T. Kirkpatrick

Abstract: The size and crystal orientation of Sn grains in Pb-free, near eutectic Sn-Ag-Cu solder joints were examined. A clear dependence of the thermomechanical fatigue response of these solder joints on Sn grain orientation was observed (Sn has a body centered tetragonal crystal structure). Fabricated joints tend to have three orientations in a cyclic twin relationship, but among the population of solder balls, this orientation triplet appears to be randomly oriented. In thermally cycled joints, solder balls with dominant Sn grains having the particular orientation with the c-axis nearly parallel to the plane of the substrate were observed to fail before neighboring balls with different orientations. This results from the fact that the coefficient of thermal expansion of Sn in the basal plane (along the alpha-axis) is half the value along the c-axis; joints observed to be damaged had the maximum coefficient of thermal expansion mismatch between solder and substrate at the joint interface, as well as a tensile stress modes during the hot part of the thermal cycle. Localized recrystallization was observed in regions of maximum strain caused by differential expansion conditions, and its connection with crack nucleation is discussed.

TL;DR: In this paper, the size and orientation of Sn grains in Pb-free, near eutectic SAC solder joints were examined and a clear dependence of the thermomechanical response of these solder joints on Sn grain orientation was observed.

TL;DR: In this article, the authors used planar planar a-Si p-i-n junction solar cells to study the effect of hot electron injection on the open circuit voltage with photon energy.

TL;DR: The design, fabrication, and performance of a nanoporous, coaxial array capacitive detector for highly sensitive chemical detection is reported, shown to achieve parts per billion level detection sensitivity to a broad class of organic molecules.

TL;DR: In this paper, the Raman spectrum of hydrogenated amorphous silicon (Si:H) was calculated under different strains and peak shifts were found for the broad peaks of the vibrational frequencies.