One board manufacturing house we use draws the LPI into the via holes with a vacuum filling them entirely before screening the material onto the board surface... then they expose the boards for imaging and develop... I believe they must have some technique for exposing the LPI material in the holes to make it solidify but I am not the board fabricator... The distinction required to get this process was changing my notes to say 'plugged' vias instead of 'tented' vias. So far it has been working very well. Bill -----Original Message----- From: Whittaker, Dewey (EHCOE) [mailto:[log in to unmask]] Sent: Wednesday, September 19, 2007 10:02 AM To: [log in to unmask] Subject: Re: [TN] Via Plugging Yes, but as an esteemed member of this forum and an Icon of the Industry says" It depends". If you are looking for long term reliability and can't tolerate any open or exposed vias, there are only three methods. Capped and covered [dry film SM cap covered by a LPISM (SMOBC)]; POFV [plated over filled via (could be a SM material for the filler followed by a LPISM over the copper if access not needed)]; and a plugged or filled via (could be a SM material) covered by a LPISM (SMOBC). The new revision of IPC-SM-840 deals with a lot of the acceptance criteria, but there are additional requirements that have already been proven out. If you don't care because it is not a functional requirement and only a processing aid for test or assembly, then anything will work. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bill Dworak Sent: Wednesday, September 19, 2007 9:37 AM To: [log in to unmask] Subject: [TN] Via Plugging Does any one know of a better way to plug vias with LPI ratehr than just the old standard method that will cover and plug the entire surface of a PCB? I am being told that it is "industry Standard" to have about a 10% non plugged ratio. Any help will be welcome. Bill Dworak --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------