Properties of thin layers of Sn62Pb36Ag2

摘要

The increasing miniaturisation of surface mount devices(SMD)reveals some new questions concerning the reliability of solder joints.The components become larger and the solder joints smaller. Especiallythe thickness mainly influences the mean lifetime of surface mounttechnology (SMT) solder joints, where micro-fracture and damage evolveunder thermomechanical cycling. When the electrical power is switched onand off, the solder joints are heavily distorted due to the thermalexpansion mismatch of the package and the PCB. The deformation ineutectic Sn-Pb at homologous temperatures close to 1 is known to bestrongly related to grain- and phase boundary mechanisms. Therefore, achange of the mechanical behaviour is expected, if the phase size is ofthe order of the thickness of the solder layer. This paper covers thedetermination of the deformation behaviour of thin layers, down to 25μm