We have recently seen a failure of an assembly in a humidity chamber. There were two things observed. First, on an external layer, power traces (+25V) were very close to ground traces (~20 mils), and an apparent electrical bridge caused a short and a burned the area. Secondly, other areas of the board appeared to have white residue and broken down soldermask bridging between connector pins. Some of these areas took up a number of pins (thumb print size). I vaguely remember and issue where assemblies that were not thoroughly cleaned could leave residuals (chlorides?) and that when subjected to a humid environment could break down soldermask. I also believe that humid chlorides can crystallize and can be influenced by electrical potentials between pins - causing shorts. However, that's where my memory breaks down. Can anybody provide some clarity on potential reasons for soldermask to breakdown in a humidity chamber? Thank you, Anders P. Pedersen * 407-729-2143 (ph) Harris Aerospace * 407-729-2097 (fax) P.O. Box 94000, MS22-4842 * [log in to unmask] Melbourne, FL 32902 http://www.harris.com/ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################