A Comparative Reliability Analysis of Smart-Wire-Connection and Five-Busbar Architectures Under Accelerated Damp-Heat Testing

Abstract

The transition from three-busbar to multi-busbar (5BB to 12BB) and ultimately to smart-wire-connection (SWCT) module architectures has reduced silver consumption and series resistance, but the long-term reliability implications under hygrothermal stress remain incompletely characterized. This study reports an accelerated damp-heat (85 degrees Celsius, 85 percent relative humidity) reliability comparison spanning 3000 hours across paired SWCT and five-busbar test coupons fabricated from a common cell stock. Electroluminescence imaging, dark IV current-voltage spectroscopy, and peel-test adhesion measurements were used to track interconnect degradation modes. Results indicate distinct dominant failure pathways for the two architectures: solder-joint microcracking for the busbar variant versus encapsulant-wire interface delamination for SWCT. Implications for accelerated-test acceleration factors and field warranty modeling are discussed, and a revised IEC 61215 sequence-extension recommendation is proposed.