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Published online by Cambridge University Press: 15 February 2011
The microstructure of 95Pb-5Sn flip-chip solder bonds deposited on Cr/Cu/Au metallisation pads has been studied using both light and electron analysis techniques. The presence of Sn-Cu- Au ternary intermetallic phases was detected within the Pb-rich matrix at significant distances from the originally deposited interface. The distribution of the phases present after the solder has undergone a reflow heat treatment can be interpreted using recent equilibrium ternary diagram data. An investigation was also made into the effects of various non-reflow heat treatments at carefully chosen temperatures, to qualitatively evaluate the extent of solid state diffusion and the resultant phase distribution.