You got that right Joyce, And, at the same time, the they point blame to process or material that are up or down stream from themselves! I don't tend to like to be constrained by political correctness, but, in the sprit season, and in deference to those of all faiths... Have a Happy Holidays Everyone! Paul Reid -----Original Message----- From: Joyce Koo [mailto:[log in to unmask]] Sent: Tuesday, December 23, 2008 10:38 AM To: [log in to unmask]; Paul Reid Subject: Re: [TN] What could be the root cause for a failed board that passed functiona test after going through reflow for the 2nd time? Paul, my old age tells me usually the pwb house point finger to interconnect, the mfg point to material, and so on. That is why the expert make their money. The mgr want to hear the independent view they paid too dollar for. -------------------------- Sent using BlackBerry ----- Original Message ----- From: TechNet <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Sent: Tue Dec 23 08:18:22 2008 Subject: Re: [TN] What could be the root cause for a failed board that passed functiona test after going through reflow for the 2nd time? Hi Rudolph, All experts find a problem that relates to their area of expertise. If you are sick and you go to a cardiologist you find you have a heart condition. Next go to the endocrinologist and there is a hormonal imbalance causing a heart condition. The dietitian finds a nutritional deficiency due to imbalanced diet that is expressed as hormonal imbalance that causes the heart condition. The heck of it is, they can all be correct. I am a PWB guy, so I will find a PWB problem. Werner mentioned interconnect failure and I agree that is a strong possibility. The signs you describe support interconnect failure. Well here's my input. We found discrepant microvias and capped buried vias that where temperature and pressure sensitive. At ambient they are closed, at operational temperatures they are open. Manually twisted they open, release they close. If either is present in your PCB design, I would investigate the reliability of microvias and capped buried vias. Both interconnects can produce a failure mode that is self healing at ambient . Barrel cracks and interconnect separation is less prone to be self healing at ambient and are further down the list of suspect interconnect structures. Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. 235 Stafford 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 Rudolph yu Sent: Monday, December 22, 2008 1:35 PM To: [log in to unmask] Subject: [TN] What could be the root cause for a failed board that passed functiona test after going through reflow for the 2nd time? Hi: We have a proto assembly that passed the functional test initially. But after we shipped it to the customer, it failed at the their site for the same kind of test. After we received the board back, we reflowed it using the same reflow profile, and the board would funcation once again... We checked the boards under 5DX after we received it back from the customer and found no defects on it. What could be causing this? and why the assembly would pass the test in the first place? Here iare couple areas that I could think of...but not sure if they are valid. 1. Certain parts (microBGA) may be better off to have underfill underneath for thermal mismatch? ( Need to check spec) 2. During handling and shipping, the board may be stressed to a degree that a microfacture is formed. What other areas could cause this problem. Thanks Rudolph _________________________________________________________________ Life on your PC is safer, easier, and more enjoyable with Windows Vista(r). http://clk.atdmt.com/MRT/go/127032870/direct/01/ --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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