Hi Tom - there hasn't been much published on this topic in the last 5-10 years as most folks wave solder processes are reasonably controlled, the SMT capacitor manufacturers have better/more consistent fabrication processes and the preheat capacity of modern wave solder equipment is much better than in the past. A "general" industry consensus was reached that SMT capacitors temperature had to be within 100C-125C of the wave solder temperature. A combination of adequate preheat parameters, use of the chip wave, the physical distance between the chip wave and the laminar wave, and the wave solder pot temperature all came into play to avoid thermal shocking the components. We conducted an number of investigations looking at the process/parameters and found we could get a heating rate of 5-6C/second and not have any thermal shock issues. Lead-free solder processing is going to have everyone probably giving the thermal shock issue a second look as there have been some suggestions that we may need controlled cooling of our assembles as they exit solder process equipment. If controlled cooling becomes necessary, then the thermal shock concern that Werner detailed could be an ugly balancing act to achieve. There were some good papers on the whole SMT capacitor/wave solder thermal shock topic published in the early 1990s. Dave Hillman Rockwell Collins [log in to unmask] "Gervascio, Thomas L" <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 02/11/2011 02:58 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to "Gervascio, Thomas L" <[log in to unmask]> To [log in to unmask] cc Subject [TN] Wave soldering SMT capacitors A friend of mine asked a good question, why is that most SMT capacitor specs call out for a maximum heating rate at SMT of 2-4 C/sec but the same specs allow a temperature delta at wave soldering of 100-125 C? In case of wave, the time between preheat and soldering causes a heating rate in excess of the SMT heating rates. But it is OK to subject the part to the wave solder but not SMT using those heating and cooling rates? I never could recall a logical explanation. Called several capacitor manufacturer's and they seemed to dance around the question. Any information would be helpful ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------