Paul, This is not too long of a message at all. This is an excellent message. I worked in the industry as a consulting engineer prior to coming to work at GD. Many of my clients are currently reporting that PWB delamination is a major problem for them as they go to higher temps to accomodate Pb-free BGAs and flipchips. Repeatedly, the pwb materials are rated for Pb-free processing, and the Tg and Td ratings are purportedly good enough to withstand the higher temps, but the boards delaminate, even after baking to remove moisture. They are delaminating at temperatures as low as 230 C, and that is the chamber temperature, not the board. I brought this up in several postings to the Technet forum last month. There has been much discussion about it. There needs to be a time/temperature rating on pwbs for resistance to delamination, just like there is a moisture classification on components. The other properties of the materials are meaningless if they pop in the reflow oven or during hot-gas rework. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of paul reid Sent: Monday, December 12, 2005 5:10 PM To: [log in to unmask] Subject: Re: [TN] Qualification of the Pb-free capable manufacturers The problem with PCB fabricators demonstrating lead-free capabilities is really a two-fold issue. One issue is to demonstrate the proof the product is lead-free and has been appropriately documented. The other is to prove that PCBs are robust during lead-free assembly. My company focuses on PWB reliability. We measure the robustness of PWBs by testing with very specialized coupons (IST). Many of the recent studies we have been doing have been to determine if the interconnect structures and laminate are robust after lead-free assembly. We have found that lead-free assembly typically reduces the cycle to failure "entitlement" of a coupon by 50% or more, if the coupon was well made with high reliability materials. Poorly processed coupons, or coupons, with low end materials can expect reliability to be dramatically reduced with lead-free assembly temperatures. I had the pleasure of being able to co-author a microvia paper that was presented at IPC Work in Los Vegas in October. A part of the paper addressed the effect of lead-free thermal excursions on coupons that had marginal microvias. The microvias had minor amount debris and inclusions between the base of microvia and the capture pad, which was not visible with the established microsectioning techniques. The during our investigations, coupons were found to be very sensitive to the effects of lead-free thermal excursions. Tested "as received" at 150C, the known discrepant microvia coupons achieved 788 thermal cycles before failing. Preconditioned 6 X 230C the same coupons achieved 443 cycles. Precondition 6 X 260C the coupons achieved a mean of 4 thermal cycles until failure. The data presented in the paper suggested that microvias needed to have thermal cycle testing at 190C and that microsectioning techniques needed to be modified for an effective evaluation of the robustness of PWBs with microvias. We also noted that PWBs with microvias that would have been considered acceptable after exposure to tin-lead temperatures (230C), might catastrophically fail during lead-free (260C) thermal excursions. Those last 30-degrees do a lot of damage. I believe the effect of lead-free processing on the bare PWBs has not been addressed adequately. Based on the RoHS seminars I have attended, it appears the many of the assemble concerns; the components, materials and methods used in assembly have addressed the effects of lead-free. We, for example, have been contracted to do a fair bit of laminate studies to characterize the effect of lead-free processing temperatures on various laminates, but few OEMs, CM or FAB houses are specifying routine lead-free reliability studies or established minimum requirement for product acceptance, based on lead-free preconditioning. In the good ol' tin-lead days (now) copper quality was the primary influence in PWB reliability. With the advent of RoHS copper quality and material quality are beginning to play equal roles in influencing PWB reliability. In high-end application, small holes, thick boards, material is becoming the dominant factor. Then there delamination... I believe the effect of lead-free assembly on the bare PWBs is not well understood nor is there a standard established to say a good PWB meets some minimum requirement. I do believe that delamination will turn out to be one of the major concerns. Delaminated PWBs do not automatically fail during thermal cycle testing. We have found many instances where delamination artificially extends thermal cycles to failure. If you are not very diligent in you testing and failure analysis, it is possible to have delaminated coupons pass thermal cycles requirements without a failure. To address that weakness we have developed coupons that allow us to test for delamination electronically. We have developed a method to determine if coupons have significant delamination after thermal excursions to lead-free temperatures. It is conceivable to process a number of our coupons in a lead-free line (oven, wave, etc) and determine if there was significant delamination. I believe that you can expect delamination of the PWB to play a more dominant role in lead-free processing. I have also noted the failure modes of lead-free stressed PCBs have shifted, to some degree, from barrel cracks (due to metal fatigue), to internal interconnection and knee-crack type failures. I am sure this response is too long for most to bother to read but there is a lot to say on this subject. Believe it or not I have tried to be succinct...I didn't even mention ENIG! Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. (IST Testing) Tel: 613-596-4244 Ext. 229 Fax: 613-596-2200 [log in to unmask] -----Original Message----- From: Tempea, Ioan [mailto:[log in to unmask]] Sent: Friday, December 09, 2005 4:20 PM To: [log in to unmask] Subject: [TN] Qualification of the Pb-free capable manufacturers Hi Technos, IPC-1710A does not have anything specific for lead-free capability (or at least I missed it). How do you qualify your PCB fabs? Thanks, Ioan --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- 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 847-615-7100 ext.2815 -----------------------------------------------------