Dwight, How is heat to get from the device to the thermal via if you don't plate over it? Agree that CTE of the non-conductive fill must be a very close match. Regards, Karl Sauter, Sun Microsystems Dwight Mattix wrote: > We have a lot of experience w/ this type failure. I'm working on the > assumption that there's a thermal via farm in that center gnd slug area. > A couple recommendations ff the cuff... > * Stay away from conductive via fill material whenever possible when > vias are tightly packed in "thermal via farms." Conductive fill is almost > never needed -- adds very little actual thermal/conductive benefit. We've > modeled it and test it. For my money, conductive fill is almost always a > waste of time and a real pain in the patootie from reliability standpoint. > The biggest benefit is that it's easier to plate over and get good copper > adhesion and that usually only matters on probe sites. Esp > evil/unpredictable in this application is CB100 (I've had lots of dialogue > w/ Dupont over the years on this type failure). > * Use a non-conductive fill that's more closely matched in CTE (e.g.San > eh) and don't overplate the fill. > * Arguably the most significant factor: don't plate over the thermal > vias. All overplating does is give the fill something to push against and > force the whole plated area up during thermal excursions. It's like > screwing a cylinder head on tightly and then pushing all the pistons up > against it (expanding fill at temp). Pop goes the weasel! Overplating > doesn't add any grounding or thermal benefit. The solder joint in the gnd > slug will still be fine w/ the dot pattern that emerges. > * As a work around/mod: We've eliminated a couple of these problems on > finished product by just etching or laser ablating a dot of copper off over > the fill. > > there's my $.02. Free and worth every penny. ;^) > > cheers, > dw > > At 07:29 AM 10/19/2005, Steve Gregory wrote: > >> Hi Wee Mei! >> >> I've got your pictures posted. Go to: >> >> http://www.stevezeva.homestead.com/files/U2_top.JPG >> http://www.stevezeva.homestead.com/files/U2_bottom.JPG >> http://www.stevezeva.homestead.com/files/U2_delamination.JPG >> >> Are the vias filled? Are you seeing this delamination on very many >> PCB's? Are you seeing it only on the bottom of the PCB? >> >> Kind regards, >> >> -Steve Gregory- >> Senior Process Engineer >> LaBarge Incorporated >> Tulsa, Oklahoma >> (918) 459-2285 >> (918) 459-2350 FAX >> >> >> >> |---------+----------------------------> >> | | Wee Mei | >> | | <[log in to unmask] >> | | SG> | >> | | Sent by: TechNet | >> | | <[log in to unmask]>| >> | | | >> | | | >> | | 10/19/2005 03:47 | >> | | AM | >> | | Please respond to| >> | | TechNet E-Mail | >> | | Forum | >> | | <[log in to unmask]>| >> | | ; Please respond | >> | | to Wee Mei | >> | | <[log in to unmask] >> | | SG> | >> | | | >> |---------+----------------------------> >> >> >--------------------------------------------------------------------------------------------------------------| >> >> | >> | >> | To: [log in to unmask]@SMTP@Exchange >> | >> | cc: (bcc: Stephen R >> Gregory/LABARGE) >> | >> | Subject: [TN] Delamination at Thermal Via >> area? | >> >> >--------------------------------------------------------------------------------------------------------------| >> >> >> >> >> Hello, >> >> Just asked Steve to download 3 pictures on the defects. Kindly take a >> look >> at them and would appreciate some feedback on the possible root cause. >> >> Steve : Thanks for the downloading. >> >> Regards, >> Wee Mei >> >> --------------------------------------------------- >> 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 >> ----------------------------------------------------- >> >> >> >> __________________________________________________________________ >> This message may contain information that is privileged and >> confidential to >> LaBarge, Inc. 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