John, you get the prize for the first theory on this I've never (at least) heard of. Do you have a publication reference? On your site? BTW, have you thought about indexing your site articles? That would be sweet. I like Werner's BP, but the only evidence I have so far is lack of dissolution, rather than too much. From my first post, I believed it to be primarily a sub-par wetting problem. Against my recommendations the customer requested 100 BGAs to be dye-n-pry. So we know a lot about how the sub-par wetting propagates through the assembly and testing, but precious little root cause evidence (no pads found to be black). I think that I convinced them to test some bare boards. I'll get you all updates. As for FA today, from the perspective of the independent lab, very-very few are willing to spend even the bare minimum to get to root cause. All they want to know is 1) can we ship the rest of the product, and 2) give me data for an easy CAPA. That's why I'm always asking technet about signatures and their probability to root cause. There is nothing worse than running out of money with no definitive root cause. FYI, our current global failure rankings 1) cratering (not necessarily patent), 2) wetting 3) CAF 4) PB-free alloy overstress/fatigue 5) delam or cohesive laminate failure (including haloing) leading to dielectric breakdown. All [in]directly attributable to Pb-free materials/processes. Chris -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: Tuesday, October 12, 2010 6:22 PM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Actually it is highly likely for this type of defect it to ONLY occur in the BGA area. This effect occurs particularly on BGA via fields using small via holes especially in high aspect ratio boards. If the tin stripping in the outer later etching process is not removing all tin from the through hole walls the residual tin impacts the subsequent nickel plating process so that you get a very thin nickel layer both in the wall and the connected pad - over which you plate immersion gold.....giving the effect you are showing on your photographs. I would be inclined to take bare fabs from the same lot and do some XRF work in those areas impacted comparing the nickel thickness to the rest of the small component pads - I think you may be in for a surprise. John -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro Sent: Tuesday, October 12, 2010 10:07 AM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Thus.....etc I would want to inspect the rest of the board for more evidence of the black pad, such as the smaller chip caps....for it to only occur at the perimeter of the bga seems unlikely. On a chip cap pad which has had solderpaste melt and interact with the nickel underneath, the dewetting should be apparent. Dye and Pry can be misleading as to the cause of the dye penetration, especially when there are numerous possible mechanical questions. Phil -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: Tuesday, October 12, 2010 9:40 AM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? It sure looks like Black Pad to me. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez Sent: Monday, October 11, 2010 2:41 PM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Was this BGA reworked/repaired. Is it in close proximity to another BGA that was RW? Did the card/board see two consecutive thermal excursions? X" -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW Sent: Monday, October 11, 2010 1:55 PM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Never mind. I just read the original post. I'm betting the whole shebang is due to poor wetting--that's why the correlation to the fanout escape. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW Sent: Monday, October 11, 2010 2:52 PM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? What's going on with the picture of the cross section? The ball isn't wetting down the side of the plated pad. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna Sent: Monday, October 11, 2010 2:41 PM To: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Here are a few pictures http://ipc-technet.groupsite.com/gallery/16011 this job is a mixed bag. Currently we suspect soldering, cratering, ICT and t-cycling damage Chris From: [log in to unmask] [mailto:[log in to unmask]] Sent: Monday, October 11, 2010 2:22 PM To: TechNet E-Mail Forum; Chris Mahanna Cc: [log in to unmask] Subject: Re: [TN] Mech. damage or poor wetting? Hi Chris - do you have any pictures you can share? Dave Hillman Rockwell Collins [log in to unmask] Chris Mahanna <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 10/11/2010 11:29 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Chris Mahanna <[log in to unmask]> To [log in to unmask] cc Subject [TN] Mech. damage or poor wetting? We have a BGA dye-n-pry job that shows board side sj damage with a strong correlation to fan-out clocking. We also have some microsection evidence of poor wetting. All damage/dye is on perimeters. Is this an indication of heat sinking and subpar wetting, or can it be completely mechanical? Both? 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