Micromachining techniques in developing high-frequency piezoelectric composite ultrasonic array transducers.

Area of Science:

• Materials Science and Engineering
• Acoustics and Ultrasonics
• Nanotechnology and Microfabrication

Background:

• High-frequency ultrasonic array transducers are crucial for advanced medical imaging and non-destructive testing.
• Existing fabrication methods face challenges in achieving high element density and miniaturization for improved resolution.
• Piezoelectric composite materials offer enhanced performance but require sophisticated manufacturing processes.

Purpose of the Study:

• To detail novel micromachining techniques for fabricating high-frequency piezoelectric composite ultrasonic array transducers.
• To demonstrate the feasibility of a hybrid array transducer design with integrated 2-D and annular arrays.
• To establish a process flow for creating high-density, small-element arrays for improved ultrasonic imaging.

Main Methods:

• Utilized deep reactive ion etching (DRIE) for patterning piezoelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT)/epoxy 1-3 composite pillars.
• Developed techniques for attaching backing material and assembling electronic interconnections for array elements.
• Fabricated and assessed a hybrid test array transducer with 8x8 2-D and 5-element annular arrays operating at ~60 MHz.

Main Results:

• Achieved a center frequency of approximately 60 MHz with a -6-dB bandwidth of around 50%.
• Demonstrated low crosstalk (-33 dB) between adjacent 2-D array elements.
• Successfully fabricated small elements (105x105 μm for 2-D array) with fine kerfs (5 μm).

Conclusions:

• The described micromachining techniques are effective for fabricating high-frequency ultrasonic array transducers.
• The developed process flow enables the creation of larger arrays with smaller elements for enhanced ultrasonic applications.
• The novel interconnection strategy supports high-density, miniaturized array element assembly.