JP5322419B2 - Ultrasonic probe and piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe which is capable of preventing a piezoelectric element from being destroyed while it is worked or used. <P>SOLUTION: There are provided a plurality of piezoelectric elements 41 each of which includes a plurality of grooves formed in parallel and which are arrayed along a direction in parallel with the grooves; and a compound material 70 with which the plurality of grooves are filled, and which is constituted by mixing a non-conductive granular substance having a thermal expansion coefficient of almost 10<SP>-5</SP>k<SP>-1</SP>or less with a non-conductive resin member. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic probe and a piezoelectric vibrator.

There is a technique for weighting transmission sound pressure intensity and reception sensitivity for the purpose of reducing side lobes in a lens direction sound field and uniform sound field in an ultrasonic probe. As one of the methods, there is a method in which the grooves of the piezoelectric element are formed so that the area of the piezoelectric element becomes smaller from dense to sparse from the center to the end of the piezoelectric element with respect to the lens direction. In this case, the piezoelectric element may be completely divided by these grooves, or may not be completely divided. In this method, the groove of the piezoelectric element is filled only with a resin material such as an epoxy resin. However, these structures are composite structures in which the groove filled with resin and the piezoelectric element have different thermal expansion coefficients. For this reason, the degree of expansion of the groove filled with the resin and the piezoelectric element varies depending on the temperature change between storage and heat generation of the piezoelectric element, and stress and strain are generated on the piezoelectric element, resulting in deterioration of mechanical reliability. Moreover, due to the stickiness of the resin, the cutting load when cutting the piezoelectric elements in the array direction increases, and the piezoelectric elements are easily destroyed. As a result, the yield of piezoelectric elements deteriorates.
JP 2003-9288 A

  An object of the present invention is to provide an ultrasonic probe and a piezoelectric vibrator that can prevent a piezoelectric element from being broken during processing or use.

An ultrasonic probe according to an aspect of the present invention includes a plurality of grooves formed in parallel, a plurality of piezoelectric elements arranged along a direction substantially parallel to the grooves, and the plurality of grooves. It is filled into a mixing member non-conductive granulate the non-conductive resin member having a thermal expansion coefficient of approximately 10 ^-5 k ^-1 or less, which are mixed, comprising a said with respect to the mixing member The lower limit of the weight ratio of the granular material is 30 wt, and the upper limit of the weight ratio of the granular material to the mixing member is defined by the maximum amount of the granular material that can be mixed with the resin member .
It comprises.

A piezoelectric vibrator according to an aspect of the present invention has a thermal expansion coefficient of approximately 10 ⁻⁵ k ⁻¹ or less in a piezoelectric element having a plurality of grooves and a non-conductive resin member filled in the plurality of grooves. A non-conductive granular material having a mixed member, and a lower limit of the weight ratio of the granular material to the mixed member is 30 wt., And an upper limit of the weight ratio of the granular material to the mixed member is The maximum amount of the granular material that can be mixed with the resin member is defined .

  According to the present invention, it is possible to prevent destruction of the piezoelectric element during processing or use.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a configuration of an ultrasonic probe 10 in the present embodiment. As shown in FIG. 1, the ultrasonic probe 10 has a sound-absorbing back material (backing material) 20. The back material 20 is formed in a rectangular block shape. A plurality of piezoelectric vibrators 40 are joined to the upper portion of the back material 20 via a flexible wiring board (FPC) 30.

  FIG. 2 is a view showing a section 2-2 of the ultrasonic probe 10 of FIG. As shown in FIG. 2, the piezoelectric vibrator 40 includes a piezoelectric element 41, a ground electrode 32 provided above the piezoelectric element 41, and a signal electrode 31 provided below the piezoelectric element 41. . The piezoelectric element 41 is formed in a strip shape. Each of the plurality of piezoelectric elements 41 is arranged with a plurality of gaps 71 in the array direction. The piezoelectric element 41 transmits and receives ultrasonic waves. The material of the piezoelectric element 41 is a piezoelectric ceramic or a piezoelectric single crystal. The signal electrode 31 and the ground electrode 32 are formed of a metal foil such as a copper foil. The signal electrode 31 and the ground electrode 32 apply a driving voltage to the piezoelectric element 41.

  3A is a diagram showing a 3A-3A cross section of the ultrasonic probe 10 of FIG. 3B is a diagram showing a 3B-3B cross section of the ultrasonic probe 10 of FIGS. 2 and 3A. As shown in FIGS. 3A and 3B, a plurality of grooves arranged along the lens direction are formed in the upper portion of the piezoelectric element 41. The direction of each groove is parallel to the array direction. The pitch intervals of the plurality of grooves are determined based on equal intervals or a sine function. Here, the pitch interval is a distance indicated by d in FIG. 3A. Although the pitch interval is determined based on the sine function, the present invention is not limited to this, and other functions such as a Gaussian function may be used.

A plurality of grooves arranged along the lens direction shown in FIGS. 3A and 3B are filled with the composite material 70. The composite material 70 is formed by mixing a non-conductive resin material such as an epoxy resin with a non-conductive granular material such as alumina powder (hereinafter referred to as a non-conductive filler). By mixing the non-conductive filler into the resin material, the composite material 70 can be easily processed such as polishing, cutting, and dicing as compared with the resin material. That is, the composite material 70 has free machinability compared to the resin material. In consideration of acoustic impedance, the ratio of the resin material and the non-conductive filler in the composite material 70 is the temperature when the piezoelectric element 41 is used, the maximum principal stress value that the piezoelectric element 41 can withstand, and the composite material 70. The specific gravity is determined based on at least one of the linear thermal expansion coefficients of the composite material 70. Specifically, the weight ratio is preferably about 40% of the resin material and about 60% of the granular material. In addition to alumina powder, for example, silicon oxide powder, yttrium oxide powder, aluminum nitride powder, and the like are used as the non-conductive filler. The linear thermal expansion coefficient of the non-conductive filler is 10 × 10 ⁻⁶ k ⁻¹ = 10 ⁻⁵ k ⁻¹ or less. Note that k ⁻¹ is a unit of linear thermal expansion coefficient and represents the reciprocal of the Celsius temperature. The relationship between the sound field intensity distribution of the ultrasonic beam of the composite material 70, the attenuation of the sound field intensity, the signal voltage, and the time is substantially constant regardless of the type of the non-conductive filler. The particle size of these powders is preferably about one-eighth or less of the wavelength of ultrasonic waves to be transmitted and received in consideration of reflection of the ultrasonic beam.

  The plurality of signal electrodes 31 are electrically connected to the plurality of signal wirings 33 of the flexible wiring board 30, respectively. With such a configuration, a drive signal can be applied to each piezoelectric element 41 independently.

  A plurality of acoustic matching layers 50 are respectively provided on the plurality of piezoelectric vibrators 40. That is, as shown in FIG. 2, each acoustic matching layer 50 and each piezoelectric element 41 are arranged in pairs. The acoustic matching layer 50 serves to suppress reflection of ultrasonic waves due to a difference in acoustic impedance between the subject and the piezoelectric element 41.

  The acoustic matching layer 50 includes a first acoustic matching layer 52 and a second acoustic matching layer 53. Due to the multilayer acoustic matching layer, the acoustic impedance changes stepwise from the piezoelectric element 41 toward the subject.

  The first acoustic matching layer 52 is formed of a conductive material. The lower part of the first acoustic matching layer 52 is electrically connected to the piezoelectric element 41 through the ground electrode 32. The upper part of the first acoustic matching layer 52 is bonded to the second acoustic matching layer 53. The second acoustic matching layer 53 is formed of an insulating material. An acoustic lens 60 is provided on the plurality of second acoustic matching layers 53.

  The acoustic lens 60 is a lens made of silicone rubber or the like having an acoustic impedance close to that of a living body, and focuses an ultrasonic beam to improve the resolution in the lens direction.

  A plurality of gaps 71 formed in parallel in the array direction shown in FIG. 2 are filled with a resin material (non-conductive adhesive) such as an epoxy resin.

  As shown in FIGS. 3A and 3B, the flexible wiring board 30 has a two-layer structure. A ground wiring 34 is provided on the first-layer flexible wiring board (first-layer FPC). The leading end portion of the first-layer flexible wiring board is integrally formed on the side of the lower end portion of the ground extraction electrode 35. The ground wiring 34 and the ground extraction electrode 35 are electrically connected. The ground extraction electrode 35 is provided on the side surface of the first acoustic matching layer 52 made of a conductive material, and is electrically connected. The second-layer flexible wiring board (second-layer FPC) is provided with a plurality of signal wirings 33 arranged at predetermined intervals in the array direction. The tip portion of the second-layer flexible wiring board is disposed between the back material 20 and the piezoelectric element 41 as described above. The signal electrode 31 and the signal wiring 33 are electrically connected. A predetermined voltage is applied to the ground electrode 32 and the signal electrode 31.

  Although the second acoustic matching layer 53 is formed of a non-conductive material, the second acoustic matching layer 53 is formed of a conductive material, and the second acoustic matching layer 53 and the ground extraction electrode 35 are electrically connected. Also good.

Next, a manufacturing process of the ultrasonic probe 10 configured as described above will be described.
4A to 4K are views for explaining a manufacturing process of the ultrasonic probe 10 in the present embodiment. First, as shown in FIG. 4A, a piezoelectric block (piezoelectric material) 43 is prepared. Next, as shown in FIG. 4B, a plurality of grooves are formed in parallel to the piezoelectric block 43 along the array direction. This groove processing is processing for weighting the above-described ultrasonic beam. The plurality of grooves are formed with a width and a pitch interval based on a desired function. The plurality of grooves are formed halfway without penetrating the piezoelectric block 43. The grooved piezoelectric block 43 becomes the piezoelectric element 41. Next, as shown in FIG. 4C, the composite material 70 is injected into the plurality of grooves of the piezoelectric element 41. Next, as shown in FIG. 4D, the upper surface of the convex portion of the piezoelectric element 41 is exposed so as to obtain a desired frequency characteristic. When this exposure is performed, the composite agent 70 is polished as a result. However, since the composite material 70 includes a non-conductive filler, the inherent stickiness of the resin material is suppressed and the composite material 70 is easily polished. Next, as shown in FIG. 4E, the first electrode 36 is applied to the entire lower portion of the piezoelectric element 41 and the second electrode 37 is applied to the upper portion of the piezoelectric element 41 by performing plating or sputtering of gold or the like on the piezoelectric element 41. Form the whole. Thereafter, a predetermined voltage is applied to the first electrode 36 and the second electrode 37. Thus, the piezoelectric vibrator 40 is obtained.

  When the piezoelectric vibrator 40 is obtained in this manner, as shown in FIG. 4F, the first acoustic matching material 54 or the like is bonded to the upper portion of the piezoelectric vibrator 40 with an epoxy adhesive or the like, and is then placed on the second electrode 37. The first acoustic matching material 54 is electrically joined. Next, as shown in FIG. 4G, the second acoustic matching material 55 is bonded to the upper portion of the first acoustic matching material 54. Next, as shown in FIG. 4H, the flexible wiring board 30 is joined to the first electrode 36, and the signal wiring 33 and the first electrode 36 are electrically joined.

  Next, as shown in FIG. 4I, the back material 20 is bonded to the lower portion of the flexible wiring board 30 bonded to the piezoelectric vibrator 40. Next, as shown in FIG. 4J, the piezoelectric vibrator 40, the first acoustic matching material 54, the second acoustic matching material 55, the first electrode 36, the second electrode 37, and the flexible wiring board 30 along the array direction. Is diced from the second acoustic matching material 55. By the dicing process, the piezoelectric vibrator 41, the first acoustic matching material 54, the second acoustic matching material 55, the first electrode 36, the second electrode 37, and the flexible wiring board 30 are respectively arranged at regular intervals along the array direction. The plurality of piezoelectric elements 41, the first acoustic matching layer 52, the second acoustic matching layer 53, the signal electrode 31, and the ground electrode 32 are completely separated, and a gap 71 is formed between them. The composite material 70 filled in the piezoelectric element 41 is also divided during the dicing process, but the piezoelectric element 41 is not easily broken due to the free-cutting property of the composite material 70. A plurality of gaps 71 between the piezoelectric vibrators 40 and the acoustic matching layers 50 generated at this stage are filled with a non-conductive resin material.

  Next, as shown in FIG. 4K, the acoustic lens 60 is joined to the upper part of the second acoustic matching layer 53, and the ground extraction electrode 35 is joined to the side of the first acoustic matching layer 52 with a conductive adhesive. The extraction electrode 35 and the ground wiring 34 on the flexible wiring board 30 are electrically connected. Thereby, the ultrasonic probe 10 is completed.

  Further, the manufacturing process of the ultrasonic probe 10 is not limited to the manufacturing process shown in FIGS. 4A to 4K. Hereinafter, referring to FIGS. 5A to 5B, as an example, an ultrasonic probe is manufactured by a method of forming a plurality of grooves in the piezoelectric block 43 after forming electrodes on the upper and lower portions of the piezoelectric block 43. The process will be described.

  First, as shown in FIG. 5A, a predetermined voltage is applied to the first electrode 36 formed on the lower portion of the piezoelectric block 43 and the second electrode 37 formed on the upper portion by plating or sputtering of gold or the like. To do. Next, as shown in FIG. 5B, a plurality of grooves are formed in the piezoelectric body block 43 from the second electrode 37 side along the array direction with a width and a pitch interval d based on a desired function. This grooving is performed in order to weight the ultrasonic beam as in FIG. 4B. Thereby, the second electrode 37 is divided along the array direction to obtain the piezoelectric vibrator 40.

  After FIG. 5B, the ultrasonic probe 10 is manufactured by the same processes as those in FIGS. 4F to 4K. Therefore, the subsequent description is omitted. 4J, when the dicing process is performed along the array direction, the composite material 70 filled in the piezoelectric element 41 is also divided. However, due to the free-cutting property of the composite material 70, the resin-specific viscosity is suppressed, and the dicing is performed. Easy to process.

  FIG. 6 is a diagram showing another shape of the piezoelectric element 41, but the piezoelectric element 41 may be divided into a plurality of elements instead of forming a plurality of grooves as shown in FIG. In the step of FIG. 4J, the gap 71 may be filled with the composite material 70 instead of the resin material.

  The thermal expansion coefficient of the composite material 70 is about 1/3 of the thermal expansion coefficient of the resin material. Therefore, the stress on the piezoelectric element 41 due to the thermal expansion of the composite material 70 when the ultrasonic probe 10 is used is smaller than the stress on the piezoelectric element 41 due to the thermal expansion of the resin material. When the ultrasonic probe 10 is used or processed, the piezoelectric vibrator 40 generates heat. When the piezoelectric vibrator 40 generates heat, the piezoelectric element 41 and the composite material 70 have heat. However, since the piezoelectric element 41 and the composite material 70 are close to each other in degree of expansion due to heat, the piezoelectric element 41 and the composite material 70 have piezoelectricity due to the thermal expansion of the composite material 70. Stress and strain on the element 41 are unlikely to occur.

  FIG. 7 shows the linear thermal expansion coefficient (hereinafter referred to as thermal expansion) of the composite material 70 when the temperature [° C.] of the piezoelectric element 41 when the ultrasonic probe 10 is used and the linear thermal expansion coefficient of the resin material is 100. It is a figure showing a coefficient ratio [%] and maximum principal stress (tensile maximum principal stress and compression maximum principal stress) [MPa] of the piezoelectric element 41. The data shown in FIG. 7 was obtained by FEM (finite element method) analysis. In the FEM analysis, the vertical thickness of the piezoelectric element 41 was 200 μm, and the depth of the vertical groove formed in the piezoelectric element 41 was 100 μm. The upper limit value of the maximum principal stress value that the piezoelectric element 41 according to this embodiment can withstand without being broken is approximately 80 MPa. For safety, the temperature during use is required to be 60 ° C. or lower. Therefore, it is assumed that the upper limit of the temperature during use is 60 ° C. As shown in FIG. 7, when the temperature is 60 ° C., the maximum tensile principal stress applied to the piezoelectric element 41 filled with the composite material 70 having a coefficient of thermal expansion of 70% is 81.9 MPa. In this case, the piezoelectric element 41 is destroyed. Similarly, when the temperature is 60 ° C., the maximum tensile main stress applied to the piezoelectric element 41 filled with the composite material having a coefficient of thermal expansion of 30% is 46.1 [MPa]. In this case, the piezoelectric element 41 is not destroyed. The data in FIG. 7 indicates that the maximum principal stress is smaller as the coefficient of thermal expansion is lower. A portion exceeding 80 MPa is indicated by hatching. The data in FIG. 7 shows that the maximum principal stress is smaller at lower temperatures. Since the maximum tensile main stress value is larger than the maximum compression main stress value, only the maximum tensile main stress value will be considered below.

  FIG. 8 is a diagram showing the relationship between the maximum tensile principal stress [MPa] and the coefficient of thermal expansion [%] when the temperature during use is 60 ° C. As shown in FIG. 8, in order to prevent the piezoelectric element 41 from being destroyed when heated at 60 ° C., the coefficient of thermal expansion must be approximately 70% or less.

FIG. 9 is a diagram showing specific gravity [kg / m ³ ], linear thermal expansion coefficient [k ⁻¹ ], and necessary mixing ratio [wt%] for each type of non-conductive filler. Here, alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), silicon oxide (SiO ₂ ), and yttrium oxide (Y ₂ O ₃ ) are exemplified as the non-conductive filler. As shown in FIG. 9, each non-conductive filler has a linear thermal expansion coefficient of 10 × 10 ⁻⁶ k ⁻¹ or less. The necessary mixing ratio [wt%] is a weight ratio [wt%] of the non-conductive filler to the composite material 70 for setting the coefficient of thermal expansion to 70%. The required mixing ratio of each non-conductive filler is 30 wt% or more. That is, from the relationship between FIG. 8 and FIG. 9, the composite material at the time of use can be obtained by filling the groove with the composite material 70 having a non-conductive filler weight ratio of 30 wt% or more regardless of the type of the non-conductive filler. The piezoelectric element 41 is not destroyed by the thermal expansion of 70. If the weight ratio is 30 wt% or less, the piezoelectric element 41 may be destroyed during use. That is, the weight ratio of 30 wt% is the lower limit of the weight ratio of the nonconductive filler.

  The higher the weight ratio, the more the sound field intensity distribution deviates from the ideal. The intensity distribution of the sound field changes depending on the particle size of the nonconductive filler and the specific gravity of the composite material, and does not change depending on the type of nonconductive filler. Moreover, there is an upper limit for the amount of non-conductive filler that can be mixed into the resin material. This upper limit value of alumina is 60 several wt% in weight ratio.

  The characteristics of an ultrasonic beam generated from a composite material in which alumina is mixed into the resin material at a weight ratio of 4: 6 (hereinafter referred to as alumina composite material) will be described. The data shown in FIGS. 10, 11 and 12 are obtained as a result of simulation. FIG. 10 is a diagram showing the relationship between the intensity of the sound field in the slice direction of the ultrasonic beam generated from the ultrasonic probe and the type of member filled in the groove, and the vertical axis indicates the intensity of the sound field, The axis is the slice direction distance. Note that the peak positions of the sound pressures in the respective fillers are aligned.

  The solid line shown in FIG. 10 represents the intensity of the sound field of the ultrasonic beam generated from the ultrasonic probe 10 of alumina composite material, the dotted line is the resin material, and the alternate long and short dash line is air (nothing fills the groove). The two-dot chain line represents an ideal function (weight function) of the sound field strength. The ultrasonic beam generated from the ultrasonic probe 10 filled with the alumina composite material is generated from the ultrasonic probe 10 filled only with the resin material and the ultrasonic probe 10 not filled with anything. It is almost the same as the intensity distribution of the sound field of the sound beam.

  FIG. 11 is a diagram showing the relationship between the intensity [decibel, dB] of the ultrasonic field generated by the ultrasonic probe 10 and the frequency [MHz] for each type of filler.

  FIG. 12 is a diagram showing the relationship between the signal voltage [Vpp] applied to the ultrasonic probe 10 and the time [μsec] for each type of filler. As shown in FIGS. 10, 11, and 12, the ultrasonic beam generated from the ultrasonic probe 10 filled with the alumina composite material does not fill the ultrasonic probe 10 filled with the resin material or anything. Since it has substantially the same characteristics as the ultrasonic beam generated from the ultrasonic probe 10, even when the composite material 70 is used, the characteristic of the ultrasonic beam of the ultrasonic probe 10 hardly changes.

The specific gravity of the composite material 70 obtained by mixing alumina with a resin material at a weight ratio of 60 wt% is 2.82 kg / m ³ . The specific gravity of 2.82 kg / m ³ is approximately 1/3 times the specific gravity of the piezoelectric element 41.

FIG. 13 is a diagram showing the specific gravity [kg / m ³ ], linear thermal expansion coefficient [k ⁻¹ ], necessary mixing ratio [wt%], and critical mixing ratio [wt%] of the same non-conductive filler as in FIG. It is. The limit mixing ratio [wt%] is the weight ratio of the non-conductive filler when the specific gravity of the composite material 70 is 2.82 kg / m ³ . In other words, this is the upper limit value of the weight ratio of the non-conductive filler that can be mixed into the resin material. As shown in FIG. 13, for example, in the case of alumina, if the weight ratio is about 33 to 60 wt%, there is no problem regarding the intensity distribution of the sound field or the destruction of the piezoelectric element 41 during use.

  As described above, the weight ratio of the non-conductive filler of the composite material 70 is determined based on the temperature when the piezoelectric element 41 is used, the main stress value that the piezoelectric element 41 can withstand, the specific gravity of the composite material 70, and the like. By determining the weight ratio in this manner, the destruction of the piezoelectric element 41 due to the expansion of the composite material 70 accompanying the temperature rise is realized while suppressing the disturbance of the ultrasonic sound field.

  Thus, according to the present embodiment, it is possible to prevent the piezoelectric element from being broken during processing and use.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The perspective view which shows the structure of the ultrasonic probe in this embodiment. The figure which shows the 2-2 cross section of the ultrasonic probe of FIG. The figure which shows the 3A-3A cross section of the ultrasonic probe of FIG. The figure which shows the 3B-3B cross section of the ultrasonic probe of FIG.2 and FIG.3A. The figure which shows the initial stage in the manufacturing process of the ultrasonic probe of FIG. The figure which shows the groove process in the manufacturing process of the ultrasonic probe of FIG. The figure which shows the filling of the composite material in the manufacturing process of the ultrasonic probe of FIG. The figure which shows the grinding | polishing process in the manufacturing process of the ultrasonic probe of FIG. The figure which shows electrode formation in the manufacturing process of the ultrasonic probe of FIG. The figure which shows adhesion | attachment of the 1st acoustic matching layer in the manufacturing process of the ultrasonic probe of FIG. The figure which shows adhesion | attachment of the 2nd acoustic matching layer in the manufacturing process of the ultrasonic probe of FIG. The figure which shows joining of a flexible wiring board in the manufacturing process of the ultrasonic probe of FIG. The figure which shows joining of the back material in the manufacturing process of the ultrasonic probe of FIG. The figure which shows the array processing in the manufacturing process of the ultrasonic probe of FIG. The figure which shows joining of the acoustic lens in the manufacturing process of the ultrasonic probe of FIG. The figure which shows the initial stage in the manufacturing process of the ultrasonic probe different from FIG. 4A-FIG. 4K. The figure which shows the groove process in the manufacturing process of the ultrasonic probe different from FIG. 4A-FIG. 4K. The figure which shows the other shape of the piezoelectric vibrator of FIG. The figure which shows the temperature [degreeC] of the piezoelectric element at the time of use of an ultrasonic probe, the thermal expansion coefficient rate [%] of a composite material, and the maximum principal stress [MPa] of a piezoelectric element. The figure which shows the relationship between the tensile main stress value [MPa] and a coefficient of thermal expansion [%] in case the temperature at the time of use of a piezoelectric element is 60 [degreeC]. The figure which shows specific gravity [kg / m < ³ >] according to the kind of nonelectroconductive filler, linear thermal expansion coefficient [k < ^-1 >], and required mixing ratio [wt%]. The figure which shows the relationship between the intensity | strength of the sound field of the slice direction of the ultrasonic beam generated from an ultrasonic probe, and the kind of filler. The figure which shows the relationship between the intensity [dB] of the ultrasonic field of an ultrasonic beam generated from an ultrasonic probe, and the frequency [MHz] for each type of filler. The figure which shows the relationship between signal voltage [Vpp] applied to an ultrasonic probe, and time [microsec] according to the kind of filler. The figure which shows specific gravity [kg / m < ³ >], linear thermal expansion coefficient [k < ^-1 >], required mixing ratio [wt%], and limit mixing ratio [wt%] of the same nonelectroconductive filler as FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic probe, 20 ... Back material, 30 ... Flexible wiring board, 31 ... Signal electrode, 32 ... Ground electrode, 40 ... Piezoelectric vibrator, 41 ... Piezoelectric element, 50 ... Acoustic matching layer, 52 ... 1st Acoustic matching layer, 53 ... second acoustic matching layer, 60 ... acoustic lens, 70 ... composite material.

Claims (8)

A plurality of piezoelectric elements each having a plurality of grooves formed in parallel and arranged along a direction substantially parallel to the grooves;
A non-conductive resin member filled with a non-conductive granular material having a thermal expansion coefficient of approximately 10 ⁻⁵ k ⁻¹ or less, and a non-conductive resin member filled in the plurality of grooves ,
The lower limit of the weight ratio of the granular material to the mixing member is 30 wt, and the upper limit of the weight ratio of the granular material to the mixing member is defined by the maximum amount of the granular material that can be mixed with the resin member. Characteristic ultrasonic probe. The mixing ratio of the resin member and the granules, the temperature of the piezoelectric element and the stress value the piezoelectric element can withstand, the specific gravity of the mixing member, based on at least one coefficient of thermal expansion of the mixing member It is determined,
The ultrasonic probe according to claim 1. The specific gravity of the mixing member is approximately 1/3 or less of the specific gravity of the piezoelectric element.
The ultrasonic probe according to claim 1. The thermal expansion coefficient of the mixing member is determined based on the temperature of the mixing member at the time of use.
The ultrasonic probe according to claim 1, wherein: The mixing member has a thermal expansion coefficient which generates a degree of stress the mixing member is unable to destroy the piezoelectric element even when the thermal expansion,
The ultrasonic probe according to claim 1. The particle size of the granular material is about 1/8 or less of the wavelength of the ultrasonic wave transmitted and received by the piezoelectric element.
The ultrasonic probe according to claim 1. The plurality of grooves are formed in each of the piezoelectric elements so that the intensity of ultrasonic waves transmitted and received is weakened from the center to the end in the arrangement direction of the grooves.
The ultrasonic probe according to claim 1. A piezoelectric element having a plurality of grooves;
A non-conductive resin member filled with a non-conductive granular material having a thermal expansion coefficient of approximately 10 ⁻⁵ k ⁻¹ or less, and a non-conductive resin member filled in the plurality of grooves ,
The lower limit of the weight ratio of the granular material to the mixing member is 30 wt, and the upper limit of the weight ratio of the granular material to the mixing member is defined by the maximum amount of the granular material that can be mixed with the resin member. A characteristic piezoelectric vibrator.

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