Influence of Process Parameters on Surface Roughness in Spark Assisted Chemical Engraving (SACE) of High-Strength Glass

This work investigates the influence of key process parameters on cut surface quality during Spark Assisted Chemical Engraving (SACE)—a hybrid thermal-chemical technology—of a high-strength aluminosilicate glass, a potential interposer layer material for future printed circuit boards. The functional performance of SACE depends on achieving a smooth surface finish but its complex thermochemical interactions complicate optimization. This study investigates the impact of applied voltage, feed rate, and electrolyte (KOH) concentration on the resulting cut surface roughness (S_a) using a response surface methodology. The results demonstrate that surface quality is most notably influenced by the applied voltage. The increase of voltage from 33 V to 37 V resulted in an increase of S_a because it produced unstable plasma discharges that removed material aggressively and unevenly. The study also identified electrolyte concentration as a crucial factor. Higher concentration levels increased etching speed but their impact on surface roughness depended on the applied voltage level. The polishing effect became more beneficial when the concentration increased at low voltage levels but surface irregularities worsened at high voltage levels. The tool feed rate produced various effects on machining operations. High feed rate during low-energy operations produced smooth surfaces because of shorter thermal interaction periods. The achievement of a low-energy processing window stands as the key factor to reduce surface roughness. The combination of 33 V low voltage, 5 µm/s feed rate, and 27 wt.% KOH concentration resulted in a smooth surface finish (S_a ≈ 1.63 µm) which demonstrates SACE can perform high-precision machining operations on high-strength glass.