Guenter, It may be just an oxide spot on the copper. The solder mask will not adhere well to the copper oxide and can even get a small gas bubble between. It may not be a big problem, if the oxide is not an acidic contaminant then the trace will probably not be a reliability problem. It could also be an organic contaminant, also not a problem if it has not already caused a failure. Look at it under high power (like 200X) and if the copper is full height forget about the spot. Chuck Brummer Guenter Grossmann wrote: > Hi all > > I have a case here where I am not sure what I see. > - There are dark spots visible below the solder mask on the surface of the traces on a PCB. I attached 2 Pictures in JPEG that show a view onto the surface of the traces with 10x and 40x magnification. > - In microsections we see clearly a cavity between the traces and the soldermask. > - EDX is hopeless, since the dark layer is so thin that the background covers all but the copper peak. > > Before I start to work with TOF SIMS, Spectroscopy and other expensive analysis methods I'd like to ask whether one of you knows what the dark spots are. > > Thanks in advance. Have a great day. > > Guenter > > Guenter Grossmann > Swiss Federal Institute for Materials Testing and Research EMPA > Centre for Reliability > 8600 Duebendorf > Switzerland > > Phone: xx41 1 823 4279 > Fax : xx41 1823 4054 > mail: [log in to unmask] > > ############################################################## > 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. > If you need assistance - contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > ############################################################## ############################################################## 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. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################