, 32 b).

2. A surface acoustic wave device having an electrode provided on a piezoelectric substrate (54), the surface acoustic wave device comprising:

a seal having a peripheral wall (32a, 32b) disposed on the piezoelectric substrate (54) around the electrode, a first wall (80a, 80b) disposed on the piezoelectric substrate (54) facing the liquid material applied on the piezoelectric substrate (54) and extending parallel to a portion of the peripheral wall (32a, 32b), and a top plate (34a, 34b) covering the peripheral wall (32a, 32b) and the first wall (80a, 80 b).

3. The surface acoustic wave device according to claim 2, further comprising:

a seal reinforcement (40a, 40b) filling a space between the first wall (80a, 80b) and a wall portion (42a, 42b) of the peripheral wall (32a, 32b) facing the first wall (80a, 80 b).

4. The surface acoustic wave device according to claim 1, wherein the peripheral walls (32a, 32b) are made of a photosensitive resin.

5. A surface acoustic wave device according to claim 2, wherein said peripheral walls (32a, 32b) are made of photosensitive resin.

6. A liquid material property measurement apparatus including the surface acoustic wave device according to claim 4, wherein the electrodes include an input electrode (12, 22) and an output electrode (14, 24) both of which are sealed by the sealing member, and wherein the liquid material property measurement apparatus determines a physical property of the liquid material applied on a transmission path provided between the input electrode (12, 22) and the output electrode (14, 24).

7. A liquid material property measurement apparatus including the surface acoustic wave device according to claim 5, wherein the electrodes include an input electrode (12, 22) and an output electrode (14, 24) both of which are sealed by the sealing member, and wherein the liquid material property measurement apparatus determines a physical property of the liquid material applied on a transmission path provided between the input electrode (12, 22) and the output electrode (14, 24).