Effect of bias potential and dimension on electrochemical migration of capacitors for implantable devices

Dendrite formation induced by electrochemical migration (ECM) is a common reliability problem occurring on printed circuit boards (PCBs), which significantly threatens the long-term safe operations of current implantable electronic devices (IEDs). Although several factors (i.e., contaminations, humidity, temperature) are proved to be the parameters closely related to ECM susceptibility of capacitors on a PCB under climate environments, further targeted research under other environments still needs to be conducted as ECM is highly environmental-dependent. Herein, the effects of bias potential and pitch dimension on ECM sensitivity are systematically studied using various sizes of capacitors on a test PCB under a human implantation environment. The finite element method first proves that a DC voltage pattern could be regarded as an accelerated test compared to other waveforms. Subsequent chronoamperometry tests using the DC potential further indicate that dendrite formation is closely related to pitch dimension under low bias potential, while under high bias potential electric field is also the dominating factor of dendrite formation for capacitors on a PCB. Benefiting from the electrochemical impedance spectroscopy (EIS) technique, the capacitor reliability under different corrosion states is also evaluated in a detailed manner. This work offers great value both in electronic corrosion mechanisms and future rational design for reliable IEDs.