Atmospheric Plasma – A New Surface Treatment Technology for Cleaning PCBs

Low-pressure plasmas have been used for many years to surface clean and functionalize substrates prior to downstream converting operations; therefore, the benefits of plasma treatment are well recognized: reduced degradation of surface morphology, higher treatment (dyne) levels, elimination of backside treatment, and extended life of treatment over time. However, the complexity, slow speed and high cost of these contained vacuum plasma systems made them impractical for all but the most esoteric applications. Now a system has been developed that allows plasmas to be sustained at atmospheric pressure in a way that permits the surface cleaning of PCB substrates on a continuous web handling system similar to a corona treating system. The atmospheric plasma process allows treatment using a broad range of reactive gases and has been successfully tested on various metals, films, papers, foams, and powders. Further, depending upon the cleaning requirement and type of material, roll-to-roll processing speeds in excess of current PCB vacuum processing speeds can be achieved. The particular solution of significant importance to the circuit board fabrication industry described in this paper and provided by atmospheric plasma systems is removing the residues of contaminants from sensitive surfaces without damaging them to increase yields. The application of atmospheric plasma technology to PCB manufacturing and its critical parameters will be presented because of its potential increase in processing speed in sheet and roll-to-roll orientations.