ISSN:
0954-0911
Source:
Emerald Fulltext Archive Database 1994-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The elimination of lead from solders for flip-chip attachment has necessitated many new studies on the reliability of the resultant systems. There are many lead-free solder material systems. However, most of them contain a large proportion of tin. The tin in the solder reacts with the copper layer present in some types of under bump metallisation (UBM) depleting the UBM of copper, and thereby causing loss of adhesion and a weak interface. In this work, the relative reliability of Cr/Cu/Cu and Cr/Cu/Cu/Ni UBM systems was studied. The UBM systems were deposited with an electroplated Sn-3.5Ag lead-free solder alloy. The results conclusively showed that the Cr/Cu/Cu/Ni UBM system is a better choice for the Sn-3.5Ag lead-free solder. In the Cr/Cu/Cu/Ni UBM system, the thickness of the nickel layer was found to be an important parameter. Multiple reflow and high temperature storage test results showed that serious depletion of the UBM layer could occur if the UBM layers were not optimised. The thermo-mechanical reliability of Ni-based UBM bumps showed promising results up to 1,500 temperature cycling.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1108/09540910310479521
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