Role of intermetallics on the mechanical fatigue behavior of Cu-Al ball bond interfaces
- Author(s)
- A. Lassnig, R. Pelzer, C. Gammer, G. Khatibi
- Abstract
The mechanical fatigue behavior of Cu–Al interfaces
occurring in thermosonic ball bonds –typically used in microelectronic
packages for automotive applications – is investigated by means of a
specially designed fatigue test technique. Fully reversed cyclic shear
stresses are induced at the bond interface, leading to subsequent
fatigue lift off failure and revealing the weakest site of the bond. A
special focus is set on the role of interfacial intermetallic compounds
(IMC) on the fatigue performance of such interfaces. Therefore fatigue
life curves were obtained for three representative microstructural
states: The as-bonded state is compared to two annealed states at 200 °C
for 200 h and at 200 °C for 2000 h respectively. In the moderately
annealed state two IMC layers (Al2Cu, Al4Cu9)
could be identified, whereas in the highly aged state the original pad
metallization was almost entirely consumed and AlCu is formed as a third
IMC. Finally, the crack path is traced back as a function of
interfacial microstructure by means of electron microscopy techniques.
Whereas
conventional static shear tests reveal no significant decrease of the
bond shear force with increased IMC formation the fatigue tests prove a
clear degradation in the cyclic mechanical performance. It can be
concluded that during cycling the crack deflects easily into the formed
intermetallics, leading to early failure of the ball bonds due to their
brittle nature.
- Organisation(s)
- Physics of Nanostructured Materials
- External organisation(s)
- Infineon Technologies Austria AG, Technische Universität Wien, Lawrence Berkeley National Laboratory
- Journal
- Journal of Alloys and Compounds
- Volume
- 646
- Pages
- 803-809
- No. of pages
- 7
- ISSN
- 0925-8388
- DOI
- https://doi.org/10.1016/j.jallcom.2015.05.282
- Publication date
- 10-2015
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103018 Materials physics
- Keywords
- ASJC Scopus subject areas
- Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/role-of-intermetallics-on-the-mechanical-fatigue-behavior-of-cual-ball-bond-interfaces(6caef84f-259b-46d6-97fa-fea820aa5836).html