Material-Dependent Reliability Characteristics of Lead-Free Solder Joints

Solder joints of lead-free electronic assemblies are characterized by a high material diversity due to different finish types of component terminations and also pad finishes of PCB's used. Besides this various lead-free solder alloys are available. During the soldering process all the different materials interacting with each other in relation the soldering conditions forming intermetallic layers at the interface. Thus different material qualities of solder joints are generated and the reliability is material-dependent. Varying intermetallics have different brittle properties. Therefore the materials used have significant influence on the reliability besides certainly constructive properties of the packages and boards especially in the case of miniaturized solder joints. The selection or modification of the materials used is important to affect the metallurgical properties of solder joints including the intermetallic formation, i.e. type and quantity of intermetallics. Application-related development results within the research project InnoLot regarding high temperature applications are presented. Results of board level reliability are shown