60 MHz PMN-PT/Epoxy 1–3 Composite Hybrid Array Transducer
This high-frequency ultrasonic array transducer integrates a 64-element (8×8) 2D planar array with a concentric 5-element annular array on a single platform, fabricated using micromachining techniques including deep reactive ion etching (DRIE) and photolithography. The active material is a PMN-PT/epoxy 1–3 piezoelectric composite with 8 µm pillar dimensions and ~4 µm kerf widths, produced by dry etching of single-crystal PMN-PT. The transducer is designed for a center frequency of approximately 60 MHz and achieves a −6 dB bandwidth of 46.3% with inter-element crosstalk of −33 dB at center frequency. Electrical interconnection is accomplished via a custom electric interconnection board (EIB) featuring 20 µm diameter nickel pins that are pressed directly into conductive backing material, eliminating wire bonding and flexible circuit interposers. This hybrid architecture supports flexible imaging modes and demonstrates the feasibility of micromachining techniques for constructing high-frequency arrays with fine-pitch elements.
Parameter | 2D Planar Array | Annular Array |
|---|---|---|
Number of Elements | 64 (8 × 8) | 5 |
Center Frequency | 63.5 MHz | 63.5 MHz |
Bandwidth (‑6 dB) | 46.3% | — |
Piezoelectric Material | PMN‑PT/epoxy 1–3 composite (49% volume fraction) | PMN‑PT/epoxy 1–3 composite (49% volume fraction) |
Composite Thickness | 24 μm | 24 μm |
PMN‑PT Pillar Dimensions | 8 × 8 μm | 8 × 8 μm |
Element Size | 105 × 105 μm | 0.71 mm² per ring |
Array Kerf Width | 5 μm | 16 μm |
Electromechanical Coupling (kₜ) | 0.72 | 0.72 |
Capacitance (at 1 kHz) | ~5.5 pF | ~358 pF |
Insertion Loss (at 60 MHz) | −19.5 dB | — |
Crosstalk (60 MHz) | −33 dB | — |
Backing Material | E‑Solder 3022 (conductive epoxy) | E‑Solder 3022 (conductive epoxy) |
Matching Layer | Parylene | Parylene |
Electrical Interconnection | EIB with nickel pins (20 μm Ø); 1 pin/element | EIB with nickel pins; 4 pins/ring |
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