Mechanical and Electrical Behavior of Printed Silver Conductor in Adaptive Curvature Flexure Test

Flexible electronic products are becoming increasingly popular. Because of the large deformation that flexible products encounter, it is important to predict their performance in response to mechanical loadings. This article focuses on the mechanical and electrical behavior of the printed silver conductor under the adaptive curvature flexure test. In the adaptive curvature flexure test, the printed conductor is bent between two rigid parallel plates so that the bending strain will be generated through the conductor and, thus, cause resistance change. The resistance of the conductor was measured continuously by the four-wire method during the test for analysis. A series of conductors with different widths printed on two commonly used substrate materials-polyimide and polyethylene terephthalate-were tested. In the single load-unload tests, the resistance of the conductor increased nonlinearly as the gap distance between the parallel plates decreased. Cracks in the conductor were observed under a strain of approximately 3%. In the cyclic tests, the resistance of the conductor increased linearly with cycles after the first several cycles. In addition to the experimental tests, the strain distribution of the conductor was calculated by both finite-element method and theoretical analysis. Combined with the relationship between the resistivity of the conductor and the bending strain, an integral model has been developed to predict the resistance change of the printed conductor under bending.