Abstract
The effects of reflow time, high temperature aging, and current-stress on interface reactions between Under Bump Metallization (UBM) systems and electroplated bumps have been studied. Each of TiW/Cu/electroplated Cu, Cr/CrCu/Cu, NiV/Cu, and TiW/NiV UBMs was coupled with Pb/63Sn or Sn/3.5Ag flip-chip solder bump. The Sn/3.5Ag and Pb/63Sn flip-chip solder bumps were fabricated on the UBMs using alloy plating. Plated Sn/Ag solder becomes Sn/Ag/Cu by reflowing on the Cu containing UBMs. Intermetallic Compounds (IMC) such as Cu-Sn and Ni-Sn spall-off from UBM/solder interface as Cu or Ni, the solder wettable layer, is consumed during liquid-state 'reflow' process. In thermo- electromigration test, metal atoms move in the same direction as the electron current flows and the subsequent void accumulation at cathode UBM induces failures. I. Introduction The demand for Pb-free and high density flip-chip interconnection technology is growing rapidly. Electroplating bumping method is a good approach to meet fine pitch requirements. This plating method is accepted by companies for high volume production and the market is growing, as well. However, more than binary composition control of solder plating is very difficult up to now. Recent studies show that Cu is easily diffused into solder though it makes Cu-Sn IMC at the interface (1,2). It means solder composition is changed depending on UBM metallurgy and reflow condition. This composition change is of special interest to electroplated Sn/Ag bump. In the flip-chip interconnection, especially for highly reactive Sn-rich solder and small size bump, a selection of a proper UBM is very important because failures are mostly reported at the UBM/solder interface. In this study, Sn/3.5Ag and Pb/63Sn solder interface IMC growth behavior, solder composition change, diffusion barrier characteristics, and electromigration behaviors have been investigated depending on UBM and solder material. II. Experimental II-1. Bumping process
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
