Fabrication of PZT sol gel composite ultrasonic transducers using batch fabrication micromolding

A new micromolding technique for fabricating high-frequency (>20 MHz) ultrasound transducers has been developed. The technique combines sol gel processing with an epoxy-based, photo-resist Su-8 micromold to form miniature PZT structures. An advantage of this technique as compared to more traditional lithographic galvanforming and abforming (LIGA) processing is that the intermediate step of producing a nickel-plated mold is avoided. Instead, the PZT is formed directly using a photo-resist. The resulting structures can be fabricated with aspect ratios up to 3:1 and thicknesses up to 50 mu. We have successfully fabricated 50-mu thick linear array elements with 23-mu-wide elements separated by 15 kerfs. A 50-mu thick, 2.5-mm diameter, five-element annular array structure with 20-mu kerfs also has been fabricated. The micromolded PZT composite has a density of 5.7-5.8 plusmn 0.4 g/cm3 and a thickness coupling coefficient as high as 0.32

[1]  Michael Sayer,et al.  Sol-gel processing of complex oxide films , 1991 .

[2]  M. Sayer,et al.  Macroscopic Actuators Using Thick Piezoelectric Coatings , 2000 .

[3]  Qifa Zhou,et al.  Development of a high frequency (35 MHz) linear ultrasonic array using 2-2 composite elements [biomedical applications] , 2004 .

[4]  H. Torp,et al.  Which transducer array is best , 1995 .

[5]  S.W. Smith,et al.  Two-dimensional arrays for medical ultrasound , 1991, IEEE 1991 Ultrasonics Symposium,.

[6]  江刺 正喜,et al.  Novel processing of high aspect ratio 1-3 structures of high density PZT , 1998 .

[7]  K. Snook,et al.  Development of high frequency annular arrays for medical imaging , 2003, IEEE Symposium on Ultrasonics, 2003.

[8]  M. Sayer.  Piezoelectric films and coatings , 1996 .

[9]  Robert A. Street,et al.  Micro-electro-mechanical system fabrication technology applied to large area x-ray image sensor arrays , 2001 .

[10]  G. R. Lockwood,et al.  Laser micromachined high frequency ultrasonic arrays , 1999, 1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium (Cat. No.99CH37027).

[11]  H. Takada,et al.  Piezocomposite of fine PZT rods realized with synchrotron radiation lithography , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[12]  K. Shung,et al.  A 30-MHz piezo-composite ultrasound array for medical imaging applications , 2002, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[13]  S.W. Smith,et al.  Two-Dimensional Arrays for Medical Ultrasound , 1991, IEEE 1991 Ultrasonics Symposium,.

[14]  P. Vettiger,et al.  Fabrication of photoplastic high-aspect ratio microparts and micromolds using SU-8 UV resist , 1998 .

[15]  J. Mohr,et al.  The LIGA technique-what are the new opportunities , 1992 .

[16]  A. Fukumoto,et al.  Dependence of the electromechanical coupling coefficient on the width‐to‐thickness ratio of plank‐shaped piezoelectric transducers used for electronically scanned ultrasound diagnostic systems , 1979 .

[17]  J.M. Cannata,et al.  Development of a high frequency (35 MHz) linear ultrasonic array using 2-2 composite elements [biomedical applications] , 2004, IEEE Ultrasonics Symposium, 2004.

[18]  Jane M. Shaw,et al.  Micromachining applications of a high resolution ultrathick photoresist , 1995 .

[19]  W. Ehrfeld.  The LIGA Process for Microsystems , 1990 .

[20]  F. Foster,et al.  Interdigital pair bonding for high frequency (20-50 MHz) ultrasonic composite transducers , 2001, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.