The heat of a HASL coating can bring epoxy filling out in bumps if you don't have a fab house that's expert in this process, though I have had some very smooth finishes so that you cannot detect the filled holes at all. The plated surfaces wind up being smoother (ENIG and immersion tin being the other two that I've tried), but I've been disappointed with the over-plating coverage, even when the copper plating has completely capped the epoxy fill. As an overall reaction, I would say that epoxy filling is not the best process I've met in terms of consistency or cost/time effectiveness - certainly as a thermally conductive filler. Peter "Dan R. Johnson" <[log in to unmask]> 15/11/2002 07:30 AM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to "Dan R. Johnson" To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: [TN] another conductive epoxy question. I've used silver fill epoxy with thick film substrates but never with PCB's. Any hints on what finishes are compatible? I did a quick and dirty test with HASL and wasn't impressed with the adhesion. Is Gold better? None of the typical finishes I see look like they would have the "tooth" that thick film does. How do the COB folks do it? Dan --------------------------------------------------- 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 -----------------------------------------------------