Optimization of wet chemical etching for MRR and undercut by substrate orientation

This study investigates the effect of substrate orientation on undercut and material removal rate (MRR) in wet chemical etching processes. Through simulations in COMSOL Multiphysics and validation via experimental trials on copper and SS304 substrates, it was observed that part orientation significantly influences etch uniformity, cavity and efficiency. During vertical etching, the maximum MRR of 12 µm/min was recorded at 90°, while the minimum of 8.9 µm/min occurred at 0°. The undercut ranged from 157 to 227 µm for copper and 105 to 142 µm for steel in the vertical orientation. Horizontal upside-down etching yielded lower average undercut values of 86 µm for copper and 53 µm for steel, along with more uniform etch profiles, sharper edges and shorter machining times. The higher undercut and MRR in vertical orientation are attributed to gravity-assisted downward flow of the etchant, which enhances lateral etching. Stagnation zones in downward-facing regions caused asymmetric profiles and increased distortion.