Like Steve, my first thoughts were that the BGA in the picture was apparently impacted, or somehow lifted and then put back down and reflowed.
However if that had happened, it could not have happened without many other traces on each side of the lifted ones also being lifted and damaged, but they are not.
Therefore I agree with Werner, that this is a case of damage due to severe CTE mismatch. I have never seen this before.
Burke, I'll take you up on that bet. I doubt that there will be any delamination issues. This appears to be a case where the PWB expanded and shrunk back in the X and Y axis during reflow or temperature cycling, but I doubt that it saw any significant Z-axis expansion.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, February 03, 2010 8:13 AM
To: [log in to unmask]
Subject: Re: [TN] track lifting
Hi Brian,
I would appreciate pictures, possibly also to Steve, that I could use in my reliability column—this is a failure mode fairly new and unknown to most people.
If you could, I also would appreciate the base material, the peak reflow temperature, the cooling rate after reflow, the Cu trace thickness and whether it was covered with solder, and what solder. I now, its asking a lot, but only with all the pertinent info can we make sense of this.
Werner
-----Original Message-----
From: Brian Chandler <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Feb 3, 2010 7:28 am
Subject: Re: [TN] track lifting
We just conducted a study on acceptable strain levels for lead free products.
Our BGA test coupons showed this exact result from excess strain.
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