Reliability and characterization of dielectric layers used for leaded and lead-free solder application

Lots of advanced packaging forms were introduced to meet different application by using the solder balls as the interconnect media between chip and substrate. With the environment protection concerns increasing, lead free solders are playing the more and more important role in this area. The properties and characterization between solder joints and dielectric layers are key reliability issues. The present works mainly focuses on the investigation of the quality of dielectric layers for wafer level chip size packages (WLCSP). In this paper, both the negative tone (Durimide 7510/7320) and positive tone (Durimide 9005) photosensitive materials are evaluated as the dielectric layer for the E-WLCSP. In the E-WLCSP, there were two major bumping processes to be introduced here: Ti/Cu/Ni/Au UBM with 63Sn/Pb eutectic solder and Sn/3.8Ag/0.7Cu lead free solder. The target is to choose the most reliable pairs for positive- and negative-tone polyimides, to meet the different bumping process requirement, and pass the reliability test.