Hi,

 

 I was looking around and I found some references to "FR4" as having a Tg
from 100 to 130 C. I was surprised as I thought that seemed low.

 

 Now I understand that FR4 is a pretty wide brush and it covers a lot of
different materials and different suppliers.  BUT, I was wondering what
"Most" PCB vendors are supplying and how the Tg affect life with hot
components.

 

 I have some small QFN parts that tend to run hot, PCB temps of 100C or a
little more. Forgetting thermal cycling for a moment does a 100 to 120 C
temperature induce failures in other area like copper foil to base
separation, de-lamination, solder interface or any other failure mode?

 

 Any pointers to literature?

 

Thanks,

Bob K.



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