An in-situ experimental-numerical approach for detailed characterization of interface delamination properties

An in-situ experimental-numerical approach for detailed

characterization of interface delamination properties

Hoefnagels, J. P. M., Murthy Kolluri, N. V. V. R., Dommelen, van, J. A. W., & Geers, M. G. D. (2010). An in-situ experimental-numerical approach for detailed characterization of interface delamination properties. In O. Allix, & P. Wriggers (Eds.), Proceedings of the IVth European Conference on Computational Mechanics (ECCM2010), 16-21 May 2010, Paris, France (pp. 1-2)

Document status and date: Published: 01/01/2010 Document Version:

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ECCM 2010

IV European Conference on Computational Mechanics Palais des Congrès, Paris, France, May 16-21, 2010

An in-situ experimental-numerical approach for detailed

characterization of interface delamination properties

J.P.M. Hoefnagels1, M. Kolluri1,2, J.A.W. van Dommelen1, M.G.D. Geers1

1 _{Eindhoven University of Technology, Department of Mechanical Engineering, P.O.Box 513, 5600MB, Eindhoven, The Netherlands,}

j.p.m.hoefnagels@tue.nl.

2 _{Materials Innovation Institute (M2i), P.O. Box 5008, 2600GA, Delft, The Netherlands.}

Mechanical properties of interfaces between elasto-plastic materials are difficult to characterize because of the complex plastic dissipation during delamination experiment. These interfaces are typically relevant for System-In-Package (SIP) microsystems. Typical interface systems include the lead frame – molding compound epoxy (LF-MCE) interface, which is extensively studied because of its wide applications in semiconductor packaging industry and its frequent failures during manufacturing and processing.

In this work, a new miniature mixed mode bending setup for in-situ characterization of interface delamination in miniature multi-layer structures was designed and realized (Fig. 1). This setup consists of a novel test configuration to measure load-displacement curves (Fig. 2a) for the full range of mode mixities and was specially designed with sufficiently small dimensions to fit in a scanning electron microscope (SEM) or under an optical microscope to allow real-time fracture analysis during delamination (Fig. 2b)[1]. MMMB micro-tensile stage SEM chamber

(a)

(b)

(c)

(a)

(b)

(c)

Figure 1. The miniature mixed mode bending setup (a) is mounted in a micro tensile stage (b), which is placed in the SEM chamber (c) to enable in-situ delamination testing.

2 (b) Residual displacement (b) (b)

(a)

(b)

Figure 2. (a) A typical load-displacement response for mode-I delamination of a LF-MCE interface showing permanent deformation after complete unloading, and (b) real-time in-situ SEM monitoring

of the delamination mechanism as illustrated for a steel-glue-steel interface system.

Experiments on LF-MCE interfaces show permanent deformation after complete unloading, which can be caused by bulk and/or interface plasticity (Fig. 2b). This calls for an intelligent data analysis procedure to extract intrinsic interface mechanical properties from an in-situ delamination experiment. To this end, the effect of plastic dissipation on the load displacement response and the calculation of the interface fracture toughness has been analyzed from finite elements simulations of the delamination experiment. The finite elements simulations incorporate elasto-plastic bulk material models and an improved Xu-Needleman’s cohesive zone interface model, developed in our group to simulate mixed-mode loading [2]. To be able to capture the interface plasticity, the unloading behavior in this cohesive zone model was extended with damage and plasticity under coupled mixed mode load cases (Fig. 3). From the numerical delamination experiments, the additional microscopic information needed to isolate the interface properties from bulk plastic dissipation was identified. Based on this analysis, a post treatment procedure to extract the intrinsic interface properties from the experimental data is proposed.

Figure 3. Normal and tangential traction-separation curves of an irreversible coupled mixed-mode cohesive zone law to model interface plasticity. (L: Loading, UL: Unloading, RL: Reversed loading) References

[1] Int. J. Frac., Kolluri, M., Thissen, M.H.L., Hoefnagels, J.P.M., Dommelen, J.A.W. van, Geers, M.G.D., Vol. 158, 183-195, 2009.