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In situ synchrotron study of electromigration induced grain rotations in Sn solder joints.

Shen H, Zhu W, Li Y, Tamura N, Chen K - Sci Rep (2016)

Bottom Line: Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction.Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains.A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

View Article: PubMed Central - PubMed

Affiliation: Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 China.

ABSTRACT
Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction. With this technique, crystal orientation evolution is monitored at intragranular levels with high spatial and angular resolution. During the entire experiment, no crystal growth is detected, and rigid grain rotation is observed only in the two grains within the current crowding region, where high density and divergence of electric current occur. Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains. A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

No MeSH data available.


Related in: MedlinePlus

Shape mapping of Grain 1.By plotting the spatial distribution of () Laue peak intensity from each μXRD scan, the morphology and size of Grain 1 are mapped as a function of EM time. By this approach, three positions close to the center of the grain are pinpointed in each scan to investigate the orientation evolution.
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f2: Shape mapping of Grain 1.By plotting the spatial distribution of () Laue peak intensity from each μXRD scan, the morphology and size of Grain 1 are mapped as a function of EM time. By this approach, three positions close to the center of the grain are pinpointed in each scan to investigate the orientation evolution.

Mentions: The orientation maps obtained from each scan are carefully compared to monitor the orientation, shape, and size evolution of the selected grains. The shape evolution of the grain labelled “Grain 1” is plotted via intensity maps. Such intensity maps are obtained by first indexing all the Laue patterns from this crystal grain, and then tracking the intensity of a specific diffraction peak. It is noted that this peak should show up at the same position on all the Laue patterns in this grain. Here we choose the () peak. The integrated intensity of peak from all patterns is recorded, and a 2D contour map is plotted with the color coding intensity values (Fig. 2). It can be seen that the morphology and size of Grain 1 remain unchanged under the high density electric current stresses within the spatial resolution (3 μm, determined by the scanning step size) of this study. The same methodology is applied to all the other grains. No monotonic change of grain size is observed, and the size fluctuation of all the tracked 7 grains is less than 2 pixels, caused by sample drift and temperature fluctuation during the measurement, suggesting that no obvious grain growth is triggered by the electric current. The color of all the 7 grains in the orientation maps remains unchanged through the 11 scans, indicating no dramatic rotation of tens of degrees as what was reported in the Sn strips8 or appearance of cyclic twinning17.


In situ synchrotron study of electromigration induced grain rotations in Sn solder joints.

Shen H, Zhu W, Li Y, Tamura N, Chen K - Sci Rep (2016)

Shape mapping of Grain 1.By plotting the spatial distribution of () Laue peak intensity from each μXRD scan, the morphology and size of Grain 1 are mapped as a function of EM time. By this approach, three positions close to the center of the grain are pinpointed in each scan to investigate the orientation evolution.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834559&req=5

f2: Shape mapping of Grain 1.By plotting the spatial distribution of () Laue peak intensity from each μXRD scan, the morphology and size of Grain 1 are mapped as a function of EM time. By this approach, three positions close to the center of the grain are pinpointed in each scan to investigate the orientation evolution.
Mentions: The orientation maps obtained from each scan are carefully compared to monitor the orientation, shape, and size evolution of the selected grains. The shape evolution of the grain labelled “Grain 1” is plotted via intensity maps. Such intensity maps are obtained by first indexing all the Laue patterns from this crystal grain, and then tracking the intensity of a specific diffraction peak. It is noted that this peak should show up at the same position on all the Laue patterns in this grain. Here we choose the () peak. The integrated intensity of peak from all patterns is recorded, and a 2D contour map is plotted with the color coding intensity values (Fig. 2). It can be seen that the morphology and size of Grain 1 remain unchanged under the high density electric current stresses within the spatial resolution (3 μm, determined by the scanning step size) of this study. The same methodology is applied to all the other grains. No monotonic change of grain size is observed, and the size fluctuation of all the tracked 7 grains is less than 2 pixels, caused by sample drift and temperature fluctuation during the measurement, suggesting that no obvious grain growth is triggered by the electric current. The color of all the 7 grains in the orientation maps remains unchanged through the 11 scans, indicating no dramatic rotation of tens of degrees as what was reported in the Sn strips8 or appearance of cyclic twinning17.

Bottom Line: Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction.Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains.A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

View Article: PubMed Central - PubMed

Affiliation: Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, Shaanxi 710049 China.

ABSTRACT
Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction. With this technique, crystal orientation evolution is monitored at intragranular levels with high spatial and angular resolution. During the entire experiment, no crystal growth is detected, and rigid grain rotation is observed only in the two grains within the current crowding region, where high density and divergence of electric current occur. Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains. A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

No MeSH data available.


Related in: MedlinePlus