Eli, Tell your engineer that it is a Best Manufacturing Practice (BMP) to use both top and bottom side heaters. Even if there is a 5C difference between both sides, with BGAs on the board I would be very skeptical about not using the bottom side heaters as my esteemed colleagues indicated. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Eli Sarig Sent: Tuesday, January 06, 2009 3:16 PM To: [log in to unmask] Subject: Re: [TN] Question about bottom heaters of reflow oven Hi, Thank you for your quick reply! I really don't want to use only the top heaters. One of my engineers insists that the bottom heaters are not necessary. I know about the warping problem and the possible cracks. But he measure only 5 C differences between both sides. It is over 2 mm board populated with BGA components? 2009/1/6 Steve Gregory <[log in to unmask]> > Hi Eli! > > I have a couple of questions; you say that you measure *almost* the same > temperature on the top and bottom, how much is almost? > > My second question is; why would you only want to use the topside > heaters? > > Steve > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Eli Sarig > Sent: Tuesday, January 06, 2009 1:16 PM > To: [log in to unmask] > 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): 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 > ----------------------------------------------------- > --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------