The undercooling of flip-chip Pb-free solder bumps was investigated by differential scanning calorimetry (DSC) to understand the effects of solder composition and volume, with and without the presence of an Under Bump Metallurgy (UBM). In addition, the solidification of an array of individual solder bumps was monitored in-situ by video imaging technique during both heating up and cooling down cycles. Data obtained by the optical imaging method is used to compliment the DSC thermal measurements. A random solidification of the array of bumps was demonstrated during cooling which also spans a wide temperature range of 40-80°C. In contrast, an almost simultaneous melting of the bumps was observed during heating.
By: Sung K. Kang; M. G. Cho; P. Lauro; Da-Yuan Shih
Published in: RC24010 in 2006
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