Try to isolate where popcorn noise is coming from, 1. bake bare boards at a low temp (80-100'c) to drive out moisure for about 30min to 1hr, and stuff boards and reflow. And see whether this produce same popcorn noise? 2. bake suspected plastic pkg components at 80 -100'c for about 30min, and stuff them in prebaked boards. And see whether you get same popcorn noise? It could be that components and boards are complaining "I can't stand too much heat! Get me outa here!" re Matthew Park NII Norsat International Inc. >>> Koushik ATD Banerjee <[log in to unmask]> February 26, 1998 11:41 am >>> I would like to request for input / feedback on an interesting problem that we are seeing sporadically in our SMT line. Some of the PCBs, post component attach, when they are either in or are coming out of the reflow oven are making a "crackling" noise ! We have not identified any defects in the boards or the components yet and we are unsure what is causing the noise. Sometimes, we are also hearing this noise when we take a board in our hands post SMT and try to warp it a little ! The boards are approx 5" x 12", have components on both sides (passives and some actives) and is not very densely populated. Any suggestions on what could be the reason would be greatly appreciated ! Thanks,-Koushik Banerjee- ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################