| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 104 === As electronic devices become more functional and miniature, two dimensional packaging becomes insufficient. Three dimensional packaging is gradually replacing two dimensional packaging, because of its high-density input/output (I/O) interconnects. Electromigration is always a serious and persistent reliability issue. This study focuses on electromigration failure mode in different types of microbumps.
In this study, we used four types of microbumps. Their structures are Ni/16μm SnAg/Ni, Ni/8μm SnAg/Ni, Cu/16μm SnAg/Cu and Cu/8μm SnAg/Cu, respectively. Daisy chains with forty microbumps were used. Each daisy chain was heated on 150℃ hotplate and the applied current density was 8x104 A/cm2. When resistance increased 20%, 50% and 100% of their initial values, we stopped the experiments and polished the samples to observe their failure mechanism by scanning electronic microscope and energy dispersive spectrometers.
Due to the fast reaction rate of copper and tin, thick copper underbump metallization (UBM) or nickel UBM was added in flip chip to elongate lifetime of the microbumps. In this study, we find out that the ability of interconnects to resist electromigration improved greatly when microbumps transformed into intermetallic compound (IMC) microbump. The fast dissolution of UBM and fast formation of IMC are good for microbumps to resist electromigration. The approach to improve electromigration lifetime in microbump is quite different from flip chip joints.
|
|---|
