Fast diffusers in a thermal gradient (solder ball)

Lloyd, J. R.; Connelly, N.; He, Xiao; Ryan, Kris; Wood, B

doi:10.1016/j.microrel.2010.07.067

Cited by 5 publications

(4 citation statements)

References 3 publications

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“…The diffusivity of Sn varies with direction and temperature, being much faster along the c-axis than a-axis by a factor of 200 at À40°C, and 50 at 150°C. Furthermore, diffusion of Ni and Cu along the c-axis is exceptionally fast, with diffusion rates similar to a liquid (activation energies on the order of 0.2 eV 41,42 ). However, the solid solubility of these elements in Sn is extremely low, so transport of Cu and Ni in solder joints is low in an equilibrium condition.…”

Section: Anisotropic Diffusion Of Solute Elementsmentioning

confidence: 99%

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The Role of Elastic and Plastic Anisotropy of Sn in Recrystallization and Damage Evolution During Thermal Cycling in SAC305 Solder Joints

Bieler

Zhou

Blair

et al. 2011

Journal of Elec Materi

109

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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 higherstress 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.

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Section: Anisotropic Diffusion Of Solute Elementsmentioning

confidence: 99%

“…In service, there are nonequilibrium thermal, stress, and electrical gradients that provide driving forces for rapid transport of these alloying elements. 42 …”

Section: Anisotropic Diffusion Of Solute Elementsmentioning

confidence: 99%

The Role of Elastic and Plastic Anisotropy of Sn in Recrystallization and Damage Evolution During Thermal Cycling in SAC305 Solder Joints

Bieler

Zhou

Blair

et al. 2011

Journal of Elec Materi

109

View full text Add to dashboard Cite

show abstract

“…(3) The formation of IMCs has to be described under consideration of the boundary conditions. Especially blocking boundaries like Ni layers have to be considered [8]. In difference to [8], Ni and Cu do not act as ''fast diffusers'' in CuSn IMCs.…”

Section: State Of the Art And Purpose Of This Investigationmentioning

confidence: 99%

“…Especially blocking boundaries like Ni layers have to be considered [8]. In difference to [8], Ni and Cu do not act as ''fast diffusers'' in CuSn IMCs. (4) The presence of other materials like Au or Ni can change the mobility of Cu and Sn and new migration phenomena can appear [9].…”

Section: State Of the Art And Purpose Of This Investigationmentioning

confidence: 99%