Title

Thermal Cycling Induced Interconnect Stability Degradation Mechanism in Low Melting Temperature Solder Joints

Published In

2022 IEEE 72nd Electronic Components and Technology Conference (ECTC)

Document Type

Citation

Publication Date

2022

Abstract

With the increase of interest in low melting temperature solder alloys, in recent studies on Sn-Bi based system solder show relatively good thermal cycling performances comparable to conventional Sn-Ag-Cu based solder interconnects at a given thermal cycling profile. Sn-Bi eutectic system microstructures are similar to Sn-Pb eutectic microstructure but have different damage accumulation mechanism due to Bi crystal lattice with Rhombohedral A7 unit cell structure, which is less ductile compared to Sn-Pb, where Pb has face centered cubic crystal lattice. The nature of less ductility in Sn-Bi alloy system reveals a different damage accumulation process during thermal cycling compared to Sn-Ag-Cu solder material, although the thermal cycling performance is comparable with micro-elementalloying. To identify the degradation mechanism in Sn-Bi solder interconnects, the study presented here is a series of microstructure analysis on segmented thermal cycling completed components, which reveal gradual and localized microstructure evolution. 12x12 mm2 chip array BGA (CABGA) components were thermal cycled with a -40 to 100°C cycle profile and a 10min dwell time. The microstructure developments per component were analyzed with 200-250 cycles interval cross-sections until both Sn- Ag-Cu and Sn-Bi solder joints reached to full failure. The correlation between crack initiation, crack propagation and localized recrystallization were compared in a series of cross section analyses using polarized imaging and Electron- backscattered diffraction (EBSD) based strain and residual stress analysis. The analysis revealed the potential damage accumulation process in Sn-Bi solder joint under thermal cycling, which is discussed in this paper.

Rights

Copyright IEEE 2022

DOI

10.1109/ECTC51906.2022.00192

Persistent Identifier

https://archives.pdx.edu/ds/psu/38132

Publisher

IEEE

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