I don't have any practical examples of what happens if paste is left sitting for long periods before placement, but with my CEM, we work on the practice that all components must be placed within one hour. Longer than that, the flux volatiles have sufficiently evaporated off that wetting action is affected. The actual time one can bank on before wetting action is affected may depend on the particular solder paste you use and the acceptability criteria of the finished product, but I would guess that 1 hour is probably the max for most pastes. Just my opinion, but hope it helps. Peter Michael Bell <[log in to unmask]> 31/07/2002 12:26 PM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to Michael Bell To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: [TN] Paste sit time Hi all, Has anybody got any idea on how long it takes for paste, that has been stenciled onto a PCB to start and degradate. Our planning department is trying to suggest we use one printer to feed two lines and I have had little success in advising otherwise. It would basically mean that pasted PCB's would sit for 10-60minutes before placement. I have advised that this is a bad idea, but I just need some form of information to back this up. Has anyone had any experiance in this??? Any information would be appreciated, Cheers Mike --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ---------------------------------------------------------------------------------