Hello Patrick, Patrick Ducas wrote: > > Hi, I would greatly appreciate any help or any recommendation in the > following subject... > > We are having solder residues on gold fingers of PCBs, those are seeing > immediately after the reflow oven (it's a recirculation convection reflow > solder system). A visual inspection has been done after the printer > machine at high magnification and nothing showed up. We were thinking that > the problem was from the printer machine since a long time but we found > that it is not the case today. > > I suspect that the problem is coming from the reflow oven but I dont see > the problem mechanism. The reflow atmosphere is nitrogen and the ramp up > temperature at the entrence of the oven is relatively high, arround 3.4 > C/sec. > > Does anyone of you have an idea concerning this problem, thanks in advance. Allow me to share our own experience, a similar problem to yours: We were reflowing PCBs with gold-plated traces on both the top and bottom sides. SMT components populated only one side, but surprisingly, we were seeing solder splashes on the gold plated traces at the bottom side which were not populated with any components at all. We eventually traced the problem to be due to the aluminum PCB holders that we were mounting the PCBs on to carry it from screen print to reflow. The holders are needed to standardize the rail widths on our machines to reduce conversion time. It was discovered that solder balls from the solder paste accumulated on the holders as they are reused on the system. And these eventually reflowed and found its way onto the gold-plated traces on the bottomside of the PCB which was in direct contact with the holders. Our solution was to punch out the holders ensuring that the PCBs sit on them with the gold traces at the bottom not in contact with any metal. -- Luke B. Mendoza Electronic Assemblies, Inc. http://www.globe.com.ph/~eai ############################################################## 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 ##############################################################