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Experimental investigation of the visco-plastic mechanical properties of a Sn-based solder alloy for material modelling in Finite Element calculations of automotive electronics

: Metasch, René; Röllig, Mike; Kabakchiev, Alexander; Metais, B.; Ratchev, Roumen; Meier, Karsten; Wolter, Klaus-Jürgen


Institute of Electrical and Electronics Engineers -IEEE-:
15th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2014 : 7-9 April 2014, Ghent , Belgium
Piscataway, NJ: IEEE, 2014
ISBN: 978-1-4799-4791-1 (Print)
ISBN: 978-1-4799-4790-4
International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE) <15, 2014, Ghent>
Fraunhofer IKTS ()

Here, we present an advanced experimental procedure for determining the properties of a SnAg3.5 solder alloy in the strain range of primary creep under cyclic load and isothermal conditions. The challenge in this experiment is the accurate high-resolution measurement of sample elongation used for a closed-loop control, as well as avoiding the influence of sensor and specimen clamping. We realized reproducible strain rate control within a total specimen elongation of 60 μm. The tensile-compression experiment comprises strain rate variation for three strain amplitudes with integrated relaxation stages followed by a measurement of cyclic fatigue. The strain rate at every strain stage was varied in the range of 1E-3 to 1E-6 per second. At the end of every strain stage a time-limited relaxation experiment is performed, where the specimen's length is kept constant, while the stress evolution is recorded. Finally, the specimen is subjected to cyclic fatigue until a drop of 50 % of the initial materials strength is reached. The total procedure is performed in a temperature range from -40 to 150 °C. We prove the capability of common creep models to map the observed cyclic stress-strain hysteresis as well as stress dependency on strain rate. The results reveal substantial limitations of common stationary creep models and strongly suggest the application of advanced visco-plastic material models for an accurate description of the solder alloy properties. The experimental data presented can be used for the calibration of unified visco-plastic constitutive models initially proposed by Chaboché et al. and further extended during the past two decades.