Hi Inge!

I think you are the clear winner for bringing stuff up with Technet!

We are familiar with similar failures.

Conformal coat normally has a very high CTE.  This makes it very bad
stuff to completely fill gaps under a part.  If we are doing thick
coating, we use an appropriate underfill material just to make sure none
of the overcoating gets beneath the part.

Wayne Thayer

>>> [log in to unmask] 4/24/2007 12:43:00 am >>>
Hi all,
anyone had cracked solder joints with even lead lifting with Quadpaks
AND 
conformal coating? What was the reason? Vibration, mechanical shock, 
tempcycling, warpage, thermal mismatch, voiding, diffusion, Kirkendall
or 
what?  The coating is robotic dispensed and the Quadpak is 'drowned' in

coating in order to secure the leads against vibration. Personally, I 
dislike the abundant lot of coating. Am afraid that, at minus degrees,
the 
coating gets hard and less ductil. When the processor is energized and
warms 
up quickly (airgap between Quad and board), maybe the still-at-minus
coating 
(with its low heat conduction) won't match the thermal expansion of the

Quad. FEM is done and says no such problems, but FEM isn't the a
saviour 
always!

Inge 

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