A lot of it is based on common sense. If the hole walls are bare copper and you want to protect that bare copper from both board fab and assembly chemicals, you need to completely plug or cover the via. LPI can flow into the via, but there is no guarantee that there will be a complete plug or even coverage of the entire hole wall. If the hole walls are an inert finish such as ENIG, then protecting them is not the most important aspect of via protection. You would then have to consider what you are wanting to do and if an incomplete plug would suffice. Susan Mansilla --------------------------------------------------- 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 -----------------------------------------------------