Investigation of under bump metallization systems for flip-chipassemblies

摘要

The objective of this work was to investigate the quality of UnderBump Metallization (UBM) systems used for solder bump flip chipapplications. These three commercial UBM systems were (i)Al/NiV/Cu UBMwith print-and-reflow solder, (ii)Ti-W/Cu UBM with electroplated solderand (iii) Electroless Ni/Au UBM with print-and-reflow solder. The solderwas of an eutectic Sn/Pb composition. UBM quality in terms of thermalstability, corrosion-resistance and thermal-mechanical reliability wereinvestigated using various multiple solder reflow passes, hightemperature storage, pressure cooker test and temperature cycling.Analytical tools such as Scanning Electron Microscopy (SEM),Transmission Electron Microscopy (TEM) and Energy Dispersive X-raySpectrometry (EDS) were used to analyze the metallurgy reactions andfailure modes. This study showed that none of the three systemsinvestigated out-performed the other two in all aspects in the testsconducted