Lead-free alkaline niobate-based transducer for ultrasonic wirebonding applications

Lead-free piezoelectric ceramic rings (Na0.475K0.475Li0.05)(Nb0.92Ta0.05Sb0.03)O3added with 0.4 wt% CeO2and 0.4 wt% MnO2have been successfully prepared and used as the driving elements of the ultrasonic wirebonding transducers with titanium alloy front and back plates. The transducer operates at similar frequency of the commercial lead zirconate titanate (PZT) transducers (∼65 kHz). Because of the better matching of the acoustic impedances between the ceramic and titanium alloy, an effective transfer of vibration energy is achieved in the transducer, leading to a large axial vibration (1.73 μm at 0.1 W). Moreover, the transducer exhibits a small lateral vibration (0.05 μm at 0.1 W), which is essential for producing a small or narrow bond. The transducer has successfully bonded the aluminum wire on the standard die and gold-plated PCB. The bonds are of good quality, having a smaller deformation ratio (as compared to the commercial PZT transducer) and high bond strength (exceeding the industrial requirement). These clearly show that the lead-free piezoelectric ceramic is a promising candidate for replacing the lead-based ceramics as a driving element in the future generation of wire bonders.