Prediction and Regulation of Delamination at Flexible Film/Finite-Thickness-Substrate Structure Interfaces

Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic devices. However, such electronic devices need to be subjected to external loads during operation, which can easily induce delamination of the thin-film electronic device from the substrate. This study aims to investigate the instability characteristics of hard films on flexible substrate surfaces from theoretical analysis and numerical simulation perspectives. Considering finite-thickness substrates, this paper establishes theoretical models for pure bending, bent wrinkle, partial delamination, and total delamination buckling of film/substrate structures based on the nonlinear Euler–Bernoulli beam theory and the principle of minimum energy; then the effects of material and geometric parameters of the structure, interfacial adhesion strength, and pre-strain on the evolutionary path of the four patterns are discussed. The study results show that: the greater Young’s modulus of the substrate is, the larger the parameter region where partial delamination of the film/substrate structure occurs, and the smaller the parameter region where bent wrinkle occurs. By varying Young’s modulus, thickness of the film and substrate, interfacial adhesion coefficient, and pre-strain, the buckling pattern of the structure can be predicted and regulated. The parametric design intervals for each pattern are summarized in the phase diagram. The results of this paper provide theoretical support for the design and reliability evaluation of flexible electronic devices.