Our printed circuit board purchasing specification currently specifies that, when required by design, the vias shall be tented with solder mask. I am in the process of reviewing this specification for its continued applicability and have some questions about the tenting of vias. We are currently in the process of switching from an ENIG process to an OSP-based finish. Our ENIG boards were not tented, should the OSP boards be tented to reduce the possibility of oxidation occurring on the vias assuming that most (if not all) of the OSP burns off during the reflow process? I think that the vias should be plugged prior to tenting to eliminate the possibility of entrapped liquids or gases in the vias, any thoughts? We use a LPI solder mask (SMOBC process) and a dry film would not be appropriate due to the fine pitch and small traces (4 on 4) on some of our designs. What is the best process for tenting with a LPI solder mask? I guess that my primary question is do we need to tent the vias at all on an OSP finished board? We do not perform ICT testing so the vacuum issue is not a concern. I apologize for all of these questions, but as you can see I am fairly confused. Thank you in advance for any and all replies. R. Todd Dataram Corporation Ivyland, PA --------------------------------------------------------------------------------- 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 the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------