Vias can sometimes be filled with subcomposite build by filling them with the epoxy resin (blind, not through vias). In thin boards, with a multiple print, it is sometimes also possible to fill them with LPI, but this is "iffy" and time consuming. Filling them with a higher temperature solder might also be an option (paste and reflow or high temp wave). if you only need to fill one or two vias, manually filling them with an epoxy works. Another possible option is to just "tent" both ends of the hole with a thick dry film solder mask. However, if you can avoid the need to fill them, it will make building the "fab" a lot easier, and less costly. Except for product around 23 mils thick, we do not fill vias 100%. Your requirement sounds very "painful" to the manufacturing folks. Best of Luck! Perhaps you can share your "goal" (why fill them) and maybe we can propose another alternative also? Jim Herard KBL, Product Quality Engineering IBM Microelectronics Endicott t/l 857-7026 ---------------------- Forwarded by Jim Herard/Endicott/IBM on 07-31-97 06:06 PM --------------------------- [log in to unmask] 07-31-97 01:45 PM Please respond to [log in to unmask] @ internet To: [log in to unmask] @ internet cc: Subject: Fab/Assy: Thermal Vias Hello Technetters, Has anyone found a method to completely fill a via? I don't think that the standard plating process will guarantee 100 % fill. We're also looking at the option of screen printing conductive epoxy and trying to force it through the hole. But, I don't have a lot of confidence in this process either. The last option we're considering would be to plug the vias with LPI soldermask. This seems like the best guarantee of fill. Thermal conductivity is not so great, but it is better than air. I'd sure appreciate any comments. Glenn Pelkey Quality/Reliability Engineer Maxtek Components Corp. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************