DropReliability Performance Assessment forPCBAssemblies ofChipScale Packages (CSP)

Dropimpact reliability assessment ofsolder joints on thechipscale packages iscritical foruseinminiature handheld products. Replacement oflead-based withleadfree solders requires theneedofevaluating its compatibility withexisting printed circuit boardsurface finishes. A l5x15mmfine-pitch BGAwithsolder ball compositions of 36Pb-62Sn-2Ag andSn-4Ag-0.5Cu onsurface finishes of organic solderability preservative, electroless nickel immersion gold andimmersion tinweretested. Theresults revealed a strong influence ofdifferent intermetallic compound formation onsoldered assemblies drop durability. Thelead-based solder supersedes thelead-free composition regardless ofthetypes ofsurface finish. Joints onorganic solderability preservative werefoundtobestrongest for eachsolder type. Other factors affecting drop reliability such ascomponent location ontheboard anddrop orientation are reported.