Formation of octahedral corrosion products in Sn-Ag flip chip solder bump

We investigated the corrosion behavior of the Sn-2.3 wt%Ag flip-chip solder bump in distilled water. At the early stage, dendritic corrosion products were converted into pyramidal shapes. The six pyramids grew simultaneously during a prolonged corrosion process. Finally, the octahedral corrosion products are formed. The octahedral corrosion product consisted of Sn and O, and was a mixture of amorphous and nanocrystalline SnO2 phase. The mechanism of this corrosion product was essentially a galvanic cell reaction. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.