Abstract In order to achieve interconnections at extremely small scale, the latest build up laminates contain increasing amounts of spherical glass fillers, which are needed to compensate the CTE mismatch between the epoxy based resin matrix and the electroplated copper circuits. Desmear of the resin surface during industrial processing exposes these glass fillers and weakens their anchoring in the surrounding resin matrix, which decreases adhesion strength of the plated copper. We describe a newly developed cleaner process for the removal of glass fillers in industrially important build-up materials. Its effects on cleanliness and copper to resin adhesion is described in detail and illustrated by SEM imaging. Finally we propose a mechanism, explaining the adhesion increase as compared to standard processing and fluoride etch treatment.