>How thin is too thin? As assemblers, when (at what thickness or process >conditions) would you return boards to the fabricator? I beleive for most people the solder on the board is purely for solderability preservation, so if boards are assembled soon after you make them you probably won't get many complaints no matter how thin you go. However, boards often sit around for a significant period before use, during which solderability will decrease due to oxidation and intermetallic growth, both of which will alter the composition of the solder and therefore its melting point. If the solder dosn't melt then dispersion of the oxide layer will be more difficult & therfore soldering will be more difficult, The point at which this becomes a problem will depend on things such as process temperature and flux activity, i.e. there is no single answer to the question, but I am sure the practical experiences of others will set some limits? David Whalley