The reliability performance of low cost bumping on aluminum and copper wafer

A low cost bumping technology on semiconductor is described here using elec troless Ni/Au plating for Under Bump Metallurgy (UBM)) formation instead of traditional processes involving sputtering, photolithography, and etching those need many expensive equipment. The higher throughput and lower cost c an be achieved if we combine electroless Ni/Au technology and stencil solde r printing technology. Low cost bumping technology has been successfully de veloped on Al wafers. The results of reliability tests, such as high temper ature storage, temperature cycling and temperature-humidity storage, show t hat solder bumps with electroless Ni/Au as UBM exhibit good reliability and are suitable for flip-chip application. In addition to electroless Ni/Au p lating on Al pads, the development of low cost bumping on Cu wafers is also presented in this paper. The performance of Ni/Au bumps on copper, such as morphology and shear strength, is superior to that on Al pads. The reliabi lity tests of low cost solder bumps were also performed on dummy copper waf ers that consist of sputtered Cu and PI passivation. Comparisons were also made on the reliability performance of low cost solder bumps on aluminum an d copper pads in this paper.