In a message dated 02/15/2000 10:29:12 AM Central Standard Time, [log in to unmask] writes: << From my experience with troubleshooting client's processes, it is a very bad idea. You have too great a chance of mixing curing or outgassing products from the adhesive with flux residues from the paste. The two residues can interact with each other to form a detrimental combination. I published two case studies on a common detrimental effect in my Process Rx column in Circuits Assembly magazine - "Microcanyons" and "Become one with the Glue". Doug Pauls Technical Director, CSL >> I have to agree with Doug. We had a board at a past employer some years back which had some problems with the lay-out of components on the bottomside...the SOT's in particular. We were experiencing a lot of defects (no solder mostly) on the leads of the SOT's because of the orientation. Well, it was decided to print solderpaste, dispense glue, place the parts, and cure and reflow at the same time, with the thought being that we would make sure that there would be a solder fillet at those troublesome SOT's and not have to depend on the wave to form them...seemed like a good idea at the time. But as we discovered, it was a really BAD idea for just the reasons Paul talks about. Another thing, which what really caught our customers eye and got everybody looking at the issue, was that during reflow, during the hot slump of the paste (and all pastes do hot slump to some degree) the paste would slump into the epoxy and embed itself into the epoxy...you would wind-up with all these little solderballs in the epoxy. That was the first thing that was noticed and started everybody looking at the whole issue. As a result, the customer rejected all the boards we built doing that, rework was out of the question, so we had to eat 750 boards...wasn't too tasty either. -Steve Gregory- ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################