Thanks all for the responses.
The reason for my interest, we were having numerous units returned from the
field. Analysis revealed cracked solder joints on the board. It was learned
the units were occasionaly being subjected to a 20C per minute thermal cycle out
in the field. The field failure was also subsequently verified by lab testing.
The units are encapsulated for vibration protection so our thoughts were to get
as robust a solder joint as possible and make sure the CTE and modulus at the
temperature extremes were as benign as possible.
I remember when we had real components on the board (poke through) and the
module had to encapsulated with a hard polymer a buffer coating was applied
(possibly silicone) before encapsulation to help reduce the forces on the
components, is this technique still in packaging folks play book?
Dale Hart
UTC
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