At Innovia, composite material is composed of PZT ceramic and epoxy. Compared with pure PZT transducers, composite material based transducer has several advantages:
1) Increased sensitivity
2) Broader bandwidth
3) Improved impedance match
4) Reduced cross-talk
Innovia offers both 1-3 or 2-2 type composite, both of which are dice-and-fill type. Composite products are highly customizable. Wide options of properties are available, including thickness, fill factors, acoustic impedance, dielectric constant and electrodes.
Innovia develops its own proprietary processes to ensure the best valued products to be delivered. For instance, our optional Cu electrode is strong in adhesion, oxidization proof and can withstand downstream process such as soldering. Currently, PZT composite materials are actively being used by our customers on NDT and Medical Ultrasound probes.
* Note: filling factors are taylored between 25% to 60% due to the optimization of the coupling coefficient (figure below). Too much epoxy has clamping effect, while too little epoxy compromises geometry advantage.
* Dielectric constant of composite is modeled as parallel capacitors:
εComposite = vεCeramic +(1-v)εEpoxy
* Acoustic impedance of composite is modeled as parallel springs:
Zcomposite = vZCeramic + (1-v)ZEpoxy
Composites’ coupling coefficient kt is dependent on fill factors
Innovia’s composites with Cu electrodes