Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Reliability investigations of hard core solder bumps using mechanical palladium bumps and SnPb solder
    ( 2002)
    Oppermann, H.
    ;
    Kalicki, R.
    ;
    Anhöck, S.
    ;
    Kallmayer, C.
    ;
    Klein, M.
    ;
    Aschenbrenner, R.
    ;
    Reichl, H.
    The choice of solder joint metallurgy is a key issue especially for the reliability of flip-chip assemblies. Besides the metallurgical systems already widely used and well understood, new materials are emerging as solderable under bump metallization (UBM). For single chip bumping Pd stud bumps form a solid core under the solder layer. These hard core solder bumps are an adequate solution if single dies are available only and the chosen assembly technology is flip chip soldering. The scope of this paper is to summarize the results from aging of lead/tin solder bumps on Palladium. The growth of intermetallic and its impact on the mechanical reliability are investigated.
  • Publication
    Pb-free Sn/3.5Ag electroplating bumping process and under bump metallization (UBM)
    ( 2002)
    Jang, S.Y.
    ;
    Wolf, J.
    ;
    Ehrmann, O.
    ;
    Gloor, H.
    ;
    Reichl, H.
    ;
    Paik, K.W.
    Pb-free solder is one of the biggest issues in today's electronic packaging industry. This paper introduces a newly developed Sn/3.5Ag alloy plating process For wafer level bumping. The effects of Under Bump Metallization (UBM) on the process, interfacial reaction, and mechanical strength have been investigated. Four different types of sputtering-based UBM layers-TiW/Cu/electroplated Cu, Cr/CrCu/Cu, NiV/Cu, and TiW/NiV-were fabricated with eutectic Pb/63Sn and Sn/3.5Ag solder. The result shows that the Sn/Ag solder gains Cu or Ni from UBM's and becomes Sn/Ag/Cu or Sn/Ag/Ni during reflow process. Sn/Ag solder has higher reactivity with Cu and Ni than Pb/63Sn. The Intermetallic Compound (IMC) spalling from the interface between UBM/solder has been observed on Cr/CrCu/Cu and TiW/NiV UBM's. However, the IMC spalling phenomena did not decrease the bump shear strength with a bump size of 110 mum, whereas a size of 60 pm brought a decrease in shear value and failure mode change.