Study on Wet Chemical Etching of Flexible Printed Circuit Board with 16- Μ M Line Pitch

As high-precision flexible printed circuit boards (FPCBs) are required in electronic products, it is necessary to study wet chemical etching to obtain precise FPCBs with a 16- μ m line pitch. First, a π-shaped FPCB model with 16- μ m line pitch is established using the finite element method. The evolution of the Cu etching profile and the concentration and velocity distribution of the CuCl 2 solution are then analyzed. To analyze the influence of conveyor speed and nozzle spray pressure on the Cu etching profile, wet chemical etching was tested along a horizontally conveyed line with CuCl 2 as the acid etchant. The resulting profiles were analyzed by scanning electron microscopy. The experimental results agreed well with the simulation results, and the Cu etching profile obviously depended on both the conveyor speed and nozzle spray pressure. In addition, increasing the conveyor speed under constant nozzle spray pressure (0.16 MPa or 0.17 MPa) decreased the etching depth and increased the etching factor. In particular, when the conveyor speed was set to 3.8 m/min and the nozzle spray pressure raised to 0.18 MPa, the fabricated FPCB had a line pitch of 16 μ m, an etching depth of 7.55 μ m, and an etching factor of 6.45. This method can aid the selection of parameters for the wet chemical etching process, enabling the future manufacture of high-precision FPCBs and complex FPCB circuits.