23 August 2000 Discolored bondpads caused by aluminum hydroxide formation
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Discolored bondpads and poor adhesion or non-stick failure during bonding was investigated. The bondpads looked either brown in color at corners or just discolored without brownish corners. SEM inspection showed such bondpads had porous surface that was worse at corners. EDX, FIB and Auger Electron Spectroscopy (AES) were used to analyze and identify the root cause. Failure analysis showed that the discolored bondpads were caused by the formation of aluminum hydroxide. This process was an oxidation or corrosion process that could not be avoided when bondpads were exposed to atmospheric environment. EDX analysis further confirmed the existence of Al-O chemical bonding. FIB/SEM analysis showed clearly the porous layer grew thicker towards the bondpad edge by consuming more aluminum. The layer of aluminum hydroxide on the bondpads created a barrier for good bonding. It is the responsibility of both fab and assembly plant to take preventative action to avoid the excessive exposure of bondpads to moisture during manufacturing.
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Zong Min Wu, Zong Min Wu, Chong Khiam Oh, Chong Khiam Oh, Soh Ping Neo, Soh Ping Neo, Shailesh Redkar, Shailesh Redkar, } "Discolored bondpads caused by aluminum hydroxide formation", Proc. SPIE 4182, Process Control and Diagnostics, (23 August 2000); doi: 10.1117/12.410086; https://doi.org/10.1117/12.410086

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