Optimizing Vacuum Ultraviolet Irradiation Pretreatment for Wet Desmear Process: Balancing Permanganate Treatment Time Reduction with Resin Surface Quality

The wet desmear process [1] - [3] , which involves sequential chemical treatments of swelling, permanganate, and reduction, remains the industry standard for effectively removing smearthermally degraded epoxy resin residues [4] , [5] generated in via holes during laser drilling that hinder copper plating adhesion and degrade electrical connectivity-in printed circuit board (PCB) fabrication. However, the wet desmear process faces challenges in terms of efficiency and environmental impact. Specifically, the permanganate treatment produces manganese dioxide (MnO 2 ) sludge, necessitating frequent solution replacement and resulting in increased chemical consumption, waste generation, and safety risks due to its strong oxidizing nature. Consequently, reducing the permanganate treatment time has garnered considerable attention as a viable approach to improving the sustainability of the wet desmear process without compromising performance.