Buckling analysis for a rectangular membrane for touch panel applications

Thin ITO-based PET conductive membranes are the major sensing structure in resistive touch panels for network phones or other applications. However, device failures or malfunctions such as early touch and disagreement between force-applied and touched locations have been reported. By examining the surface profiles, it was found that these membranes have considerable initial out of plane deformation. This could be a sign of membrane buckling since the clamped design could cause additional in-plane compression which could trigger the structural buckling. As a result, it is important to analyze the buckling behavior of ITO/PET membranes due to initial imperfection, residual stress, or assembly issues, for developing engineering solutions for quality assurance. In this work, both finite element analyses and essential experimental characterizations are performed as the first step toward solving this problem. However, it could be difficult for analyzing the complete membrane and its elastomer support structure in a single model. Rather, it is better to split the study into two interrelated models. That is, the first model is focused on studying the elastomer behavior due to assembly loads and the other model is for investigating the behavior of a thin rectangular plate subjected to various in- and out-of-plane loadings. In parallel, several experimental investigations have been conducted for characterizing material properties of the membrane, elastomer, and adhesion tapes, for supporting the above stress analysis. By both simulation and experimental investigations, the major control factor for causing malfunction of touch panel could be identified and the corresponding engineering solutions would be developed for enhancing the device reliabilities.