I had a BGA via-in-pad design a few years ago where the assembler used kapton (or some heat resistant tape) on the back side of the pads so the solder wouldn't flow through, worked well. Ken __________________________________________ Kenneth Wood Saturn PCB Design, Inc. www.saturnpcb.com -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: Tuesday, February 05, 2008 1:23 PM To: [log in to unmask] Subject: Re: [TN] Open via in pad - any success? Wayne, If I had blind vias and a choice, I would spec over-plated vias... With small vias you can't guarantee that the plugging operation will not entrap additional materials in the closed end of the vias.. Besides I would rather have a single point of failure instead of having 2... Paul -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne Sent: Monday, February 04, 2008 6:59 PM To: [log in to unmask] Subject: Re: [TN] Open via in pad - any success? Dwight- What's the difference between plugging and filling? I'd heard overplating the vias was recommended in this case because there was a high chance of voids/outgassing to originate at the site of the fill/plug. I keep wanting to try this technique beneath QFN parts but my CAM artist keeps "accidentally" specifying the overplate! Wayne Thayer ________________________________ From: TechNet on behalf of Dwight Mattix Sent: Mon 2/4/2008 8:20 PM To: [log in to unmask] Subject: Re: [TN] Open via in pad - any success? At 04:55 PM 2/4/2008, Ryan Grant wrote: >Hi All, > >I just got told by a design engineer that LaserJet printers are built >using via in pad where the via is NOT plugged. He claims the via is >filled with solder first, then goes through the normal SMT process. > >He intends to use this to connect a BGA ball on one side of the board >to a cap on the other side using an mechanically drill via that is not >plugged. > >Before I call BS on this, and tell him "do not pass go until that via >is plugged, flattened and plated over", has anyone been successful with >a via in pad that is not plugged? >If so, was it double sided? >And, was one side connected to a BGA ball? Yes, yes, and yes. However as you might imagine, the devil's in the details. Filled (not plugged) with matched CTE non-conductive epoxy (ie SanEi or Peters) and planarized (ie flattened) makes life easier and with less unintended consequences to manage. However, there shouldn't be a need to overplate the via fill. Unless you're probing filled pads that's just needless extra plating process and adds risk of via failures (expansion lifts pad and cracks via at knee). >Thanks, >Ryan > >--------------------------------------------------- >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 ----------------------------------------------------- ======================================================================== ====== This email and any attachments thereto may contain private, confidential, and privileged material for the sole use of the intended recipient. 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