A via plug isn't necessary to avoid the solder wicking problem that is being described. Simply coating the vias in the BGA area with LPI soldermask could accomplish this without the additional processes required for "via plugging". Thank you, Eddie Rocha South Bay Circuits Hi Paul, I am fully agreed with Richard. The problem is even worse if your finish is ENIG (adhesion problem of the solder mask to the gold). Regards, Dr. Gil Zilber Technologist, Elta system Ltd. Tel. +972-8-8577240 Mobile +972-54-4983222 http://www.iai.co.il/site/en/iai.asp?pi=17887 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard Sent: Wednesday, November 30, 2005 3:59 PM To: [log in to unmask] Subject: Re: [TN] Plugging vias necessary? Without the plug, the solder from the sphere can wet down into the adjacent via to the backside of the pwb during reflow. On a dogbone pattern, with one side the pad and the other side the connecting via, the small soldermask dam that goes over the thinnest part of the dogbone pattern is not enough to stop the solder wicking. The solder will wick right under that flimsy little dam, and the via will rob the solder. This is called solder thieving. The soldermask plug prevents that from happening. If you ever need to rework that BGA, the site prep operation nearly always makes the little soldermask dam worse, and after you replace the part you get even more solder thieving, and the entire rework/X-ray/test/rework cycle spins on down into a black hole called scrap. One almost never sees BGAs with daisychained dogbones without the soldermask plug, and that is a good thing, as Martha says. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Black, Paul Sent: Wednesday, November 30, 2005 7:50 AM To: [log in to unmask] Subject: [TN] Plugging vias necessary? Hi Everyone, I have a board with a 357 pin PBGA. Each pad has a short etch leading to an adjacent via. Currently, the fabrication drawing calls for each via to be plugged. The assembly process for this board does not contain a wave solder step and the test engineer assures me that plugging the vias is not necessary for vacuum during incircuit testing, so is there some other reason for plugging these vias? They are plugged with soldermask, and I feel like we are unnecessarily introducing potential problems into the process. Thanks in advance for your opinions. 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