Cyclic Depth-Sensing Indentation of Gold Wire |
| Journal |
Key Engineering Materials (Volumes 378 - 379) |
| Volume |
Advances in Understanding the Fatigue Behavior of Materials |
| Edited by |
Dr. T. S. Srivatsan, FASM, FASME |
| Pages |
163-174 |
| DOI |
10.4028/www.scientific.net/KEM.378-379.163 |
| Online since |
March, 2008 |
| Authors |
Thirumany Sritharan,
T. Saraswati,
S. Mhaisalkar
|
| Keywords |
Cyclic, Deformation Mechanism, Gold, Wire |
| Abstract |
Conventional depth-sending indentation and novel cyclic indentation were performed to
study the mechanical properties and strengthening mechanism of pure gold and Ca-doped gold of up
to 90 ppm. The system was chosen because it is popular materials for microelectronics
interconnection, yet the strengthening mechanism is not well-understood. Conventional depthsensing
indentation showed an increase in hardness and modulus of gold with increasing Ca content
of up to 90 ppm, which remained significantly higher after annealing. Cyclic depth sensing
indentation, where the specimen is loaded to a specific value, unloaded and immediately reloaded,
produced a cyclic loop between unloading and reloading curves. The path of the unloading and
reloading curves tell the story of the different response of the dislocations generated under the
indentation, in different materials, pure gold and Ca-doped gold at different level. Thus their
dislocation movement and deformation behavior could be studied by cyclic depth-sensing
indentation method. This paper reports cyclic indentation study performed in calcium doped gold
widely used in wire bonding and shows that a few ppm level of calcium could result in dislocationssolute
interactions, leading to significant strengthening of the materials. TEM micrographs of the
material shows that it consists of elongated grains parallel to the drawing direction about 200
nanometers in diameter and a few micrometers in length. It is concluded that cyclic nanoindentation
could be used as an extended technique to extract sensitive material information that are not
reflected in the conventional test. |
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