Does anyone have any information concerning mounting
LCCC (Leadless ceramic chip carrier) on FR4 PWBs?

I know it is not a recommended practice since the CTE of
the two materials is mismatched. However we have some designs
in which the parts are only available in LCCC's or designs
have already been fabricated.


The operating environment is mild, 0 - 45 C.
Thermal cycling will be less than 1000 cycles.
Number of units built, < 20 units.
Component lead count, 40, 28, and 20.
Component area 0.5 x 0.5 inches and 0.36 x 0.36 inches.



At what temperature is the CTE mismatch a problem?

Do any vendors sell preformed leads which can be added to the LCCC?

Are there special solders which will tolerate more stress?


Any help is appreciated.



Tom Obarski
Harris Corp

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