Dwight, just out of curiosity, why not plate ALL of the vias with 3 mils of copper. Wouldn't this be cheaper than drilling, plating, drilling and plating again? Jim Marsico Senior Engineer Production Engineering EDO Electronics Systems Group [log in to unmask] <mailto:[log in to unmask]> 631-595-5879 -----Original Message----- From: Dwight Mattix [SMTP:[log in to unmask]] Sent: Monday, April 29, 2002 1:26 PM To: [log in to unmask] Subject: Re: [TN] Via Plug At 11:29 AM 4/24/2002 -0700, John Foster wrote: >Thanks Jim > >Did you do this extra plating selectively. Or did you just overplate the >whole PCB. We have a lot of applications where we spec thermal vias to be selectively plated to a minimum of 3 mils annular copper. The fabricator drills the thermal vias and selectively plates to 2 mils. Then they drill and (plate the rest of the board to 1 mil (adding to thermal via copper as well). It's way more effective at heat transfer than any conductive epoxy we've tried. This approach is also very effective at controlling solder wicking to the bottom of the board -- we'll use it sometimes when we don't have a thermal problem but just want to control solder flow into unplugged fields of gnd vias (saves masking backside). Dwight ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------