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 [1], 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) [2]. To double check with the result, the balloon model [3] is further used to compare with the stress value from our model at the center of parylene membranes and good agreements are obtained