Patent ID: 6224690
Filing Date: 2001-05-01
Classification: B23K,B32B,C22C,H01L

Abstract:
An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising:a two-layer ball-limiting metallurgy comprising an adhesion/barrier layer and a copper-free solderable layer wherein said adhesion/barrier layer is between a microelectronic device and said copper-free solderable layer and wherein said copper-free solderable layer is of a metal selected from the group consisting of Ni, Co, Fe, NiFe, NiCo and NiCoFe, each said metal from said group being sufficiently non-reactive with components of a tin-containing lead free solder, such that said copper-free solderable layer remains after being placed in contact therewith in a soldering action; andone or more lead-free solder balls selectively situated on said copper-free solderable layer, said lead-free solder balls consisting of tin as the predominant component and one or more alloying components selected from the group consisting of Bi, Ag and Sb, whereby said lead-free solder ball substantially avoids alpha particle emission and induced soft logic errors which result therefrom.