Are there any issues with lead-free wave-soldering?
A18. Yes, for example, maintaining the composition of the solder bath, and advice should be sought from your solder and equipment suppliers. For example, the copper levels must be taken into account when replenishing the solder bath, and copper dissolution of the tracks and pads can result in their being less than the minimum acceptable thickness. There may also be an issue with the compatibility of the solder pots, pump impellors and solder bath nozzles (or any components in contact with the solder) especially at the higher soldering temperatures associated with lead-free soldering. As a result, some manufacturers have now upgraded their products and applied protective coatings as appropriate. Process settings should be based on the results of trials or R&D exercises. Using nitrogen inerting during soldering will widen the process window. Dross rates using lead-free solders vary markedly – they can be twice that with SnPb for solders containing silver, to less than half that of SnPb.
