The Study Of Design Method And Acoustic Properties Of Acoustic Matching Layer For Ultrasonic Transducer

Piezoelectric ultrasonic transducer has been widely used in numerous fields. Itcan convert electrical signals into acoustic signals or convert acoustic signals intoelectrical signals by the dielectric which has piezoelectric effect so as to achieveenergy conversion. The matching layer is an important component of piezoelectricultrasonic transducer. It can achieve acoustic impedance matching or transition,improve the sensitivity of transducer and broaden the band. For a given frequency,the thickness of matching layer should be/4. The acoustic impedance values ofmatching layer is the geometric average of the piezoelectric material and the humantissue.In this paper, composite material is chosen to fabricate matching layers.Alumina powder with a2.5-μm and a10-μm particle size, copper powder andtungsten powder are selected as particle filler, epoxy resin E51, amine curing agentW93and aromatic amine curing agent DEDDM are selected as matrix. Traditionalultrasonic spectrum method is used to test the acoustic impedance and the acousticattenuation, and to study the effect of temperature, thickness, particle size, types ofcuring agent and types of particle filler on acoustic characteristics of matching layersamples.The test results suggest that matching layers which made of different particlesize, curing agent and particle filler have the same change rule of density andacoustic impedance. The density and acoustic impedance values linearly increasewith the volume fraction of the particle filler. Particle size has little effect onacoustic impedance values. The acoustic impedance values of matching layerswhich made of aromatic amine curing agent DEDDM are smaller than those ofmatching layers which made of amine curing agent W93. The change of particle size,curing agent and particle filler produce an effect on the sound velocity and theacoustic attenuation of matching layer samples.Casting method can be used to fabricate matching layers. In the matching layersamples which are made of Alumina powder with a2.5-μm, epoxy resin E51andamine curing agent W93, when the volume fraction of Alumina powder grows from5%to25%, the acoustic impedance values of matching layer samples increase from3.68MRayl to5.30MRayl. While tungsten powder is chosen instead of Aluminapowder as particle filler, when the volume fraction of tungsten powder grows from5%to25%, the acoustic impedance values of matching layer samples increase from4.064MRayl to8.507MRayl. The range of acoustic impedance value of matching layers is usually between3MRayl and15MRayl. The range of acoustic impedancevalue of matching layers in this paper is between3MRayl and9MRayl, which meetthe requirements of acoustic impedance matching.Doctor-blade technique is suitable for the preparation of thin matching layer.This method lays a foundation of the fabrication of high Frequency transducer. Thematching layer samples which are made in this way have the same acousticproperties with the samples which are made by casting method. In this experiment,Alumina powder with a2.5-μm, epoxy resin E51and amine curing agent W93arechosen to fabricate matching layers. In this work, when the volume fraction ofAlumina powder grows from5%to20%, the acoustic impedance values of matchinglayer samples increase from3.75MRayl to4.84MRayl. They linearly increase withthe volume fraction of Alumina powder.