Hi Paul -- there could be adhesive failure, or delamination, in c-stage no? Ian -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Reid Sent: Wednesday, October 21, 2009 9:53 AM To: [log in to unmask] Subject: Re: [TN] delamination signatures Hi Chris, I think that the signatures of material damage should be taken as an indicator not an absolute for determining root cause. I cannot bring myself to call cracks in areas that were never laminated, adhesive delamination. I can thank my colleague Jason Furlong who, years ago, said to me "If that area was never laminated how can you call the crack delamination?" As it stands now I can't call cracks in the middle of the B or C stage adhesive delamination. For me if the crack does not follow an internal interface it is "cohesive failure" not adhesive delamination. If we can agree that adhesive failures tend to be a breakdown of an internal interface, cohesive failure a breakdown of the epoxy system and crazing a separation between the individual glass fibers and the epoxy system then these symptoms may give indication of where to look for root cause. At least this interpretation of failure signature could direct you to look into areas that would contribute to those types of failures. Consider the alternative. If each delamination signature does not narrow the area of investigation for root cause then one could naively start with material shelf life and storage, move to lamination (cycle, times, pressures, platen planarity, heat distribution, etc), go on to drilling (feeds, speeds, and hit count etc) and proceed through the other 97 steps of PCB fabrication, (not forgetting oxide coating, cleaning, rinsing etc.). If that investigation is not fruitful then move on to design and methods engineering variables like grid size, % resin etc. You might find out in the end you were using a DICY cured laminate in a lead/free HDI application and the material damage was cohesive failure. There may be hundreds of root causes of material degradation I can think of at least a hundred. I say - Let the cross section talk to you and narrow your investigation based on observation and experience. Don't forget... when in doubt bake! It doesn't much help but it does give one reason to hope. 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 Chris Mahanna Sent: October 19, 2009 9:24 PM To: [log in to unmask] Subject: [TN] delamination signatures Hello TN, I'm wondering how certain one can be about the root cause of delam. simply by reading its signature. Our experience is similar to Paul Reid's (post attached below). One obvious question: what about when it is both co and adhesive failure? Are there other features to the signature that are important in determining primary root cause? Chris ------------------------------------------------------------------------ ------------------ My sense is that moisture induced delamination presents as adhesive delamination that is horizontal cracks that resemble blisters and are located at a laminated interface (b-stage to c-stage or copper, or along bundles of glass). It may be that the vapor pressure exerted by trapped moisture induces a mechanical failure at laminated interfaces. Material degradation induced delamination more often presents as cohesive failure that may exhibit cracks with vertical sections, often bifurcating and spanning across b-stage and c-stage material, even through glass bundles, and tend to propagate with sharper angles. This failure mode appears to be more a chemical degradation of the epoxy system. Sincerely, Paul Reid --------------------------------------------------- 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 -----------------------------------------------------