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February 2010

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Werner Engelmaier <[log in to unmask]>
Date:
Wed, 3 Feb 2010 09:40:54 -0500
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 Hi Everybody,
I sent Steve another 'buckle-up' trace lifting picture to put on his site. So now, together with Brian's case we have 3 documented occurrences.
So, please, as I wrote to 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: Stadem, Richard D. <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
Sent: Wed, Feb 3, 2010 9:33 am
Subject: RE: [TN] track lifting


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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