Papers

ICMCTF2010 Session H6: Coatings for Compliant Substrates

Friday, April 30, 2010 8:00 AM in Room Royal Palm 1-3

Friday Morning

Start	Invited?	Item
8:00 AM		H6-1 Processes Controlling Delamination and Buckling in Thin Hard Film-Compliant Substrate Systems Neville Moody, E.David Reedy, Jr., Edmundo Corona, David Adams (Sandia National Laboratories); John Yeager, David Bahr (Washington State University); Daniel Huber, Hamish Fraser (Ohio State University) Performance and reliability are important factors governing the use of emerging thin film compliant substrate devices where compressive stresses can lead to delamination and buckling. We are therefore studying these effects combining compressively stressed thin hard tungsten films on compliant PMMA substrates with simulations employing cohesive zone elements to describe interface fracture. Following film deposition, high compressive film stresses triggered spontaneous buckling on all samples creating networks of small telephone cord buckles interspersed with regions of larger rosette-like and isolated straight walled buckles. Cohesive zone simulations showed that fracture energies varied strongly with buckle size and differed significantly with rigid elastic substrate models. Although all buckles formed by delamination along the film-substrate interface, FIB cross-sections showed that two crack tip deformation processes led to the two distributions of buckles. Sharp cracks led to large delamination-driven buckles while crack tip blunting led to small deformation-limited buckles. In this presentation we will use the observations and simulations to show how substrate deformation processes control delamination of thin hard films on compliant substrates. This work was supported by Sandia National Laboratories under USDOE Contract DE-AC04 94AL85000.
8:20 AM		H6-4 Mechanical Integrity of Thin Inorganic Coatings on Polymer Substrates Under Quasi-Static, Thermal and Fatigue Loadings Yves Leterrier, A. Mottet, N. Bouquet, D. Gilliéron, P. Dumont, A. Pinyol, L. Lalande, J.H. Waller, J.-A.E. Manson (Ecole Polytechnique Fédérale de lausanne (EPFL), Switzerland) The interplay between residual stress state, cohesive and adhesive properties of coatings on substrates is reviewed. Attention is paid to thin inorganic coatings on polymers, characterized by a very high hygro-thermo-mechanical contrast between the brittle and stiff coating and the compliant and soft substrate. An approach to determine the intrinsic, thermal and hygroscopic contributions to the coating residual stress is detailed. The critical strain for coating failure, coating toughness and coating/substrate interface shear strength are derived from the analysis of progressive coating cracking under strain. Electro-fragmentation and electro-fatigue tests in situ in a microscope are described. These methods enable reproducing the thermo-mechanical loads present during processing and service life, hence identifying and modeling the critical conditions for failure. Several case studies relevant to food and pharmaceutical packaging, flexible electronics and thin film photovoltaic devices are discussed to illustrate the benefits and limits of the present methods and models.