Hi All, Here is my two cents worth. I am pretty sure this is crazing. It is a separation between the glass and the epoxy. What you see is light refracted by the fine air gap between the glass fiber and epoxy. Viewed on the glass fiber end this condition looks like small half moon cracks. It is the path for CAF. It is due to material or drilling problems 9 out of 10 times. On occasion design can contribute to the condition. PTHs drilled on a .020" grid are prone to this condition. Moisture or other volatiles in the separation may be a contributor to propagation during assembly and in the end-use environment. I have been told thermal cycling in a humid end-use environment may cause water to be condensed in the air gaps. The condition can be in the b-stage or c-stage epoxy layers but is mostly found in the b-stage layers. This condition causes changes in capacitance between copper planes in an IST test coupon with DELAM circuits. We have found this condition is more common in lead-free assembly and rework. 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 Victor Hernandez Sent: Tuesday, May 20, 2008 11:43 AM To: [log in to unmask] Subject: Re: [TN] Blue Voids Keith, Can you share any information on CAF. Victor, -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Barbara Burcham Sent: Tuesday, May 20, 2008 10:16 AM To: [log in to unmask] Subject: Re: [TN] Blue Voids Interesting, very very interesting. I received a technical presentation from Keith Larson at DDi this week and when I saw this post and looked at the photos, I recalled a photo that I had seen in the DDi paper by Gil White of a cross section of a plated hole. It was in the section about Conductive Anodic Filament Growth (CAF), and I quote, "Conditions that contribute CAF: De-lamination of the glass polymer interface resulting from: Excessive temperature (I.e. 260deg.C for standard FR-4) Thermal cycling CAF is accelerated by: Moisture Applied potential (higner potential accelerates the process) Their photo shows the same smeared appearance across the hole and says the smears are copper migration along glass fibers. I have copied Keith into this email so that he can respond. I think they may have the answer to this thread. Or, contact Keith at this email address to get the paper or reach Gil White. [log in to unmask] Regards, Barbara Burcham -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson Sent: Tuesday, May 20, 2008 9:36 AM To: [log in to unmask] Subject: Re: [TN] Blue Voids Well, since our supplier hadn't seen this condition in their microsections, and the independent lab used different equipment (Scanning Electron Microscope and Differential Interference Contrast photography), the question became whether the supplier's lab could even see the condition if it was present. The independent lab still has the sample panel with the known condition, and they agreed to send back half of the panel so the supplier can experiment with it. In the meantime, our company issued a corrective action request so we get some kind of follow-up on the results. Thanks to everyone who looked at the evidence and sent their opinion. http://frontdoor.biz/PCBportal/bluevoid.jpg p.s. I think its kind of fun to do this (especially when it is not MY company's sample) Maybe we should have more community "case studies", I find the group feedback to be very educational, especially when the descriptions in IPC-A-600 are vague. Thanks again. onward thru the fog, Jack -----Original Message----- What became of this issue? I have not seen any more threads of e-mail. Victor, From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask] Sent: Tuesday, April 29, 2008 9:59 PM To: [log in to unmask] Subject: Re: [TN] Blue Voids Are the voids in the glass bundle or between the glass bundle and the resin? If the former, you have a glass supplier problem (not all the weaving assistant burned off?)-- if the latter, then I would suspect incorrect pH in the adhesion promoter application bath. Bill Kenyon Global Centre Consulting 3336 Birmingham Drive Fort Collins, CO 80526 Tel: 970.207.9586 Cell: 970.980.6373 --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------