A wideband PVDF-on-silicon ultrasonic transducer array with microspheres embedded low melting temperature alloy backing

A PVDF-based 8-element ultrasound transducer array (1 mm × 1 mm element size with an inter-element spacing of 1 mm) on a silicon carrier substrate is fabricated and characterized. To improve the performance of the transducer, new CMOS-compatible fabrication technologies are introduced. These include: (1) adhesive micro-contact printing on non-radiating areas, and (2) glass microspheres (7–20 μm in diameter) embedded low melting temperature alloy (LMA) for backside electrical connection. The first improvement removes the adverse effects of adhesive layer (e.g., lower sensitivity) between the PVDF and backside contact while the second one improves the pulse-echo signal quality by eliminating reflections at the backing/water interface. The fabricated array elements are tested in a water tank and their pulse-echo response are recorded. The central frequency of each element is 25 MHz with a 100% measured 6-dB bandwidth (60% 3-dB bandwidth).

[1]  H. Ermert,et al.  A 100-MHz ultrasound imaging system for dermatologic and ophthalmologic diagnostics , 1996, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[2]  Crosstalk reduction with a micromachined diaphragm structure for integrated ultrasound transducer arrays , 1990, IEEE Symposium on Ultrasonics.

[3]  R. D. Briggs,et al.  A micromachined poly(vinylidene fluoride-trifluoroethylene) transducer for pulse-echo ultrasound applications , 1996, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[4]  Shuvo Roy,et al.  Miniature high frequency focused ultrasonic transducers for minimally invasive imaging procedures , 2003 .

[5]  J. Plummer,et al.  Integrated silicon-PVF2acoustic transducer arrays , 1979, IEEE Transactions on Electron Devices.

[6]  K. Kirk Shung,et al.  Ultrasonic transducers and arrays , 1996 .

[7]  Edward Hæggström,et al.  Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology , 2003 .

[8]  R. Newnham,et al.  Acoustic properties of particle/polymer composites for ultrasonic transducer backing applications , 1990 .

[9]  G. Whitesides,et al.  Fabrication of Three-Dimensional Microfluidic Systems by Soft Lithography , 2001 .

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

[11]  Younan Xia,et al.  Template-assisted self-assembly: a practical route to complex aggregates of monodispersed colloids with well-defined sizes, shapes, and structures. , 2001, Journal of the American Chemical Society.