Manufacturability and reliability of lead-free package

Abstract

The European Community has been finalized to phase out on July 1,2006 for Lead(Pb) in electronic products. This cause the semiconductor industry is required to study new materials for replace the lead in its products. This paper presents the manufacturability and reliability study of the commercial lead-free alternatives to replace the currently used solder plating. This paper presents the findings of a series of experiment to evaluate various commercial lead-free plating alternatives, including tin and tin-bismuth products. The 2 different IC package types (Gull wing and J-Bend) were used in both off line and in a production environment to evaluate plating quality on solderability aspects including plating thickness, composition, ionic impurity, morphology grade, solderability (tested after a variety of thermal & humidity conditioning parameters), wettability and lead pull tests of surface mounted packages (using different reflow profiles - both NEMI and JEDEC recommended), and tin whisker growth. Since no lead-free plating standards of quality were available at the time of the study, normal solder plating standards were used as a reference. Tin and tin-bismuth plating were further investigated in production processes to attempt to eliminate the initial quality issues, and to develop, fine-tune and optimize the plating process, through a manufacturability study and reliability study. Tin plating looked the most promising material. Tin whisker growth is a major reliability problem when Pb-free deposits are implemented. This paper also presents some of the tin whisker mechanistic studies undertaken on one of the Pb-free chemistries tested.