Cal, If it's an ongoing assembly, I'd get some dedicated selective wave carriers made to mask the bottom side surface mount. The masking process you're currently doing shouldn't be causing any of the potential problems you are concerned about, but does consume a huge amount of labor that could be directed to something more productive.... Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Cal Driscoll Sent: Thursday, March 04, 2004 1:22 PM To: [log in to unmask] Subject: [TN] Removable masking/ Double sided reflow Hello All- WOW !!! two postings from me in two days... Here is the case: We run a double sided reflow process. We Print, Place, and Reflow the bottom of the boards.. Then Print, paste, and reflow the top side. Since the bottom side is mostly discrete and Resistor networks (unlike the one pictured on Steve's Site) it works well. For the through hole components we hand insert and solder them. I just went down to the wave soldering room and found the operator........... Covering the bottom side components with removable masking material (Chemtronics Brand) and sending the boards through wave. Once Soldered...he removes the masking and all looks well. Question(s); 1) Is this an acceptable practice? 2) What documentation is available to support or disclaim this? 3) What reliability issues are there due to any thermal mismatch? 4) Any leaching of masking material into the solder join causing poor joint integrity? Please advise, Cal P.s. Steve be a fountain; not a drain...keep up the excellent work --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------