an interconnection structure suitable for flip - chip attachment of microelectronic device chips to packages , comprising a two , three or four layer ball - limiting metallurgy including an adhesion / reaction barrier layer , and having a solder wettable layer reactive with components of a tin - containing lead free solder , so that the solderable layer can be totally consumed during soldering , but a barrier layer remains after being placed in contact with the lead free solder during soldering . one or more lead - free solder balls is selectively situated on the solder wetting layer , the lead - free solder balls comprising tin as a predominant component and one or more alloying components .