I'm not sure how detailed you want your material model to be. A fellow student working in the Packaging Research Center digitized a series of non-linear stress-strain curves for electro-deposited copper at different temperatures to get a *really* accurate model. (He has since graduated, but if you contact Dr. Suresh Sitaraman, [log in to unmask], I'm sure he can tell how much of that work is in the public domain.) The following is a isotropic, nonlinear stress-strain relationship published by Dasgupta and Ramappan in the ASME Journal of Electronic Packaging which appears to be pretty close to the values posted to this list by Andy Magee. I can't do greek letters, so I'll use the quantity names instead: Strain = stress/E + {stress/K}^(1/n) E = 17.5 x 10^6 psi Poissons ratio = 0.35 K = 9.2 x 10^4 psi n = 0.15 And Fatigue information, in case you're interested: Ultimate strength = 45,000 psi Fatigue ductility = 17% A couple of caveats: 1) This model assumes isotropic properties, which is a common assumption among those who model EP problems. However, some pretty accurate measurements (using a laser extensometer in a temperature controlled oven) by one of the labs here on campus has shown copper foil has at least orthotropic properties. To my knowledge they have not tried to relate these to microscopic features such as grain size or distribution. 2) These are 'average' properties. According to other posters to this list, there are wide fluctuations in 'as delivered' material properties. If you search the Technet archive, Werner Engelmaier among others has had some interesting things to say on this topic. Hope it helps, Andy REFS: Dasgupta, A. and Ramappan, V. "Simulation of the Influence of Manufacturing Quality on Reliability of Vias" Journal of Electronic Packaging, Vol. 117, June 1995, pp.141-146. ----------