I totally agree with Werner. I have attempted to develop profiling matrixs for given sizes/types of boards, but they seldom worked very well. My experience has been there are too many surprises (unknown factors) such that you can never really look at an assembly drawing and guess at which profile to use, they must always be fully profiled with TCs all over the assembly to really dial it in properly, and the matrix is only good for getting you somewhat close to a starting point, maybe. Especially for Pb-free, as the higher the overall temperature, the more of a delta exists between the coolest (defined as longest time to reach liquidus, not necessarily the lowest maximum reflow temperature) and the hottest (again defined in terms of shortest time required to reach liquidus, but not necessarily the hottest MRT on the PWB). Recently I needed to validate the reflow oven recipe for an assembly that was 24" high by 36" wide, with 48 layers, 24 on layer one of a separate PWB soldered to a second 24-layer PWB much like a giant BGA. This PWB had 6 miles of traces alone, not including the internal power, ground, and heatsink planes. Just the PWB alone weighed 40 lbs. Boy, did I learn a lot about temperature deltas and profiling. To obtain a profile (process window) that minimized the longest TALTS and yet provided sufficient TALTs for the coolest portions was very challenging, but we pulled it off. We then built a validation assembly and sacrified it for microsectioning to validate the profile. 47 microsections of the hottest, coolest, and intermediate SJs were made at an outside laboratory, 100% displayed excellent solder joint formation and good IMF. My concern was oxidation of the hottest MRT (longest TALT) portions (much like the dross formation on a solder pot), and insufficient IMF formation on the coolest. Neither of these manifested itself. But in general, for any given PWB, the effects of factors such as copper weight, power/ground plane quantity and size and distribution, type of material used for the substrate, the PWB thickness, and the effects of the components themselves are all very, very significant. You can have two PWBs of the same size, type of PWB substrate, but slightly different component types and different copper structure and the "optimized" profiles for the two assemblies can be completely different. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Friday, June 15, 2007 9:13 AM To: [log in to unmask] Subject: Re: [TN] Reflow Ovens for Printed Circuit Boards Hi Ted, DataPaq would have to have a huge component library for these kind of estimates to come even close to being accurate. I would need to see data developed with DataPaq and actual measurements that are ratrher close before I would trust this. Werner ************************************** See what's free at http://www.aol.com. --------------------------------------------------- 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 -----------------------------------------------------