The Role of Elastic and Plastic Anisotropy of Sn in Recrystallization and Damage Evolution During Thermal Cycling in SAC305 Solder Joints
- Michigan
Because failures in lead-free solder joints occur at locations other than the most highly shear-strained regions, reliability prediction is challenging. To gain physical understanding of this phenomenon, physically based understanding of how elastic and plastic deformation anisotropy affect microstructural evolution during thermomechanical cycling is necessary. Upon solidification, SAC305 (Sn-3.0Ag-0.5Cu) solder joints are usually single or tricrystals. The evolution of microstructures and properties is characterized statistically using optical and orientation imaging microscopy. In situ synchrotron x-ray measurements during thermal cycling are used to examine how crystal orientation and thermal cycling history change strain history. Extensive characterization of a low-stress plastic ball grid array (PBGA) package design at different stages of cycling history is compared with preliminary experiments using higher-stress package designs. With time and thermal history, microstructural evolution occurs mostly from continuous recrystallization and particle coarsening that is unique to each joint, because of the specific interaction between local thermal and displacement boundary conditions and the strong anisotropic elastic, plastic, expansion, and diffusional properties of Sn crystals. The rate of development of recrystallized microstructures is a strong function of strain and aging. Cracks form at recrystallized (random) boundaries, and then percolate through recrystallized regions. Complications arising from electromigration and corrosion are also considered.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- NSFINDUSTRY
- OSTI ID:
- 1047318
- Journal Information:
- J. Electro. Mater., Vol. 41, Issue (2) ; 2012; ISSN 0361-5235
- Country of Publication:
- United States
- Language:
- ENGLISH
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Related Subjects
AGING
ANISOTROPY
BOUNDARY CONDITIONS
CORROSION
CRACKS
CRYSTALS
DAMAGE
DEFORMATION
DESIGN
ELECTROPHORESIS
EXPANSION
FAILURES
FORECASTING
FUNCTIONS
GAIN
GRIDS
INTERACTIONS
JOINTS
MICROSCOPY
ORIENTATION
PARTICLES
PLASTICS
RECRYSTALLIZATION
RELIABILITY
SOLIDIFICATION
STRAINS
SYNCHROTRON RADIATION
THERMAL CYCLING