Numerical Simulation Analysis of Flexible Printed Circuits under Bending Conditions

Flexible Printed Circuits (FPC) have been extensively used in daily life. It is inevitable to perform high-frequency reciprocating bending when using FPC., which induces deviation of the circuit board structure., separation of the adhesive layer and finally damage of the device. To solve the problem., it is suggested to change the FPC laminate design and adjust the internal structure and materials of the FPC so that the stress of the Cu layer is concentrated in the neutral layer during the bending process of the FPC and reducing the strain of the adhesive layer. In this paper., we systematically investigate the impact factors to the bending process of the FPC by using the finite element analysis (FEA). The characterized factors include the stacked structure and elastic modulus of each layer., the thickness of the glue/Cu layer., and the bending radius of the FPC. We find that different stack structures drastically influence the position of the stress neutral layer; the stress increases as the elastic modulus of material increases., but decreases with reducing the adhesive layer. Whereas., the elastic modulus of the material and the thickness of the adhesive layer have little effect on the position of the stress neutral layer of the FPC. Furthermore., the increasement in the thickness of the Cu layer increases the stress of the FPC and moving the position of the stress neutral layer downward. As the bending radius increases., the stress on FPC decreases., while the position of the neutral layer hardly changes. We also find that the smaller elastic modulus and thinner glue/Cu layer reduce the stress of the Cu layer. These simulation results provide a guidance for the design of structures and material selection of FPC., which may help solving the mechanical problems during the bending process.