Hi Rob, Shengyi S1170 or any other PCB resin—bake at any temperature is no substitute for a bad lamination process—your boards are scrap if the problem is bad lamination. You need to understand what happens during the lamination process. 1) the purpose of the lamination process is to a) join the laminate layers by using the prepreg layers, and b) to fill the spaces where Cu was etched away with resin; 2) the prepreg layers consist of sheets of woven glass impregnated with partially cured resin; 3) during lamination, the pressure first facilitates good heat transfer from the press platens, the resin partially liquefies, excess resin is squeezed out [the amount depends on whether you use regular, low-flow, or no-flow prepregs] forming beats around the panel circumference; 4) adequate heating in the lamination press results in the curing of the prepreg resin [however, the cure is never totally complete—it takes too long—that is why the resin content in prepreg layers is higher than in laminate layers and the layers have different properties]; 5) delaminations can occur for two reasons: a) not enough curing time in the lamination press, b) too much pressure in the lamination press resulting in resin-starved prepreg layer. You need to determine which of these two root causes you have—but in neither case will baking at any temperature improve what you have—SCRAP. Werner -----Original Message----- From: Rob Strecker <[log in to unmask]> To: [log in to unmask] Sent: Mon, 11=2 0May 2009 12:39 pm Subject: Re: [TN] PCB baking Dewey, The laminate material is Shengyi S1170. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE) Sent: Monday, May 11, 2009 10:32 AM To: [log in to unmask] Subject: Re: [TN] PCB baking You didn't say what the laminate material was, but even at that I would not accept PBs that were baked at 180ºC for two hours. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Rob Strecker Sent: Monday, May 11, 2009 8:51 AM To: [log in to unmask] Subject: Re: [TN] PCB baking Sorry for not letting this thread die but... we are still battling with our PCB supplier with regards to baking PCBs at 180C for 2 hours. We started to see delimitation again and the root cause was an insufficient pressing time. The center boards in the stack when pressing did not reach the required temperature. The corrective action is to bake all PBCs at 180C for 2 hours. We do not agree with this corrective action. I would like to know why 180C?? My assumption here is we are not dealing with PCB moisture absorption (water), we are dealing with uncured prepreg. I assume that requires a higher temperature to complete the curing process? Would anyone out there accept reworked boards that were baked at 180C for 2 hours due to the above root cause? BTY, boards are ENIG. Rob Strecker -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid Sent: Monday, May 04, 2009 1:00 PM To: [log in to unmask] Subject: Re: [TN] PCB baking Hi Ioan, I agree with Werner. As you know we have performed reliability testing on almost every material available for PWB fabrication in almost every PWB configuration. We test both the copper and material reliability. A moderate bake at 105°C is adequate for all but exotic materials (which may have volatiles other then water). What is often overlooked is many low Tg materials, particularly if the PWB has sequential lamination processing, are greatly degraded by baking near 125°C. I mean by degradation, the inherent strength of the dielectric is degraded, chemically changed. Concurrently, along with the degradation, the increased force attributed to the difference in vapor pressure of water at 105°C compared to 125°C conspire to damage the PWB. It is better to remove the water slowly at a lower temperature, that is less degrading to the dielectric, and produces less force from increased vapor pressure. You have to consider the fabrication process, material robustness, product build and surface finish degradation in selecting the bake temperature. Generally a lower temperature is better for overall PWB reliability. Stay away from temperatures near Tg as measured by TMA. Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. 235 St afford Rd., West, Unit 103 Nepean, Ontario Canada, K2H 9C1 613 596 4244 ext. 229 Skype paul_reid_pwb [log in to unmask] <mailto:[log in to unmask]> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea Sent: Monday, May 04, 2009 9:25 AM To: [log in to unmask] Subject: [TN] PCB baking Dear Technos, I know this has been oftenly discussed here, but I would like to lively up the traffic a little bit... Is there any IPC standard reglementing the bake out time for PCBs, in terms of temperature/dwell time? Thanks, Ioan Tempea, ing. Ingénieur Principal Fabrication / Sr. Manufacturing Engineer 30 ans déjà! - Already 30 years! 950 rue Bergar, Laval, Québec, H7L 5A1 t : 450-967-7100 ext : 244 Mtl : 514-990-5762 f : 450-967-7444 [log in to unmask] <mailto:[log in to unmask]> www.digico.cc <http://www.digico.cc/> P N'imprimer que si nécessaire - Print only if you must --------------------------------------------------- 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=2 0all 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 a rchives 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 -----------------------------------------------------