Incorporation of metallic particulate reinforcements in eutectic Sn-Ag solder re sults in the formation of intermetallic compounds (IMCs) along particulate/ solder interfaces with different morphologies. For instance, "sunflower" and "blocky faceted" IMC shapes have been observed around Ni particle reinforce ments incorporated in the eutectic Sn-Ag solder matrix. The time and tempera ture above solder liquidus during the heating stage of the reflow process has been found to play a significant role in determining the IMC morphology in these Ni particulate-reinforced solders. Similar studies were carried out with Cu and Ag particulate reinforcements using the same solder matrix. The amount of heat input caused no significant change in morphology of the IMCs formed around Cu and Ag particulate reinforcements. Also, the IMC morphol ogy around Ni particles was sensitive to the Cu content in the solder, whether the Cu came from the substrate during reflow or it was already present within the solder.Key words: Lead-free composite solder, intermetallic morphology, metallic particle reinforcements in-situ methods 8,9 or mechanically incorporated, INTRODUCTION metallic particles, which upon reflow completely or Intermetallic compounds (IMCs) formed both partially transform into IMCs. [10][11][12] Ternary and quaat the solder/substrate interface and within the ternary alloys being considered for enhanced service solder during reflow exhibit different morphological performance also derive their better attributes befeatures depending on the conditions employed. Sigcause of IMC particles present within the solder. nificant efforts have been devoted to characterize Significantly different morphologies of the IMC that solder/substrate interface IMCs. 1-5 The brittle naform around Ni particles present within the eutectic ture of IMCs formed at the solder/substrate inter-96.5Sn-3.5Ag (wt.%) solder matrix have been obface and their potential to degrade the mechanical served. These morphologies were dependent on the performance of the solder joints provides the main reflow conditions. 13 Incidentally, these morphologi impetus to study these compounds. However, it has cal features, which develop during reflow, will differ been clearly documented in several studies that between the reinforcements. 14,15 The Ni particlecatastrophic failure caused by thermomechanical reinforced solder showed change in the morphology fatigue or creep occurs by crack growth within the of the IMC around the Ni particles as a consequence solder near the solder/substrate interface, not in the of an imposed reflow profile. Depending on time and interface IMC layer. 6,7 temperature above solder liquidus during reflow, The composite solder approach has been demonsunflower or blocky morphology of the IMC was strated to be a viable means to achieve better service noted. The strong role of time and temperature performance, particularly, in lead-free solders. [8][9][10][11][12] above solder liquidus during reflow, especially Such solders may contain a IMC produced...