Impression creep characterization of 90Pb-10Sn microelectronic solder balls at subsolvus and supersolvus temperatures |
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Authors: | D Pan I Dutta S G Jadhav G F Raiser S Ma |
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Affiliation: | (1) Center for Materials Science and Engineering, Department of Mechanical and Astronautical Engineering, Naval Postgraduate School, 93943 Monterey, CA;(2) Intel Corporation, Assembly Technology Development, MS CH5-165, 85226 Chandler, AZ |
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Abstract: | The creep behavior of Pb-10wt.%Sn, a common high-lead solder used in microelectronic packaging, was studied by impression
creep testing of ball-gridarray (BGA) solder balls attached to an organic substrate, both above and below the solvus temperature
(408 K). Below the solvus temperature, the solder microstructure consists of roughly equiaxed grains of the Pb-rich solid
solution α, which contains <5wt.%Sn in solution, with a coarse dispersion of Sn-rich β precipitates. Here, the creep behavior
of the solder is controlled by dislocation climb via dislocation core diffusion, yielding n≈4 and Q≈60 kJ/mole. Above the
solvus temperature, where the entire 10wt.%Sn is in solution, the creep mechanism becomes controlled by viscous glide of dislocations,
limited by solute drag, with n≈3 and Q≈92 kJ/mole. Based on experimental data, creep equations for the as-reflowed solder
in the two temperature regimes are given. Comparison of the present data with those available in the literature showed good
agreement with the proposed laws. |
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Keywords: | 90Pb-10Sn high lead solder microstructure impression creep |
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