Physical - metallurgical relations in lead - free solders structure and their interfaces in joints

Project start:	01.01.2006
Project end:	31.12.2008
Programme:	VEGA
Project number:	2/6160/26
Institute position in the project:	The only one project investigator
Project leader:	Pavol Šebo

The topic of project was to know relations of development of lead-free solders based on SnAgCu system in dependence on the type and quantity of additive element. To reach mentioned intent it was necessary to know the connectivity between the structure and physical and mechanical properties of solders, to know and control the processes of interaction of the solders with metallic, ceramic and composite substrate and to know the relations between the structure and properties of the joints made of mentioned materials. Determination of the phases arising at the interface between lead-free solder of Sn3.5Ag0.4Cu type close to eutectic composition and copper substrate after wetting at 280°C and 1800 s was elaborated. Effect of  indium in the solder on the phase composition was also studied. Using EDX analyse, standard as well as scanning x-ray  diffraction methods two phases were indicated at the interface for the solders containing  indium up to ~ 30 wt.%: Cu₆Sn₅ a InSn₄. For higher amount of indium in the solder (up to 75 wt.%) Cu₄₁Sn₁₁ a In₃Sn phases are present.