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WO2016138622A1 - 超声波换能器及其制造方法 - Google Patents

超声波换能器及其制造方法 Download PDF

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Publication number
WO2016138622A1
WO2016138622A1 PCT/CN2015/073517 CN2015073517W WO2016138622A1 WO 2016138622 A1 WO2016138622 A1 WO 2016138622A1 CN 2015073517 W CN2015073517 W CN 2015073517W WO 2016138622 A1 WO2016138622 A1 WO 2016138622A1
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Prior art keywords
layer
tuning
piezoelectric
piezoelectric layer
ultrasonic transducer
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PCT/CN2015/073517
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English (en)
French (fr)
Inventor
王文娟
周丹
欧阳波
莫建华
Original Assignee
深圳市理邦精密仪器股份有限公司
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Priority to PCT/CN2015/073517 priority Critical patent/WO2016138622A1/zh
Priority to US14/651,499 priority patent/US10134973B2/en
Publication of WO2016138622A1 publication Critical patent/WO2016138622A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
    • B06B1/067—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface which is used as, or combined with, an impedance matching layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
    • B06B1/0681—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface and a damping structure
    • B06B1/0685—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface and a damping structure on the back only of piezoelectric elements
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/05—Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
    • H10N30/871—Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes

Definitions

  • the invention belongs to the technical field of transducers, and in particular to an ultrasonic transducer and a method for manufacturing the ultrasonic transducer.
  • the existing ultrasonic transducer structure is as shown in FIG. 1 , and mainly includes a piezoelectric layer 101 , a matching layer 102 , a backing layer 103 , and an acoustic lens 104 (or an acoustic retarder).
  • the piezoelectric vibrator When the piezoelectric layer 101 is charged at both ends, the piezoelectric vibrator generates vibration and radiates the acoustic wave signal forward and backward respectively, and the forward radiated acoustic signal passes through the matching layer 102 and the acoustic lens 104 (or the acoustic retarder), and then a certain attenuation occurs into the detected object,
  • the post-radiated acoustic signal is mostly absorbed by the heavily attenuated backing layer 103 and is wasted in the form of thermal energy, so that the backward radiated sound waves are not effectively utilized.
  • the acoustic energy reflection coefficient R at the interface of the piezoelectric layer 101 and the backing layer 103 is:
  • Z p is the acoustic impedance of the piezoelectric layer and Z b is the acoustic impedance of the backing layer.
  • FIG. 2 is a time-domain and frequency-domain characteristic diagram of a conventional ultrasonic transducer structure simulation.
  • the Chinese patent proposes to add a layer of de-matching layer with relatively high acoustic impedance after the wafer, and the acoustic impedance can have an acoustic impedance between 40Mrayls and 120Mrayls to increase the forward ultrasonic energy.
  • the high acoustic impedance de-matching layer is mostly made of metal material. The metal material is not easy to cut in the array ultrasonic probe process, which is easy to damage the array cutting blade, and the acoustic impedance is increased on the rear surface of the wafer.
  • the high de-matching layer reflects most of the sound waves as a hard interface, and the thickness of the corresponding wafer is 1/4 wavelength. Compared with the soft interface of the ordinary backing, the thickness of the corresponding wafer is 1/2 wavelength, which is equivalent to the same operating frequency. Probe with solution matching Layer probes require thinner wafers and a thickness of 1/2, which adds to the difficulty of the process.
  • a post-efficiency layer with multiple layers of different acoustic impedance values is added after the wafer.
  • the post-efficiency layer of the invention is used more, and the acoustic impedance of the efficiency layer of each layer is successively decreased. To a certain extent, the complexity and instability of the process are increased, and the manufacturing difficulty is increased.
  • an ultrasonic transducer comprising:
  • a piezoelectric layer for radiating an acoustic wave signal forward or backward, wherein the piezoelectric layer is respectively plated with electrodes;
  • a matching layer disposed at a front end of the piezoelectric layer and configured to transmit a sound wave signal radiated forward;
  • a tuning layer disposed at a rear end of the piezoelectric layer, and the piezoelectric layer is located between the tuning layer and the matching layer;
  • a backing layer for absorbing an acoustic wave signal radiated backward from the piezoelectric layer and located on a side of the tuning layer facing away from the piezoelectric layer.
  • the acoustic impedance value Zt of the tuning layer, the acoustic impedance value Zb of the backing layer, and the acoustic impedance value Zp of the piezoelectric layer simultaneously satisfy the relationship:
  • the tuning layer has an acoustic impedance ranging from 1 to 4 MRayl.
  • the acoustic impedance value Zt of the tuning layer, the acoustic impedance value Zb of the backing layer, and the acoustic impedance value Zp of the piezoelectric layer simultaneously satisfy the relationship:
  • the tuning layer has an acoustic impedance of 40 to 110 MRayl.
  • the thickness of the tuning layer ranges from 1/5 to 4/5 wavelength, wherein the wavelength is determined by a ratio between a speed of sound of the tuning layer and an operating frequency of the tuning layer.
  • the thickness of the tuning layer is 1/2 wavelength or 1/4 wavelength.
  • the invention also provides a probe comprising an ultrasonic transducer, the ultrasonic transducer comprising:
  • a piezoelectric layer for radiating an acoustic wave signal forward or backward, wherein the piezoelectric layer is respectively plated with electrodes;
  • a matching layer disposed at a front end of the piezoelectric layer and configured to transmit a sound wave signal radiated forward;
  • a tuning layer disposed at a rear end of the piezoelectric layer, and the piezoelectric layer is located between the tuning layer and the matching layer;
  • a backing layer for absorbing an acoustic wave signal radiated backward from the piezoelectric layer and located on a side of the tuning layer facing away from the piezoelectric layer.
  • the probe is a Doppler probe, a one-dimensional array probe or a multi-dimensional surface array probe.
  • the invention also provides a method for manufacturing an ultrasonic transducer, comprising the following steps:
  • Polarization treatment providing a piezoelectric layer made of a piezoelectric material and plating electrodes on both sides of the piezoelectric layer, applying voltage to both sides of the piezoelectric layer to complete polarization;
  • Providing an acoustic layer respectively providing a matching layer and a tuning layer at the front end and the rear end of the piezoelectric layer;
  • a backing layer is disposed, and the backing layer is disposed on one side of the tuning layer such that the backing layer and the piezoelectric layer are disposed opposite to both sides of the tuning layer.
  • the matched matching layer and the piezoelectric layer are completely cut through and partially cut into the tuning layer.
  • the technical effect of the present invention relative to the prior art is to prevent a portion of the acoustic wave signal from entering the back by providing a tuning layer between the piezoelectric layer and the backing layer to effectively utilize the acoustic wave signal radiated backward by the piezoelectric layer.
  • the lining is attenuated in the form of thermal energy while utilizing the tuning
  • the layer tuned the pulse reverberation of the ultrasonic probe to improve the time domain response and frequency domain response of the ultrasonic transducer to some extent.
  • FIG. 1 is a schematic structural view of an ultrasonic transducer in the prior art
  • FIG. 2 is a schematic diagram of pulse echo spectrum simulation of the ultrasonic transducer structure of FIG. 1;
  • FIG. 3 is a schematic structural diagram of an ultrasonic transducer according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram showing the simulation of the overall effective acoustic impedance Z bprime of the back surface of the piezoelectric layer (including the tuning layer and the backing layer) of FIG. 3;
  • Figure 5 is a schematic view showing the acoustic energy reflection coefficient at the interface between the piezoelectric layer and the tuning layer in Figure 3;
  • FIG. 6 is a schematic diagram of a pulse echo spectrum simulation of the tuning layer having a thickness of 1/2 in FIG. 3;
  • FIG. 7 is a schematic diagram of a pulse echo spectrum simulation of the tuning layer having a thickness of 1/4 wavelength in FIG. 3;
  • FIG. 8 is a schematic diagram of a pulse echo spectrum simulation of the tuning layer having a thickness of 1/4 wavelength and using a high acoustic impedance backing layer;
  • FIG. 9 is a process flow diagram of a method for manufacturing an ultrasonic transducer according to an embodiment of the present invention.
  • Figure 10 is a schematic view of the front cutting process of Figure 9.
  • an ultrasonic transducer provided by an embodiment of the present invention includes:
  • the piezoelectric layer 10 radiates sound wave signals forward or backward, respectively, and the piezoelectric layer 10 is respectively plated with electrodes on both sides thereof;
  • a matching layer 20 disposed at the front end of the piezoelectric layer 10 and configured to transmit a sound wave signal radiated forward;
  • a tuning layer 40 disposed at a rear end of the piezoelectric layer 10, and the piezoelectric layer 10 is located between the tuning layer 40 and the matching layer 20;
  • the backing layer 50 is configured to absorb the acoustic wave signal radiated backward by the piezoelectric layer 10 and is located on a side of the tuning layer 40 facing away from the piezoelectric layer 10.
  • the ultrasonic transducer provided by the embodiment of the present invention provides a tuning layer 40 between the piezoelectric layer 10 and the backing layer 50 to effectively utilize the sound wave signal radiated backward by the piezoelectric layer 10, thereby preventing part of the acoustic wave signal from entering.
  • the backing layer 50 is attenuated in the form of thermal energy, while the tuning layer 40 is used to tune the pulse aftershock of the ultrasonic probe, thereby improving the time domain response and the frequency domain response of the ultrasonic transducer to some extent.
  • the tuning layer 40 is bonded between the piezoelectric layer 10 and the backing layer 50, and the backing layer 50 is bonded to the tuning layer 40. It will be understood that the matching layer 20, the piezoelectric layer 10, the tuning layer 40 and the backing layer 50 are stacked from top to bottom.
  • the piezoelectric layer 10 is made of a piezoelectric material, such as a piezoelectric ceramic, a piezoelectric single crystal, a piezoelectric film, a piezoelectric composite, or the like, and combinations thereof, and preferably, zirconium and titanium. Lead-acid piezoelectric ceramics.
  • the electrodes plated on both sides of the piezoelectric layer 10 may be electrodes made of silver electrodes, copper electrodes, gold electrodes or other materials.
  • the ultrasonic transducer can be widely used in the fields of medical diagnosis and non-destructive testing.
  • the ultrasonic transducer further includes an acoustic lens 30 for collecting the sound field, and is disposed on the opposite surfaces of the matching layer 20 from the piezoelectric layer 10, respectively.
  • the acoustic wave retardation layer 30 is bonded to the matching layer 20, the acoustic lens 30, the matching layer 20, the piezoelectric layer 10, the tuning layer 40 and the backing layer 50. Set up from top to bottom.
  • the acoustic lens 30 is used to concentrate the sound field to concentrate the acoustic wave energy at the focus and thereby narrow the beam width.
  • the acoustic lens 300 can be replaced by an acoustic retarder for thickness measurement.
  • tuning layer 40 and the backing layer 50 constitute an acoustic structure on the back side of the piezoelectric layer 10.
  • the effective acoustic impedance of the acoustic structure is defined as Z bprime , and Z bprime is expressed as:
  • the acoustic energy reflection coefficient R t of the piezoelectric layer 10 and the tuning layer 40 is:
  • Z p is the acoustic impedance of the piezoelectric layer 10
  • Z t is the acoustic impedance of the tuning layer 40
  • Z b is the acoustic impedance of the backing layer 50
  • l is the thickness of the tuning layer 40
  • v is the speed of sound of the tuning layer 40
  • f is the operating frequency of the tuning layer 40.
  • the tuning layer 40 between the piezoelectric layer 10 and the backing layer 50 to form an integral acoustic structure on the positive side of the signal of the piezoelectric layer 10, effective for the overall acoustic structure.
  • the acoustic impedance Z bprime is calculated according to the above formula, and combined with the calculation formula of the acoustic energy reflection coefficient R t , the acoustic energy reflection coefficient at the interface between the piezoelectric layer 10 and the tuning layer 40 can be obtained.
  • Z bprime is numerically equal to Z b
  • R t is the same as R
  • Z bprime When the thickness of the tuning layer 40 When it is 1/4 wavelength, Z bprime can be expressed as The acoustic impedance value Z t of the tuning layer 40, the acoustic impedance value Z b of the backing layer 50, and the acoustic impedance value Z p of the piezoelectric layer 10 simultaneously satisfy the relationship:
  • R t is greater than R, which can improve the reflection coefficient of the forward radiated sound energy of the transducer.
  • the inequality also indicates that the low-impedance tuning layer 40 or the high-impedance backing layer 50 can be used to improve the sensitivity of the transducer.
  • the time-frequency domain response of the tuning probe is preferably such that the acoustic impedance Z t of the tuning layer 40 ranges from 1-4 Mrayls and the acoustic impedance Z b of the backing layer 50 ranges from 10 to 30 MRayls.
  • the acoustic impedance of the tuning layer 40 and the backing layer 50 can also be adjusted simultaneously.
  • the inequality further enhances the acoustic energy reflection coefficient and improves the sensitivity of the transducer.
  • Z bprime can be expressed as The acoustic impedance value Z t of the tuning layer 40, the acoustic impedance value Z b of the backing layer 50, and the acoustic impedance value Z p of the piezoelectric layer 10 simultaneously satisfy the relationship:
  • R t is greater than R, which indicates that the high impedance tuning layer 40 or the low impedance backing layer 50 can be employed to increase the sensitivity of the transducer, tuning the time-frequency domain response of the probe, preferably, the tuning layer 40
  • the acoustic impedance Z t ranges from 40 to 110 Mrayls and the acoustic impedance Z b of the backing layer 50 is 1-3 MRayls.
  • the acoustic impedance of the tuning layer 40 and the backing layer 50 can also be adjusted simultaneously.
  • the inequality further enhances the acoustic energy reflection coefficient and improves the sensitivity of the transducer.
  • the curve of the effective acoustic impedance Z bprime and the reflection coefficient R t with the thickness of the tuning layer 40 is simulated.
  • the acoustic impedance Z t of the tuning layer 40 is 2Mrayls
  • the acoustic impedance Z of the backing layer 50 is assumed.
  • b takes 2, 5, 10, 30 Mrayls in turn
  • Figure 4 shows the simulated Z bprime size as a function of the thickness of the tuning layer 40
  • Figure 5 shows the acoustic energy reflection coefficient. With the thickness of the tuning layer 40.
  • the KLM (Krimholtz-Leadom-Mettaei) equivalent circuit model is applied, which is the application of transmission line theory to analyze and study the performance of ultrasonic transducers.
  • the time domain and frequency domain characteristics of the transducer. 6 is a simulation result of the ultrasonic transducer structure of the present invention, after loading a layer 1/2 wavelength thickness tuning layer 40 between the piezoelectric layer 10 and the backing layer 50, and FIG. 2, the ultrasonic wave of the present invention
  • the sensitivity of the transducer is increased by 1.61 dB, and the bandwidth of -6 dB is increased by 11.3%.
  • FIG. 7 is a structure of the ultrasonic transducer of the present invention, and a thickness of 1/4 is applied between the piezoelectric layer 10 and the backing layer 50.
  • the sensitivity of the ultrasonic transducer of the present invention is improved by 2.19 dB and the -6 dB bandwidth is decreased by 5.4%;
  • FIG. 8 is based on the simulation of FIG.
  • the backing layer 50 replaces the low-resistance backing layer 50, and the simulation results show that the sensitivity is again increased by 0.58 dB, which is consistent with the variation of the reflection curve shown in FIG. Figure 2, Figure 6 ⁇ 8 simulation data comparison analysis shown in the following table:
  • Table 1 Figure 2 are simulation data comparison analysis table after loading different thickness low-impedance tuning layers
  • a tuning layer 40 having a thickness ranging from 1/5 to 4/5 is applied between the piezoelectric layer 10 and the backing layer 50,
  • the tuning layer 40 has a thickness of 1/2 wavelength or 1/4 wavelength, and both can modulate the echo characteristics and the spectral shape of the ultrasonic transducer.
  • the wavelength is determined by the ratio between the speed of sound of the tuning layer 40 and the operating frequency of the tuning layer 40.
  • the tuning layer 40 has an acoustic impedance ranging from 1 to 4 MRayl, but is not limited thereto; by setting the thickness of the tuning layer 40, Preferably, the thickness of the tuning layer 40 ranges from 1/5 to 4/5 wavelength, but is not limited to the thickness range; by setting the impedance ratio of the tuning layer 40 and the backing layer 50, preferably, the tuning layer 40
  • the impedance ratio to the backing layer 50 ranges from 0.01 to 1.0; the effective reflection coefficient of the back surface of the piezoelectric layer 10 is tuned to improve the sensitivity, and the superposition of the amplitude and phase of the waveform on the back side of the piezoelectric layer 10 is tuned to Improve the time domain response and frequency domain response curve of the ultrasonic transducer.
  • the acoustic impedance of the matching layer 20 is between the acoustic impedance of the piezoelectric layer 10 and the tuning layer 40, and the acoustic impedance of the tuning layer 40 is much smaller than the voltage.
  • the tuning layer 40 employs a low impedance acoustic material that differs greatly from the acoustic impedance of the piezoelectric layer 10, such as epoxy, plastic, and composites filled with low density powder.
  • the acoustic impedance of the piezoelectric layer 10 is largely different from the acoustic impedance of the human body, the acoustic signal is not propagated to the human body, but the acoustic impedance of the matching layer 20 is between the piezoelectric layer 10 and the tuning layer 40. Between the acoustic impedances, the matching layer 20 acts as a transition, and can effectively transmit the sound waves generated by the piezoelectric layer 10 into the human body, thereby better detecting the human tissue signal.
  • the matching layer 20 is at least one layer.
  • the matching layer 20 may be two or more layers.
  • the acoustic impedance of the matching layer 20 is smaller than the acoustic impedance of the piezoelectric layer 10, and the acoustic impedance of the matching layer 20 of each layer gradually decreases away from the piezoelectric layer 10.
  • Embodiments of the present invention also provide a probe including the above ultrasonic transducer.
  • the probe is a Doppler probe, a one-dimensional array probe or a multi-dimensional surface array probe.
  • the probe of the present invention is suitable for use in probes in the fields of medical and industrial non-destructive testing, for example, including a single piezoelectric layer, a bi-piezoelectric layer 10, a one-dimensional array, and a two-dimensional array of ultrasonic probes.
  • an embodiment of the present invention further provides a method for manufacturing an ultrasonic transducer, comprising the following steps:
  • a polarization treatment providing a piezoelectric layer 10 made of a piezoelectric material and plating electrodes on both sides of the piezoelectric layer 10, applying a voltage to both sides of the piezoelectric layer 10 to complete polarization;
  • a matching layer 20 and a tuning layer 40 are respectively disposed at the front end and the rear end of the piezoelectric layer 10;
  • a backing layer 50 is disposed, and the backing layer 50 is disposed on the side of the tuning layer 40 such that the backing layer 50 and the piezoelectric layer 10 are disposed opposite to both sides of the tuning layer 40. It can be understood that the backing layer is filled on the side of the tuning layer 40 and solidified to form the backing layer 50, the lens glue is poured on the side of the matching layer 20, and finally the encapsulation process is performed.
  • the method for manufacturing an ultrasonic transducer prevents the partial sound wave by effectively providing the sound wave signal radiated backward by the piezoelectric layer 10 by providing the tuning layer 40 between the piezoelectric layer 10 and the backing layer 50.
  • the signal entering the backing layer 50 is attenuated in the form of thermal energy while the tuning layer 40 is used to tune the pulse aftershock of the ultrasonic probe to improve the time domain response and frequency domain response of the ultrasonic transducer to some extent.
  • the introduction of the tuning layer 40 also plays a better supporting and fixing effect on the piezoelectric layer 10, which is beneficial to improving the front cutting process of the probe and suppressing the crosstalk phenomenon of the probe, especially in There are significant advantages in the manufacture of convex array probes.
  • the electrodes formed on both sides of the piezoelectric layer 10 may be silver electrodes, copper electrodes, gold electrodes or electrodes made of other materials.
  • the piezoelectric layer 10 is made of a piezoelectric material, and since the piezoelectric material itself does not have a piezoelectric effect, the piezoelectric layer 10 needs to be polarized for this purpose.
  • an oil bath polarization method is adopted, that is, a DC high voltage is applied to both sides of the piezoelectric layer 10 to form an electrode at a certain temperature, and after the polarization treatment is finished, two according to the polarization direction
  • the electrodes on the side are labeled as signal ground and signal positive, respectively, for transmitting and receiving ultrasonic waves.
  • the method for manufacturing the ultrasonic transducer further includes the steps of:
  • the acoustic lens 30 is disposed on the side of the matching layer 20 such that the acoustic lens 30 and the piezoelectric layer 10 are disposed opposite to each other on the matching layer 20 .
  • the acoustic lens 30 can be replaced by an acoustic component such as an acoustic retarder.
  • the acoustic impedance of the matching layer 20 of each layer is smaller than the acoustic impedance of the piezoelectric layer 10, and gradually decreases from the piezoelectric layer 10.
  • the acoustic impedance of the matching layer 20 is between the acoustic impedance of the piezoelectric layer 10 and the tuning layer 40, and the acoustic impedance of the tuning layer 40 is much smaller than the acoustic impedance of the piezoelectric layer 10.
  • the tuning layer 40 adopts the same A low-impedance acoustic material having a large difference in acoustic impedance of the piezoelectric layer 10, such as an epoxy resin, a plastic, and a composite material filled with a low-density powder. Since the acoustic impedance of the piezoelectric layer 10 is largely different from the acoustic impedance of the human body, the acoustic signal is not propagated to the human body, but the acoustic impedance of the matching layer 20 is between the piezoelectric layer 10 and the tuning layer 40. Between the acoustic impedances, the matching layer 20 acts as a transition, and can effectively transmit the sound waves generated by the piezoelectric layer 10 into the human body, thereby better detecting the human tissue signal.
  • the matching layer 20 acts as a transition, and can effectively transmit the sound waves generated by the piezoelectric layer 10 into the human body, thereby better detecting the human tissue signal.
  • the matched matching layer 20 and the piezoelectric layer 10 are completely cut through and partially cut into the tuning layer 40.
  • the tuning layer 40 functions to fix and support the piezoelectric layer 10, and is cut along the matching layer 20 toward the side of the tuning layer 40 during the pre-cut process, and the The matching layer 20 and the piezoelectric layer 10 are completely cut through and partially cut into the tuning layer 40 to effectively suppress crosstalk of adjacent array elements and improve the performance of the ultrasonic transducer.
  • the number of the array elements is 64, 96, 128 or other quantities. It can be understood that a complete piezoelectric layer 10 is cut into a plurality of array elements by mechanical cutting or the like during the cutting process, and the number of array elements may be 64, 96 or 128, and the number of the array elements may also be Is the other quantity.
  • the cut array elements are arranged in a linear arrangement or a curved curvature.
  • the array elements after cutting can be linearly arranged to obtain a line array probe or a phased array probe.
  • the convex array probe can be obtained by arcing in a certain curvature, and the tuning layer 40 is utilized when cutting the piezoelectric layer 10.
  • the piezoelectric layer 10 is fixed and supported, and is easier to process into a convex array probe, and can effectively suppress the crosstalk between the array elements and improve the performance of the ultrasonic transducer.

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Abstract

一种超声波换能器，包括：压电层（10），用于向前或者向后辐射声波信号，压电层（10）的两侧分别镀设有电极；匹配层（20），设置于压电层（10）前端并用于传送向前辐射的声波信号；调谐层（40），设置于压电层（10）后端，且压电层（10）位于调谐层（40）与匹配层（20）之间；背衬层（50），用于吸收压电层（10）向后辐射的声波信号，位于调谐层（40）的背离压电层（10）的一侧。还包括该超声波换能器的制造方法。采用该超声波换能器及其制造方法，在压电层（10）和背衬层（50）之间设置调谐层（40），利用压电层（10）向后辐射的声波信号，避免部分声波信号进入背衬层（50）以热能的形式被衰减，并利用调谐层（40）调谐超声探头的脉冲余响从而改善超声波换能器的时域响应和频域响应。

Description

超声波换能器及其制造方法 技术领域
本发明属于换能器的技术领域，尤其涉及一种超声波换能器以及该超声波换能器的制造方法。
背景技术
现有的超声波换能器结构如图1所示，主要包括压电层101、匹配层102、背衬层103和声透镜104(或者声延迟片)，当在压电层101两端加载电信号时，压电振子产生振动并分别向前向后辐射声波信号，向前辐射的声信号经过匹配层102与声透镜104(或者声延迟片)后，发生一定的衰减进入被检测对象，向后辐射的声波信号则大部分被衰减较大的背衬层103吸收，以热能的形式被浪费，因而向后辐射的声波未能得到有效的利用。在该超声波换能器结构中，压电层101一背衬层103界面处的声能反射系数R为：
Figure PCTCN2015073517-appb-000001
其中，Zp为所述压电层的声阻抗，Zb为所述背衬层的声阻抗。
图2为传统超声波换能器结构模拟的时域和频域特性图。
中国专利(申请号为：ZL201210339333.8)中提出在晶片后加入一层声阻抗相对高的解匹配层，其声阻抗可具有40Mrayls到120Mrayls之间的声阻抗，以增加向前发射超声波能量，改善超声波换能器性能，但是高声阻抗解匹配层大部分采用金属材料，金属材料在阵列式超声探头工艺中为不易切割材料，容易损伤阵列切割的刀片，而且在晶片后表面增加声阻抗较高的解匹配层作为硬质界面反射大部分声波，对应晶片的厚度为1/4波长，相比于普通背衬的软质界面，对应晶片的厚度为1/2波长，相当于同样工作频率的探头，采用解匹配 层的探头要求晶片更薄，厚度为原来的1/2，这些都增加了工艺的难度。
中国专利(申请号为：ZL201310002007.2)中提出在晶片后加入多层不同声阻抗值的后效率层，该发明采用的后效率层数偏多，并且各层后效率层声阻抗依次递减，在一定程度上增加了工艺的复杂性及不稳定性，制造难度加大。
技术问题
本发明的目的在于提供一种超声波换能器，通过在压电层和背衬层之间设置调谐层，旨在解决现有技术中超声波换能器向后辐射的声波信号不能充分利用的技术问题。
发明内容
本发明是这样实现的，一种超声波换能器，包括：
压电层，用于向前或者向后辐射声波信号，所述压电层的两侧分别镀设有电极；
匹配层，设置于所述压电层前端并用于传送向前辐射的声波信号；
调谐层，设置于所述压电层后端，且所述压电层位于所述调谐层与所述匹配层之间；
背衬层，用于吸收所述压电层向后辐射的声波信号，并位于所述调谐层之背离所述压电层的一侧。
进一步地，所述调谐层的声阻抗值Zt、所述背衬层的声阻抗值Zb和所述压电层的声阻抗值Zp同时满足关系式：
0<Zt<Zb以及
Figure PCTCN2015073517-appb-000002
进一步地，所述调谐层的声阻抗范围为1～4MRayl。
进一步地，所述调谐层的声阻抗值Zt、所述背衬层的声阻抗值Zb和所述压电层的声阻抗值Zp同时满足关系式：
Zt>Zb>0以及
Figure PCTCN2015073517-appb-000003
进一步地，所述调谐层的声阻抗为40～110MRayl。
进一步地，所述调谐层的厚度范围为1/5～4/5波长，其中，所述波长由所述调谐层的声速和所述调谐层的工作频率之间的比值确定。
进一步地，所述调谐层的厚度为1/2波长或者1/4波长。
本发明还提供了一种探头，包括超声波换能器，所述超声波换能器包括：
压电层，用于向前或者向后辐射声波信号，所述压电层的两侧分别镀设有电极；
匹配层，设置于所述压电层前端并用于传送向前辐射的声波信号；
调谐层，设置于所述压电层后端，且所述压电层位于所述调谐层与所述匹配层之间；
背衬层，用于吸收所述压电层向后辐射的声波信号，并位于所述调谐层之背离所述压电层的一侧。
进一步地，所述探头为多普勒探头、一维阵列探头或者多维面阵列探头。
本发明还提供了一种超声波换能器的制造方法，包括以下步骤：
极化处理，提供由压电材料制成的压电层并对所述压电层的两侧镀电极，对所述压电层两侧施加电压完成极化；
设置声学层，在所述压电层的前端和后端分别设置匹配层和调谐层；
切割声学层，沿所述匹配层朝向所述调谐层对所述声学层切割，所形成的切槽深入所述调谐层，以切割形成多个独立的阵元；
设置背衬层，在所述调谐层一侧设置所述背衬层以使所述背衬层与所述压电层相对设置于所述调谐层两侧。
进一步地，在切割声学层的步骤中，切割后的所述匹配层和所述压电层均完全切穿并部分切入所述调谐层。本发明相对于现有技术的技术效果是：通过在压电层和背衬层之间设置调谐层，以有效利用所述压电层向后辐射的声波信号，避免部分声波信号进入所述背衬层以热能的形式被衰减，同时利用该调谐 层调谐超声探头的脉冲余响，从而在一定程度上改善超声波换能器的时域响应和频域响应。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对本发明实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有技术中超声波换能器的结构示意图；
图2为图1中超声波换能器结构的脉冲回波频谱仿真示意图；
图3为本发明实施例提供的超声波换能器的结构示意图；
图4为图3中压电层背面(包括调谐层和背衬层)整体有效声阻抗Zbprime的仿真示意图；
图5为图3中在压电层与调谐层界面处的声能反射系数示意图；
图6是图3中调谐层厚度为1/2波长的脉冲回波频谱仿真示意图；
图7是图3中调谐层厚度为1/4波长的脉冲回波频谱仿真示意图；
图8是图3中调谐层厚度为1/4波长且采用高声阻抗背衬层的脉冲回波频谱仿真示意图；
图9本发明实施例提供的超声波换能器的制造方法的工艺流程图；
图10为图9中前切加工工艺示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
请参照图3，本发明实施例提供的超声波换能器包括：
压电层10，分别向前或者向后辐射声波信号，所述压电层10的两侧分别镀设有电极；
匹配层20，设置于所述压电层10前端并用于传送向前辐射的声波信号；
调谐层40，设置于所述压电层10后端，且所述压电层10位于所述调谐层40与所述匹配层20之间；
背衬层50，用于吸收所述压电层10向后辐射的声波信号，并位于所述调谐层40之背离所述压电层10的一侧。
本发明实施例提供的超声波换能器通过在压电层10和背衬层50之间设置调谐层40，以有效利用所述压电层10向后辐射的声波信号，避免部分声波信号进入所述背衬层50以热能的形式被衰减，同时利用该调谐层40调谐超声探头的脉冲余响，从而在一定程度上改善超声波换能器的时域响应和频域响应。
在该实施例中，所述调谐层40粘接于所述压电层10与所述背衬层50之间，所述背衬层50与所述调谐层40粘接。可以理解地，所述匹配层20、所述压电层10、所述调谐层40和所述背衬层50由上至下层叠设置。
在该实施例中，所述压电层10由压电材料制成，例如，压电陶瓷、压电单晶、压电薄膜、压电复合材料等及其组合，优选地，可以是锆钛酸铅压电陶瓷。
在该实施例中，在所述压电层10两侧所镀电极可以是银电极、铜电极、金电极或者其他材料制成的电极。
在该实施例中，所述超声波换能器可以广泛应用于医学诊断以及无损检测等领域。
在该实施例中，所述超声波换能器还包括声透镜30，用于聚集声场，并与所述压电层10分别设置于所述匹配层20之相背对的两表面上。可以理解地，所述声波延迟层30与所述匹配层20粘接，所述声透镜30、所述匹配层20、所述压电层10、所述调谐层40和所述背衬层50由上至下层叠设置。所述声透镜30用于聚集声场以使焦点处声波能量集中进而收窄波束宽度。优选地，该声透镜300可以由声延迟片替代，用于厚度测量。
进一步地，所述调谐层40与所述背衬层50构成位于所述压电层10背面的声学结构，该声学结构的有效声阻抗定义为Zbprime，Zbprime表示为：
Figure PCTCN2015073517-appb-000004
所述压电层10与所述调谐层40的声能反射系数Rt为：
Figure PCTCN2015073517-appb-000005
其中，Zp为所述压电层10的声阻抗，Zt为所述调谐层40的声阻抗，Zb为所述背衬层50的声阻抗，l为所述调谐层40的厚度，v为所述调谐层40的声速以及f为所述调谐层40的工作频率。
可以理解，通过在所述压电层10和所述背衬层50之间设置所述调谐层40以在所述压电层10的信号正极侧形成整体声学结构，对于该整体声学结构的有效声阻抗Zbprime按上述公式计算得出，并结合声能反射系数Rt的计算公式可以得到所述压电层10与所述调谐层40界面处的声能反射系数。
根据上述公式推导可以得到以下结论：
(1)当所述调谐层40的厚度
Figure PCTCN2015073517-appb-000006
时，即1/2波长时，Zbprime在数值上和Zb相等，Rt与R相同；
(2)当所述调谐层40的厚度
Figure PCTCN2015073517-appb-000007
时，即1/4波长时，Zbprime可以表示为
Figure PCTCN2015073517-appb-000008
所述调谐层40的声阻抗值Zt、所述背衬层50的声阻抗值Zb和所述压电层10的声阻抗值Zp同时满足关系式：
0<Zt<Zb以及
Figure PCTCN2015073517-appb-000009
如果满足
Figure PCTCN2015073517-appb-000010
不等式时，Rt大于R，可以提高换能器向前辐射声能的反射系数，该不等式同时也表明，可以采用低阻抗调谐层40或者采用高阻抗背衬 层50来改善换能器的灵敏度，调谐探头的时频域响应，优选地，所述调谐层40的声阻抗Zt范围为1-4Mrayls以及所述背衬层50的声阻抗Zb范围为10-30MRayls。与此同时，也可以同时调整调谐层40和背衬层50的声阻抗，满足
Figure PCTCN2015073517-appb-000011
不等式，进一步增强声能反射系数，提高换能器的灵敏度。优选地，
Figure PCTCN2015073517-appb-000012
可以远远小于Zp。
(3)当所述调谐层40的厚度
Figure PCTCN2015073517-appb-000013
时，即1/4波长时，Zbprime可以表示为
Figure PCTCN2015073517-appb-000014
所述调谐层40的声阻抗值Zt、所述背衬层50的声阻抗值Zb和所述压电层10的声阻抗值Zp同时满足关系式：
Zt>Zb>0以及
Figure PCTCN2015073517-appb-000015
如果满足
Figure PCTCN2015073517-appb-000016
不等式时，Rt大于R，该不等式表明，可以采用高阻抗调谐层40或者低阻抗背衬层50来提高换能器的灵敏度，调谐探头的时频域响应，优选地，所述调谐层40的声阻抗Zt范围为40-110Mrayls以及所述背衬层50的声阻抗Zb为1-3MRayls。与此同时，也可以同时调整调谐层40和背衬层50的声阻抗，满足
Figure PCTCN2015073517-appb-000017
不等式，进一步增强声能反射系数，提高换能器的灵敏度。优选地，
Figure PCTCN2015073517-appb-000018
可以远远大于Zp。
结合上述理论分析，对有效声阻抗Zbprime和反射系数Rt随调谐层40厚度变化的曲线进行了仿真，仿真中不妨假设调谐层40声阻抗Zt为2Mrayls，背衬层50的声阻抗Zb依次取2、5、10、30Mrayls，图4为仿真的Zbprime大小随调谐层40厚度变化曲线，图5为声能反射系数
Figure PCTCN2015073517-appb-000019
随调谐层40厚度规律。
接下来采用KLM(Krimholtz-Leadom-Mettaei)等效电路模型，即应用传输线的理论对超声波换能器性能进行分析和研究，结合该模型可以模拟超声波 换能器的时域和频域特性。图6为本发明中超声波换能器结构，在压电层10和背衬层50之间加载一层厚度为1/2波长厚度调谐层40后的仿真结果，相对图2，本发明的超声波换能器的灵敏度提高了1.61dB，-6dB带宽提高了11.3％；图7为本发明中超声波换能器结构，在压电层10和背衬层50之间加载一层厚度为1/4波长厚度的调谐层40后的仿真结果，相对图2，本发明的超声波换能器的灵敏度提高了2.19dB，-6dB带宽下降了5.4％；图8在图7仿真的基础上，将高阻背衬层50替代低阻背衬层50，仿真结果表明灵敏度再次提高0.58dB，这和图4表示的反射曲线变化规律也是一致的。图2、图6～8仿真数据对比分析如下表所示：
表1图2、图6～8为加载不同厚度低阻抗调谐层后的仿真数据比较分析表
Figure PCTCN2015073517-appb-000020
综上仿真数据可知，在本发明提供的超声波换能器结构中，通过在压电层10和背衬层50之间加载一层厚度范围为1/5～4/5波长的调谐层40，优选地，该调谐层40的厚度为1/2波长或1/4波长，均能调谐超声波换能器的回波特性及频谱形状。其中，波长由所述调谐层40的声速和所述调谐层40的工作频率之间比值确定。
另外，采用低阻抗的调谐层40，通过设置调谐层40的声阻抗，优选地，所述调谐层40的声阻抗范围为1～4MRayl，但不限于此范围；通过设置调谐层40的厚度，优选地，所述调谐层40的厚度范围为1/5～4/5波长，但不限于此厚度范围；通过设置调谐层40和背衬层50的阻抗比值，优选地，所述调谐层40 与所述背衬层50的阻抗比值范围为0.01～1.0；调谐所述压电层10背面的有效反射系数以提升灵敏度，以及调谐所述压电层10背面的波形幅值和相位的叠加以改善超声波换能器的时域响应和频域响应曲线。
请参照图3，进一步地，所述匹配层20的声阻抗介于所述压电层10和所述调谐层40的声阻抗之间，且所述调谐层40的声阻抗远小于所述压电层10的声阻抗。可以理解，所述调谐层40采用与所述压电层10的声阻抗差异较大的低阻抗声学材料，例如，环氧树脂、塑料以及填充低密度粉末的复合材料。由于所述压电层10的声阻抗与人体的声阻抗差异较大，不利于声波信号向人体传播，但是所述匹配层20的声阻抗介于所述压电层10和所述调谐层40的声阻抗之间，所述匹配层20起到过渡作用，能有效地将所述压电层10产生的声波传导到人体内，进而更好地检测人体组织信号。
进一步地，所述匹配层20至少为一层。所述匹配层20可以是两层或者两层以上。所述匹配层20的声阻抗小于所述压电层10的声阻抗，且各层所述匹配层20的声阻抗远离所述压电层10逐渐减小。
本发明实施例还提供了一种探头，包括上述超声波换能器。
进一步地，所述探头为多普勒探头、一维阵列探头或者多维面阵列探头。
本发明的探头适用于医疗和工业无损探伤等领域的探头，例如，包括单压电层、双压电层10、一维阵列以及二维阵列的超声波探头。
请参照图3、图9和图10，本发明实施例还提供了一种超声波换能器的制造方法，包括以下步骤：
极化处理，提供由压电材料制成的压电层10并对所述压电层10的两侧镀电极，对所述压电层10两侧施加电压完成极化；
设置声学层，在所述压电层10的前端和后端分别设置匹配层20和调谐层40；
切割声学层，沿所述匹配层20朝向所述调谐层40对所述声学层切割，所形成的切槽60深入所述调谐层40，以切割形成多个独立的阵元；
设置背衬层50，在所述调谐层40一侧设置所述背衬层50以使所述背衬层50与所述压电层10相对设置于所述调谐层40两侧。可以理解，在所述调谐层40一侧灌注背材胶并固化形成背衬层50，在所述匹配层20一侧灌注透镜胶，最后进行封装处理。
本发明实施例提供的超声波换能器的制造方法通过在压电层10和背衬层50之间设置调谐层40，以有效利用所述压电层10向后辐射的声波信号，避免部分声波信号进入所述背衬层50以热能的形式被衰减，同时利用该调谐层40调谐超声探头的脉冲余响，从而在一定程度上改善超声波换能器的时域响应和频域响应。从工艺实施的角度上来说，所述调谐层40的引入对所述压电层10也起到较好的支撑固定作用，有利于改善探头的前切加工工艺，抑制探头串扰现象，特别是在凸阵探头的制造中具有明显的优势。
在该实施例中，在所述压电层10两侧形成的电极可以是银电极、铜电极、金电极或者其他材料制成的电极。
在该实施例中，所述压电层10由压电材料制成，由于压电材料本身不具备压电效应，为此需要对所述压电层10进行极化处理。在极化处理过程中采用油浴极化法，即在一定的温度下，将直流高压加载到所述压电层10两侧以形成电极，待极化处理结束后，根据极化方向将两侧的电极分别标记为信号地极和信号正极，以用于发射和接收超声波。
进一步地，所述超声波换能器的制造方法还包括步骤：
设置声透镜30，在所述匹配层20一侧设置所述声透镜30以使所述声透镜30与所述压电层10相对设置于所述匹配层20两侧。优选地，该声透镜30可以由声延迟片等声学部件替代。
进一步地，在设置声学层的步骤中，所述各层所述匹配层20的声阻抗小于所述压电层10的声阻抗，且从所述压电层10开始逐渐减小。所述匹配层20的声阻抗介于所述压电层10和所述调谐层40的声阻抗之间，且所述调谐层40的声阻抗远小于所述压电层10的声阻抗。可以理解，所述调谐层40采用与所 述压电层10的声阻抗差异较大的低阻抗声学材料，例如，环氧树脂、塑料以及填充低密度粉末的复合材料。由于所述压电层10的声阻抗与人体的声阻抗差异较大，不利于声波信号向人体传播，但是所述匹配层20的声阻抗介于所述压电层10和所述调谐层40的声阻抗之间，所述匹配层20起到过渡作用，能有效地将所述压电层10产生的声波传导到人体内，进而更好地检测人体组织信号。
请参照图10，进一步地，在切割声学层的步骤中，切割后的所述匹配层20和所述压电层10均完全切穿并部分切入所述调谐层40。可以理解，所述调谐层40起固定和支撑所述压电层10的作用，在实施前切工艺的过程中，沿所述匹配层20朝向所述调谐层40一侧切割，并将所述匹配层20和所述压电层10完全切穿且部分切入所述调谐层40，以有效抑制相邻阵元件的串扰现象，改善超声波换能器的性能。
请参照图10，进一步地，在切割声学层的步骤中，所述阵元的数量为64个、96个、128个或者其他数量。可以理解，在切割过程中采用机械切割等方式将一片完整的压电层10切割成多个阵元，阵元的数量可以是64个、96个或者128个，所述阵元的数量也可以是其他数量。
进一步地，在切割声学层的步骤中，切割后的阵元按照线性排列或者曲率弧形排列。可以理解，切割后的阵元按照线性排列可以得到线阵探头或者相控阵探头，按照一定曲率弧形排列可以得到凸阵探头，在切割所述压电层10时，利用所述调谐层40对所述压电层10起到固定和支撑作用，较易于加工成凸阵探头，而且可以有效抑制阵元间的串扰现象，提高超声波换能器的性能。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (11)

  1. 一种超声波换能器，其特征在于，包括：
    压电层，用于向前或者向后辐射声波信号，所述压电层的两侧分别镀设有电极；
    匹配层，设置于所述压电层前端并用于传送向前辐射的声波信号；
    调谐层，设置于所述压电层后端，且所述压电层位于所述调谐层与所述匹配层之间；
    背衬层，用于吸收所述压电层向后辐射的声波信号，并位于所述调谐层之背离所述压电层的一侧。
  2. 如权利要求1所述的超声波换能器，其特征在于，所述调谐层的声阻抗值Zt、所述背衬层的声阻抗值Zb和所述压电层的声阻抗值Zp同时满足关系式：
    0<Zt<Zb以及
    Figure PCTCN2015073517-appb-100001
  3. 如权利要求2所述的超声波换能器，其特征在于，所述调谐层的声阻抗范围为1～4MRayl。
  4. 如权利要求1所述的超声波换能器，其特征在于，所述调谐层的声阻抗值Zt、所述背衬层的声阻抗值Zb和所述压电层的声阻抗值Zp同时满足关系式：
    Zt>Zb>0以及
    Figure PCTCN2015073517-appb-100002
  5. 如权利要求4所述的超声波换能器，其特征在于，所述调谐层的声阻抗为40～110MRayl。
  6. 如权利要求1所述的超声波换能器，其特征在于，所述调谐层的厚度范围为1/5～4/5波长，其中，所述波长由所述调谐层的声速和所述调谐层的工作频率之间的比值确定。
  7. 如权利要求6所述的超声波换能器，其特征在于，所述调谐层的厚度为1/2波长或者1/4波长。
  8. 一种探头，其特征在于，包括超声波换能器，所述超声波换能器包括：
    压电层，用于向前或者向后辐射声波信号，所述压电层的两侧分别镀设有电极；
    匹配层，设置于所述压电层前端并用于传送向前辐射的声波信号；
    调谐层，设置于所述压电层后端，且所述压电层位于所述调谐层与所述匹配层之间；
    背衬层，用于吸收所述压电层向后辐射的声波信号，并位于所述调谐层之背离所述压电层的一侧。
  9. 如权利要求8所述的探头，其特征在于，所述探头为多普勒探头、一维阵列探头或者多维面阵列探头。
  10. 一种超声波换能器的制造方法，其特征在于，包括以下步骤：
    极化处理，提供由压电材料制成的压电层并对所述压电层的两侧镀电极，对所述压电层两侧施加电压完成极化；
    设置声学层，在所述压电层的前端和后端分别设置匹配层和调谐层；
    切割声学层，沿所述匹配层朝向所述调谐层对所述声学层切割，所形成的切槽深入所述调谐层，以切割形成多个独立的阵元；
    设置背衬层，在所述调谐层一侧设置所述背衬层以使所述背衬层与所述压电层相对设置于所述调谐层两侧。
  11. 如权利要求10所述的超声波换能器的制造方法，其特征在于，在切割声学层的步骤中，切割后的所述匹配层和所述压电层均完全切穿并部分切入所述调谐层。
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