In addition to what Graham has said about salts under conformal coating, consider also that when a salt crystal encounters water, which WILL come through conformal coatings, it will expand up to 200 times its original volume, creating a localized blister. This effect is often referred to as "mealing". Once the blister is formed, it is a place for water vapor to collect and condense. Liquid water together with the original salt material forms an electrolytic solution, which is generally detrimental to circuit reliability. Doug Pauls CSL ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################