Pb-free microjoints (50 /spl mu/m pitch) for the next generation microsystems: the fabrication, assembly and characterization

Description

This item was taken from the IEEE Conference ' Pb-free microjoints (50 /spl mu/m pitch) for the next generation microsystems: the fabrication, assembly and characterization ' To support the next generation highly integrated microsystem with 3D silicon integration using fine pitch interconnection and Si carrier, we develop a fabrication and assembly process at IBM Research to produce solder micro-joints (fine pitch flip-chip interconnections) for our system-on-package (SOP) technology. We fabricate solder bumps with 25 /spl mu/m (or less) in diameter on 50 /spl mu/m pitch size, as well as 50 /spl mu/m in diameter on 100 /spl mu/m pitch size, at wafer level (200mm) by electroplating method. There are up to 10208 micro-bumps (25 /spl mu/m) built on a chip surface less than 0.4 cm/sup 2/. The process can be applied to various solder compositions, including eutectic SnPb, Pb-free (CuSn), AuSn and high Pb (3Sn97Pb) solders. The test matrix includes different solder/UBM (under bump metallization) combination. In this paper, the discussion focuses on the fabrication, assembly and characterization of the micro-joints made with of Pb-free (CuSn) and eutectic SnPb solders with Ni and/or Cu stack plating. The preliminary electrical and mechanical test results indicated that reliable and high yield micro-bumps can be successfully made with this fabrication and assembly process.