Hi Chris,

 What do you mean by 'fanout clocking?'


 I think you have a combination of 'Black Pad' and component warpage.
'What points to 'Black Pad' is the periphery location—during soldering the periphery gets a lot more heat than the interior, thus more Ni goes into solution with Sn, thus leaving a higher P-concentration at periphery pads, thus they are weaker, thus component warping causes interfacial separation on the periphery & pad cratering where the P-concentration is lower.
Werner

 

-----Original Message-----
From: Chris Mahanna <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Oct 11, 2010 2:40 pm
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
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Chris Mahanna <[log in to unmask]>
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10/11/2010 11:29 AM
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[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?

Thanks

Chris

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