Role of Intermetallics in Lead-Free Alloys

Abstract

Intermetallics are intermediate compounds formed between two metals. They are usually brittle. The presence of intermetallics leads to deterioration in mechanical properties. This chapter reviews the intermetallic compounds formed during the manufacture of lead-free alloys. Intermetallic compounds formed in ordinary lead-based alloys are also discussed. The role of rare earth, especially indium and lanthanum, additions on intermetallic formation is examined. Microstructures of intermetallics are analysed. Hardness values of lead-free alloys are compared with emphasis on type and nature of intermetallics. SEM photographs of lead-free solders are discussed with regard to type of fracture, and the role of intermetallics in nature of fracture is examined. Lastly, the general mechanisms of formation of intermetallics are touched upon, and these mechanisms are extended to intermetallic formation in lead-free alloys.