Efficient in-situ reliability monitoring of in-plane NED Bending Actuators during accelerated aging

Abstract:
Fraunhofer IPMS develops since 2015 NED bending actuators, which are integrated in many different applications, such as micro-positioning platforms, micro machined ultrasonic transducers, micro speakers and so on. All the applications need to be analyzed from the reliability point of view. For that reason different tests are performed to force the accelerated aging of the structures, e.g. tests in the climatic chamber. During the accelerated aging the actuator could for example change their resonance frequency or deflection could drop. Big and quick deflections, as by ultrasonic applica-tions result also in a high damping, thus a certain design adjustments may need to be implemented. To analyze all these effects the frequency dependent acquisition of the actuator movements need to be performed. But it is often impossible, because of the measure setup. During the accelerated aging the chips lays typically in a climatic chamber or during the damping tests in a vacuum chamber, so no in-situ measurements are possible. In such cases the analysis of the electrical impedance response can bring the necessary information. For that reason, a simple analytical impedance response model has been developed and verified, which helps to monitor efficiently the changes in the actuator behavior during the stress tests.