Next Generation Solder-Systems for Thermal Interface and Interconnect Applications via Liquid Phase Sintering

This paper reports on a new paradigm for highly flexible solder design, proffering high electrical and thermal conductivity, in conjunction with good mechanical compliance, via a novel Liquid Phase Sintering (LPS) approach. The new LPS solders comprise a high melting point phase HMP (e.g., Cu or Sn) with a small amount of a low melting-point phase LMP (e.g., In) at grain boundaries, such that different properties can be controlled by different constituents. In general, conductivity is dominated by the majority HMP constituent, while deformation is controlled by the minority, LMP grain boundary constituent. The LPS solders are suitable for both thermal interface material (TIM) and interconnect applications. As the application space for solders shifts in the future, and requirements for new property-sets emerge, the flexibility of the LPS solder approach will allow integration of different materials into new LPS solder-systems.