| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 102 === These years, the higher gold price has forced a number of groups in industry and academy to develop new wire bonding materials to replace the gold wire. The newly developing Ag alloy wire has a great deal of advantages include either cost or reliability and is a better approach for the electronic packaging industry doubtlessly. Thanks to the continually improving lithography of upstream, the function of 3C products in our daily life keeps on improving. To prolong Moore’s Law, 3D IC was invented, and the metal bumps are necessitated during packaging. However, the prevailing method such as electroplating has raised a few pollution issues. In contrast, Stud Bump rules out electroplating and fulfills the environment-friendly need. This research assesses the possibility if the Ag alloy wire could substitute the traditional gold wire to make highly reliable metal bumps.
In this research, the first part is to assess the electrochemical property of current bonding wire, the corrosion potential and current on the polarization curve decide the corrosion resistance. The results show that the Al wire has the poorest corrosion resistance, and after EFO burning, the Pd layer of Pd-coated Cu wire will diffuse inside the core. Different to them, Ag can gain much higher corrosion resistance after alloying with noble metals Pd and Au. The corrosion resistance trend is : Ag-8Au-3Pd > Pd-Coated Cu > Ag-3Pd > Al.
Second part is the simulation of Stud Bump interface. In the results, Au will diffuse into Sn layer abundantly to form AuSn4 after the reaction between traditional gold bump and solder (Sn-3Ag-0.5Au), gold embrittlement and the interface will result crack. It also shows that in the reaction between Cu and solder, the formation breaks with cracks because the IMC is too thin, and the reliability is poor. In contrast, the interface between Ag alloy and solder after reacting is simple - the only IMC Ag3Sn forms stably, and the average thickness is between the two reactions above. However, after aging for a long time at 200℃, Sn will go across Ag3Sn and form AuSn or PdSn4 with Au and Pd, furthermore, and results in cracks.
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