Ultrasonic probe and backing manufacturing method

Abstract

An ultrasonic probe and a backing manufacturing method are provided. The backing (18) includes: a particle aggregate (30) composed of a thermally conductive material and having a gap network (38) with irregularities; and a filler material (32) filled in the gap network (38). Ultrasonic waves radiated rearward from a piezoelectric layer (24) are scattered and attenuated inside the backing (18). Heat generated in the piezoelectric layer (24) is transferred to a heat sink (20) via the particle aggregate (30).

Description

Technical Field

[0001] This disclosure relates to ultrasonic probes and methods for manufacturing backing, and particularly to the construction and manufacturing of backing. Background Technology

[0002] In ultrasound diagnosis, an ultrasound probe is used. The ultrasound probe has a transmitting and receiving surface. With the transmitting and receiving surface in contact with the body surface of the patient, ultrasound waves are sent from the ultrasound probe into the patient's body, and the ultrasound probe receives the reflected waves from the body.

[0003] An ultrasonic probe includes a transducer assembly. The transducer assembly consists, for example, a backing (soft backing), a piezoelectric layer (piezoelectric element array), a matching layer (matching element array), and an acoustic lens, arranged from the non-living body side (rear side) to the living body side (front side). Sometimes a hard backing layer (hard backing element array) is also provided between the backing and the piezoelectric layer.

[0004] The backing attenuates ultrasonic waves leaking behind the vibrating layer (or behind the rigid backing). In the past, the composition of the backing was optimized to absorb ultrasonic waves within the backing, thus sufficiently attenuating them. Ultrasonic wave attenuation occurs through absorption and scattering. Existing backings primarily attenuate rearward-radiated ultrasonic waves through absorption attenuation.

[0005] Document 1 (JP Patent Application Publication No. 2015-221214) discloses a special ultrasonic probe. This ultrasonic probe has a semiconductor substrate on which a CMUT (Capacitive Micro-machined Ultrasound Transducer) is formed. Furthermore, the ultrasonic probe has a first backing layer and a second backing layer stacked together. Paragraph 0035 of Document 1 describes that the first backing layer is fabricated by filling a porous ceramic with resin (the same matter is described in paragraph 0047 of US2013 / 0285174A1). In paragraph 0035, the reason for using porous ceramic is stated as being to make the coefficient of linear expansion of the first backing layer match the coefficient of linear expansion of the semiconductor substrate. Document 1 (and US2013 / 0285174A1) do not describe a piezoelectric layer containing piezoelectric material, nor do they describe the specific structure or function of the porous ceramic.

[0006] The magnitude of ultrasonic wave attenuation due to absorption is proportional to the square of the ultrasonic wave frequency. In existing backings that follow absorption attenuation mechanisms, low-frequency ultrasonic wave components cannot be sufficiently attenuated within the backing. In this case, reflected waves are generated behind the backing. If these reflected waves reach the piezoelectric layer, noise will appear in the ultrasonic image. On the other hand, a relatively large amount of heat will be generated in the piezoelectric layer. From the perspective of further improving biosafety and protecting the piezoelectric layer, a technology is sought to effectively dissipate the heat generated in the piezoelectric layer to the outside. Summary of the Invention

[0007] The purpose of this disclosure is to provide a backing material that can provide good ultrasonic attenuation and good thermal conductivity, and a method for manufacturing the same.

[0008] The ultrasonic probe disclosed herein is characterized by comprising: a piezoelectric element array including a plurality of piezoelectric elements and radiating ultrasonic waves toward the front of the organism; a backing disposed on the rear side of the piezoelectric element array; and a heat-absorbing member joined to the backing, the backing comprising: a porous member made of a thermally conductive material and having an irregularly spaced mesh distributed throughout the entire backing; and a filling material filling the mesh, wherein ultrasonic waves radiated from the piezoelectric element array toward its rear side are attenuated by scattering within the porous member, and heat generated in the piezoelectric element array is transferred to the heat-absorbing member via the porous member.

[0009] The backing manufacturing method disclosed herein includes the following steps: filling a gap network of a particle aggregate containing multiple particles with a filler material; and after the filler material has cured, grinding at least the biological side of the backing containing the particle aggregate and the filler material, wherein the gap network occupies a volume ratio of 30% to 70% in the backing, and the size of the multiple particles is in the range of 0.05 to 2 mm. Attached Figure Description

[0010] Figure 1 This is an xz cross-sectional view of the ultrasonic probe involved in the implementation method.

[0011] Figure 2 This is a yz cross-sectional view of the ultrasonic probe involved in the implementation method.

[0012] Figure 3 This is an enlarged cross-sectional view of the backing.

[0013] Figure 4 This is a flowchart illustrating the backing manufacturing process.

[0014] Figure 5 This is a flowchart illustrating the manufacturing method of an ultrasonic probe.

[0015] Figure 6 This is the xz cross-sectional view of the ultrasonic probe involved in the modified example. Detailed Implementation

[0016] The following description of the implementation method is based on the accompanying drawings.

[0017] (1) Overview of the implementation method

[0018] The ultrasonic probe described in this embodiment includes a piezoelectric element array, a backing, and a heat-absorbing component. The piezoelectric element array comprises multiple piezoelectric elements that radiate ultrasonic waves toward the front of the biological body. The backing is disposed behind the piezoelectric element array. The heat-absorbing component is a component bonded to the backing. The backing is composed of a porous component and a filling material. The porous component is made of a thermally conductive material and has an irregularly spaced network of gaps throughout the entire backing. The filling material is a component that fills the gap network. Ultrasonic waves radiated from the piezoelectric element array toward its rear side are attenuated by scattering within the porous component. Heat generated in the piezoelectric element array is transferred to the heat-absorbing component via the porous component.

[0019] According to the above structure, ultrasonic waves radiated rearward from the piezoelectric element array are scattered within the backing, thereby attenuating the ultrasonic waves within the backing. Specifically, due to the irregularity of the gap mesh, i.e., due to the irregular variations on the surface of the porous component, irregular reflections of ultrasonic waves repeatedly occur on the surface of the porous component, effectively attenuating the ultrasonic waves. Since the attenuation caused by scattering is independent of or almost independent of the frequency of the ultrasonic waves, it is difficult to produce problems such as the retention of low-frequency components within the backing and reflections. As a result, the advantage of being able to reduce the thickness of the backing is also obtained.

[0020] On the other hand, since the porous component is made of a thermally conductive material, the heat generated in the piezoelectric element array is efficiently transferred to the heat-absorbing component via the porous component. As a result, the temperature rise of the piezoelectric element array can be suppressed, further improving biosafety and protecting the vibrating element array. For example, when using a heat-sensitive material as the piezoelectric material, it is desirable to further suppress the temperature rise of the wave-sending and receiving surfaces of the ultrasonic probe, employing the backing described in the embodiment. A thermally conductive material refers to a material with a higher thermal conductivity than the filling material.

[0021] In this implementation, the volume ratio (size ratio) of the gap mesh in the backing is in the range of 30% to 70%. If the volume ratio of the gap mesh is less than 30%, the ultrasonic waves will no longer be sufficiently attenuated, or the backing will become too large. If the volume ratio of the gap mesh exceeds 70%, the ultrasonic waves will no longer be sufficiently attenuated, and sufficient heat dissipation will also be impossible.

[0022] In this embodiment, the porous component is a particle aggregate containing multiple particles. In this embodiment, the multiple particles have irregular shapes (also referred to as random or non-uniform shapes). Furthermore, the multiple particles have irregular sizes (also referred to as random or non-uniform sizes). With the multiple particles having irregular shapes and sizes, the increased irregularity of the gap mesh shape enhances the scattering of ultrasonic waves within the backing.

[0023] In this embodiment, the size of the multiple particles is in the range of 0.05 to 2 mm. When this condition is met, good attenuation characteristics can be obtained from the perspective of the frequency range of the ultrasonic wave used. The size of the multiple particles can be set in the range of 0.2 to 1 mm. Here, size refers to the maximum length of the amorphous particles. In the particle aggregate, adjacent particles can contact each other or merge. The particle aggregate is constructed such that multiple heat conduction paths are continuously formed between the multiple piezoelectric elements and the heat-absorbing member. That is, the particle aggregate is a dense mass of multiple particles.

[0024] In this embodiment, the multiple particles are all insulating ceramic particles. When both the filler material and each particle are made of an insulating material, no electrical short circuit occurs between the multiple piezoelectric elements. Alternatively, the upper layer of the particle aggregate can be composed of multiple insulating particles, and the lower layer can be composed of multiple conductive particles with high thermal conductivity. According to this structure, thermal conductivity can be improved while preventing electrical short circuits.

[0025] In one embodiment, a hard-backed element array is disposed on the rear side of the piezoelectric element array. The rear of the hard-backed element array is joined to the front of the porous component. The rear of the porous component is joined to the front of the heat-absorbing component.

[0026] The backing manufacturing method according to the embodiments includes a filling step and a grinding step. In the filling step, a filler material is filled into the gap network of a particle aggregate containing multiple particles. In the grinding step, after the filler material has cured, at least the biological side of the backing containing the particle aggregate and the filler material is ground. The volume ratio of the gap network in the backing is in the range of 30% to 70%. The size of the multiple particles is in the range of 0.05 to 2 mm.

[0027] Based on this structure, a backing material that exhibits good ultrasonic attenuation and thermal conductivity can be easily fabricated. In this embodiment, the multiple particles have irregular sizes and shapes. Furthermore, the multiple particles are composed of insulating ceramic.

[0028] (2) Details of the implementation method

[0029] Figure 1 This is a cross-sectional view (xz section view) of the ultrasonic probe 10 according to the embodiment. More specifically, in Figure 1 The diagram schematically shows the probe head portion of the ultrasound probe 10. The ultrasound probe 10 is connected to the main body of the ultrasound diagnostic device (not shown). The ultrasound probe 10 and the main body of the ultrasound diagnostic device constitute the ultrasound diagnostic device. The ultrasound diagnostic device is a medical device used during ultrasound examinations of a patient. Ultrasound waves are radiated from the ultrasound probe 10 into the patient's interior, and the ultrasound probe 10 detects the reflected waves from the patient's interior.

[0030] exist Figure 1 In the diagram, the z-direction is the direction of ultrasonic radiation. Figure 1 The upper side of the middle part is the front side of the organism. Figure 1 The lower side of the middle part is the non-living body side, i.e., the posterior side. Figure 1 The y-direction, not shown, is the electron scanning direction. The x-direction is the elevation direction, which is orthogonal to both the z-direction and the y-direction.

[0031] The ultrasonic probe 10 has a housing 12 and a transducer assembly 14. The majority of the transducer assembly 14 is housed within the housing 12. The housing 12 is, for example, a hollow resin housing. The transducer assembly 14 has a laminate 16, a backing 18, a heat dissipation block 20, and an acoustic lens 22.

[0032] In the illustrated structural example, the laminate 16 comprises a piezoelectric layer 24, a rigid backing layer 26 disposed behind it, and a matching layer 28 disposed in front of the piezoelectric layer 24. The piezoelectric layer 24 is composed of a plurality of piezoelectric elements (an array of piezoelectric elements) arranged in the y-direction. The rigid backing layer 26 is composed of a plurality of rigid backing elements (an array of rigid backing elements) arranged in the y-direction. The matching layer 28 is composed of a plurality of matching elements (an array of matching elements) arranged in the y-direction. Multiple matching layers can be stacked on top of the piezoelectric layer 24. For example, an array of matching elements can be provided as a first matching layer, and an undivided matching layer can be provided on top of it as a second matching layer.

[0033] An acoustic lens 22 is provided on the biological side of the laminate 16. A transmitting / receiving wavefront 22A is located in front of the acoustic lens 22. The transmitting / receiving wavefront 22A abuts against the surface of the biological body. In the contact state, ultrasonic waves are transmitted and received. The housing 12 is held by the examiner (physician, examination technician, etc.). The ultrasonic probe 10 is a portable ultrasonic transceiver.

[0034] A backing 18 is provided on the rear side of the laminate 16. The backing 18 serves to attenuate unwanted ultrasonic waves radiated rearward and to guide the heat generated in the piezoelectric layer 24 to the heat dissipation block 20. Specifically, the backing 18 is composed of a particle aggregate 30 as a porous component and a filling material 32 filling the gap network of the particle aggregate 30. Details regarding the backing 18 will be explained later.

[0035] A heat dissipation block 20, serving as a heat absorption member, is provided on the rear side of the backing 18. The heat dissipation block 20 is a heat conduction member, where heat is absorbed or transferred to the outside. Various shapes are considered for the shape of the heat dissipation block 20.

[0036] The front of the backing 18 is joined to the rear of the hard backing layer 26, and the rear of the backing 18 is joined to the front of the heat dissipation block 20. In the absence of the hard backing layer 26, the rear of the piezoelectric layer 24 is joined to the front of the backing 18.

[0037] The piezoelectric layer 24 and the hard backing layer 26 are integrated, forming a resonator. The thicknesses of the piezoelectric layer 24 and the hard backing layer 26 are adjusted such that the thickness of the resonator is λ / 2. Here, λ is the wavelength corresponding to the center frequency of the transmitted ultrasonic wave.

[0038] Ultrasonic waves radiated rearward from the piezoelectric layer 24 are reflected behind the rigid backing layer 26 and travel towards the front, i.e., the side of the organism. However, some of the ultrasonic waves radiated rearward leak out from the rigid backing layer 26 and enter the interior of the backing 18. In order to prevent the leaked ultrasonic waves from becoming a source of noise, the backing 18 attenuates the leaked ultrasonic waves.

[0039] The piezoelectric layer 24 is made of a piezoelectric material, specifically a PMN-PT single crystal or a PZN-PT single crystal. These materials are relatively heat-sensitive, making heat dissipation from the piezoelectric layer 24 important. Heat dissipation from the piezoelectric layer 24 is also important for suppressing temperature rise of the receiving and transmitting wavefronts 22A. Alternatively, the piezoelectric layer 24 can be made of polycrystalline PZT. The acoustic impedance of the piezoelectric layer 24 is, for example, 25–30 MRayls. The hard backing layer 26 is, for example, made of metal, and its acoustic impedance is, for example, 80–120 MRayls. The average acoustic impedance of the backing 18 is, for example, 3–4 MRayls.

[0040] The thickness (z-axis dimension) of the backing 18 is set, for example, in the range of 5 to 20 mm. In the backing 18, the particle aggregate 30 is composed of a large number of densely packed, interconnected particles 30a. The particle aggregate 30 has an irregular network of gaps throughout the entire backing 18. The individual portions constituting the network of gaps have random shapes. The volume ratio (volume proportion) of the network of gaps relative to the backing 18 or the particle aggregate 30 is, for example, in the range of 30 to 70%.

[0041] A filler material 32 is filled into the gap network. In other words, the backing 18 is formed by impregnating the particle aggregates 30 with the filler material. The filler material 32 is composed of resin and fillers added therein. As fillers, viscosity-adjusting fillers, thermal conductivity-adjusting fillers, acoustic impedance-adjusting fillers, etc., are known. The average particle size in the filler is, for example, in the range of 1 to 15 μm. The particle aggregates 30 have a higher thermal conductivity than the average thermal conductivity of the filler material 32, and thus function as thermal conductive components.

[0042] Specifically, each particle 30a constituting the particle aggregate 30 is a solid particle made of insulating ceramic material, having an irregular shape and size. That is, the shapes of the multiple particles are irregular (random), and the sizes of the multiple particles are also irregular (random). The sizes of the multiple particles are, for example, in the range of 0.05 to 2 mm, and ideally in the range of 0.2 to 1 mm. Here, particle size refers to the maximum length of the particle. By crushing the ceramic material, a large number of amorphous particles can be produced. By classifying the crushed particles, specifically by sieving, particles of various sizes within a given range can be extracted.

[0043] When the particle size is too small, the reflection of ultrasound waves at the particle surface is weak. When the particle size is too large, the reflection of ultrasound waves at the particle surface becomes too large. The particle aggregate is configured such that moderate scattering of ultrasound waves is generated within the backing 18, thereby allowing the ultrasound waves to be sufficiently and effectively attenuated within the backing 18.

[0044] The backing involved in the embodiment attenuates ultrasonic waves through reflection attenuation. According to this reflection attenuation method, ultrasonic waves can be attenuated with almost no relation to their frequency. According to this embodiment, the problem of residual low-frequency components can be solved.

[0045] Examples of materials constituting particle 30a include alumina (Al₂O₃), zirconium oxide (ZrO₂), barium titanate (BaTiO₃), silicon carbide (SiC), aluminum nitride (AlN), and boron nitride (BN). Examples of resins include epoxy resin, polyurethane resin, acrylic resin, phenolic resin, and silicone resin. Fillers are added to the resin for viscosity adjustment, attenuation adjustment, and thermal conductivity adjustment. Examples of such fillers include silica fillers, tungsten fillers, tungsten silicide fillers, silicon carbide fillers, boron nitride fillers, and silicone rubber fillers. The heat dissipation block is made of metals such as copper, aluminum, or iron, or of materials such as carbon, graphite, or ceramics. A heat sink can be installed as the heat dissipation block.

[0046] like Figure 1 As shown, because a large number of densely arranged heat-conducting particles 30a are randomly arranged between the hard backing layer 26 and the heat dissipation block 20, the heat generated in the piezoelectric layer 24 can be efficiently guided to the heat dissipation block 20. Ultrasonic wave reflection from the backing layer 18 is not generated, or the reflection is so small as to be negligible. Therefore, it is not necessary to match the acoustic impedance of the heat dissipation block 20 with that of the backing layer 18, and the heat dissipation block 20 can be constructed from various materials.

[0047] Figure 2 This is a cross-sectional view (yz cross-sectional view) of the ultrasonic probe according to the embodiment. As described above, the laminate 16 is composed of a piezoelectric layer 24, a hard backing layer 26, and a matching layer 28. The piezoelectric layer 24 is an array of piezoelectric elements composed of a plurality of piezoelectric elements 24a arranged in the y direction. The hard backing layer 26 is an array of hard backing elements composed of a plurality of hard backing elements 26a arranged in the y direction. The matching layer 28 is an array of matching elements composed of a plurality of matching elements 28a arranged in the y direction.

[0048] Alternatively, the laminate 16 can be composed of multiple element stacks 34 arranged in the y-direction, each element stack 34 consisting of a piezoelectric element 24a, a rigid backing element 26a, and a matching element 28a. During the manufacturing process of the ultrasonic probe, a non-segmented laminate is formed on the front of the backing 18. Multiple separation grooves 36 are formed by dicing this laminate, simultaneously dividing the laminate into multiple element stacks 34. The ends 36a of each separation groove 36 extend into the backing 18. Filling material is injected into each separation groove 36.

[0049] Multiple hard backing elements 26a are thermally connected to the heat dissipation block 20 via particle aggregates in the backing 18. The particle aggregates are configured such that multiple heat transfer paths are continuously formed between the multiple hard backing elements 26a and the heat dissipation block 20.

[0050] exist Figure 3In the image, the cross-section of backing 18 is shown as an enlarged view. Figure 3 This is a simulated microscope image. The magnification used to obtain the microscope image was 50x. The brighter areas represent the multiple particles 30a that make up the particle aggregate 30. The darker areas represent the interstitial network 38, which is filled with filler material 32. Although in Figure 3 While this doesn't manifest well in the general form, in particle aggregate 30, adjacent particles are interconnected. They can then merge.

[0051] The individual particles 30a constituting the particle aggregate 30 have irregular shapes and sizes. In other words, both shape and size are random. Ultrasonic waves are diffusely reflected from the surface of each particle 30a within the backing 18. During repeated diffuse reflection, the ultrasonic waves effectively attenuate. d represents the maximum length of the particle 30a with its three-dimensional shape.

[0052] exist Figure 4 The backing manufacturing method described in the embodiment is shown as a flowchart. In S10, particles are made by crushing ceramic. Then, the particles are graded. In S12, the particles are placed in a mold box to form a particle aggregate. At this time, pressure and heating of the particles can also be used.

[0053] In S14, a process is performed to impregnate the particle aggregates with filler material by injecting filler material into the mold box. This process can be performed outside the mold box. The particle aggregates have a gap network, which is filled with filler material. At this time, filler material is injected to fully remove air bubbles from the gap network. S16 is the resin curing process. At this time, heat or pressure can be applied. The backing is formed by resin curing.

[0054] In S18, the surfaces of the backing are ground. In S18, shaping is also performed as needed. During grinding, at least the surfaces that bond with the laminate (specifically the hard backing layer) are ground.

[0055] exist Figure 5 An example of a method for manufacturing an ultrasonic probe is shown. In S20, a non-segmented laminate is formed on a backing. In S22, the laminate is cut to divide it into multiple element stacks. At this time, filler material is filled into the formed separation grooves. In S24, a transducer assembly having a backing, multiple element stacks, an acoustic lens, etc., is fabricated. In S26, the transducer assembly is installed inside a housing.

[0056] exist Figure 6The ultrasonic probe 10A involved in the modified example is shown. Side panels 40 and 42 are joined to the first and second sides of the backing 18. Side panels 40 and 42 are heat-conducting members, for example, made of metal. The heat absorbed by side panels 40 and 42 is guided to the heat dissipation block.

[0057] On the first and second sides of the backing 18, there are gaps (exposed portions) 40A and 42A that are not covered by the side panels 40 and 42. If the entire first and second sides of the backing 18 are covered by the side panels 40 and 42, reflected waves generated by the surfaces of the side panels 40 and 42 may become a problem. Figure 6 In the structure shown, intervals of 40A and 42A are provided to prevent such problems. The first and second sides are orthogonal to the x-direction. Two side panels can be provided for the third and fourth sides, which are orthogonal to the y-direction.

[0058] In the ultrasonic probe described in the embodiments, multiple piezoelectric elements are arranged in a planar shape, but they can also be arranged in a curved shape. The structure described in the embodiments can be applied to ultrasonic probes having a two-dimensional array of vibrating elements.

Claims

1. An ultrasonic probe, characterized in that, Include: The piezoelectric element array (24) contains multiple piezoelectric elements and radiates ultrasonic waves toward the front side of the organism. A backing (18) is provided on the rear side of the piezoelectric element array (24); and The heat-absorbing component (20) is joined to the backing. The backing (18) comprises: The porous component (30) is made of a thermally conductive material and has an irregularly spaced network (38) that is distributed throughout the backing (18); and Filler material (32) is used to fill the gap mesh (38). The porous component (30) is a particle aggregate containing multiple particles (30a). In the particle aggregate, adjacent particles are connected to each other, thereby forming multiple heat conduction paths within the particle aggregate. Ultrasonic waves radiated from the piezoelectric element array (24) to its rear side are attenuated by scattering inside the porous component (30). The heat generated in the piezoelectric element array (24) is transferred to the heat-absorbing member (20) via the porous member (30). In the particle aggregate, adjacent particles fuse with each other. The plurality of particles (30a) are insulating ceramic particles.

2. The ultrasonic probe according to claim 1, characterized in that, The volume ratio of the gap mesh (38) in the backing (18) is in the range of 30% to 70%.

3. The ultrasonic probe according to claim 1, characterized in that, The plurality of particles (30a) have irregular shapes.

4. The ultrasonic probe according to claim 1, characterized in that, The plurality of particles (30a) have irregular sizes.

5. The ultrasonic probe according to claim 4, characterized in that, The size of the plurality of particles (30a) is in the range of 0.05 to 2 mm.

6. The ultrasonic probe according to claim 1, characterized in that, A hard-backed element array (26) is provided on the rear side of the piezoelectric element array (24). The rear of the hard-backed element array (26) and the front of the porous member (30) are joined together. The rear of the porous component (30) and the front of the heat-absorbing component (20) are joined together.

7. A method for manufacturing a backing, characterized in that, It includes the following processes: Filling material (32) into the gap network (38) of the particle aggregate (30) containing multiple particles (30a); and After the filler material (32) has cured, at least the biological side of the backing (18) containing the particle aggregates (30) and the filler material (32) is ground. In the particle aggregate (30), adjacent particles are connected to each other, thereby forming multiple heat conduction paths in the particle aggregate (30). The volume ratio of the gap mesh (38) in the backing (18) is in the range of 30% to 70%. The size of the plurality of particles (30a) is in the range of 0.05 to 2 mm. In the particle aggregate (30), adjacent particles fuse with each other. The plurality of particles (30a) are insulating ceramic particles.

8. The backing manufacturing method according to claim 7, characterized in that, The plurality of particles (30a) have irregular size and irregular shape.

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