CN115644922A - An ultrasonic probe using a gradient matching layer - Google Patents
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Abstract
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Translated fromChinese技术领域technical field
本发明涉及超声探头技术领域，具体为一种使用梯度匹配层的超声探头。The invention relates to the technical field of ultrasonic probes, in particular to an ultrasonic probe using a gradient matching layer.
背景技术Background technique
水声探测、无损检测、医用超声图像诊断中使用的超声换能器，其主要的性能指标是灵敏度和带宽，灵敏度越高，探测距离越远，带宽越宽，图像的分辨率越高，为提高超声换能器的灵敏度和带宽，常采用以下技术：The main performance indicators of ultrasonic transducers used in underwater acoustic detection, non-destructive testing, and medical ultrasonic image diagnosis are sensitivity and bandwidth. The higher the sensitivity, the longer the detection distance, the wider the bandwidth, and the higher the image resolution. To improve the sensitivity and bandwidth of ultrasonic transducers, the following techniques are often used:
1、使用高性能的压电材料，使发射和接收的能力增强，带宽增加，如：采用用具有超高压电系数的压电陶瓷、压电单晶如PMN-PT等，采用具有高机电耦合系数的2-2/1-3型等特殊结构的压电陶瓷或单晶的复合材料；1. Use high-performance piezoelectric materials to enhance the ability of transmitting and receiving, and increase the bandwidth, such as: using piezoelectric ceramics with ultra-high piezoelectric coefficients, piezoelectric single crystals such as PMN-PT, etc., using high electromechanical Piezoelectric ceramics or single crystal composite materials with special structures such as 2-2/1-3 coupling coefficients;
2、使用多层声阻抗匹配层技术，降低传输过程中的损耗，拓宽带宽，在2MHz～10MHz的医用诊断超声探头中，现一般使用2层、3层匹配层，少数探头使用4层甚至5层匹配层，而在更高频的超声探头中，因加工难度的关系，一般采用一层或两层匹配层；2. Use multi-layer acoustic impedance matching layer technology to reduce the loss in the transmission process and widen the bandwidth. In the medical diagnostic ultrasound probes of 2MHz to 10MHz, 2 or 3 matching layers are generally used, and a few probes use 4 or even 5 layers. One-layer matching layer, and in higher-frequency ultrasonic probes, one or two matching layers are generally used due to the difficulty of processing;
目前一维阵列式超声探头的基本结构所示，从内往外，分别是声吸收层(背衬)、压电材料、声匹配层和声透镜，压电材料的两面有电极，由线路引出，压电材料的声阻抗都比较高，压电陶瓷或单晶的声阻抗一般在35MRayl左右，压电或单晶复合材料的声阻抗一般在20MRayl左右，而人体组织的声阻抗一般在1.5MRayl，根据声功率透射公式，声阻抗的巨大差异导致声信号的透射率特别低，为提高声信号的透射效率，我们引入了声阻抗匹配层，一般，声阻抗匹配层是四分之一波长厚度的均匀的材质，理论计算表明：在不考虑匹配层衰减的情况下，最佳的单层匹配层，其透射率为32.3％，双层匹配层最高透射效率为45.3％，三层为54.6％，10层为79.9％，完美匹配层为100％；The basic structure of the current one-dimensional array ultrasonic probe is shown. From the inside to the outside, there are sound absorbing layer (backing), piezoelectric material, acoustic matching layer and acoustic lens. There are electrodes on both sides of the piezoelectric material, which are drawn out from the line. The acoustic impedance of piezoelectric materials is relatively high. The acoustic impedance of piezoelectric ceramics or single crystals is generally around 35MRayl, the acoustic impedance of piezoelectric or single crystal composite materials is generally around 20MRayl, and the acoustic impedance of human tissue is generally 1.5MRayl. According to the acoustic power transmission formula, the huge difference in acoustic impedance leads to a particularly low transmittance of the acoustic signal. In order to improve the transmission efficiency of the acoustic signal, we introduce an acoustic impedance matching layer. Generally, the acoustic impedance matching layer is a quarter wavelength thick Uniform material, theoretical calculations show that: without considering the attenuation of the matching layer, the best single-layer matching layer has a transmittance of 32.3%, the highest transmission efficiency of the double-layer matching layer is 45.3%, and the highest transmission efficiency of the three-layer is 54.6%. 79.9% for 10 layers and 100% for a perfectly matched layer;
为进一步提高透射率，人们发明了声阻抗连续变化的超材料，一般是在基材上加工出紧密排列的圆锥形的孔，填充不同密度的材料，这样其声阻抗在厚度方向成指数形式连续变化，如说明书附图图4所示，这种锥孔复合法制成的声阻抗匹配层，能比多层的匹配层结构的透射率高很多，可达到92％以上，这种声阻抗梯度超材料，阻抗从十几MRayl变化到几MRayl，在低频的水声单阵元换能器中已经得到应用，也有采用沉降法获得声阻抗连续变化的梯度材料：通过选用声阻抗值不同的填料以及调节填料在匹配层中的体积分数，通过离心沉降法处理，使填料粒子在聚合物基底中的浓度在垂直方向上呈梯度分布，再经过固化就可以得到声阻抗梯度匹配层材料，为进一步提高匹配效果，也可以在压电材料和声阻抗梯度材料之间再加一层均匀的高阻抗的匹配材料，匹配层的厚度跟波长相关，总的厚度一般为四分之一波长到2倍波长，即，工作频率低，波长长，匹配层的厚度就厚，加工起来容易，工作频率高，波长短，匹配层的厚度就薄，加工起来难度就大，匹配层中存在衰减，故匹配层的厚度不宜过厚，匹配层中的声速一般为2000～3000m/s，水声换能器一般工作在几百KHz，所以，水声换能器的匹配层中波长为mm级，而医用超声换能器一般在2MHz～10MHz，匹配层中的波长为0.1mm级；In order to further improve the transmittance, metamaterials with continuously changing acoustic impedance have been invented. Generally, closely arranged conical holes are processed on the substrate and filled with materials of different densities, so that the acoustic impedance is exponentially continuous in the thickness direction. Changes, as shown in Figure 4 of the attached drawing of the specification, the acoustic impedance matching layer made by the tapered hole composite method can have a much higher transmittance than the multi-layer matching layer structure, which can reach more than 92%. Materials, whose impedance varies from a dozen MRayl to several MRayl, have been used in low-frequency underwater acoustic single-element transducers. There are also gradient materials that use the sedimentation method to obtain continuous changes in acoustic impedance: by selecting fillers with different acoustic impedance values and Adjust the volume fraction of the filler in the matching layer, and through the centrifugal sedimentation method, the concentration of the filler particles in the polymer substrate is distributed in a gradient in the vertical direction, and then the material of the acoustic impedance gradient matching layer can be obtained after curing. Matching effect, you can also add a layer of uniform high-impedance matching material between the piezoelectric material and the acoustic impedance gradient material. The thickness of the matching layer is related to the wavelength, and the total thickness is generally 1/4 wavelength to 2 times the wavelength. , that is, if the working frequency is low and the wavelength is long, the thickness of the matching layer will be thick, which is easy to process. If the working frequency is high and the wavelength is short, the thickness of the matching layer will be thin, and it will be difficult to process. There is attenuation in the matching layer, so the matching layer The thickness of the matching layer should not be too thick, the sound velocity in the matching layer is generally 2000 ~ 3000m/s, and the underwater acoustic transducer generally works at several hundred KHz, so the wavelength in the matching layer of the underwater acoustic transducer is mm level, while the medical ultrasonic transducer The transducer is generally in the range of 2MHz to 10MHz, and the wavelength in the matching layer is 0.1mm;
匹配层一般由环氧胶中添加一些不同密度的金属粉或者金属氧化物粉，如钨粉、氧化铝粉、氧化铋粉，以及玻璃微珠等，按照一定的比例混合而成，有着特定的声阻抗(密度和声速)，其声衰减比较小，匹配层的加工方法有浇铸法、旋涂法、离心法等；The matching layer is generally made by adding some metal powder or metal oxide powder of different densities to epoxy glue, such as tungsten powder, alumina powder, bismuth oxide powder, and glass microspheres, etc., mixed according to a certain proportion, with a specific Acoustic impedance (density and sound velocity), its sound attenuation is relatively small, the processing methods of the matching layer include casting method, spin coating method, centrifugal method, etc.;
而目前为提高超声换能器的灵敏度，压电材料的性能提升已经快达到极限，新型的压电材料不断的投入到使用中，1-3、2-2或其他构型的复合材料已得到普遍应用，新的突破方向将在匹配层的理论和工艺上，理论上，多层声学匹配层相对单层匹配层可以在更大程度上提高换能器的带宽，并且可以使换能器的声波透射效率进一步提高，但实际上，每增加一层声学匹配层，都带来了工艺上的很多问题，例如：粘合难度加大、存在气泡的概率提高、厚度增加等，这些影响因素会导致相对带宽无法达到理论值，而且灵敏度可能还有下降，故现有医用超声探头多采用2层或3层匹配层，极少数采用4层，现有的声阻抗连续变化的梯度材料，主要有两种方法：锥孔复合法、离心沉降法，锥孔复合法，能够精确控制阻抗沿厚度方向的变化曲线和匹配层的厚度，加工尺度范围都是mm级，圆锥直径在0.1mm级，适合于水声频率范围，特别是单阵元的水声换能器，而医用超声和检查超声常用的频率范围内需要的0.1mm级厚度的匹配层，这种厚度下该加工方法的难度特别大，均匀性差，不适合做成阵列式阵元换能器的匹配层，故而不适用，离心沉降法，工艺过程简单，但工艺参数复杂，跟很多因数相关，其声阻抗不能精细控制，无法做到声阻抗沿着声学匹配层厚度方向呈特定曲线的连续变化，也无法对声阻抗进行方便、灵活地调节，而且，厚度较厚，不适合医用超声和检测超声需要的薄片型场合，故现有的技术，很难将医用超声和检测超声换能器匹配层的透射率提高到60％以上，灵敏度和带宽难以再提高。At present, in order to improve the sensitivity of ultrasonic transducers, the performance improvement of piezoelectric materials has almost reached the limit. New piezoelectric materials are continuously put into use, and composite materials with 1-3, 2-2 or other configurations have been obtained. Generally applied, the new breakthrough direction will be in the theory and technology of the matching layer. In theory, the multi-layer acoustic matching layer can improve the bandwidth of the transducer to a greater extent than the single-layer matching layer, and can make the transducer’s The sound wave transmission efficiency is further improved, but in fact, each additional layer of acoustic matching layer brings many problems in the process, such as: increased difficulty in bonding, increased probability of bubbles, increased thickness, etc. These influencing factors will As a result, the relative bandwidth cannot reach the theoretical value, and the sensitivity may decrease. Therefore, most of the existing medical ultrasound probes use 2 or 3 matching layers, and very few use 4 layers. The existing gradient materials with continuously changing acoustic impedance mainly include Two methods: cone compound method, centrifugal sedimentation method, and cone compound method can precisely control the change curve of impedance along the thickness direction and the thickness of the matching layer. The processing scale range is mm level, and the diameter of the cone is 0.1mm. In the frequency range of underwater acoustics, especially for single-array underwater acoustic transducers, the matching layer with a thickness of 0.1 mm is required in the frequency range commonly used in medical ultrasound and inspection ultrasound. The processing method is particularly difficult under this thickness. , the uniformity is poor, it is not suitable to make the matching layer of the array element transducer, so it is not applicable, the centrifugal sedimentation method, the process is simple, but the process parameters are complicated, related to many factors, its acoustic impedance cannot be finely controlled, and it cannot be done The acoustic impedance changes continuously along the thickness direction of the acoustic matching layer with a specific curve, and the acoustic impedance cannot be adjusted conveniently and flexibly. Moreover, the thickness is thick, which is not suitable for the sheet-type occasions required by medical ultrasound and detection ultrasound. With some technologies, it is difficult to increase the transmittance of the matching layer of medical ultrasound and detection ultrasound transducers to more than 60%, and it is difficult to improve the sensitivity and bandwidth.
发明内容Contents of the invention
本发明提供一种使用梯度匹配层的超声探头，可以有效解决上述背景技术中提出现有的技术，很难将医用超声和检测超声换能器匹配层的透射率提高到60％以上，灵敏度和带宽难以再提高的问题。The present invention provides an ultrasonic probe using a gradient matching layer, which can effectively solve the problem that the existing technology proposed in the above-mentioned background technology is difficult to increase the transmittance of the matching layer of medical ultrasonic and detection ultrasonic transducers to more than 60%, and the sensitivity and It is difficult to improve the bandwidth problem.
为实现上述目的，本发明提供如下技术方案：一种使用梯度匹配层的超声探头，该超声探头包括压电材料和匹配层；To achieve the above object, the present invention provides the following technical solutions: an ultrasonic probe using a gradient matching layer, the ultrasonic probe includes a piezoelectric material and a matching layer;
所述匹配层设置在压电材料的前表面上，其中，电极形成在压电材料的前表面和后表面上；The matching layer is disposed on the front surface of the piezoelectric material, wherein electrodes are formed on the front and rear surfaces of the piezoelectric material;
所述压电材料和匹配层被加工成单阵元、多阵元的一维或二维阵列；The piezoelectric material and the matching layer are processed into a one-dimensional or two-dimensional array of single array elements or multiple array elements;
所述匹配层设置为单层匹配层，以替代目前的多层匹配层来应用在超声换能器上。The matching layer is set as a single-layer matching layer to replace the current multi-layer matching layer to be applied on the ultrasonic transducer.
根据上述技术方案，该单层匹配层主要通过声阻抗梯度材料的制备方法来进行制作，具体包括如下制作步骤：According to the above technical solution, the single-layer matching layer is mainly produced by the preparation method of the acoustic impedance gradient material, which specifically includes the following production steps:
S1、混合；S1, mixing;
S2、脱泡；S2, defoaming;
S3、成型；S3, forming;
S4、固化。S4, curing.
根据上述技术方案，所述S1中，混合是指将制备的原材料混合物按照成分的变化顺序进行编号，并将原材料进行充分搅拌混合处理，其中原材料包括以环氧树脂为基底，加入金属粉末、金属氧化物粉末和玻璃微珠，环氧树脂为E41、E51及同类型的其他牌号；According to the above technical solution, in the above-mentioned S1, mixing refers to numbering the prepared raw material mixture according to the change order of the components, and fully stirring and mixing the raw materials, wherein the raw materials include epoxy resin as the base, adding metal powder, metal Oxide powder and glass beads, epoxy resin E41, E51 and other grades of the same type;
金属粉末、金属氧化物粉末主要为钨粉、氧化钨粉、氧化铋粉等高密度粉末；而低密度的氧化铝粉末等则适用于中低声阻抗场合，粉末选择超细的。Metal powder and metal oxide powder are mainly high-density powders such as tungsten powder, tungsten oxide powder, and bismuth oxide powder; while low-density alumina powder is suitable for medium and low acoustic impedance occasions, and the powder is selected to be ultra-fine.
根据上述技术方案，所述S2中，脱泡主要用于消除原材料混合物在混合过程中所产生的气泡，其中，具体脱泡方式可选用抽真空脱泡、离心脱泡、离心加真空脱泡多种脱泡方式中的一种，需要注意的是，不同的脱泡和成型方法，对声阻抗会产生影响。According to the above technical scheme, in the above-mentioned S2, the defoaming is mainly used to eliminate the bubbles generated during the mixing process of the raw material mixture, wherein, the specific defoaming methods can be vacuum defoaming, centrifugal defoaming, centrifugal plus vacuum defoaming, etc. One of the defoaming methods, it should be noted that different defoaming and molding methods will have an impact on the acoustic impedance.
根据上述技术方案，所述S3中，成型是指采用流延处理的方式来使混合脱泡后的原料制成薄膜，并控制该成型后薄膜的厚度为25um。According to the above technical solution, in the above-mentioned S3, forming refers to adopting the method of tape casting to make the mixed and defoamed raw materials into a film, and the thickness of the formed film is controlled to be 25um.
根据上述技术方案，在流延成型处理时，20-100nm氧化铝粉末和环氧胶E51的混合物，粘度适中，方便流延成型，流延设备的厚度控制精度可达±2um，厚度可从10um到200um，调整好流延设备的刀高，流延带缓慢移动，混合物在流延带上形成一层薄膜，经60度缓慢加热，成半固化的流延膜，将流延膜按照0-9的顺序进行编号，流延膜宽度可设置成100mm宽或者200mm宽，并通过流延设备的切刀来按照编号顺序将流延膜裁成方片。According to the above technical scheme, during the tape casting process, the mixture of 20-100nm alumina powder and epoxy glue E51 has moderate viscosity and is convenient for tape casting. The thickness control accuracy of the tape casting equipment can reach ±2um, and the thickness can be from 10um To 200um, adjust the knife height of the casting equipment, the casting belt moves slowly, the mixture forms a thin film on the casting belt, and slowly heats at 60 degrees to form a semi-cured casting film. Numbering in the order of 9, the width of the cast film can be set to 100mm wide or 200mm wide, and the cast film is cut into square pieces according to the numbering order by the cutter of the casting equipment.
根据上述技术方案，所述S4中，固化是指对流延生产的流延膜进行固化处理，在流延膜裁切为方片后，在规定的时间范围内，在叠层机下按照顺序，将方片按照编号0-9的顺序依次叠合起来，依序去掉流延带。According to the above technical solution, in the above S4, curing refers to curing the cast film produced by casting. After the cast film is cut into square pieces, within the specified time range, under the laminator in order, Stack the squares in the order of numbers 0-9, and remove the casting tapes in sequence.
根据上述技术方案，在S4中，叠合时，叠层机提供真空和一定温度，叠好的薄膜刚好250um，然后在室温下固化后，在烘箱里继续固化，在未完全固化时用叠层机叠合，其附着力足够，完全固化后，经过高低温循环试验，没有脱开，中间也没有气泡，质量可靠；According to the above technical solution, in S4, when stacking, the laminator provides vacuum and a certain temperature, and the stacked film is just 250um, and then after curing at room temperature, it continues to cure in the oven. Machine lamination, its adhesion is sufficient, after complete curing, after high and low temperature cycle test, no disengagement, no bubbles in the middle, reliable quality;
将固化完成后的方片在划片机上划成指定的尺寸，即可用在换能器的制作上，在制作时，方片在跟压电材料叠合时，高氧化铝质量分数的那一面须紧靠着压电材料，制作成功的64阵元相控阵探头，相对于常规的2层匹配层探头，其性能大为提高。Divide the cured square sheet into the specified size on the dicing machine, which can be used in the production of transducers. During the production, when the square sheet is laminated with the piezoelectric material, the side with a high alumina mass fraction The 64-element phased array probe must be close to the piezoelectric material, and its performance is greatly improved compared with the conventional 2-layer matching layer probe.
根据上述技术方案，所述S1中，在制备混合物时，需要配比不同质量组分的混合物，并进行性能测试，在测试过程中，随着氧化铝粉末在混合物中比例的增加，固化后的材料的密度增大，声速缓慢增加，v＝3000m/s，声阻抗呈线性增加，从纯环氧树脂E51的3.1MRayl到6.7MRayl；According to the above-mentioned technical scheme, in the above-mentioned S1, when preparing the mixture, it is necessary to proportion the mixture of different quality components, and perform a performance test. During the test, as the proportion of alumina powder in the mixture increases, the cured The density of the material increases, the speed of sound increases slowly, v=3000m/s, and the acoustic impedance increases linearly, from 3.1MRayl of pure epoxy resin E51 to 6.7MRayl;
其线性拟合方程为：Z＝7.2X+3.1(公式1)，其中，Z为声阻抗，X为氧化铝的质量分数。Its linear fitting equation is: Z=7.2X+3.1 (Formula 1), where Z is the acoustic impedance, and X is the mass fraction of alumina.
根据上述技术方案，最佳透射率计算的结果表明，理想的匹配层的声阻抗随距离变化的曲线呈指数衰减，采用多层结构，每层内部性能均匀一致，多层叠合起来，就是声阻抗准连续的梯度材料；According to the above technical scheme, the calculation results of the optimal transmittance show that the curve of the ideal matching layer’s acoustic impedance changing with distance is exponentially attenuated. With a multi-layer structure, the internal performance of each layer is uniform, and the multi-layer stacking is the acoustic impedance. quasi-continuous gradient materials;
根据指数规律，每层的声阻抗的表达式为：
与现有技术相比，本发明的有益效果：本发明结构科学合理，使用安全方便：Compared with the prior art, the beneficial effect of the present invention is that the structure of the present invention is scientific and reasonable, and the use is safe and convenient:
1、通过一种声阻抗梯度材料的制备方法来制作出单层匹配层，替代目前的多层匹配层，应用在超声换能器上，其性能得到大幅提升，且声阻抗梯度材料，采用超薄多层的结构，同样厚度，多层叠合在一起，其阻抗成台阶状指数分布，因层数多，效果等同于阻抗连续分布，突破了传统锥孔复合法和离心沉降法对厚度的限制，尺寸大大缩小，性能均匀、可控，适合批量生产，满足医用超声和检测超声换能器的需求，用此匹配层制作的单阵元、一维阵列、二维阵列的超声探头，灵敏度可增加约2.5dB以上，带宽可增加20％以上，性能大幅提高；1. A single-layer matching layer is produced by a preparation method of an acoustic impedance gradient material, which replaces the current multi-layer matching layer. It is applied to an ultrasonic transducer, and its performance is greatly improved, and the acoustic impedance gradient material adopts super Thin multi-layer structure, the same thickness, multi-layer stacked together, its impedance is distributed exponentially in a step shape, because of the large number of layers, the effect is equivalent to the continuous distribution of impedance, breaking through the thickness limitations of the traditional cone-hole composite method and centrifugal sedimentation method , the size is greatly reduced, the performance is uniform and controllable, it is suitable for mass production, and meets the needs of medical ultrasound and detection ultrasound transducers. The ultrasonic probes made of this matching layer, single array element, one-dimensional array, and two-dimensional array, can be sensitive. Increase by about 2.5dB or more, the bandwidth can be increased by more than 20%, and the performance is greatly improved;
并且，该制备方法制作的声阻抗梯度材料，阻抗可控，性能均匀，厚度精准，可用于小尺寸的换能器上，替代目前的两层或三层匹配层的方案，提高其灵敏度，增加带宽，提高图像的分辨率。Moreover, the acoustic impedance gradient material produced by this preparation method has controllable impedance, uniform performance, and precise thickness, and can be used on small-sized transducers, replacing the current two-layer or three-layer matching layer scheme, improving its sensitivity, increasing Bandwidth, increase the resolution of the image.
附图说明Description of drawings
附图用来提供对本发明的进一步理解，并且构成说明书的一部分，与本发明的实施例一起用于解释本发明，并不构成对本发明的限制。在附图中：The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:
图1是本发明声阻抗梯度材料制备方法的流程图；Fig. 1 is the flowchart of the preparation method of acoustic impedance gradient material of the present invention;
图2是本发明匹配层中氧化铝的质量分数与声阻抗的关系图；Fig. 2 is the relation figure of the mass fraction of alumina and acoustic impedance in the matching layer of the present invention;
图3是本发明最优透射率的阻抗连续变化的示意图；Fig. 3 is the schematic diagram of the impedance continuous change of optimum transmittance of the present invention;
图4是声阻抗连续变化的梯度材料(锥孔法)的示意图。Fig. 4 is a schematic diagram of a gradient material with continuously changing acoustic impedance (cone method).
具体实施方式Detailed ways
以下结合附图对本发明的优选实施例进行说明，应当理解，此处所描述的优选实施例仅用于说明和解释本发明，并不用于限定本发明。The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.
实施例：如图1-3所示，本发明提供一种技术方案，一种使用梯度匹配层的超声探头，该超声探头包括压电材料和匹配层；Embodiment: As shown in Figures 1-3, the present invention provides a technical solution, an ultrasonic probe using a gradient matching layer, the ultrasonic probe includes a piezoelectric material and a matching layer;
匹配层设置在压电材料的前表面上，其中，电极形成在压电材料的前表面和后表面上；a matching layer is disposed on the front surface of the piezoelectric material, wherein electrodes are formed on the front and rear surfaces of the piezoelectric material;
压电材料和匹配层被加工成单阵元、多阵元的一维或二维阵列；Piezoelectric materials and matching layers are processed into one-dimensional or two-dimensional arrays of single array elements or multi-array elements;
匹配层设置为单层匹配层，以替代目前的多层匹配层来应用在超声换能器上。The matching layer is set as a single-layer matching layer to replace the current multi-layer matching layer to be applied on the ultrasonic transducer.
基于上述技术方案，该单层匹配层主要通过声阻抗梯度材料的制备方法来进行制作，具体包括如下制作步骤：Based on the above technical solution, the single-layer matching layer is mainly produced by the preparation method of the acoustic impedance gradient material, which specifically includes the following production steps:
S1、混合；S1, mixing;
S2、脱泡；S2, defoaming;
S3、成型；S3, molding;
S4、固化。S4, curing.
基于上述技术方案，S1中，混合是指将制备的原材料混合物按照成分的变化顺序进行编号，并将原材料进行充分搅拌混合处理，其中原材料包括以环氧树脂为基底，加入金属粉末、金属氧化物粉末和玻璃微珠，环氧树脂为E41、E51及同类型的其他牌号；Based on the above technical solution, in S1, mixing refers to numbering the prepared raw material mixture according to the change order of the components, and fully stirring and mixing the raw materials, wherein the raw materials include epoxy resin as the base, adding metal powder, metal oxide Powder and glass beads, epoxy resin E41, E51 and other grades of the same type;
金属粉末、金属氧化物粉末主要为钨粉、氧化钨粉、氧化铋粉等高密度粉末可提高混合物的阻抗，而低密度的氧化铝粉末等则适用于中低声阻抗场合，粉末选择超细的，是为了加工过程中可得到超薄厚度的产品。Metal powder and metal oxide powder are mainly high-density powders such as tungsten powder, tungsten oxide powder, and bismuth oxide powder, which can improve the impedance of the mixture, while low-density alumina powder is suitable for medium and low acoustic impedance occasions. The powder selection is ultra-fine The purpose is to obtain products with ultra-thin thickness during processing.
基于上述技术方案，S2中，脱泡主要用于消除原材料混合物在混合过程中所产生的气泡，其中，具体脱泡方式可选用抽真空脱泡，需要注意的是，不同的脱泡和成型方法，对声阻抗会产生影响。Based on the above technical solution, in S2, the defoaming is mainly used to eliminate the bubbles generated during the mixing process of the raw material mixture. Among them, the specific defoaming method can be vacuum defoaming. It should be noted that different defoaming and molding methods , will affect the acoustic impedance.
基于上述技术方案，S3中，成型是指采用流延处理的方式来使混合脱泡后的原料制成薄膜，并控制该成型后薄膜的厚度为25um。Based on the above-mentioned technical solution, in S3, molding refers to making a film from mixed and defoamed raw materials by tape casting, and controlling the thickness of the formed film to 25um.
基于上述技术方案，在流延成型处理时，20-100nm氧化铝粉末和环氧胶E51的混合物，粘度适中，方便流延成型，流延设备的厚度控制精度可达±2um，厚度可从10um到200um，调整好流延设备的刀高，流延带缓慢移动，混合物在流延带上形成一层薄膜，经60度缓慢加热，成半固化的流延膜，将流延膜按照0-9的顺序进行编号，流延膜宽度可设置成100mm宽，并通过流延设备的切刀来按照编号顺序将流延膜裁成方片。Based on the above technical scheme, during the tape casting process, the mixture of 20-100nm alumina powder and epoxy glue E51 has moderate viscosity and is convenient for tape casting. The thickness control accuracy of the tape casting equipment can reach ±2um, and the thickness can be from 10um To 200um, adjust the knife height of the casting equipment, the casting belt moves slowly, the mixture forms a thin film on the casting belt, and slowly heats at 60 degrees to form a semi-cured casting film. Numbering in the order of 9, the width of the casting film can be set to 100mm wide, and the casting film is cut into square pieces according to the numbering order by the cutter of the casting equipment.
基于上述技术方案，S4中，固化是指对流延生产的流延膜进行固化处理，在流延膜裁切为方片后，在规定的时间范围内，在叠层机下按照顺序，将方片按照编号0-9的顺序依次叠合起来，依序去掉流延带。Based on the above-mentioned technical scheme, in S4, curing refers to curing the cast film produced by casting. After the cast film is cut into square pieces, within the specified time range, the square pieces are placed in order under the laminating machine. The sheets are stacked in order of numbers 0-9, and the casting tapes are removed in sequence.
基于上述技术方案，在S4中，叠合时，叠层机提供真空和一定温度，叠好的薄膜刚好250um，其中250um的薄膜是指3MHz的探头，而频率越高，其厚度越薄，每薄层的厚度要相应变薄，然后在室温下固化后，在烘箱里继续固化，在未完全固化时用叠层机叠合，其附着力足够，完全固化后，经过高低温循环试验，没有脱开，中间也没有气泡，质量可靠；Based on the above technical solution, in S4, when stacking, the laminator provides a vacuum and a certain temperature, and the stacked film is just 250um, and the 250um film refers to a 3MHz probe, and the higher the frequency, the thinner the thickness. The thickness of the thin layer should be correspondingly thinned, and then after curing at room temperature, continue to cure in the oven, and laminate it with a laminator when it is not completely cured, and its adhesion is sufficient. Disengage, there is no air bubble in the middle, and the quality is reliable;
将固化完成后的方片在划片机上划成指定的尺寸，即可用在换能器的制作上，在制作时，方片在跟压电材料叠合时，高氧化铝质量分数的那一面须紧靠着压电材料，制作成功的64阵元相控阵探头，相对于常规的2层匹配层探头，其灵敏度提高了3.1dB，相对带宽从63％提高到85％。Divide the cured square sheet into the specified size on the dicing machine, which can be used in the production of transducers. During the production, when the square sheet is laminated with the piezoelectric material, the side with a high alumina mass fraction The 64-element phased array probe must be close to the piezoelectric material. Compared with the conventional 2-layer matching layer probe, the sensitivity is increased by 3.1dB, and the relative bandwidth is increased from 63% to 85%.
基于上述技术方案，S1中，在制备混合物时，需要配比不同质量组分的混合物，并进行性能测试，在测试过程中，随着氧化铝粉末在混合物中比例的增加，固化后的材料的密度增大，声速缓慢增加，v＝3000m/s，声阻抗呈线性增加，从纯环氧树脂E51的3.1MRayl到6.7MRayl，如图2所示；Based on the above technical solution, in S1, when preparing the mixture, it is necessary to proportion the mixture of different quality components, and perform a performance test. During the test, with the increase of the proportion of alumina powder in the mixture, the cured material's The density increases, the sound velocity increases slowly, v=3000m/s, and the acoustic impedance increases linearly, from 3.1MRayl to 6.7MRayl of pure epoxy resin E51, as shown in Figure 2;
其线性拟合方程为：Z＝7.2X+3.1(公式1)，其中，Z为声阻抗，X为氧化铝的质量分数。Its linear fitting equation is: Z=7.2X+3.1 (Formula 1), where Z is the acoustic impedance, and X is the mass fraction of alumina.
基于上述技术方案，最佳透射率计算的结果表明，理想的匹配层的声阻抗随距离变化的曲线呈指数衰减，如图3所示，采用多层结构，每层内部性能均匀一致，多层叠合起来，就是声阻抗准连续的梯度材料；Based on the above technical scheme, the calculation results of the optimal transmittance show that the curve of the acoustic impedance of the ideal matching layer as a function of distance decays exponentially, as shown in Figure 3, the multi-layer structure is adopted, and the internal performance of each layer is uniform. Taken together, it is a quasi-continuous gradient material of acoustic impedance;
根据指数规律，每层的声阻抗的表达式为：
一般，选择匹配层的厚度为四分之一波长，小于这个厚度，透射率下降，高于这个厚度，因衰减，信号会减弱，综合考虑，厚度一般选四分之一波长。Generally, the thickness of the matching layer is selected to be a quarter wavelength. If the thickness is less than this thickness, the transmittance will decrease. If the thickness is higher than this thickness, the signal will be weakened due to attenuation. Considering comprehensively, the thickness is generally selected as a quarter wavelength.
最后应说明的是：以上所述仅为本发明的优选实例而已，并不用于限制本发明，尽管参照前述实施例对本发明进行了详细的说明，对于本领域的技术人员来说，其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。Finally, it should be noted that: the above is only a preferred example of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it can still The technical solutions recorded in the foregoing embodiments are modified, or some of the technical features are equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.
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