Werner, I’ve tried to describe it better
Fan-out clocking correlation: The fractures/poor wetting appear to start at the trace to land junction, rather than what one might expect from t-cycling fatigue, or ict strain. In the pictures I posted, I tried to show the damage clocking around with the traces.
I thought that I had heard or read somewhere that this is common, but you guys are a lot faster than a literature search.
Chris
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Monday, October 11, 2010 4:10 PM
To: [log in to unmask]; Chris Mahanna
Subject: Re: [TN] Mech. damage or poor wetting?
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]> [mailto:[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]<mailto:[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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10/11/2010 11:29 AM
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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?
Thanks
Chris
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