Current Crowding and Stress Effects in WCSP Solder Interconnects: A Simulative and Practical Study about the Effects of Major Electromigration Failure Mechanisms in DC and Pulsed-DC Conditions

Abstract

Electromigration (EM) induced failure is inevitable in wafer-level chip scale package microelectronic packages (WCSP), especially with the implementation of lead-free solders. Many factors contribute to EM failure such as joule heating and current crowding. EM can induce void formation, which can eventually lead to open-circuit failure. Due to its nature, EM is a critical failure concern to the microelectronic industry and can be influenced by current conditions. This study examines the failure mechanisms in solder joints implemented in WCSP packages in Direct Current (DC) and DC-pulse current conditions with varying Duty Factors (DF). DF represents the on-off time for DC to flow through the device under test (DUT). Further, a transient simulative study using finite element method (FEM) explores the failure mechanism and investigates the stress development with DC and DF conditions. Findings suggested that a lower duty factor yielded longer time to failure (TTF). Meanwhile, higher pulsed DC DF yielded a lower TTF than DC. This study aims to explain the failure mechanism with each DF. This study aims to explain this phenomenon and suggests the need for further exploration.