Due　to　the　hazards　to　human　environment　caused　by　lead,　lead-free　solder　is　a　trend　for　wide　application　in　the　industries.　The　difference　on　the　microstructure　between　lead-free　solder　and　lead　solder　leads　to　a　different　constitutive　behaviour,　which　makes　their　lives　different.　It　has　been　found　that　energy　model　which　relates　to　stress-strain　loop,　can　be　measured　accurately.　Therefore　energy　models　are　applied　to　predict　the　life　of　solder　joints　in　electronic　packing.　The　failure　of　a　solder　can　be　attributed　to　plastic　strain,　elastic　strain,　steady-state　strain　and　transient-creep　strain.　This　paper　systematically　introduces　the　constitutive　behaviour　of　lead-free　solder　through　plastic　strain,　elastic　strain,　transient-state　strain,　and　summarizes　the　energy　model　applied　in　the　life　prediction　of　lead-free　solder　joints.