Ultrasonic Detection of Defects in Multilayered Ceramic Capacitors for Active Implantable Medical Devices

摘要

Resonant ultrasound spectroscopy (RUS) was used to measure the acoustic frequencies of surface-mountable multilayered ceramic capacitors (MLCC), with the aim of determining whether a resonant acoustic technique can serve as a nondestructive method for detecting structural flaws in capacitors. Structural flaws are currently considered to be the primary source of in-service electrical failure of MLCC incorporated in active implantable medical devices. Measurements were made on capacitors in the as-manufactured condition and after exposure to a variety of treatments, including elevated vibration/temperature/current, thermal shock, microindentation, and focused-ion-beam (FIB) milling of a linear flaw. Changes in RUS spectra induced by the indentations and FIB flaw were found to be comparable in magnitude to the uncertainties in the measurements. However, accelerated stress and thermal shocks resulted in much more noticeable changes. These results provide preliminary evidence that RUS measurements provide a feasible basis for detecting structural flaws that are precursors to electrical failure of MLCC.