To determine the role of microstructure in the creep and thermomechanical fatigue (TMF) properties of solder joints made with eutectic Sn‐Ag solder, and Sn‐Ag solder with Cu and/or Ni additions.
Quaternary alloys containing small amounts of Cu and Ni exhibit better high temperature creep resistance and also better resistance to damage under TMF cycles with a longer dwell time at the high temperature extreme, than eutectic Sn‐Ag, and Sn‐Ag‐Cu ternary alloy solder joints. Microstructural evaluation was conducted to investigate the effects of Ni additions to Sn‐Ag‐based solder joints.
Microstructural studies of the quaternary solder alloys revealed the presence of small ternary Cu‐Ni‐Sn intermetallic compound particles at Sn‐Sn grain boundaries. These precipitates can retard the grain boundary sliding that will occur during TMF with longer dwell times at the high temperature extreme, and during high temperature creep.
The findings of this paper will help to provide an understanding of the effects of alloying elements on Sn‐Ag based solder joints.
