Ultrafine scale piezoelectric composite materials for high frequency ultrasonic imaging arrays

Intravascular and endoscopic acoustic imaging typically require high ultrasonic operating frequencies, over 7 MHz. At these frequencies the ceramic transducer dimensions become very small; pitches in the order of 20 to 80 μm are needed. Moreover, such arrays must be compatible with existing interconnect approaches and be fabricated at low cost. These piezoelectric transducer array requirements severely challenge the ability of conventional PZT ceramic technologies in terms of cost-effective fabrication. To meet the demand for such transducer shapes, MSI has developed a net shape ceramic injection molding process for production of piezoelectric ceramics in complex shapes. Using this technique, MSI has produced ultrafine scale 2-2 piezocomposite arrays having PZT elements less than 25 μm wide and pitches under 50 μm. This paper reviews recent advances in the net shape molding technology, and compares the characteristics of an injection molded 7 MHz 2-2 configuration with that of a similar array prepared by conventional dicing