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December 2010

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Subject:
From:
Ioan Tempea <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ioan Tempea <[log in to unmask]>
Date:
Wed, 15 Dec 2010 10:08:56 -0500
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Dear Technos,

 

We see intermittence in the functioning of 1206 ceramic caps after mechanical assembly. Everything OK in Test, prior to assembly. Due to mechanical constraints, the board is rather roughed up during integration, so I was not surprised with the issue. But now the things get complicated: if the caps are touched up, the intermittence goes away and everything works again. So we've had the capacitors x-sectionned, see images at http://ipc-technet.groupsite.com/gallery/17220

 

So here come the questions:

ˇ         If I am not wrong, I have seen comments on this very forum about touch-up of ceramic caps actually fixing internal damage of the component, rather than the joints, which is misleading and just a temporary fix, the cap will stop functioning in a short while. Do I see it right?

ˇ         Although there is an 0603 in close neighbourhood of the problem 1206, see image, the damage is only on the 1206. Am I wrong considering this normal, bigger size, higher bending, more damage?

ˇ         The lab couldn't find anything wrong, neither in the joints, nor internally in the part. I see a dark line at the interface between the solder and the part in the right side image; is this normal, or an actual crack?

ˇ         It seems the plates of the caps are perpendicular to the PCB, instead of parallel. This is how they came in the tape, we are not flipping them. Would this orientation of the plates make the component more prone to internal cracking than parallel?

ˇ         There indeed does not seem to be any 45 degrees cracking of the ceramic package at the corners (indicative of mechanical stress). Since nothing internal has been detected either and the joints were deemed good, what else could be the issue?

 

Thanks,

 

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>  
W | www.digico.cc <http://www.digico.cc/> 

 
 N'imprimer que si nécessaire - Print only if you must

 


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