You must first decide if this is a functional requirement, such as part of a via protection strategy or simply a manufacturing aid, then we can talk. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden Sent: Monday, April 13, 2009 10:45 AM To: [log in to unmask] Subject: Re: [TN] Info on LPI tenting of vias, both sides Yes, it was my mistake. I intended to say dry-film tenting of vias on both sides. I have IPC-4761, and it basically covers an LPI tented via as Type I. What is not clear is if by inclusion in the specification that this is a preferred format or not, or was simply included because it is common practice, right or wrong. In section 3.2 there is also a statement "Plugging of vias from both sides of the hole results in manufacturability and reliability issues". I have heard warnings that tenting both sides can be problematic in that if the seal is not perfect or somehow compromised (adhesion loss / puncture) moisture or other contaminants can make their way in and the results can be more catastrophic then a blind or single-side-tented via. I have also been warned that at one time LPI tenting was "verboten" in MIL-STD-2000, so that alone is questionable whether it was a scientifically derived requirement, as some of the old requirements did not have the benefit of today's research. Thanks, Kevin -----Original Message----- From: Chris Mahanna [mailto:[log in to unmask]] Sent: Monday, April 13, 2009 1:25 PM To: TechNet E-Mail Forum; Kevin Glidden Subject: RE: [TN] Info on LPI tenting of vias, both sides Kevin, Generally LPI and Tent don't go in the same sentence unless there is a secondary cover. Is your intent via protection? Does your solderable final finish process follow the mask? Chris Chris Mahanna Robisan Laboratory Inc. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden Sent: Monday, April 13, 2009 12:45 PM To: [log in to unmask] Subject: [TN] Info on LPI tenting of vias, both sides Hello everyone, I am looking for information on the potential pitfalls of using LPI via tenting on both sides, leaving an air pocket in the vias. Application is NOT Pb-Free. I located this article description, and wanted to see if anyone had it, but other information, inputs, or articles are also welcome: Title: An Evaluation of Via Hole Tenting with Solder Mask Designed to Pass MIL-P-55110D Thermal Shock Requirements Author(s): J.J. Davignon, F. Gray Journal: <http://www.emeraldinsight.com/0305-6120.htm> Circuit World Thanks! --------------------------------------------------- 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 -----------------------------------------------------