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On the intermetallic corrosion of Cu-Al wire bonds

 
: Boettcher, T.; Rother, M.; Liedtke, S.; Ullrich, M.; Bollmann, M.; Pinkernelle, A.; Gruber, D.; Funke, H.-J.; Kaiser, M.; Lee, K.; Li, M.; Leung, K.; Li, T.; Farrugia, M.L.; O'Halloran, O.; Petzold, M.; März, B.; Klengel, R.

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Postprint urn:nbn:de:0011-n-1725864 (3.6 MByte PDF)
MD5 Fingerprint: e9a77da2b9adac23bdb849e06aa34ca9
© 2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Created on: 20.4.2013


Institute of Electrical and Electronics Engineers -IEEE-, Singapore Section, Reliability CPMT EDS Chapter; IEEE Components, Packaging, and Manufacturing Technology Society:
12th Electronics Packaging Technology Conference, EPTC 2010 : Singapore, 8 - 10 December 2010
New York, NY: IEEE, 2010
ISBN: 978-1-4244-8560-4
ISBN: 978-1-4244-8561-1
pp.585-590
Electronics Packaging Technology Conference (EPTC) <12, 2010, Singapore>
English
Conference Paper, Electronic Publication
Fraunhofer IWM ()

Abstract
A detailed description of the Cu-Al wire bond interface is presented, which can possibly explain the often observed corrosion failures in humidity reliability tests. Using micro-structural analysis techniques, it is shown that the unstressed interface contains up to three intermetallic phases, where the Cu-rich phases are located at the Cu-ball interface. Upon humidity stress test only the high-Cu containing intermetallic layers close to the Cu wire ball bond undergo a corrosion process, whilst the Cu-lean layers are stable in all environment stress tests. The failing layers consist out of an amorphous Al-based oxide matrix with embedded Cu precipitates. The failure process can be explained as galvanic corrosion of the intermetallic phases. The Cu-rich phases corrode faster compared to Al-rich phases, since they have an electrochemical potential lower than the Cu cathode and form, hypothetically, a less stable self-passivation oxide. The observed time-to-failure is then determined by the composition, thickness and volume of the intermetallic layers. This was verified by reliability test results performed on open wire bonds and on plastic encapsulated products. ©2010 IEEE.

: http://publica.fraunhofer.de/documents/N-172586.html