WO2024130820A1 - 一种声学传感器声头及其制作方法 - Google Patents

一种声学传感器声头及其制作方法 Download PDF

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WO2024130820A1
WO2024130820A1 PCT/CN2023/073478 CN2023073478W WO2024130820A1 WO 2024130820 A1 WO2024130820 A1 WO 2024130820A1 CN 2023073478 W CN2023073478 W CN 2023073478W WO 2024130820 A1 WO2024130820 A1 WO 2024130820A1
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crystal
composite material
acoustic sensor
strip
piezoelectric
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PCT/CN2023/073478
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English (en)
French (fr)
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蒋子博
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上海怡英新材料科技有限公司
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Publication of WO2024130820A1 publication Critical patent/WO2024130820A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
    • G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
    • G01H11/08—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means using piezoelectric devices

Definitions

  • the invention relates to a sensor sound head, in particular to a method for manufacturing an acoustic sensor sound head, and belongs to the technical field of generating equipment.
  • Piezoelectric composite material is a sensor vibrator in a piezoelectric sensor. It is composed of a piezoelectric active material and a softer non-piezoelectric material to improve the electromechanical coupling coefficient and acoustic impedance of the sensor array.
  • the electromechanical coupling coefficient of the piezoelectric material is related to its length-to-thickness ratio or width-to-thickness ratio, the use of piezoelectric materials can maximize the use of the optimized length-to-thickness ratio or width-to-thickness ratio of the piezoelectric material without changing the size design of the vibrator.
  • piezoelectric crystal composite materials generally adopt the thickness vibration mode, that is, the polarization direction is consistent with the vibration direction.
  • this vibration mode has high machining performance and electromechanical coupling coefficient, it is not suitable for low-frequency transducers with a vibration frequency of less than 500KHz.
  • the main reasons are: 1. Polarization is difficult. The thickness of the piezoelectric crystal corresponding to a frequency less than 500KHz is greater than 3 mm, and the corresponding polarization voltage is greater than 1200V. This polarization voltage can easily cause the crystal to crack and locally overpolarize under a large electric field, permanently damaging the crystal. 2. Increase production costs. Crystals are expensive and positively correlated with volume.
  • relaxor ferroelectric crystals are symmetrical, so in addition to the d33 thickness vibration mode, there is also a d31 lateral vibration mode.
  • the use of relaxor ferroelectric crystal composites with lateral vibration modes solves the above two problems, that is, by using side polarization and vibration in the end direction. Without changing the difficulty of polarization and machining, composite materials and transducers with the same high electromechanical coupling coefficient are produced.
  • the purpose of the present invention is to provide an acoustic sensor head and a method for manufacturing the same in order to solve at least one of the above technical problems.
  • an acoustic sensor sound head comprising a sound head composed of a 2-2 type composite material and an electrode material, the frequency range of the sound head application is between 10kHz and 40MHz;
  • the 2-2 type composite material is composed of at least one piezoelectric crystal strip and at least one high molecular polymer strip;
  • the electrode material is covered on the piezoelectric crystal strip and the high molecular polymer strip in parallel, and the piezoelectric crystal strip and the high molecular polymer strip form a parallel circuit after being covered with the electrode material.
  • the piezoelectric crystal strip can be lead magnesium niobate-lead titanate crystal, lead indium niobate-lead magnesium niobate-lead titanate crystal, lead indium niobate-lead titanate crystal, lead zinc niobate-lead titanate crystal, lead titanate crystal, and the above crystals are doped with modified elements.
  • the long polymer strip is composed of a material with weak rigidity and strong viscosity, such as epoxy resin, silicone rubber, gel, etc.
  • the electrode surface of the piezoelectric crystal strip is the side surface of the crystal, the surfaces receiving and generating the maximum strain are the cross sections at both ends; and the length in the direction of the crystal side surface is at least twice the length in the direction.
  • the composite material can be formed by selecting a piezoelectric crystal whose upper and lower surfaces are crystal sides, and cutting or etching along the cross-sectional directions at both ends to obtain it.
  • the composite material can be formed by pouring a high molecular polymer into the grooves at both ends of the cross section, and then grinding it after solidification.
  • the 2-2 composite material can be formed by forming an electrode on the surface of the 2-2 composite material that has been ground by chemical plating, vacuum sputtering, silver brushing and curing.
  • the composite material can be formed by subjecting the composite material after obtaining the electrode to direct current or alternating current polarization.
  • the acoustic head can be formed by bonding the 2-2 composite material to the acoustic optimization layers such as the matching layer and the backing.
  • An acoustic sensor head the method for making the head comprises the following steps: A is a 2-2 type composite material composed of one or more piezoelectric crystal strips and one or more high molecular polymer strips; B. Covering the electrode material in parallel on the piezoelectric crystal strip and the high molecular polymer strip of the 2-2 composite material; C The 2-2 type composite material is bonded to the electrode material by bonding acoustic optimization layers such as a matching layer and a backing.
  • the present invention utilizes the symmetry of the maximum piezoelectric effect and electromechanical coupling effect in the end direction of the relaxor ferroelectric crystal polarized in the state of large length-to-thickness ratio and width-to-thickness ratio, processes such crystals, so that the piezoelectric sensor array has the form of a 2-2 type composite material in structure, which is suitable for underwater acoustic sensors with a frequency lower than 1 MHz, that is, vibrates along the side direction of the long strip of crystal, polarizes and collects electrical signals in the end face direction at 90 degrees thereto, and utilizes domain engineering means of size optimization and crystal orientation optimization in lateral vibration to achieve the purpose of optimizing the sensitivity and bandwidth of the transducer;
  • the polarization direction of the crystal is 90 degrees to the vibration direction, so that the thickness (T) direction of the crystal can be as small as possible within the design tolerance range, so that the polarization voltage is reduced, and the polarization quality and yield rate are improved.
  • the present invention has not sacrificed the piezoelectric properties of the crystal on the basis of greatly improving the machining performance and polarization efficiency of the low-frequency composite material.
  • the present invention introduces AC poling to polarize the crystal, that is, the unpolarized crystal is polarized with a controlled AC electric field instead of a traditional DC electric field to polarize the crystal composite material, so that its electromechanical coupling coefficient and piezoelectric effect are further improved.
  • FIG1 is a schematic diagram of the structure of a relaxor ferroelectric crystal according to the present invention
  • FIG2 is a schematic diagram of different vibration modes of a relaxor ferroelectric crystal of the present invention
  • FIG. 3 is a graph showing the relationship between the transverse vibration electromechanical coupling coefficient and the aspect ratio of the PMN-PT crystal of the present invention.
  • An acoustic sensor head comprising a head composed of a 2-2 composite material and an electrode material, wherein the frequency range of the acoustic head is between 10 kHz and 40 MHz;
  • the 2-2 type composite material is composed of at least one piezoelectric crystal strip and at least one high molecular polymer strip;
  • the electrode material is covered in parallel on the piezoelectric crystal strip and the high molecular polymer strip.
  • the piezoelectric crystal strip and the high molecular polymer strip form a parallel circuit after being covered with the electrode material.
  • the piezoelectric crystal strip can be lead magnesium niobate-lead titanate crystal, lead indium niobate-lead magnesium niobate-lead titanate crystal, lead indium niobate-lead titanate crystal, lead zinc niobate-lead titanate crystal, or lead titanate crystal, and the above crystals can be doped with modified elements.
  • the high molecular polymer strip is made of a material with weak rigidity and strong viscosity, such as epoxy resin, silicone rubber, gel, etc.
  • the electrode surface of the piezoelectric crystal strip is the side surface of the crystal, the surfaces receiving and generating the maximum strain are the cross sections at both ends; and the length in the direction of the crystal side surface is at least twice the length in the direction.
  • the 2-2 composite material can be formed by selecting a piezoelectric crystal whose upper and lower surfaces are crystal sides, and cutting or etching along the cross-sectional directions at both ends to obtain the crystal.
  • the 2-2 composite material can be formed by pouring a high molecular polymer into the grooves at both ends of the cross section that have been formed, and grinding it after curing.
  • the 2-2 composite material can be formed by forming an electrode on the surface of the 2-2 composite material that has been ground by chemical plating, vacuum sputtering, silver brushing and curing.
  • the 2-2 composite material can be formed by subjecting the composite material after obtaining an electrode to direct current or alternating current polarization.
  • the acoustic head can be formed by bonding the 2-2 composite material to the acoustic optimization layers such as the matching layer and the backing.
  • An acoustic sensor head the method for making the head comprises the following steps: A is a 2-2 type composite material composed of one or more piezoelectric crystal strips and one or more high molecular polymer strips; B. Covering the electrode material in parallel on the piezoelectric crystal strip and the high molecular polymer strip of the 2-2 composite material; C The 2-2 type composite material is bonded to the electrode material by bonding acoustic optimization layers such as a matching layer and a backing.
  • an acoustic sensor head taking relaxor ferroelectric crystal as an example, relaxor ferroelectric crystal is increasingly widely used in ultrasonic and acoustic imaging, ultrasonic and acoustic diagnosis and treatment, precision displacement and other scenarios due to its ultra-high piezoelectric constant, dielectric constant and electromechanical coupling coefficient.
  • commercial relaxor ferroelectric crystals include lead magnesium niobate-lead titanate (PMN-PT), lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT), lead indium niobate-lead titanate (PIN-PT), lead zincate-lead titanate (PZN-PT) and the above crystals doped with manganese, aluminum, cesium and samarium.
  • PMN-PT lead magnesium niobate-lead titanate
  • PIN-PMN-PT lead indium niobate-lead magnesium niobate-lead titanate
  • PIN-PT lead indium niobate-lead titanate
  • PZN-PT lead zincate-lead titanate
  • relaxor ferroelectric crystals are frequently used is ultrasonic imaging, where the frequency of use is in the range of 1 MHz to 40 MHz.
  • relaxor ferroelectric crystals usually use the thickness vibration mode of the crystal, namely the d33 vibration mode.
  • the thickness vibration mode the expansion and contraction direction of the crystal is the same as the perpendicular direction of the electrode. Since the speed of sound propagation in the crystal is about 4100 m/s, the crystal thickness that matches the ultrasonic application frequency is usually between 10 microns and 900 microns.
  • the industry usually uses crystals grown in the cross-sectional direction. The manufacturing method is to cut the wafer along the axial direction, and then perform semiconductor-like processes such as slicing, grinding, coating, polarization, and detection on the wafer to obtain the crystal required for making ultrasonic transducers.
  • the frequency of use is between 50KHz and 1MHz.
  • relaxor ferroelectric crystals use the transverse vibration mode of the crystal, i.e., the d31 vibration mode, in order to avoid the problem that the crystal cannot be fully polarized due to being too thick.
  • the transverse vibration mode the expansion and contraction direction of the crystal is at a 90-degree angle to the vertical direction of the electrode. Since the propagation speed of sound in the crystal is about 4100 m/s, the length (L) direction of the crystal that matches non-destructive testing or underwater sonar is usually between 0.9 mm and 80 mm. It is necessary to maximize the use of the high electromechanical coupling coefficient and piezoelectric coefficient of the crystal through crystal domain engineering and composite material technology to achieve the purpose of making high-end non-destructive testing and underwater sonar transducers.
  • the present invention needs to use a side wafer of a crystal grown in the side direction, and at the same time perform crystal orientation screening in the radial direction of the side wafer, so that the electrode of the crystal is perpendicular to the side direction (thickness T direction), and at the same time, the expansion direction of the crystal is maximized in the radial cross-sectional direction (length L direction), thereby making full use of the electromechanical coupling coefficient of the crystal.
  • the above is a domain engineering innovation of the crystal.
  • the length (L) to thickness (T) ratio of the crystal determines the size of the transverse electromechanical coupling coefficient of the crystal.
  • the electromechanical coupling coefficient k31 of the transverse vibration when the L:T ratio is equal to 2, the electromechanical coupling coefficient k31 of the transverse vibration is close to 90%; and when the L:T ratio is equal to 0.5, the electromechanical coupling coefficient k31 of the transverse vibration is close to 60%. If converted into transducer bandwidth, the bandwidth of the former is 2.25 times that of the latter. Therefore, when making a transducer sound head, a crystal strip with a length (L) to thickness (T) ratio greater than 2 should be used to improve the bandwidth of the transducer and the clarity of imaging. Based on the same principle, the higher the length (L) to width (W) ratio, the larger the bandwidth.
  • the present invention selects a wafer with a thickness T direction of ⁇ 011> for cutting or etching, so that the direction of the cutting or etching groove is along ⁇ 100>, that is, the cross-sectional (L) direction, and the ⁇ 0-11> direction radially perpendicular to the cross-sectional direction is the width (W) direction.
  • the present invention plates electrodes on the two vertical sides of the crystal (i.e., the side surfaces) and leads, and installs acoustic matching layers and acoustic backing on both sides of the two vertical sides of the cross section of the crystal (i.e., the cross-sectional surface) to further optimize the sensitivity and bandwidth of the acoustic transducer.
  • the piezoelectric effect of crystals is symmetrical, that is, according to the symmetry theory, after polarizing the crystal and applying an electric field in a certain direction, the efficiency of vibration in a certain direction is maximized (the main vibration direction).
  • the acoustic transducer working at a low frequency requires the size of its piezoelectric material to be higher in the vibration direction. The relationship between frequency and size is as follows:
  • d is the size of the piezoelectric material in the vibration direction
  • c is the sound velocity of the piezoelectric material
  • f is the application frequency.
  • the present invention chooses to use the crystal transverse vibration mode to design a crystal composite material for a low-frequency transducer, making full use of the processing bonus generated by the inconsistency between the vibration direction and the polarization direction, that is, polarizing in the direction that is easy to polarize, leaving enough size in the direction with the highest vibration efficiency, and finally optimizing the sensitivity and bandwidth of the transducer.

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  • General Physics & Mathematics (AREA)
  • Transducers For Ultrasonic Waves (AREA)

Abstract

一种声学传感器声头，包括由2-2型复合材料以及电极材料拼接组成的声头；2-2型复合材料由至少由1条以上压电晶体长条以及1条以上高分子聚合物长条组成；电极材料平行覆盖在压电晶体长条与高分子聚合物长条上。还公开了一种声学传感器声头制作方法。利用侧面方向极化的弛豫铁电晶体在较大长厚比和宽厚比的状态下，在端方向上出现极大压电效应和机电耦合效应的对称性，对此类晶体进行加工，使得压电传感器阵子在结构上出现2-2型复合材料的形态，适用于频率低于1MHz的水声传感器，沿着晶体长条形的侧面方向上振动，呈90度的端面方向上极化和收集电信号，利用横向振动中尺寸最优化和晶向最优化的畴工程手段，使换能器灵敏度与带宽达到最优化。

Description

一种声学传感器声头及其制作方法 技术领域
本发明涉及一种传感器声头，具体为一种制作声学传感器声头方法，属于发生设备技术领域。
 背景技术
压电复合材料是一种压电传感器中的传感器振子，它是由一种压电活性材料与一种较软的非压电材料组成，用于改善传感器阵子的机电耦合系数和声阻抗。当压电材料的机电耦合系数与其长厚比或者宽厚比相关时，压电材料的使用能够在不改变振子的尺寸设计的前提下最大限度地利用压电材料优化的长厚比或者宽厚比。
目前压电晶体复合材料普遍采用的是厚度振动模式，即极化方向与振动方向一致，该振动模式虽然有很高的机加工性能和机电耦合系数，但不适用于振动频率小于500KHz的低频率换能器使用。其原因主要是：一、极化困难。频率小于500KHz的对应的压电晶体厚度大于3毫米，对应的极化电压大于1200V，该极化电压极易引起晶体在大电场下的崩裂和局部过极化现象，永久损坏晶体。二、提高制作成本。晶体价格昂贵，并且与体积正相关。制作小于500KHz的复合材料需要选取大于4毫米的晶圆进行初加工，如果需求量不大那么分摊在每件复合材料上的成本就会很高。与普通压电材料不同的是，弛豫铁电晶体具有对称性，所以除了d33厚度振动模式之外，还有d31横向振动模式，使用横向振动模式的弛豫铁电晶体复合材料解决了以上两个问题，即采用侧面方向极化，在端面方向上振动，在不改变极化难度和机加工难度的基础上，制作机电耦合系数同样高的复合材料与换能器。
 发明内容
本发明的目的就在于为了解决上述至少一个技术问题而提供一种声学传感器声头及其制作方法。
本发明通过以下技术方案来实现上述目的：一种声学传感器声头，包括由2-2型复合材料以及电极材料拼接组成的声头，声头应用的频率范围在10kHz到40MHz之间；
2-2型复合材料由至少由1条以上压电晶体长条以及1条以上高分子聚合物长条组成；
电极材料平行覆盖在压电晶体长条与高分子聚合物长条上，压电晶体长条与高分子聚合物长条在覆盖电极材料后形成并联电路。
作为本发明再进一步的方案：压电晶体长条可以是铌镁酸铅－钛酸铅晶体、铌铟酸铅－铌镁酸铅－钛酸铅晶体、铌铟酸铅－钛酸铅晶体、铌锌酸铅－钛酸铅晶体、钛酸铅晶体，且以上晶体掺杂改性元素。
作为本发明再进一步的方案：高分子聚合物长条由环氧树脂、硅橡胶、凝胶等刚性弱、粘性强的物质构成。
作为本发明再进一步的方案：压电晶体长条的电极面为晶体侧面，接收与产生最大应变面为两端截面；且其晶体侧面方向上的长度为方向上的长度的至少2倍以上。
作为本发明再进一步的方案：2-2复合材料形成的方式可以为选择上下表面为晶体侧面的压电晶体，并且沿着两端截面方向进行切割或蚀刻获得。
作为本发明再进一步的方案：2-2复合材料形成的方式可以为在业已形成两端截面槽中灌入高分子聚合物，并且固化后研磨获得。
作为本发明再进一步的方案：2-2复合材料形成的方式可以在业已研磨行程的2-2复合材料表面通过化学镀膜、真空溅射、刷银固化等方式形成电极后获得。
作为本发明再进一步的方案：2-2复合材料形成的方式可以通过对在获得电极后的复合材料进行直流或者交流极化后获得。
作为本发明再进一步的方案：声头形成的方式可以通过将2-2复合材料与匹配层、背衬等声学优化层相粘接后获得。
一种声学传感器声头，声头的制作方法包括以下步骤：
A由1条以上压电晶体长条以及1条以上高分子聚合物长条组成2-2型复合材料；
B将电极材料平行覆盖在2-2型复合材料的压电晶体长条与高分子聚合物长条上；
C通过匹配层、背衬等声学优化层相粘接的方式将2-2型复合材料与电极材料粘接在一起。
本发明的有益效果是：本发明利用了侧面方向极化的弛豫铁电晶体在较大长厚比和宽厚比的状态下，在端方向上出现极大压电效应和机电耦合效应的对称性，对此类晶体进行加工，使得压电传感器阵子在结构上出现2-2型复合材料的形态，适用于频率低于1MHz的水声传感器，即沿着晶体长条形的侧面方向上振动，在与其呈90度的端面方向上极化和收集电信号，利用横向振动中尺寸最优化和晶向最优化的畴工程手段，达到使换能器灵敏度与带宽最优化的目的；
晶体的极化方向与振动方向呈90度，这样可以晶体的厚度（T）方向在设计承受范围内尽量小，令极化电压减小，提高了极化质量与成品率。其次，可以选择厚度较薄的晶元进行加工，而且可以使用多少选取多少，最大程度地节约了晶体，与此同时，横向振动的机电耦合系数k31并不低于厚度振动的机电耦合系数k33，因此本发明在大幅度改进低频复合材料机加工性能和极化效率的基础上，并没有牺牲晶体的压电性能，此外，本发明引入了交流极化（AC Poling）来极化晶体，即对未极化的晶体用控制的交流电场而非传统的直流电场来极化晶体复合材料，使得其机电耦合系数以及压电效应的进一步提高。
附图说明
图1为本发明弛豫铁电晶体结构示意图；
图2为本发明弛豫铁电晶体的不同振动模式示意图；
图3为本发明PMN-PT晶体横向振动机电耦合系数与长厚比关系图。
实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
实施例
一种声学传感器声头，包括由2-2型复合材料以及电极材料拼接组成的声头，所述声头应用的频率范围在10kHz到40MHz之间；
所述2-2型复合材料由至少由1条以上压电晶体长条以及1条以上高分子聚合物长条组成；
所述电极材料平行覆盖在压电晶体长条与高分子聚合物长条上，所述压电晶体长条与高分子聚合物长条在覆盖电极材料后形成并联电路。
在本发明实施例中，压电晶体长条可以是铌镁酸铅－钛酸铅晶体、铌铟酸铅－铌镁酸铅－钛酸铅晶体、铌铟酸铅－钛酸铅晶体、铌锌酸铅－钛酸铅晶体、钛酸铅晶体，且以上晶体可以掺杂改性元素。
在本发明实施例中，高分子聚合物长条由环氧树脂、硅橡胶、凝胶等刚性弱、粘性强的物质构成。
在本发明实施例中，压电晶体长条的电极面为晶体侧面，接收与产生最大应变面为两端截面；且其晶体侧面方向上的长度为方向上的长度的至少2倍以上。
在本发明实施例中，2-2复合材料形成的方式可以为选择上下表面为晶体侧面的压电晶体，并且沿着两端截面方向进行切割或蚀刻获得。
在本发明实施例中，2-2复合材料形成的方式可以为在业已形成两端截面槽中灌入高分子聚合物，并且固化后研磨获得。
在本发明实施例中，2-2复合材料形成的方式可以在业已研磨行程的2-2复合材料表面通过化学镀膜、真空溅射、刷银固化等方式形成电极后获得。
在本发明实施例中，2-2复合材料形成的方式可以通过对在获得电极后的复合材料进行直流或者交流极化后获得。
在本发明实施例中，声头形成的方式可以通过将2-2复合材料与匹配层、背衬等声学优化层相粘接后获得。
实施例
一种声学传感器声头，声头的制作方法包括以下步骤：
A由1条以上压电晶体长条以及1条以上高分子聚合物长条组成2-2型复合材料；
B将电极材料平行覆盖在2-2型复合材料的压电晶体长条与高分子聚合物长条上；
C通过匹配层、背衬等声学优化层相粘接的方式将2-2型复合材料与电极材料粘接在一起。
实施例
如图1至图2所示，一种声学传感器声头，以弛豫铁电晶体为例，弛豫铁电晶体由于其超高的压电常数、介电常数机电耦合系数，被越来越广泛地运用于超声和声学成像、超声和声学诊疗、精密位移等场景。目前，商业化的弛豫铁电晶体包括铌镁酸铅－钛酸铅（PMN-PT）、铌铟酸铅－铌镁酸铅－钛酸铅（PIN-PMN-PT）、铌铟酸铅－钛酸铅（PIN-PT）、锌酸铅－钛酸铅（PZN-PT）以及掺杂锰、铝、铯、钐素的以上晶体。
在弛豫铁电晶体频繁应用的领域之一：超声成像领域，其使用频率在1MHz到40MHz之间的范围内。弛豫铁电晶体作为压电传感材料，通常使用晶体的厚度振动模式，即d33振动模式。在厚度振动模式中，晶体的伸缩方向与电极的垂直方向相同。由于声音在晶体中的传播速度大约在4100 m/s，与超声应用频率相匹配的晶体厚度通常在10微米到900微米之间。针对该应用，业界通常使用截面方向生长的晶体。制作方式为沿轴向切割晶圆，再通过在晶圆上进行划片、研磨、镀膜、极化、检测等类半导体制程得到制作超声换能器所需要的晶体。
在弛豫铁电晶体频繁应用的其他领域：无损探伤或水底声纳领域，其使用频率在50KHz到1MHz之间的范围内。弛豫铁电晶体作为压电传感材料，为了避免出现晶体由于太厚而无法充分极化的问题，使用晶体的横向振动模式，即d31振动模式。在横向振动模式中，晶体的伸缩方向与电极的垂直方向呈90度夹角。由于声音在晶体中的传播速度大约在4100 m/s，与无损探伤或水底声纳相匹配的晶体长度（L）方向通常在0.9毫米到80毫米之间。需要通过晶体的畴工程和复合材料技术来最大限度地利用晶体较高的机电耦合系数和压电系数，以达到制作高端无损探伤和水底声纳换能器的目的。
针对该构想，如图3所示，本发明需要使用侧面方向生长的晶体侧面晶圆，同时在侧面晶圆的径向进行晶向筛选，使得晶体的电极与侧面方向（厚度T方向）垂直，同时晶体的伸缩方向在径向截面方向（长度L方向）上最大化，从而充分利用晶体的机电耦合系数。以上为晶体的畴工程创新。另一方面，在横向振动模式时，晶体的长（L）厚（T）比决定了晶体横向机电耦合系数的大小。譬如，当L：T比值等于2时，横向振动的机电耦合系数k31接近90%；而当L：T比值等于0.5时，横向振动的机电耦合系数k31接近60%。如果转换成换能器带宽，前者的带宽为后者的2.25倍。所以，在制作换能器声头时，应该使用长（L）厚（T）比大于2的晶体长条，从而提高换能器的带宽以及成像的清晰度。基于同样的原理，长（L）宽（W）比也是越高，带宽就越大。因此，本发明选择在厚度T方向为<011>的晶圆进行切割或者刻蚀，使得切割或者刻蚀开槽的方向沿着<100>即截面（L）方向，则在径向垂直于截面方向的〈0-11〉方向为宽度（W）方向。之后在槽中填入环氧树脂、硅橡胶、凝胶等刚性弱、粘性强的物质，再在截面方向的上下表面进行研磨或者抛光，得到了压电晶体长条与非压电物质彼此相邻排列而成的复合材料，使得其中的压电长条无论在长厚比上还是在长宽上比都得到了优化，最后在晶体复合材料的厚度（L）。
本发明在获得了复合材料之后，在晶体的侧面垂直两面（即侧面面）上镀上电极，并且引线，在晶体的截面垂直两面（即截面面）两侧分别安装声学匹配层与声学背衬，进一步优化声学换能器的灵敏度和带宽。
工作原理：晶体的压电效应具有对称性，即根据对称性理论，在一定方向给晶体极化和加电场后，在某一方向振动的效率最大化（主要振动方向）。利用这种原理，我们可以让晶体在我们希望其振动的方向上进行工作，并且设计换能器的感知方向。而低频工作的声学换能器的在振动方向上要求其压电材料的尺寸较高，频率与尺寸的关系如下：
其中，d是振动方向上的压电材料尺寸，c为压电材料的声速，f为应用频率。当材料性质基本恒定时，频率越低，振动方向上的尺寸越大。根据机加工的容易程度和极化的容易程度，本发明选择用晶体横向振动模式为低频换能器设计晶体复合材料，充分利用了振动方向与极化方向不一致产生的加工红利，即在容易极化的方向上极化，在振动效率最大的方向上留足尺寸，最终使得换能器灵敏度和带宽达到优化的效果。
对于本领域技术人员而言，显然本发明不限于上述示范性实施例的细节，而且在不背离本发明的精神或基本特征的情况下，能够以其他的具体形式实现本发明。因此，无论从哪一点来看，均应将实施例看作是示范性的，而且是非限制性的，本发明的范围由所附权利要求而不是上述说明限定，因此旨在将落在权利要求的等同要件的含义和范围内的所有变化囊括在本发明内。不应将权利要求中的任何附图标记视为限制所涉及的权利要求。
此外，应当理解，虽然本说明书按照实施方式加以描述，但并非每个实施方式仅包含一个独立的技术方案，说明书的这种叙述方式仅仅是为清楚起见，本领域技术人员应当将说明书作为一个整体，各实施例中的技术方案也可以经适当组合，形成本领域技术人员可以理解的其他实施方式。

Claims (10)

  1.  一种声学传感器声头，其特征在于：包括由2-2型复合材料以及电极材料拼接组成的声头，所述声头应用的频率范围在10kHz到40MHz之间；
    所述2-2型复合材料由至少由1条以上压电晶体长条以及1条以上高分子聚合物长条组成；
    所述电极材料平行覆盖在压电晶体长条与高分子聚合物长条上，所述压电晶体长条与高分子聚合物长条在覆盖电极材料后形成并联电路。
  2. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述压电晶体长条可以是铌镁酸铅－钛酸铅晶体、铌铟酸铅－铌镁酸铅－钛酸铅晶体、铌铟酸铅－钛酸铅晶体、铌锌酸铅－钛酸铅晶体、钛酸铅晶体，且以上晶体掺杂改性元素。
  3. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述高分子聚合物长条由环氧树脂、硅橡胶、凝胶等刚性弱、粘性强的物质构成。
  4. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述压电晶体长条的电极面为晶体侧面，接收与产生最大应变面为两端截面；且其晶体侧面方向上的长度为方向上的长度的至少2倍以上。
  5. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述2-2复合材料形成的方式可以为选择上下表面为晶体侧面的压电晶体，并且沿着两端截面方向进行切割或蚀刻获得。
  6. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述2-2复合材料形成的方式可以为在业已形成两端截面槽中灌入高分子聚合物，并且固化后研磨获得。
  7. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述2-2复合材料形成的方式可以在业已研磨形成的2-2复合材料表面通过化学镀膜、真空溅射、刷银固化等方式形成电极后获得。
  8. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述2-2复合材料形成的方式可以通过对在获得电极后的复合材料进行直流或者交流极化后获得。
  9. 根据权利要求1所述的一种声学传感器声头，其特征在于：所述声头形成的方式通过将2-2复合材料与匹配层、背衬声学优化层相粘接后获得。
  10. 一种基于权利要求1所述的一种声学传感器声头的制作方法，其特征在于：所述制作方法包括以下步骤：
    A由1条以上压电晶体长条以及1条以上高分子聚合物长条组成2-2型复合材料；
    B将电极材料平行覆盖在2-2型复合材料的压电晶体长条与高分子聚合物长条上；
    C通过匹配层、背衬等声学优化层相粘接的方式将2-2型复合材料与电极材料粘接在一起。
PCT/CN2023/073478 2022-12-20 2023-01-26 一种声学传感器声头及其制作方法 WO2024130820A1 (zh)

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