Abstract
ABSTRACTIn the flip chip interconnection on organic substrates using eutectic Pb/Sn solder bumps, highly reliable Under Bump Metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as l.tm Al/0.2 μm Ti/5 μm Cu, l μm A1/0.2 μm Ti/l μm Cu, 1 μm A1/0.2 μm Ni/1 μm Cu and 1 μm At/10.2μm Pd/l μm Cu, laid under eutectic Pb/Sn solder of low melting point, were investigated with regard to their interfacial reactions and adhesion properties. The effects of numbers of solder reflow and aging time on the growth of intermetallic compounds (IMC) and on the solder ball shear strength were investigated. Good ball shear strength was obtained with 1 μm AI/0.2μm Ti/5μm Cu and 1 μm Al/0.2 μm Ni/l μm Cu even after 4 solder reflows or 7 day aging at 150°C. In contrast, l μm Al/0.2 μm Ti/l μm Cu and l μm A1/0.21μm Pd/μm Cu shows poor ball shear strength. The decrease of the shear strength was mainly due to the direct contact between solder and nonwettable metal such as Ti and Al resulting in a delamination. Thin 1 μm Cu and 0.2 μm Pd diffusion barrier layer were completely consumed by Cu-Sn and Pd-Sn reaction.
Published Version
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