Space Charge Redistribution in Epoxy Mold Compounds of High-Voltage ICs at Dry and Wet Conditions: Theory and Experiment

Abstract

Space charge profile plays an important role in defining the charge transport and breakdown field of an insulator. Non-destructive experimental techniques (e.g., PEA measurement) have recently been used to track in-situ the time-evolution of space charge profiles within complex insulators, such as epoxy mold compounds. Unfortunately, the published results are often inconsistent (both positive and negative charge build-up have been reported), and the discrepancy remains unexplained. In this paper, we (i) derive a physics-based compact analytical model of homocharge injection, (ii) explain the time-and voltage-dependent redistribution of homo- and heterocharge, (iii) investigate experimentally and explain theoretically the importance of moisture ingress regarding space charge redistribution, and finally, (iv) summarize strategies to suppress space-charge related instability in modern ICs encapsulated by epoxy mold compounds.