Mark, We have done some CAF testing with Thermount, epoxy resin version. When the plated-through holes (PTHs) are oriented along the X or Y axis, then boards made with the Thermount laminate material (which have broken and random orientation of reinforcement fibers) showed significantly more resistance to CAF failures than standard FR-4 laminate materials. However, when PTHs are diagonally oriented the Thermount boards (epoxy resin version) showed slightly less resistance to CAF when compared with boards made using standard FR-4 laminate materials with X and Y oriented woven glass reinforcement. In retrospect this seems understandable since the Thermount will have some fiber segments that do run in a diagonal direction. Since most boards (but perhaps not substrates) have the closest vias and other PTHs oriented in-line with the X or Y axis, then using the Thermount epoxy resin laminate material as an alternative in those cases should produce boards that are significantly more CAF resistant. Regards, Karl Sauter, Staff Engineer (and Vice-Chair of IPC committee on CAF) Sun Microsystems Inc. (650) 786-7663 > Date: Fri, 20 Dec 2002 09:46:10 -0800 > From: Mark Mazzoli <[log in to unmask]> > Subject: Re: [TN] Thermount for Burn In boards > X-To: "TechNet E-Mail Forum." <[log in to unmask]> > To: [log in to unmask] > > Thanks for the info David. I wasn't aware that CAF could form in that short > amount of time. We've made numerous attempts to locate the actual shorts > but they don't show themselves. Clearly, if we could find one it would make > decision making much easier. > > Thermount is billed as an anti CAF material due to the randomness of the > fiber. Since it does not contain woven strands for channeling CAF, some > believe it to be resistant to that effect. Our concern is its enthusiasm > for water absorption. I can see how the absence of fiber "channels" would > inhibit filament growth but it seems like the accelerated water absorption > would create a fine growing environment for conductive incubation. > > Are you aware of the materials used in the IPC testing? > > -----Original Message----- > From: David Douthit [mailto:[log in to unmask]] > Sent: Friday, December 20, 2002 8:58 AM > To: TechNet E-Mail Forum.; Mark Mazzoli > Subject: Re: [TN] Thermount for Burn In boards > > Mark, > > Some round robin testing being done by the IPC committee on CAF indicates > that there is a "damage" ring around drilled holes/vias of up to .020 > inches. > CAF will form there very quickly (hours!) in high >80% humidity and mild > temperatures (>5 degrees C and < 45 degrees C). > This damage area would most likely include edge routing and scoring. > > > You need to do some cross section work ups before you start "guessing"! > > > David A. Douthit > Manager > LoCan LLC > > > Mark Mazzoli wrote: > > > > > For those of you designing or building burn in boards, are any of you > building them on Thermount material? One of our customers has shown an > interest in this material for their burn in boards and we're trying to > decide if that's a wise move or not. Most of their boards use 0.8mm and > 0.5mm BGA's and have traditionally been built on Polyimide. The problem is > that some percentage of them develop low voltage shorts in the field. Hole > to internal traces may be as low as 3 mils when drill wander and material > movement are at their worst but normally it's maintained at 6-mils or > better. The boards are tested at 40 volts prior to shipping and all pass > but some number of them will develop the field problem. CAF is suspected > but I'm not so sure. The field failures develop in days or weeks rather > than months. I suspect rather than CAF it may be due to the resin system > itself. I understand that most Poly manufacturers use a common Poly resin > from Ciba and that it has been suspected of developing this low voltage > shorting issue (sulfur content I believe). > > > Anyone out there have any comments about the situation itself or comments > regarding Thermount (85RT and 55ST)? > > > Thanks, > > > Mark Mazzoli > --------------------------------------------------- Technet Mail List > provided as a free 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 <http://listserv.ipc.org/archives> > Please visit IPC web site http://www.ipc.org/html/forum.htm > <http://www.ipc.org/html/forum.htm> for additional information, or contact > Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > ----------------------------------------------------- > > > --------------------------------------------------- > Technet Mail List provided as a free 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/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------