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CALCE Webinar - Pitfalls of Creep Indentation Testing of Sintered Silver InterconnectsThursday, August 19, 2021 11:00 am US EDT
The experimental portion of this study consists of nanoindentation testing on sintered silver test coupons. Constant force tests at room temperature and at elevated temperatures were conducted using a Berkovich indenter and spherical indenters of various diameters. FEA models of the indentation, were used to estimate creep curves, by parametrically fitting the experimental results using an iterative inverse method. There is an element of non-uniqueness in the FEA inverse extraction process, since there are many material constants that have to be estimated from relatively few test conditions. The study has also shown that simpler closed-form models commonly used in the literature to extract creep material properties may underestimate creep resistance of sintered materials by an order of magnitude, because of their nanoscale and microscale heterogeneity. Furthermore, the heterogeneous microstructure may also introduce intrinsic length-scale effects, which result in different apparent creep properties, depending on the radius of the indenter tip. Overall, further work is needed before indentation offers a viable approach for assessing scale-dependent creep properties for heterogeneous materials. This information cannot be obtained from testing of bulk specimens and must necessarily rely on indentation testing with a suitable family of indenter tips. About the Presenter: David Leslie is currently a PhD candidate in Mechanical Engineering and a graduate research assistant at the Center of Advance Life Cycle Engineering (CALCE), at the University of Maryland, College Park. He is advised by Professor Abhijit Dasgupta, and his dissertation research is in the field of nanoindentation of viscoplastic heterogeneous solids with specific application to pressure-less sintered silver interconnect materials used in high-temperature electronic systems. |
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