Investigations of Au-Sn alloys on different end-metallizations for high temperature applications [solders]

Au-Sn solder is becoming increasingly important in the field of microelectronic packaging. For high temperature and fluxless applications in particular, for example in optoelectronics, Au-Sn solder bumps are used. The Au-Sn solders come in contact with different end-metallization systems such as nickel, platinum or palladium used as underbump-metallization. Information about the Au-Ni-Sn, Au-Pd-Sn and Au-Pt-Sn ternary systems in terms of metallurgical fundamentals are very important for understanding and controlling the technological processes. This knowledge is the base for investigations of reliability, phase formations, growth and stability, diffusion mechanisms and diffusion pathways. This paper summarizes the work done on different Au-Ni-Sn, Au-Pd-Sn and Au-Pt-Sn alloys with maximum 20 at.% Ni, Pd and Pt contents, and investigations on diffusion and interface reactions of Au-Sn solders on Ni, Pd and Pt. Isothermal sections of the solid state are introduced. The presence of unknown Au-Ni-Sn and Au-Pd-Sn phases in the tie-triangle is discussed. Results of diffusion investigations and interface reactions are shown.