Evolution of Intermetallic Compounds, Phase Transformation and the Interfacial Reaction Modified by the Bonding Order of the Under Bump Metallization in Cu/Sn-Ag/Ni Micro-bump
| Autor: | Tu, Wei, 杜威 |
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| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 With the highly demand for the miniaturization of large-scale-integration of circuits on Si chips, the electronic packaging technology has been evolved from conventional flip-chip bumps to small micro-bumps. Dramatically reduction of soldering volume results in a great concern of packaging reliability. Furthermore, in micro-bumps, not only the characteristics of interfacial reaction will be a main concern but also more limitation in fabrication process. As a result, architecture control through process modification to alter the microstructure of micro-bumps was demonstrated to affect the interfacial reaction in micro-bumps. Meanwhile, the understanding of interfacial reaction in micro-bumps is a potential way to solve the critical issues in this small solder volume system. In this study, two steps of boing process were investigated. One with ENIG substrate bonded ahead of the Cu substrate, the other with OSP-Cu substrate bonded ahead of the Ni substrate. By bonding the ENIG substrate ahead of the Cu substrate, the microstructure evolution of ENIG/Sn-3.5Ag/Cu micro-bumps after reflow was studied. Due to the short diffusion path between two opposite substrates, the effects of substrate dissolution by two-steps reflowing process in ENIG/Sn-3.5Ag/Cu micro-bumps revealed a complex 5 layered structure. After 30 sec of reflow, only ENIG side has a dual phase structure composed of H-(Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. After longer reflow time, it is interesting to note that dual phase structure appeared at both Cu and ENIG sides. H-(Cu,Ni)6Sn5 and L-(Cu,Ni)6Sn5 showed up at the Cu side, meanwhile, H-(Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 were at the ENIG side after reflow for 5 min. The dual phase structures are believed to be vulnerable to cracks and lead to degradation of micro-bumps’ reliabilities. In contrast, by bonding the OSP-Cu substrate ahead of the Ni substrate, the microstructure evolution of OSP-Cu/Sn-3.5Ag/Ni micro-bumps after reflow was also studied. It is noted that the microstructure of IMCs on both interface of the substrates showed a significant difference as only one phase was found, which was L-(Cu,Ni)6Sn5. Also, the deteriorative dual phase structures found in ENIG/Sn-3.5Ag/Cu micro-bumps were no longer shown in OSP Cu/Sn-3.5Ag/Ni micro-bumps. With the aid of the field emission electron probe micro-analyzer (FE-EPMA), the mechanisms of the microstructural evolution are probed in detail by the phase diagram and the diffusion related migration of the constituents. It is expected that the results derived in this study can provide useful information for the industry of microelectronic packaging. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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