What you didn't mention is the relative rate this phenomenon occurs. Having it occur on the same board type built by two different assemblers could just be a coincident. If it is, then I have seen this and it is an elusive problem that can be very difficult to eliminate. There are many sources of gold finger contamination, but I only have a short list. 1. traces of solder paste on the board support tooling in the screen printer. (Check there first!) 2. accumulated solder paste in the stencil wash redepositing on boards washed there. 3. not washing misprinted boards in an ultrasonic stencil wash, thus allowing solder powder to surface from every crevice on the board. 4. traces of solder paste on the underside of the stencil allowing solder balls that find their way onto the edge fingers. 5. aggressive reflow ramp rates that cause solder balls which get onto the fingers. 6. other unidentified causes. If it is not a coincident that both vendors have this problem, I'm at a loss for explanations. Kind Regards Ryan Grant Advanced Technology Engineer MCMS (208) 898-1145 [log in to unmask] > -----Original Message----- > From: Bev Christian [SMTP:[log in to unmask]] > Sent: Friday, September 14, 2001 8:34 AM > To: [log in to unmask] > Subject: [TN] Technical question - immersion gold > > Here's the situation: > > We have immersion gold over nickel boards made by two different board > shops, populated by different companies and in both cases we have spots of > reflowed solder on the gold contact pads after reflow. > > The board shops use no tin/lead in their gold/nickel processes. The > boards did not come in with this problem. These pads were not screen > printed with paste. Both ovens use edge fingers. Both ovens are > convection. Some boards were actually run through the oven up-side down > and the problem was still observed. The problem is only seen on the one > board type, although we have others that are immersion gold over nickel. > > Has anyone every seen anything like this? What do you think caused it? I > have my suspicions, but I will keep them to myself and see what you have > to say first. > > regards, > Bev Christian > Research in Motion --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------