Effect of cleaning agents and process parameters on thin-film adhesion to microwave dielectric ceramics

This study investigates the impact of cleaning agents on thin-film delamination in microwave dielectric ceramics, a critical issue in the fabrication of components for 5G wireless communication systems. The results show that when the sodium dodecylbenzene sulfonate (SDBS) concentration was below 1.5 %, contaminants remained on the surface, adversely affecting the thin film's adhesion. At a 3 % SDBS concentration, crystals began to precipitate from the supersaturated solution, leading to deteriorated surface quality. Prolonged SDBS cleaning times, particularly beyond 15 min, induced cracks between adjacent ceramic grains due to weakened intergranular bonding, likely caused by SDBS infiltration into grain boundaries. In contrast, organic acid-based cleaning agents, such as oxalic acid, showed a corrosive effect when concentrations exceeded 7 %, forming metal oxalate precipitates on the ceramic surface. At 11 % oxalic acid concentration, oxalic acid crystals induced by the supersaturated solution were also observed. The study further reveals that under optimal cleaning conditions (SDBS 1.5 %-10 min, Oxalic acid 5 %-10 min), both the contact angle and surface roughness decreased initially. However, when cleaning agent concentration or cleaning duration surpassed the optimal level, these parameters increased, correlating with reduced thin-film adhesion strength, as evidenced by lower critical load values in nano-scratch tests. This research aims to identify the underlying causes of thin-film delamination and provide quantitative guidelines for selecting appropriate cleaning agents for dielectric ceramic substrates.