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|Correlations of Long-Term Reliability and Irregularly Electrodeposited Metal Surface Induced Corrosion on Module Tabs|
|Keywords: Device reliability, Corrosion, Electrodeposition|
|In order to ensure long-term reliabilities of electronic devices, one needs to minimize chemical, physical, and thermomechanical failures. Of them, the most common chemical failure is corrosion in metallization, bonding pads, and bonding wires. Particularly, localized corrosion occurring at irregularly deposited less noble metal (anode) surrounded by large noble metal (cathode) has a severe effect on reliability of devices. In the meantime, a major factor causing the localized corrosion is the heterogeneity either in metal or in electrolyte. It is also related to geometrical effects. Heterogeneity in metal is categorized by the involvement of second phases or nonmetal and by unevenly distributed microstructures. In this study, we will discuss the extremely accelerated local attack that results in holes in electrodeposited Au on electroless nickel immersion gold (ENIG) upon Cu substrates. The driving force for this local corrosion is roughly deposited metal surfaces which makes the galvanic potential difference at the interface of Au and Ni. Although it is not easy to detect holes because of their small size, once the hole is formed the rate of metal erosion incredibly increases. We use electrochemical approaches to measure the corrosion kinetics while scanning probe microscope and focused ion beam techniques reveal the corroded metal structures. On the basis of these analyses we can predict the reliability of devices and suggest the inhibition methods to the localized corrosion.|
|Joohan Lee, Senior Engineer
Samsung Electronics Co., Ltd.
Asan-City, Chungchungnamdo 336-851,