JP6548201B2 - Heat transfer and acoustic matching layer for ultrasonic transducers - Google Patents

Description

  Embodiments of the present technology generally relate to ultrasound transducers configured to provide improved thermal properties.

  This application is a continuation-in-part and claims the priority of US Patent Application No. 12 / 833,101 filed July 9, 2010, the disclosure of which is incorporated herein by reference. Incorporated into the book.

  As shown in FIG. 1, a conventional ultrasound transducer 100 comprises a lens 102, impedance matching layers 104 and 106, a piezoelectric element 108, a backing 110, and electrical elements for connecting to an ultrasound system. It may be composed of the various layers involved.

  The piezoelectric element 108 can convert the electrical signal to ultrasound that is transmitted towards the target, and can convert the received ultrasound to an electrical signal. Arrows 112 depict the ultrasound waves transmitted from and received at transducer 100. The received ultrasound may be used by the ultrasound system to generate an image of the target.

  Impedance matching layers 104, 106 are disposed between the piezoelectric element 108 and the lens 102 to increase the energy exiting the transducer 100. In the prior art, it is optimal when the matching layers 104, 106 separate the piezoelectric element 108 and the lens 102 by a distance x of about 1/4 to 1/2 of the desired wavelength of the ultrasound wave transmitted at the resonant frequency. It is believed that impedance matching is achieved. The conventional idea is that such an arrangement can maintain the ultrasound waves reflected within the matching layers 104, 106 in phase as they exit the matching layers 104, 106.

  Transmitting ultrasound from transducer 100 may heat lens 102. However, the transducer in contact with the patient has a maximum surface temperature of about 40 degrees Celsius to avoid patient discomfort and to meet the defined temperature limit. Thus, lens temperature can be a factor that limits the wave transmission power and the performance of the converter.

  Many known thermal management techniques focus on the back of the transducer to minimize reflections of ultrasonic energy towards the lens. However, there is a need for an improved ultrasonic transducer with improved thermal properties.

  Embodiments of the present technology generally relate to ultrasonic transducers and methods of manufacturing ultrasonic transducers.

  In one embodiment, the ultrasound transducer includes piezoelectric elements defining front and back sides, wherein the piezoelectric elements are configured to convert the electrical signal into ultrasound waves transmitted from the front towards the target. Also, the piezoelectric element is configured to convert the received ultrasound into an electrical signal. The ultrasonic transducer includes a lens connected to the front side of the piezoelectric element, a heat sink connected to the back side of the piezoelectric element, and a rear matching layer disposed between the piezoelectric element and the heat sink. The back matching layer is thermally connected to the piezoelectric element and the heat sink. The back matching layer is configured to conduct heat from the piezoelectric element to the heat sink.

  In one embodiment, the ultrasound transducer includes piezoelectric elements defining front and back sides. The piezoelectric element is configured to convert the electrical signal into ultrasound waves transmitted from the front side towards the target. The piezoelectric element is configured to convert the received ultrasound into an electrical signal. The ultrasonic transducer includes a lens connected to the front side of the piezoelectric element, a heat sink connected to the back side of the piezoelectric element, and a back matching layer connected to both the piezoelectric element and the heat sink. The rear matching layer includes wings configured to extend beyond the end of the piezoelectric element to the heat sink. The back matching layer is configured to conduct heat from the piezoelectric element to the heat sink.

  In one embodiment, a method of manufacturing an ultrasonic transducer includes attaching a matching layer to the front of the piezoelectric element, attaching a back matching layer to the back of the piezoelectric element, and connecting the back matching layer to a heat sink And where the heat sink faces the back of the piezoelectric element.

FIG. 1 is a cross-sectional view showing the layers of a prior art ultrasonic transducer. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. 7 is a table representing the nature of the matching layer of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 1 is a perspective view of the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. 7 is a result of computer simulation of an ultrasound transducer used in accordance with an embodiment of the present technology. FIG. 7 is a graph depicting experimental results of temperature measurements at a lens surface of a conventional transducer and a transducer constructed in accordance with an embodiment of the present technology. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 1 is a perspective view of an ultrasonic transducer used in accordance with an embodiment of the present technology. FIG. 2A is a cross-sectional view showing the layers of an ultrasonic transducer used in accordance with an embodiment of the present technology. It is a graph showing simulation data. It is a graph showing simulation data.

  The foregoing summary, as well as the following detailed description of certain embodiments, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, specific embodiments are shown in the drawings. However, it should be understood that the invention is not limited to only the arrangements and instrumentality shown in the attached drawings.

  Embodiments of the present technology generally relate to ultrasound transducers configured to provide improved thermal properties. In the drawings, like elements are indicated with like reference numerals.

  FIG. 1 is a cross-sectional view of the layers of a prior art ultrasonic transducer 100. Transducer 100 is described in the background and includes two matching layers 104, 106 disposed between lens 102 and piezoelectric element 108. The matching layers 104, 106 form a combined distance x between the lens 102 and the piezoelectric element 108, this distance x being about 1/4 to 1/1 of the desired wavelength of the ultrasound wave transmitted at the resonant frequency. It is a distance of 2.

  FIG. 2A depicts a cross-sectional view of the layers of ultrasonic transducer 200 used in accordance with an embodiment of the present technology. Transducer 200 includes a lens 102, impedance matching layers 203-206, a piezoelectric element 108, a backing 110, and electrical elements for connection to an ultrasound system. The backing 110 includes a heat sink and a thermal management portion. In certain embodiments, matching layers 203-206, piezoelectric element 108 and lens 102 may be bonded together using an epoxy or adhesive material that cures under pressure applied by, for example, tools and / or a press machine .

  As with conventional ultrasound transducers, the piezoelectric element 108 can convert the electrical signal into ultrasound that is transmitted towards the target, and also converts the received ultrasound into an electrical signal. can do. Arrows 112 depict the ultrasound waves transmitted from and received at transducer 200. The received ultrasound may be used by the ultrasound system to generate an image of the target.

  Impedance matching layers 203-206 are disposed between the piezoelectric element 108 and the lens 102 to increase the energy exiting the transducer 100. The piezoelectric element 108 and the lens by a distance y which the matching layers 203-206 may be less than or greater than the distance x (a distance of about 1/4 to 1/2 of the desired wavelength of the ultrasound wave transmitted at the resonant frequency) Separate from 102.

  As shown in FIG. 1, conventional transducers generally include two matching layers 104,106. Such matching layers generally comprise an epoxy and a filler. It has been found that having a matching layer near the piezoelectric element having a relatively high acoustic impedance and a relatively high thermal conductivity can improve the thermal and / or acoustic properties. The embodiments presented herein illustrate inventive transducers with three or four matching layers. However, embodiments may include only two matching layers, and may also include more than four matching layers, such as five or six matching layers.

  FIG. 2B is a table of the nature of matching layers 203-206 of the inventive ultrasonic transducer embodiment. The matching layer 206 disposed between the piezoelectric element 108 and the matching layer 205 may comprise a material having an acoustic impedance of about 10-20 MRayl and a thermal conductivity greater than about 30 W / mK. Matching layer 206 may have a thickness of less than about 0.22 λ, where λ is the desired wavelength of the ultrasound wave transmitted at the resonant frequency. In certain embodiments, matching layer 206 may be, for example, copper, copper alloy, copper (s), such as copper, magnesium, magnesium alloy, etc. with embedded graphite pattern, semiconductor material such as silicon, aluminum (plate Or bar) and / or an aluminum alloy may be included. The metal may have a relatively high acoustic impedance so that ultrasound can travel through the layer at high speeds, thus requiring a thicker matching layer to obtain the desired acoustical properties.

  The matching layer 205 disposed between the matching layer 206 and the matching layer 204 may comprise a material having an acoustic impedance of about 5-15 MRayl and a thermal conductivity of about 1-300 W / mK. Matching layer 205 may have a thickness of less than about 0.25 λ. In certain embodiments, matching layer 205 may be, for example, copper, copper alloy, copper, magnesium, magnesium alloy, aluminum (plate or bar), metal such as aluminum alloy, etc., having a graphite pattern embedded therein. It may include filled epoxy, glass ceramic, composite ceramic, and / or macor.

  The matching layer 204 disposed between the matching layer 205 and the matching layer 203 may comprise a material having an acoustic impedance of about 2-8 MRayl and a thermal conductivity of about 0.5-50 W / mK. Matching layer 204 may have a thickness of less than about 0.25 λ. In certain embodiments, the matching layer 204 can include non-metals such as epoxy with a filler such as a silica filler. In certain embodiments, matching layer 204 can include, for example, a material of graphite type. Non-metals, such as epoxy with filler, may have relatively low acoustic impedance so that ultrasound can travel through the layer at low speeds, and thus thinner to obtain the desired acoustical properties A matching layer is required.

  The matching layer 203 disposed between the matching layer 204 and the lens 102 may comprise a material having an acoustic impedance of about 1.5 to 3 MRayl and a thermal conductivity of about 0.5 to 50 W / mK. The matching layer 203 may have a thickness of less than 0.25λ. In certain embodiments, matching layer 203 may include, for example, a non-metal such as a plastic and / or an epoxy having a filler such as a silica filler.

  In one embodiment, the acoustic impedance of the matching layers 203-206 decreases as the distance from the piezoelectric element 108 of the matching layers 203-206 increases. That is, matching layer 206 can have a higher acoustic impedance than matching layer 205, matching layer 205 can have a higher acoustic impedance than matching layer 204, and matching layer 204 has a higher acoustic impedance than matching layer 203. Can. Improve the acoustic properties, for example by increasing the sensitivity and / or the border bandwidth, by providing three or more matching layers with decreasing acoustic impedance in this way Is possible. By improving the acoustic properties in this way, the sensing of structures in the target, such as the human body, is improved.

  In one embodiment, the thermal conductivity of the matching layers 205, 206 is higher than the thermal conductivity of the matching layers 203, 204. Thermal properties can be improved by placing matching layers (eg, matching layers 205 and / or 206, etc.) having relatively high thermal conductivity close to the piezoelectric element 108. For example, these matching layers can more easily dissipate the heat generated by the piezoelectric element 108 than matching layers with lower thermal conductivity, such as matching layers 203 and 204, for example.

  FIG. 3 depicts a cross-sectional view of layers of an ultrasonic transducer 300 used in accordance with an embodiment of the present technology. Transducer 300 includes a first impedance matching layer 303, a second impedance matching layer 304, a third impedance matching layer 305, a piezoelectric element 308 and a backing 310. The layers shown include large notches 312 and small notches 314. The large notches 312 extend through the matching layers 303-305 and further through the piezoelectric element 308 into the backing 310. Large cutouts 312 can form electrical isolation between portions of piezoelectric element 308. The small notches 314 extend through the matching layers 303-305 and also partially through the piezoelectric element 308. The small notches do not extend completely past the piezoelectric element 308 and thus do not extend into the backing 310. The small notches 314 do not form an electrical isolation between the portions of the piezoelectric element 308. The small notches 314 can improve acoustic performance, for example by damping horizontal vibrations between adjacent portions of the layer. In certain embodiments, the notches may be provided such that the ratio of notch depth to notch width is about 30: 1. In certain embodiments, large notches may be provided to have a notch depth of about 1.282 mm and small notches are provided to have a notch depth of about 1.085 mm. Well, both types of notches are also provided, for example with a notch width of 0.045 mm. In certain embodiments, the notch may be provided to have a notch width of, for example, about 0.02 millimeters to 0.045 millimeters. By minimizing the thickness of matching layers 203-206, it has been found that it is possible to dice the layers of the transducer shown in FIG. 3 and to improve acoustic performance. It has also been found that by minimizing the thickness of the matching layers 203-206, it is possible to perform dicing with a ratio of notch depth to notch width of less than 30: 1. When using current dicing techniques, such as dicing using dicing saws, it is difficult to obtain a ratio of notch depth to notch width greater than 30 to 1. For example, a notch can be made in the layers of the transducer using a laser or another known technique.

  FIG. 4 depicts a cross-sectional view of layers of an ultrasonic transducer 400 used in accordance with an embodiment of the present technology. Transducer 400 is configured similar to transducer 200 shown in FIG. 2A. However, transducer 400 includes matching layer 401 instead of matching layer 206. The matching layer 401 is disposed between the piezoelectric element 108 and the matching layer 205 and can have the same material and thickness as the matching layer 206 shown in FIG. 2A. Matching layer 401 includes wings 402 that extend beyond the end of piezoelectric element 108 to backing 110.

  Wings 402 may be formed by providing matching layer 401 such that wings 402 extend beyond the end of piezoelectric element 108. A plurality of notches 403 may be provided in the surface of the matching layer 401, and the portion of the matching layer 401 beyond the end of the piezoelectric element 108 folds away from the notches 403 towards the piezoelectric element 108 and the backing 110. It may be curved so that the notches 403 are arranged at the outer elbow of the bend and / or around the outer elbow as shown in FIG. Once the wing 402 is positioned around the end of the piezoelectric element 108 and the end of the backing 110, the bending process is complete.

  Wings 402 are configured to conduct heat from piezoelectric element 108 to a heat sink and / or thermal management portion at backing 110. The relatively high thermal conductivity of the matching layer 401 and the wings 402 can assist in the desired heat transfer to the backing 110 of the transducer 400 and the desired heat transfer away from the lens 102. Wings 402 can also form a ground for transducer 400 by connecting to a suitable ground circuit, such as a flexible circuit typically disposed between piezoelectric element 108 and backing 110. Wings 402 may also function as an electrical shield for transducer 400.

  FIG. 5 depicts a cross-sectional view of layers of an ultrasonic transducer 500 used in accordance with an embodiment of the present technology. Transducer 500 is configured similar to transducer 200 shown in FIG. 2A. However, transducer 500 includes matching layer 501 instead of matching layer 206. The matching layer 501 is disposed between the piezoelectric element 108 and the matching layer 205, and can have the same material and thickness as the matching layer 206 shown in FIG. 2A. However, the matching layer 501 extends beyond the end of the piezoelectric element 108. For example, in one embodiment, matching layer 501 may extend beyond the end of piezoelectric element 108 by about one millimeter or less. Attached to the extension of the matching layer 510 is a sheet 502 which extends over the end of the piezoelectric element 108 to the backing 110. The sheet 502 may be attached to the matching layer 501 using a thermally conductive epoxy. The sheet 502 comprises a material having a relatively high thermal conductivity, such as the same material as the matching layer 501, such as, for example, graphite and / or thermally conductive epoxy. The sheet 502 is configured to conduct heat from the piezoelectric element 108 to a heat sink and / or thermal management portion at the backing 110. The relatively high thermal conductivity of matching layer 501 and sheet 502 can assist in the desired heat transfer to the backing 110 of the transducer 500 and the desired heat transfer away from the lens 102.

  FIG. 6 depicts a perspective view of an ultrasonic transducer 600 used in accordance with an embodiment of the present technology. Transducer 600 includes an impedance matching layer 401 with wings 402, a piezoelectric element 308 and a backing 310. Other impedance matching layers and lenses are not depicted in FIG. The layer being drawn includes large notches 312 and small notches 314, which are substantially perpendicular to the azimuthal direction (a) and substantially parallel to the elevational direction (e). It is. The large notch 312 extends through the matching layer and further through the piezoelectric element 308 into the backing 310. Small notches 314 extend through the matching layer and also partially through the piezoelectric element 308. The small notches do not extend completely past the piezoelectric element 308 and thus do not extend into the backing 310. Wings 402 are disposed around the four sides of transducer 600 and bent towards piezoelectric element 308 and backing 310 so that wing 402 is from piezoelectric element 308 at backing 110 Heat can be conducted to the heat sink and / or the thermal management part. In another embodiment, wings 402 may be provided around one, two, three or four sides of the transducer. For example, in certain embodiments, wings 402 may be provided along only two opposite sides of the transducer, where the wings are substantially perpendicular to the notches 312 and 314 Be placed. In such an embodiment, wings 402 extend along the azimuth direction (a) and not along the elevation direction (e).

  FIG. 7 depicts the results of computer simulation of an ultrasound transducer used in accordance with an embodiment of the present technology. FIG. 7 represents the results of a simulation study of a 3.5 MHz one-dimensional linear array converter with three matching layers. The matching layer (first matching layer) closest to the piezoelectric element comprises an aluminum bar having an acoustic impedance of 13.9 MRayl. The second matching layer comprises filled epoxy with an acoustic impedance of 6.127 MRayl. The third matching layer comprises an undefined material with an acoustic impedance of 2.499 MRayl (which may be, for example, plastic and / or epoxy with a filler such as a silica filler). In the case of these acoustic impedances, the layers have respectively a thickness of 0.2540 mm (aluminum bar), 0.1400 mm (filled epoxy), 0.1145 mm (material not defined) according to the simulation It is shown that it can do. This computer simulation shows that the distance from the inner matching layer to the outer matching layer (such as the distance y from matching layer 206 to 203 shown in FIG. 2) is the desired wavelength of the ultrasound wave transmitted at the resonant frequency. It has been demonstrated that it can be thinner than the matching layer of a conventional transducer as shown in FIG. 1 which may have a matching layer of about 1/4 thickness. For such simulations, for example, KLM models, Mason models and / or finite element method simulations may be used to determine the desired properties.

  The simulation for the study of acoustic performance is to minimize the thickness of the matching layer with the desired acoustic impedance and the desired thermal conductivity, thereby enabling the cutting process to be performed more effectively. It can be used to optimize the properties of the matching layer.

  FIG. 8 is a graph 800 depicting experimental results of temperature measurements at the lens surface of a conventional transducer and a transducer constructed in accordance with an embodiment of the present technology. This graph plots the temperature at the lens surface against time. A conventional transducer temperature measurement is shown at line 802 and a transducer temperature measurement constructed in accordance with an embodiment of the present technology is shown at line 804. During the experiment, both transducers were connected to the ultrasound system under the same conditions and the same settings. Transducers constructed in accordance with embodiments of the present technology have maintained lens surface temperatures about 3 to 4 degrees Celsius lower than conventional transducers for 40 minutes or more.

  FIG. 9 depicts a cross-sectional view of the layers of ultrasonic transducer 900. Transducer 900 includes three matching layers 902, 904 and 906 disposed between lens 908 and piezoelectric element 910. Alternate embodiments can include different numbers of matching layers. For example, some embodiments may include only two matching layers, and another embodiment may include four or more matching layers. The piezoelectric element 910 can convert the electrical signal to ultrasound that is induced at the target, and can convert the received ultrasound to an electrical signal. Piezoelectric element 910 is shaped to define a front side 912 and a back side 914. In the present disclosure, the front side 912 is defined to include the side of the piezoelectric element 910 where the ultrasound is emitted towards the lens 908. The back side 914 is defined to include the side of the piezoelectric element 910 that faces away from the lens 908 opposite the front side 912. The ultrasound transducer 900 includes a dematching layer 916 connected to the back side 914 of the piezoelectric element 910 and a flex 918 attached to the mismatch layer 916. The piezoelectric element 910 may be a piezoelectric material such as lead zirconate titanate (PZT) or a PZT composite. According to another embodiment, the piezoelectric material may further include a single crystal such as PMN-PT. The ultrasonic transducer 900 also includes a back matching layer 920, a thermal backing 922 and a heat sink 924.

  In some embodiments, matching layers 902, 904 and 906, piezoelectric element 910, and lens 908 are an epoxy or other adhesive material that cures under pressure such as that supplied by tools including a press machine. It can be glued together using. Arrows 927 depict the ultrasound waves transmitted from and received at ultrasound transducer 900. The received ultrasound may be used by the ultrasound system to generate an image of the target.

  Matching layers 902, 904 and 906 are disposed between piezoelectric element 910 and lens 908 to increase the energy of the waves transmitted from ultrasonic transducer 900. Each of matching layers 902, 904 and 906 may be made of epoxy and one or more different fillers. Fillers may be used to adjust the acoustic impedance of each of the matching layers 902, 904 and 906 in accordance with one embodiment. Although the embodiment shown in FIG. 10 includes three matching layers, alternative embodiments may have fewer matching layers or additional matching layers. For example, another embodiment may have one matching layer, two matching layers, or four or more matching layers instead of the matching layers 902, 904 and 906 shown in FIG.

  As described above, the thickness of each of the three matching layers 902, 904 and 906 may be less than or equal to 1⁄4 of the wavelength at the resonant frequency of the ultrasonic transducer 900. However, in another embodiment, the matching layers 902, 904 and 906 may be greater than 1⁄4 of the wavelength at the resonant frequency of the ultrasonic wave changer 900. For example, one or more of the matching layers may be about half the wavelength at the resonant frequency in one embodiment. The acoustic impedance of each matching layer 902, 904 and 906 may be selected to reduce the acoustic impedance mismatch between the piezoelectric element 910 and the lens 908. Matching layers 902, 904 and 906 reduce the reflection and / or refraction of ultrasound between piezoelectric element 910 and lens 908. The lens 908 can have an acoustic impedance of about 1.5 MRayl, and the piezoelectric element 910 can have an acoustic impedance of 30 MRayl. In another embodiment, the lens 908 may have an acoustic impedance in the range of 1.2 MRayl to 1.6 MRayl, and the piezoelectric element 910 has an acoustic impedance in the range of 20 MRayl to 40 MRayl. Can. The first matching layer 902 can have an acoustic impedance of 10 to 20 MRayl, the second matching layer 904 can have an acoustic impedance of 5 to 15 MRayl, and the third matching layer 906 has an acoustic impedance of 2 to 8 MRayl. It can have an impedance.

  Each of matching layers 902, 904 and 906 is less than or equal to about one-quarter of the desired wavelength to minimize destructive interference caused by waves reflected at the interface between each of matching layers 902, 904 and 906. You may Matching layers 902, 904 and 906 are each made of, for example, copper, copper alloy, copper with embedded graphite pattern, magnesium, magnesium alloy, metal such as aluminum, aluminum alloy, filled epoxy, glass ceramic, composite The material may include ceramic and / or macor.

  In one embodiment, the acoustic impedance of matching layers 902, 904 and 906 decreases as the distance from matching element 902, 904 and 906 to piezoelectric element 910 increases. That is, the first matching layer 902 can have a higher acoustic impedance than the second matching layer 904, and the second matching layer 904 can have a higher acoustic impedance than the third matching layer 906. In one embodiment, each of the matching layers 902, 904 and 906 can have a relatively high thermal conductivity, such as greater than 30 W / mK.

  Mismatch layer 916 has a higher acoustic impedance than piezoelectric element 910 to increase the force of the ultrasonic waves transmitted to lens 908. In one embodiment, the mismatched layer 916 may be made of a metal such as, for example, a carbide alloy, and in an exemplary embodiment has an acoustic impedance of 40 MRayl to 120 MRayl. The acoustic impedance of the mismatched layer 916 acoustically "clamps" the piezoelectric element such that relatively high amounts of acoustic energy are transferred from the front side 912 of the piezoelectric element 910. There is. It should be appreciated that alternative embodiments may also use mismatched layers made of different materials and / or have acoustic impedances selected from different ranges. In another embodiment, the ultrasonic transducer may have no mismatched layer.

  The back matching layer 920 is attached to the flex 918. The back matching layer 920 may be aluminum in one embodiment, but thermally conductive materials including aluminum alloys, copper, copper alloys and other metals may also be used.

  The back matching layer 920 is indirectly connected to the piezoelectric element 910 via the flex 918 and the mismatched layer 916. In the present disclosure, the expression "connected indirectly" is defined as including two structures connected to one another via one or more additional structures or components. In one embodiment, the piezoelectric element 910, the mismatched layer 916 and the flex 918 can be bonded together using a thermally conductive material such as an epoxy with a conductive additive. Heat is conducted from the piezoelectric element 910 through the mismatched layer 916 and the flex 918 to the back matching layer 920. In one embodiment, the flex 918 may be relatively thin, such as less than about 100 μm. Although the flex 918 may include copper traces with the insulating polyimide layer, heat is effectively transferred from the mismatched layer 916 through the flex 918 to the back matching layer 920 because the flex 918 is thin. Further details of the back matching layer 920 will be described below.

  While the mismatched layer 916 eliminates most of the acoustic energy emitted from the back side of the piezoelectric element 910, some acoustic energy may be transmitted through the mismatched layer 916, the flex 918 and the back matching layer 920 is there. The ultrasound transducer 900 includes a thermal backing 922 to attenuate this acoustic energy. The thermal backing 922 is made of a material that has relatively high acoustic attenuation so that the ultrasound from the piezoelectric element 910 can be attenuated. For example, the thermal backing 922 can be made of an epoxy with a filler such as titanium dioxide. The thermal backing 922 may be about 2 mm thick. In another embodiment, the thermal backing 922 may be between 1 mm and 2 mm thick. However, the thermal backing 922, when made of filled epoxy, tends to have a relatively low thermal conductivity, eg, the thermal conductivity of an epoxy with titanium dioxide is generally 10 W / m.sup.2. It is less than K.

  Heat sink 924 is attached to thermal backing 922 and comprises a material having a high specific heat capacity, such as aluminum or an aluminum alloy. Because heat is not effectively conducted through the thermal backing 922, the back matching layer 920 includes wings 926 that extend beyond the edge of the piezoelectric element 910. Wings 926 may be bent to contact heat sink 924. Wings 926 may be connected to heat sink 924 by a thermally conductive epoxy, solder, or any other technique that creates a thermally conductive joint. In the present disclosure, the term "heat conduction" is at least 10 W / m. Defined as including a conductive connection that transfers heat at a rate of K. However, the conductive connection is preferably 20 W / m. Transfer heat at a rate above K. In the illustrated embodiment, the back matching layer 920 is in the front surface of the back matching layer 920 to facilitate folding the back matching layer 920 to reach a position to contact the heat sink 924. Multiple notches 928 can be included.

  In one embodiment, the layers to be drawn have a plurality of large notches (not shown) through the matching layers 902, 904 and 906 and the piezoelectric element 910 to form an electrical isolation between the portions of the piezoelectric element 910. Can be included. Furthermore, the layers to be drawn can include matching layers 902, 904 and 906 and a plurality of small notches passing through a portion of the piezoelectric element 910 to effectively damp horizontal vibrations.

  FIG. 10 is a perspective view of the ultrasonic transducer 900 shown in FIG. Common reference numerals are shown to indicate common components between FIGS. 9 and 10. FIG. 10 shows wings 926 in an extended position prior to being bent downward to contact heat sink 924. The cross-sectional view of FIG. 9 shows only two of the four wings 926. In FIG. 10, the aft matching layer 920 clearly includes four wings 926. Coordinate axes 930 are also shown in FIG. The embodiment shown in FIG. 10 extends from the ultrasonic transducer 900 in both the positive and negative x-axis directions, and further extends from the ultrasonic transducer 900 in both the positive and negative y-axis directions. Wing 926 is included.

  The rear matching layer of another embodiment may include fewer than four wings. For example, one embodiment (not shown) can have a matching layer with only two wings. If the embodiment has only two wings, it may be advantageous for the wings to be arranged substantially parallel to either notch during the dicing process. That is, if the dicing of the notch is in the y-direction, in the positive and negative directions of the y-axis so that the undiced portion of the piezoelectric element 910 can provide a good thermal path from the piezoelectric element 910 to the wing 926 It may be advantageous to have the wings extend.

  In embodiments having four wings 926, such as the embodiment shown in FIG. 10, any gap created during the dicing process may be a thermally conductive but electrically insulating material such as RTV or epoxy. May be filled with Filling the notches made during the dicing process allows heat to flow from the piezoelectric element 910 through the back matching layer 920 to the heat sink 924. Those skilled in the art will recognize that the wings 926 shown in FIG. 10 are thermally connected to the heat sink 924 before the ultrasonic transducer 900 is used. Further, it should be appreciated that alternative embodiments may have one or more wings disposed substantially perpendicular to any notches made during the dicing process .

  FIG. 11 depicts a cross-sectional view of the layers of ultrasonic transducer 950. Common reference numerals are used to indicate components that are substantially identical to the components described above in connection with FIG. The components described above will not be described in detail again. Ultrasonic transducer 950 includes a back matching layer 952 that includes two portions 954 that extend beyond end 955 of piezoelectric element 910. A thermally conductive sheet 956 thermally connects each portion 954 to a heat sink 924. Similar to the embodiment shown in FIG. 9, the back matching layer 952 is configured to conduct heat to the heat sink 924. The back matching layer 952 may be aluminum or an aluminum alloy in the illustrated embodiment. The thermally conductive sheet 956 may also be aluminum or an aluminum alloy. The thermally conductive sheet 956 may be directly connected to the back matching layer 952 or may be adhered to the back matching layer 952 using a material such as thermally conductive epoxy or solder.

  In particular embodiments, the techniques described herein may be applied in conjunction with one-dimensional linear array transducers, two-dimensional transducers, and / or annular array transducers. In particular embodiments, the techniques described herein may be applied in conjunction with transducers of any geometry.

  FIG. 12 shows a graph showing simulation data. Graph 970 shows the transmit and receive functions of both a conventional ultrasonic transducer without a back matching layer and an ultrasonic transducer according to one embodiment with a 200 μm back matching layer on an aluminum backing ( It shows transmit / receive transfer function). A plot of a conventional ultrasound transducer is shown as a line, and a plot of an ultrasound transducer with a back-matching layer is shown as a dotted line. In the portion of the spectrum where the two plots are equal, only the dotted line is shown in the graph 970. The transmission and reception functions are approximately equal over most of the frequencies. The transmission and reception functions are divided into 1.5 MHz to 2.8 MHz and 3.2 MHz to 4.5 MHz. At all other frequencies, the transmit and receive functions of the ultrasonic transducer and the conventional ultrasonic transducer according to one embodiment can not be seen in the graph 970. The similarity of the graphs of the transmission and reception functions of the transducer according to one embodiment and the conventional ultrasonic transducer is such that the acoustic performance of the ultrasonic transducer according to one embodiment is very close to the acoustic performance of the conventional ultrasonic transducer Is shown. This simulation demonstrates that the acoustic performance of the ultrasonic transducer according to one embodiment is not impeded by the presence of the back matching layer.

  FIG. 13 shows a graph showing simulation data. Graph 975 shows pulse echoes of both a conventional ultrasonic transducer without a back matching layer and an ultrasonic transducer according to one embodiment having a 200 μm back matching layer on an aluminum backing. ing. A plot of a conventional ultrasound transducer is shown as a line, and a plot of an ultrasound transducer with a back-matching layer is shown as a dotted line. In the portion of the spectrum where the two plots are equal, graph 975 shows only the dotted line. The pulse echoes of both the conventional ultrasonic transducer and the ultrasonic transducer according to one embodiment are approximately equal. These pulse echoes differ in time from about 0.9 s to 1.1 s and just 1.2 s to near 1.8 s. At all other times on graph 975, pulse echoes of conventional ultrasound transducers and pulse echoes of ultrasound transducers according to one embodiment can not be distinguished on graph 975. This is because the acoustic performance of the ultrasonic transducer according to one embodiment is very similar to that of the conventional ultrasonic transducer, and the acoustic performance of the ultrasonic transducer according to one embodiment that a back matching layer is interposed It shows that it does not disturb.

  The application of the techniques herein produces the technical effect that the acoustic and / or thermal properties are improved. For example, by inducing heat away from the lens of the transducer, it is possible to increase the power level and use the transducer, thereby improving signal quality and image quality.

  The invention described herein extends to the converter described herein as well as the method of manufacturing such a converter.

  Although the invention has been described with reference to a plurality of embodiments, it will be understood by those skilled in the art that various modifications may be made and equivalents may be substituted without departing from the scope of the invention. . In addition, many modifications may be made to adapt a particular situation and material to the teachings of the present invention without departing from the scope of the present invention. Accordingly, it is intended that the invention not be limited to the specific embodiments disclosed, but the invention includes all embodiments falling within the scope of the appended claims.

DESCRIPTION OF SYMBOLS 100 conventional ultrasonic transducer 102, 908 lens 104, 106 matching layer 108, 308, 910 piezoelectric element 110, 310 backing 112, 927 arrow 200, 300, 400, 500, 600, 900, 950 ultrasonic transducer 203, 204, 205, 206, 303, 304, 305, 401, 501, 902, 904, 906 impedance matching layer 312 large notch 314 small notch 402, 926 wing 403 notch 502 sheet 912 front 914 aft 916 mismatch layer 918 Flex 920, 952 Back Matching Layer 922 Thermal Backing 924 Heat Sink 930 Coordinate Axis 955 End of Piezoelectric Element 954 Two Portions Stretching Beyond End of Piezoelectric Element 956 Thermally Conductive Sheet

Claims (1)

An ultrasonic transducer (900),
Piezoelectric element (910) defining an anterior side (912) and a posterior side (914), configured to convert electrical signals into ultrasound waves transmitted from said anterior side (912) towards a target A piezoelectric element (910), configured to convert the received ultrasound into an electrical signal,
A lens (908) connected to the front side (912) of the piezoelectric element (910);
A heat sink (924), a thermal backing (922) and a mismatch layer (916) connected to the back side (914) of the piezoelectric element (910);
A back matching layer (920) connected to both the piezoelectric element (910) and the heat sink (924), extending beyond the end of the piezoelectric element (910) to the heat sink (924) A rear matching layer (920) comprising wings (926) configured to conduct heat from the piezoelectric element (910) to the heat sink (924);
Including
The thermal backing (922) is comprised of an epoxy with titanium dioxide,
The mismatch layer (916) is disposed between the piezoelectric element (910) and the back matching layer (920), and the back matching layer (920) corresponds to the mismatch layer (916). Connected to the piezoelectric element (910) via
An ultrasonic transducer disposed between the back matching layer (920) and the heat sink (924) and configured to attenuate ultrasound from the piezoelectric element (910), a thermal backing (922) (900).