Because Fe has a more negative standard reduction potential than Ni, the simultaneous electroless deposition of Fe and Ni is difficult. In this study, Fe-42Ni（P） electroless deposit was prepared by using disodium ethylene diarnine tetraacetate （ETDA-2Na） as complexing agent to reduce the difference in the electrode potential between Ni2＋ and Fe2＋o The solderability and the interfacial reaction between Fe-42Ni（P） alloy and Sn were investigated. It was found that the electroless Fe-42Ni（P） alloy has excellent wettability with Sn. Moreover, the interfacial reaction rate between Fe-42Ni（P） and Sn is very slow. These results suggest that Fe-42Ni（P） alloy may become an attractive under-bump metallization （UBM）.
The reactive Sn63Pb37 spreading on patterned film structures was examined in a reducing atmosphere （H2 5%＋Ar 95%）. Liquid solder spreading was observed to follow the wheel pattern made of Au/Cu thin film. At the center, a liquid cap was formed around the hub by viscous spreading of the liquid front. Ahead of the main viscous flow front, a liquid film was found to be extended on thin Au-Cu lines at a fast rate to a great distance by rapid Sn-Au chemical reaction.
The thermodynamic conditions for dewetting of a liquid solder drop on copper thin films were examined under a hot-stage optical microscope in a flowing protective atmosphere.Dewetting of liquid solder was found to depend strongly on the copper film thickness and preceded by spalling of Cu 6 Sn 5 intermetallic compounds.However,the loss of interfacial bonding by spalling was not sufficient to cause immediate dewetting of solder drops if the wetting tip was still strongly bonded to the copper film.By introducing a pinning force on the wetting front,a sufficient condition was found from a force balance analysis for dewetting of the liquid solder drop,in general agreement with the experimental results.
