Having no formal education on the subject,let me give my two cents anyway.Use F with these examples.
Semiconductor@90f mounted to heatsink @ 30f.High transfer
Semiconductor@90f mounted to heatsink @ 50f Good transfer
Semiconductor@90f mounted to haetsink @ 90f Any transfer?
Semiconductor@90f mounted to heatsink @ 91f Any transfer?
Or the reverse, absorption?
Semiconductor@90f mounted to heatsink @ 30f.High transfer
Semiconductor@90f mounted to heatsink @ 50f Good transfer
Semiconductor@90f mounted to haetsink @ 90f Any transfer?
Semiconductor@90f mounted to heatsink @ 91f Any transfer?
Or the reverse, absorption?