Yield strength of thin-film parylene-c

For the first time, the yield strength of thin-film parylene-c is measured from membrane load-deflection experiments and surface profile analysis. To do so, the onset pressure which causes plastic deformation of the membrane is first experimentally measured. Then a new 2-step displacement model, together with the energy minimization technique, is developed to convert the onset pressure to the yield strength on the pre-stressed parylene membrane under a uniform pressure loading. The results depict a Yield Strength of 59 MPa (or 0.012 of strain) for thin-film parylene-c in comparison to 55 MPa reported by parylene vendor (measured from large samples). To double check with the result, the balloon model is further used to compare with the stress value from our model at the center of parylene membranes and good agreements are obtained.