Delamination in Plastic-Encapsulated Microcircuits Under Hygrothermal Stress: Identifying the Most Critical Interfaces

Plastic-encapsulated microcircuits (PEMs) are ubiquitous in modern electronics; their non-hermetic nature, however, renders them susceptible to moisture-induced interfacial delamination, posing a significant challenge to longterm reliability. This study addresses this challenge through a synergistic approach that combines multi-physics finite element (FE) modeling with extensive experimental validation. A fully coupled thermo-hygro-mechanical model was developed to simulate stress distribution and pinpoint the most vulnerable interfaces under various hygrothermal loads: Temperature Cycling (TC), Damp Heat (DH), and Highly Accelerated Stress Test (HAST). The simulation findings were then systematically validated via these accelerated tests on 14 PEM types, with subsequent failure analysis performed using Scanning Acoustic Microscopy (SAM). The simulations predicted that high strain concentrations would render the wire-bond and leadframeencapsulant interfaces the most critical failure sites. These predictions were experimentally corroborated, revealing that delamination predominantly initiated and propagated at the leadframe-encapsulant interface, a phenomenon particularly pronounced under HAST conditions (130°C, 85% RH⁵, 230kPa). By establishing a strong correlation between the predicted highstrain locations and empirically observed delamination sites, this work presents a validated predictive framework for assessing and enhancing the long-term reliability of PEMs in humid environments.