Investigation on spraying pressure in etching process of flexible printed circuit board (FPCB) with 18 μm line pitch

Abstract

In the wet etching process of the flexible printed circuit board (FPCB), to obtain a better etching profile and improve the yield, it is necessary to control the etching spraying pressure and etching time as far as possible. In this paper, a numerical method implemented with the Euler multiphase flow model is proposed to investigate the impact of etching spraying pressure and etching time on the quality of FPCB. The FPCB sample with 18 μm line pitch is manufactured based on the process parameters obtained by simulations. A comparison between the microscopic analysis of actual structures and the cavity profiles predicted by the simulations validates the numerical simulation method. The results of simulations demonstrate that the average pressure on the upper surface of the FPCB is 2,510 Pa. The maximum etching cavity width and lateral etching width are about 10 μm and 1 μm, respectively. The cavity profiles extracted from simulation and experiments are in good agreement except upper left and right with a deviation less than 2 μm.