Achieving optimum performance with UV curable solder masks

The development of UV curing technology has introduced new solder masks which will replace the thermally‐cured masks of the past. In doing so, processing efficiency will be increased in terms of time, energy and space saving. In considering the effective use of the new technology, thought must be given to many factors which influence the optimum performance of UV cured solder masks. The thickness of deposit will most certainly be greatly influenced by the choice of screen fabric, mesh size and squeegee which will subsequently impact upon the rate and extent of cure. One must also prepare the substrate surface adequately to compensate for the minimal wet adhesion and dwell time of a solventless ink prior to cure. Other factors such as flux chemistry, solder temperature, and soldering conditions play an important part in the performance of a solder mask and are discussed in detail. This paper was originally presented at the First Printed Circuit World Convention held at the Cafe Royal, London, in June, 1978.