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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

Crystal orientation distribution in the solder joint before the EM test obtained from μXRD.(a,b) The orientation maps and their inverse pole figures of the in-plane X- and Y-directions, respectively. Electric current flow direction as well as the current crowding region are marked, and 7 grains are numbered for detailed study.
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f1: Crystal orientation distribution in the solder joint before the EM test obtained from μXRD.(a,b) The orientation maps and their inverse pole figures of the in-plane X- and Y-directions, respectively. Electric current flow direction as well as the current crowding region are marked, and 7 grains are numbered for detailed study.

Mentions: The cross-section of a Pb-free Sn-based solder joint was raster scanned with μXRD before and during the EM test, and 11 scans were made in total within a 43 h period. More experimental details are given in the Methods section. To express the crystal orientation, a Cartesian coordinate system O-XYZ was established, with its X- and Y-axes parallel with the horizontal and vertical scanning directions, respectively, and its Z-axis perpendicular to the sample surface (shown in Fig. 1). Two dimensional orientation maps were generated by indexing all the Laue diffraction patterns. Fig. 1a,b show the crystal orientation distributions of the cross-section of the Sn solder joint along the X- and Y-scanning directions, respectively, before the EM test. Black curves in Fig. 1a,b display the grain boundaries, which are defined as disorientation angles greater than 5° between two adjacent pixels, and herein 34 grains are counted in the maps16. Most of the grains, especially in the middle and right half of the solder joint, show green and purple color in Fig. 1a,b, respectively, indicating preferential crystal orientation. This preferential texture is also evident from the inverse pole figures, shown in Fig. 1c,d.


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)

Crystal orientation distribution in the solder joint before the EM test obtained from μXRD.(a,b) The orientation maps and their inverse pole figures of the in-plane X- and Y-directions, respectively. Electric current flow direction as well as the current crowding region are marked, and 7 grains are numbered for detailed study.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Crystal orientation distribution in the solder joint before the EM test obtained from μXRD.(a,b) The orientation maps and their inverse pole figures of the in-plane X- and Y-directions, respectively. Electric current flow direction as well as the current crowding region are marked, and 7 grains are numbered for detailed study.
Mentions: The cross-section of a Pb-free Sn-based solder joint was raster scanned with μXRD before and during the EM test, and 11 scans were made in total within a 43 h period. More experimental details are given in the Methods section. To express the crystal orientation, a Cartesian coordinate system O-XYZ was established, with its X- and Y-axes parallel with the horizontal and vertical scanning directions, respectively, and its Z-axis perpendicular to the sample surface (shown in Fig. 1). Two dimensional orientation maps were generated by indexing all the Laue diffraction patterns. Fig. 1a,b show the crystal orientation distributions of the cross-section of the Sn solder joint along the X- and Y-scanning directions, respectively, before the EM test. Black curves in Fig. 1a,b display the grain boundaries, which are defined as disorientation angles greater than 5° between two adjacent pixels, and herein 34 grains are counted in the maps16. Most of the grains, especially in the middle and right half of the solder joint, show green and purple color in Fig. 1a,b, respectively, indicating preferential crystal orientation. This preferential texture is also evident from the inverse pole figures, shown in Fig. 1c,d.

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