Hi Eli, Ever heard of the 'bimetallic strip' effect? That top-to-bottom delta-T will cause warping; that was bad enough with SnPb but has much worse effects with the EU-RoHS-mandated Pb-free solders. The possible consequences are pad cratering, foil/resin interfacial failure, trace fracture, head-on-pillow SJs. Werner Future workshops: Pb-Free Soldering Processes: Survival, Quality, Reliability—PROBLEMS & SOLUTIONS, March 3, IPC/JEDEC Santa Clara, CA Solder Joint Reliability: Part 1—Solder Joint Reliability Fundamentals, March 29, IPC EXPO/APEX Las Vegas Pb-Free Soldering Processes: Survival, Quality, Reliability: PROBLEMS & SOLUTIONS, March 30, IPC EXPO/APEX Las Vegas -----Original Message----- From: Eli Sarig <[log in to unmask]> To: [log in to unmask] Sent: Tue, 6 Jan 2009 2:16 pm Subject: [TN] Question about bottom heaters of reflow oven Hi all, My question is related to the necessity of down heaters in the reflow oven. When we solder double sided boards, we *can* create a suitable reflow profile using *only* the top heaters of the oven. In that case, the bottom heaters remain at room temperature. We measure almost the same temperature on top and bottom of the board. Are there any limitations or problems that might happen using this kind of process? Thanks, Eli. --------------------------------------------------- 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):20SIGNOFF 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------