Ultrasonic transducer and backing structure thereof

Abstract

The invention discloses an ultrasonic transducer and a backing structure thereof, and belongs to the technical field of ultrasound, the backing structure is connected to the back surface of a piezoelectric layer, and the backing structure comprises a first reflecting layer, a backing layer and a second reflecting layer which are sequentially stacked in the direction away from the piezoelectric layer; the impedance of the first reflecting layer is between that of the backing layer and that of the piezoelectric layer, and the impedance difference between the first reflecting layer and the piezoelectric layer is lower than a first threshold value; the impedance of the second reflecting layer is higher than that of the backing layer, and the impedance difference value between the second reflecting layer and the backing layer is higher than a second threshold value. Through the arrangement of the first reflecting layer and the second reflecting layer, reverse ultrasonic waves generated on the back surface of the piezoelectric layer can be reflected for multiple times in the backing layer, so that the reverse ultrasonic waves are absorbed by the backing layer as much as possible, the absorptivity of the reverse ultrasonic waves is effectively improved, and the interference of the reverse ultrasonic waves on forward ultrasonic waves is reduced.

Description

Technical Field

[0001] The invention relates to the field of ultrasonic technology, and in particular to an ultrasonic transducer and a backing structure thereof. Background Art

[0002] Ultrasound has been widely used in medical imaging diagnosis due to its obvious advantages such as no radiation, real-time dynamic imaging, and the ability to observe blood flow. The replacement of ultrasonic transducers is an important part of the development of medical ultrasonic diagnostic systems, and medical ultrasonic transducers are one of the most important parts.

[0003] With the development of medical technology, interventional surgery is becoming more and more widely used. Interventional ultrasound (such as transesophageal ultrasound) medical devices have also achieved unprecedented development, and the corresponding procedures are becoming more and more widely used. However, due to the limitations of interventional ultrasound application scenarios and in order to reduce the harm to the patients, the size of ultrasound transducers is also constantly shrinking.

[0004] Piezoelectric ultrasonic probes are used in many occasions such as medical diagnosis, treatment and ultrasonic flaw detection. With the demand for efficient and accurate diagnosis, people are also putting forward higher and higher requirements on the performance of ultrasonic imaging equipment. Among the various performances of piezoelectric ultrasonic probes, improving the performance of probes is one of the effective ways to improve the quality of detection images. However, with the development of software and electronic circuit technology, the performance of ultrasonic probes has increasingly become one of the bottlenecks for improving the image quality of ultrasonic imaging equipment.

[0005] When the ultrasonic transducer is working, the piezoelectric ceramic is stimulated by the excitation signal to vibrate. The ultrasonic wave will propagate in the forward and reverse directions of the piezoelectric ceramic. The forward propagating ultrasonic wave is transmitted to the target or medium through the matching layer. The sound waves in this direction are what we want to see, so the larger the better. A large part of the reverse propagating ultrasonic wave will be reflected back to the piezoelectric ceramic, thereby prolonging the vibration time of the piezoelectric ceramic and increasing the ringing interference, resulting in a long signal ringing time and large fluctuations, which in turn leads to a significant deterioration in image quality. The image quality is directly related to the use effect and the accuracy of precision medicine. It can be seen that the reverse propagating ultrasonic wave is usually harmful. We hope to consume this part of the ultrasonic wave as much as possible to reduce the impact on the forward ultrasonic wave.

[0006] For example, the acoustic impedance of general piezoelectric ceramics is about 33 MRayl, and the acoustic impedance of the backing material is generally 2~8 MRayl. According to the reflection law of sound waves, only less than 40% of the energy of the negative reflected sound waves can be transmitted to the backing, and more than 60% of the sound waves are re-reflected back to the piezoelectric ceramics. After superposition with the forward radiated sound waves, they will propagate into the medium or the detection target together, which also has a great impact on the image quality of ultrasonic imaging.

[0007] The conventional treatment method is to add a backing layer on the back of the piezoelectric ceramic to transmit the reverse propagating ultrasound to the backing layer. The backing layer is generally made of low-density, high-attenuation materials. The reverse ultrasound will be quickly converted into heat energy when propagating in the backing layer, thereby achieving the purpose of attenuating the reverse ultrasound. In this attenuation process, most of the energy of the ultrasound is converted into heat energy.

[0008] The absorption efficiency of traditional backing materials for ultrasound is proportional to its thickness. In order to absorb ultrasound as much as possible, traditional backing materials must be thick enough, but this greatly increases the volume of the ultrasonic transducer. However, as the size of the ultrasonic transducer continues to shrink, the various components of the ultrasonic transducer have to be compressed and reduced accordingly, which poses a huge challenge to the constituent materials of the ultrasonic transducer, especially the backing material.

[0009] The acoustic impedance of traditional backing materials is generally less than 8MRayl. The preparation materials usually include epoxy resin, glass beads, tungsten powder and iron powder. The attenuation coefficient is generally 5~10dB / mm@5MHz. In order to reduce the backing echo interference, the overall attenuation effect of the backing must reach more than 30dB, so the backing thickness is usually between 2~5mm. However, interventional probes are generally used in blood vessels or heart cavities, with a size of no more than 1.5mm, and the space actually reserved for the backing is no more than 0.8mm. Therefore, traditional backings cannot meet the needs of attenuating reflected signals.

[0010] In order to solve this problem, the most direct approach is to improve the sound absorption efficiency per unit size of the backing material. However, due to the current difficulty in material development and processing, as well as the cost of material processing, it is difficult to effectively improve the performance of the backing material in a short period of time.

[0011] In addition, in order to increase attenuation, traditional backing materials mostly use lightweight materials such as epoxy resin and glass beads. The use of these materials also leads to a decrease in the thermal conductivity of the backing material, making it difficult for the heat converted from ultrasound to be transmitted outward by heat conduction. In this way, during use, the heat of the ultrasonic transducer will continue to accumulate, causing the internal temperature of the ultrasonic transducer to continue to rise. However, the accumulation of heat will not only affect the performance of the ultrasonic transducer and reduce image quality, but also more seriously damage the life of the ultrasonic transducer and limit the application of ultrasonic transducers in heat-sensitive scenarios. Summary of the invention

[0012] In view of the problem in the prior art that the backing structure of the ultrasonic transducer has low absorption and attenuation efficiency for reverse ultrasonic waves, an object of the present invention is to provide an ultrasonic transducer and a backing structure thereof so as to at least partially solve the above problem.

[0013] To achieve the above object, the technical solution of the present invention is: In a first aspect, the present invention provides a backing structure for an ultrasonic transducer, wherein the backing structure is connected to the back side of a piezoelectric layer, and comprises a first reflecting layer, a backing layer, and a second reflecting layer stacked in sequence in a direction away from the piezoelectric layer; the impedance of the first reflecting layer is between the backing layer and the piezoelectric layer, and the impedance difference between the first reflecting layer and the piezoelectric layer is lower than a first threshold; the impedance of the second reflecting layer is higher than the backing layer, and the impedance difference between the second reflecting layer and the backing layer is higher than a second threshold.

[0014] In some preferred embodiments, the surface where the first reflective layer contacts the backing layer has a concavo-convex structure, and / or the surface where the second reflective layer contacts the backing layer has a concavo-convex structure.

[0015] In some preferred embodiments, the concavo-convex structure is configured as a zigzag structure or a wavy structure.

[0016] In some preferred embodiments, the first reflective layer and the second reflective layer are both made of conductive materials.

[0017] In some preferred embodiments, both the first reflective layer and the second reflective layer are grounded.

[0018] In some preferred embodiments, the first reflective layer and the second reflective layer are both made of thermally conductive materials.

[0019] In some preferred embodiments, the first threshold is one-half to one-quarter of the impedance value of the piezoelectric layer, and the second threshold is more than ten times the impedance value of the backing layer.

[0020] In some preferred embodiments, the backing structure also includes a backing sub-layer and a third reflecting layer stacked in sequence between the first reflecting layer and the backing layer along a direction away from the piezoelectric layer; the impedance of the third reflecting layer is higher than those of the backing layer and the backing sub-layer, and the impedance of the third reflecting layer is between the first reflecting layer and the second reflecting layer.

[0021] In some preferred embodiments, the backing layer and the backing sublayer are the same.

[0022] In a second aspect, the present invention further provides an ultrasonic transducer, comprising a piezoelectric layer and the backing structure as described above, wherein the backing structure is connected to the back side of the piezoelectric layer.

[0023] By adopting the above technical solution, the beneficial effects of the present invention are: The present invention arranges the first reflecting layer and the second reflecting layer so that the reverse ultrasonic wave generated on the back of the piezoelectric layer can be reflected multiple times in the backing layer, so that the reverse ultrasonic wave is absorbed by the backing layer as much as possible, which effectively improves the absorption rate of the reverse ultrasonic wave, reduces the interference of the reverse ultrasonic wave on the forward ultrasonic wave, improves the signal-to-noise ratio, and thus improves the performance of the ultrasonic transducer.

[0024] The present invention effectively improves the absorption effect of the backing layer, so that a backing that is thinner and smaller than the traditional backing can be used to achieve the same absorption effect, thereby effectively reducing the size of the transducer and breaking the application limitations of ultrasonic transducers in small-size scenarios.

[0025] The present invention allows the reverse ultrasonic wave to be reflected multiple times in the backing layer so that the reverse ultrasonic wave is absorbed as much as possible by the backing layer, thereby greatly expanding the selection range of the backing material, so that some materials with a small attenuation coefficient but other excellent properties can also be used as backing materials.

[0026] The present invention adds a first reflective layer and a second reflective layer at both ends of the backing layer, and these two materials are generally made of metal, which effectively improves the strength of the backing layer and increases the overall reliability of the transducer. The addition of the metal reflective layer also facilitates the installation and use of the transducer in various applications, and facilitates the use of the transducer. In addition, the heat energy generated by the ultrasonic transducer during operation can be conducted outward with the help of the first reflective layer and the second reflective layer, thereby effectively reducing the temperature of the ultrasonic transducer during use and increasing its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of an ultrasonic transducer in the prior art.

[0028] Figure 2 This is a schematic structural diagram of the backing structure in Example 1 of the present invention.

[0029] Figure 3 Schematic diagram of the grounding of the backing structure in Example 1 of the present invention.

[0030] Figure 4 It is a schematic diagram of the propagation of reverse ultrasonic waves in the backing structure disclosed in Example 1 of the present invention.

[0031] Figure 5 Schematic diagram of the contact surface between the first reflective layer, the second reflective layer and the backing layer in Example 2 of the present invention.

[0032] Figure 6 This is a schematic diagram of the structure of the backing structure in Example 3 of the present invention.

[0033] Figure 7Schematic diagram of the structure of the ultrasonic transducer in Example 4 of the present invention.

[0034] Figure 8 Schematic diagram of another structure of the ultrasonic transducer in Example 4 of the present invention.

[0035] In the figure: 1- piezoelectric layer, 2-first reflective layer, 3-backing layer, 4-second reflective layer, 5-backing sublayer, 6-third reflective layer. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] It should be noted that, in the description of the present invention, the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are descriptions of the structure of the present invention based on the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0038] The "first" and "second" in this technical solution are only used to distinguish the names of the same or similar structures, or corresponding structures with similar functions, and are not an arrangement of the importance of these structures, nor do they have a ranking, comparison of size, or other meanings.

[0039] In addition, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection between the two structures. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood based on the overall idea of ​​the present invention and the specific context of the present solution.

[0040] Example 1 The embodiment of the present invention provides a backing structure for an ultrasonic transducer. The backing structure is fixedly connected to the back side of the piezoelectric layer 1 when in use. Figure 2 As shown, the backing structure includes a first reflective layer 2 , a backing layer 3 and a second reflective layer 4 which are sequentially stacked and arranged in a direction away from the piezoelectric layer 1 .

[0041] The material of the piezoelectric layer 1 is usually piezoelectric ceramics, and its acoustic impedance is about 33 MRayl. Of course, the material of the piezoelectric layer 1 can also be piezoelectric crystals or piezoelectric composite materials. The backing layer 3 is usually made of epoxy resin, glass beads, tungsten powder, iron powder and other materials, and its acoustic impedance is generally 2~8 MRayl. Of course, other materials can also be used. Due to the large difference in acoustic impedance between the piezoelectric layer 1 and the backing layer 3, the ultrasonic wave on the back side of the piezoelectric layer 1 will produce a strong reflection at the contact surface between the piezoelectric layer 1 and the backing layer 3, usually exceeding 60% of the reflectivity, resulting in reverse ultrasonic interference.

[0042] In this embodiment, the acoustic impedance of the first reflective layer 2 is configured to be between the backing layer 3 and the piezoelectric layer 1, and the impedance difference between the first reflective layer 2 and the piezoelectric layer 1 is further configured to be lower than a first threshold value, which is generally one-half to one-quarter of the impedance value of the piezoelectric layer 1, that is, the acoustic impedance of the first reflective layer 2 is closer to the acoustic impedance of the piezoelectric layer 1. This configuration allows the reverse ultrasonic wave of the piezoelectric layer 1 to enter the backing layer 3 more.

[0043] The material of the first reflective layer 2 is aluminum, aluminum alloy or other light metals, so that the first reflective layer 2 has both electrical and thermal conductivity. The electrical conductivity of the first reflective layer 2 can produce a shielding effect after being grounded, such as Figure 3 As shown, this is beneficial to reducing the noise of the ultrasonic transducer, thereby improving the signal-to-noise ratio and improving the performance of the ultrasonic transducer. The thermal conductivity of the first reflective layer 2 is beneficial to timely conduct the heat energy absorbed by the backing layer 3, and is also beneficial to conduct the heat generated by the piezoelectric layer 1, thereby helping to reduce the temperature of the ultrasonic transducer when in use.

[0044] In this embodiment, the impedance of the second reflecting layer 4 is higher than that of the backing layer 3, and the impedance difference between the second reflecting layer 4 and the backing layer 3 is higher than a second threshold value, which is usually more than ten times the impedance value of the backing layer 3, that is, the acoustic impedance of the second reflecting layer 4 is much higher than that of the backing layer 3, so that the reverse ultrasonic wave forms a higher reflectivity at the contact point between the second reflecting layer 4 and the backing layer 3, so that the reverse ultrasonic wave is reflected into the backing layer 3 again, so that the backing layer 3 can fully attenuate the reverse ultrasonic wave and convert it into heat energy absorption.

[0045] The material of the second reflective layer 4 is tungsten, tungsten carbide or tungsten metal compound, so that the second reflective layer 4 has both electrical and thermal conductivity. The electrical conductivity of the second reflective layer 4 can produce a shielding effect after the grounding wire, such as Figure 3 As shown, this is beneficial to reduce the noise of the ultrasonic transducer, thereby improving the signal-to-noise ratio and the performance of the ultrasonic transducer. The thermal conductivity of the second reflective layer 4 is beneficial to timely conduct the heat energy absorbed by the backing layer 3, thereby helping to reduce the temperature of the ultrasonic transducer when in use.

[0046] Compared with the conventional technology, the embodiment of the present invention enables the reverse ultrasonic wave generated on the back of the piezoelectric layer 1 to be reflected multiple times in the backing layer 3 by setting the first reflecting layer 2 and the second reflecting layer 4. Figure 4 As shown, the reverse ultrasonic wave is absorbed as much as possible by the backing layer 3, which effectively improves the absorption rate of the reverse ultrasonic wave and reduces the interference of the reverse ultrasonic wave on the forward ultrasonic wave. In addition, the heat energy generated by the ultrasonic transducer during operation can be conducted outward by means of the first reflecting layer 2 and the second reflecting layer 4, thereby effectively reducing the temperature of the ultrasonic transducer during use and increasing its service life.

[0047] Example 2 In this embodiment, the surface of the first reflective layer 2 and the backing layer 3 in contact with each other has a concavo-convex structure, and the surface of the second reflective layer 4 and the backing layer 3 in contact with each other has a concavo-convex structure, for example, the concavo-convex structure is configured as a zigzag structure, such as Figure 5 shown.

[0048] Of course, in other preferred embodiments, the concavo-convex structure can also be configured as a wavy structure. Or in other preferred embodiments, the concavo-convex structure can also be a plurality of protrusions arranged on the surface of the first reflective layer 2 and a plurality of grooves arranged on the surface of the backing layer 3, and of course, it can also be the other way around, with the protrusions arranged on the surface of the first reflective layer 2 and the grooves arranged on the surface of the backing layer 3.

[0049] Example 3 In this embodiment, the backing structure further includes a backing sub-layer 5 and a third reflective layer 6 which are sequentially stacked and arranged between the first reflective layer 2 and the backing layer 3 in a direction away from the piezoelectric layer 1. Figure 6 shown.

[0050] The material of the backing sublayer 5 can refer to the backing layer 3. The acoustic impedance of the third reflective layer 6 is higher than that of the backing layer 3 and the backing sublayer 5. Specifically, the third reflective layer 6 is configured as a medium acoustic impedance material, for example, the material of the third reflective layer 6 is configured as copper or a copper alloy. Generally, the acoustic impedance of the third reflective layer 6 is between the first reflective layer 2 and the second reflective layer 4.

[0051] Such arrangement enables the reverse ultrasonic wave to be further absorbed by the backing sublayer 5, thereby improving the absorption efficiency of the reverse ultrasonic wave.

[0052] Example 4 The embodiment of the present invention further provides an ultrasonic transducer, comprising a piezoelectric layer 1 and a backing structure as disclosed in the above embodiment, wherein the backing structure is connected to the back side of the piezoelectric layer 1, and the front side of the piezoelectric layer 1 is usually connected to a matching layer and a lens. Figure 7 , which is a schematic diagram of the structure of an ultrasonic transducer prepared based on the backing structure disclosed in Example 1; for example Figure 8 Shown is a schematic diagram of the structure of an ultrasonic transducer prepared based on the backing structure disclosed in Example 3.

[0053] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A backing structure for an ultrasonic transducer, the backing structure being connected to the back side of a piezoelectric layer, characterized in that: The backing structure comprises a first reflection layer (2), a backing layer (3) and a second reflection layer (4) which are stacked in sequence in a direction away from the piezoelectric layer (1); the impedance of the first reflection layer (2) is between the backing layer (3) and the piezoelectric layer (1), and the impedance difference between the first reflection layer (2) and the piezoelectric layer (1) is lower than a first threshold; the impedance of the second reflection layer (4) is higher than that of the backing layer (3), and the impedance difference between the second reflection layer (4) and the backing layer (3) is higher than a second threshold.

2. The backing structure for ultrasonic transducer according to claim 1, characterized in that: The surface where the first reflective layer contacts the backing layer has a concavo-convex structure, and / or the surface where the second reflective layer contacts the backing layer has a concavo-convex structure.

3. The backing structure for ultrasonic transducer according to claim 2, characterized in that: The concavo-convex structure is configured as a zigzag structure or a wavy structure.

4. The backing structure for ultrasonic transducer according to claim 1, characterized in that: The first reflective layer and the second reflective layer are both made of conductive material.

5. The backing structure for ultrasonic transducer according to claim 4, characterized in that: The first reflective layer and the second reflective layer are both grounded.

6. The backing structure for ultrasonic transducer according to claim 1, characterized in that: The first reflective layer and the second reflective layer are both made of heat-conducting materials.

7. The backing structure for ultrasonic transducer according to claim 1, characterized in that: The first threshold is one-half to one-quarter of the impedance value of the piezoelectric layer, and the second threshold is more than ten times the impedance value of the backing layer.

8. The backing structure for ultrasonic transducer according to claim 1, characterized in that: The backing structure further comprises a backing sublayer (5) and a third reflecting layer (6) which are stacked in sequence between the first reflecting layer (2) and the backing layer (3) in a direction away from the piezoelectric layer (1); the impedance of the third reflecting layer (6) is higher than that of the backing layer (3) and the backing sublayer (5), and the impedance of the third reflecting layer (6) is between that of the first reflecting layer (2) and the second reflecting layer (3).

9. The backing structure for ultrasonic transducer according to claim 8, characterized in that: The backing layer and the backing sublayer are the same.

10. An ultrasonic transducer, characterized in that: It comprises a piezoelectric layer and a backing structure as claimed in any one of claims 1 to 9, wherein the backing structure is connected to the back side of the piezoelectric layer.

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