As I understand it, some relatively significant effort goes into matching
thermal expansion coefficients of SMT components to those of "typical" PCB
materials.  Changes in value aren't half so worrisome as components that
actually BREAK under the stress.  This works the other way around.  People
who make exotic PCB materials make an effort to match the thermal expansion
of "typical" PCB materials and/or SMT components...

BillW

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