Role of intermetallics on the mechanical fatigue behavior of Cu-Al ball bond interfaces

Autor(en)

A. Lassnig, R. Pelzer, C. Gammer, G. Khatibi

Abstrakt

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(en)

Physik Nanostrukturierter Materialien

Externe Organisation(en)

Infineon Technologies Austria AG, Technische Universität Wien, Lawrence Berkeley National Laboratory

Journal

Journal of Alloys and Compounds

Band

646

Seiten

803-809

Anzahl der Seiten

7

ISSN

0925-8388

DOI

https://doi.org/10.1016/j.jallcom.2015.05.282

Publikationsdatum

10-2015

Peer-reviewed

Ja

ÖFOS 2012

103018 Materialphysik

Schlagwörter

ASJC Scopus Sachgebiete

Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/6caef84f-259b-46d6-97fa-fea820aa5836