I and a colleague actually designed a test panel which replicated this condition. It is generally a function of the hole size (smaller is worst) and the aspect ratio (higher is worst). Blocking with resist prevents fluid change over, but when they are all on the same net this is unlikely as a cause. The test panel we created took via holes of 8 mil to 22 mil in a 110 mil thick multi layer panel. Each hole size was replicated into a BGA design. Some holes were signal, some power, and some ground replicating an actual design scenario. Basically the panel when put down a board line gives a visual indication of where the technology fails in terms of aspect ratio, stripping, Bernoulli's laws etc. So an immediate and visual indicator of hole size for aspect ratio can be assessed for the line, and the line tweaked accordingly. The panel was created to test the capability of a board line to eliminate skip plating, and was a project by myself and James Townsend at Extreme Networks. I believe Extreme own the copyright on this board which James (JT) and I named FDAT (Fluid dynamics assessment tool) but which is also affectionately known as the Bernoulli bus. If anyone wants to try it, I will ping JT to see if the artwork could be released as this work is now over 3 years old. John -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell Sent: Monday, September 18, 2006 5:14 PM To: [log in to unmask] Subject: Re: [TN] ENIG I've witnessed sporadic poor covered pads but never even considered verifying their connection via traces to the varied pads. Typical cause in the majority I observed were poor tin strip/poor predip (75% of observed) and poor resist develop (15% of observed) with the remaining undetermined. Of the observations made above, these were in instances where we confirmed bath operating optimally. Is there enough (electrical) activity occurring in these baths where a short or other board condition would result in robbing plating from those type areas??? Franklin -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz Sent: Monday, September 18, 2006 7:03 PM To: [log in to unmask] Subject: Re: [TN] ENIG In a message dated 9/18/2006 7:50:57 P.M. Eastern Daylight Time, [log in to unmask] writes: There is one thing I did leave out. The pads that aren't taking ENIG all happen to be in the same net. Has anyone encountered this? To me, this says that there is some "electrical" cause, stronger than the catalyst that initiates the electroless nickel plating. Remember, the catalyst in the ENIG process is a tightrope between getting plating everywhere (extraneous plating) and not covering some pads (skip plating). Here you have skip plating If the same net skips board-to-board, likely it is a design issue where something is grounded out unintentionally and plating is getting defeated in one spot. It could be that some via is tented consistantly holding a poisoning fluid - tin stripper for instance. If different nets skip on the panel, then I suspect a more random error - incomplete tin strip, etc. I guess it could be marginally weak catalyst. I would expect developer residues to be random pads - not all in a single net. Something "electrical" is going on here. Denny Fritz MacDermid --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------