Or the Bear facts about CAF....8-) -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker Sent: Thursday, June 22, 2006 8:46 AM To: [log in to unmask] Subject: Re: [TN] Board material Richard You should write a book about this. You could call it The CAF and the Bear! Best regards Lee J. Lee Parker, Ph.D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: "Stadem, Richard D." <[log in to unmask]> To: "TechNet E-Mail Forum" <[log in to unmask]>; "Lee parker" <[log in to unmask]> Sent: Thursday, June 22, 2006 9:57 AM Subject: RE: [TN] Board material Hi, Lee Good enough. My experience with it began in 1977 on telephone network circuit cards used in Saskatchewan, Canada. I was a telephone tech at that time and ran into CAF when attempting to troubleshoot the boards while straddling the pole. I eventually had to pull the entire network cards out and replace them. Nobody could figure out why the boards were "leaking" current from the power supply to the signal lines, disrupting the service. They finally figured it out that with the extremely cold mornings turning into extremely hot days, the condensation was actually infiltrating the pwb along the power supply buss terminal (not conformal coated), and over time CAF formed. I ran into CAF again in 1979 at Honeywell, and this time I recognized it. When the pwb supplier changed to the different pre-preg, no more problems. Those were the good old days, straddling the pole and trying to debug the network while simultaneously shooting the brown bears trying to climb the pole to eat me for breakfast, all in a howling sandstorm on the God-forsaken wide open sand prairies near Saskatoon. Nobody around for several hundred miles, and sometimes I would not see another person for three or four days while I worked. The last thing I needed was CAF. Impossible to see or detect using standard troubleshooting tools of the time. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker Sent: Thursday, June 22, 2006 8:34 AM To: [log in to unmask] Subject: Re: [TN] Board material Richard Actually CAF was first identified by Dave Lando who was in the same Bell Laboratories organization as Werner and myself. This was in 1974, just after we opened the new and world's largest PCB shop in Richmond. Probably the most important attribute of CAF is as the name suggest, the filaments grow from the anode to the cathode which is the opposite of what one would anticipate. Best regards Lee J. Lee Parker, Ph.D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: "Stadem, Richard D." <[log in to unmask]> To: <[log in to unmask]> Sent: Thursday, June 22, 2006 9:06 AM Subject: Re: [TN] Board material In about 1978, when CAF was realized as a problem in standard PTH power supply boards, the strands were continuous through the pre-preg. It was then that the fab shops started to used chopped fiberglass mat weave, in order to provide shorter strand lengths so CAF formation was less likely to happen. However, because of circuitry being so close together sometimes with fairly high potential, CAF has become more of an issue again. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon Sent: Thursday, June 22, 2006 7:36 AM To: [log in to unmask] Subject: Re: [TN] Board material Hi Werner, could you expand on "Having PCB materials without continuous glass fibers makes them immune to internal CAFs"? I was under the impression that the continuous glass fibers were the strength of the board. Regards, Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Wednesday, June 21, 2006 3:58 PM To: [log in to unmask] Subject: Re: [TN] Board material Hi George, CAF stands for 'Conductive Anodic Filament'-CAFs are capillary paths, typically from PTH to PTH, along the glass fibers of the PCB glass fiber reinforcements. The get started by damage done during PTH drilling with a dull drill, propagate further depending on internal vapor pressures, and on application of a potential difference transport metallic ions forming a conductive path. Now, this conductive path does not give you a dead open, but lowers insulation resistance by couple of orders of magnitude. Having PCB materials without continuous glass fibers makes tham imune to internal CAFs. Regards, Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------