Published online by Cambridge University Press: 21 February 2011
It is proposed that the stresses in a thin polyimide film can be analyzed using the solution to the problem of a vibrating membrane. The polyimide membrane is supported on a copper substrate and excited with a small speaker. The membrane vibrates uniformly in response to its resonant frequencies. The vibration pattern will be recorded using holographic interferometry. The biaxial stress in the film is calculated from the measured characteristic frequency, the density of the material, and the mode of vibration. This technique may also be used to determine the Poisson's ratio of the film by combining uniaxial and biaxial stress analyses.