The effects of aged Cu-Al intermetallics to electrical resistance in microelectronics packaging

• Published in: Microelectronics international 2002-08, Vol.19 (2), p.38-43
• Main Authors: Chee Wei, Tan, Razak Daud, Abdul
• Format: Article
• Language: English
• Subjects: Aging; Aluminum; Applied physics; Applied sciences; Copper; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Energy; Exact sciences and technology; Manufacturing; Materials; Microelectronics; Studies; Testing, measurement, noise and reliability
• ISSN: 1356-5362; 1758-812X
• DOI: 10.1108/13565360210427889

A Cu-Al bonding system exists when copper wire is bonded onto an aluminum bond pad using thermosonic wire bonding technology. Aged Cu-Al bonding system was analyzed by measuring the intermetallics layer thickness and its correlation to electrical contact resistance. Result shows that the thickness of Cu-Al intermetallics layer grows almost linearly to aging time. The activation energy needed for Cu atoms to diffuse into Al was calculated using Fick's law; Q=129.66 kJ mole and D0=1.628×10−4 m2 s. The calculation of activation energy and impurity diffusity using Model Kidson also shows linear relationship. Electrical resistance of Cu-Al intermetallics layer was calculated from contact resistance of Cu-Al bonding system. The result shows that the electrical resistance of Cu-Al intermetallics layer increases linearly with intermetallics thickness. Its growth rate that was calculated using Model of Braunovic and Alexandrov is double of Model of Murcko.