Process Theoretical Studies On Conformal Peeling Technology Of Multi-layer Flexible Structure

One of the key technologies in device and product packaging is the transfer printing (peeling, transferring) of flexible electronics. Roll-to-roll (R2R) system, which is known for its high efficiency and low cost continuous manufacturing, is compatible with flexible substrates. The characteristics make R2R system an ideal manufacturing way for flexible electronics. Therefore, to integrate the R2R manufacturing system with flexible electronics transferring, which can realize large area fabrication of flexible electronics, has significant meaning on improving production efficiency and reducing the cost. Based on the R2R system's conformal peeling process, the device-adhesive-substrate structure is chosen as the research object in this thesis. The conformal peeling technology and R2R transferring of flexible electronics are studied from the mechanics modeling, mechanism analysis to process experiment. The main research work and innovations include:Firstly, a mechanical model is established to address the conformal peeling of the device-adhesive-substrate structure, and the corresponding analytical solution about the shear stress and peeling stress of adhesive layer is given. In this model, the influence of different layers' thickness to energy release rate are considered. Based on the analysis results, the proper thickness of device layer and substrate layer is decided, which provides a judge reference for peeling flexible electronics.Secondly, combined with conformal peeling process mechanism, the influence of materials' properties, geometrical size, peeling radius and conformal angle on peeling are analyzed, and a competition model of device fracture and peeling is established. Then a peeling blade which contains multiple radius is designed, and the design is proofed by multilayer structure peeling experiment.Thirdly, the influence of web tension and velocity on conformal peeling are given. A tension auxiliary conformal peeling method is proposed to improve the peeling success ratio. The proper tension range is decided. The mechanical model of multilayer composite structure, based on viscoelasticity theory, is built. Then the relationship between interfacial fracture energy and velocity by peeling test is obtained, which provide theory method to select suitable R2R parameters (web tension and velocity).Fourthly, the generation mechanism of interfacial residual stress during R2R transferring process is studied, a transferring method with low interfacial residual force is proposed. Considering the influence of device and process parameters, such as material, structure, process temperature, the strain mismatch model in transferring process is deduced, and the collaborative optimization of material properties and structure parameters is given. The feasibility of reducing the interfacial residual stress is verified by R2R experiment platform.The above research work has been verified in the multilayer R2R laminated system. It's proved in the practice that the design and method had a better application.