Dear Techneters
For years we have been reflow soldering TO 220 transistors to ceramic 
substrates to provide good thermal dissipation . now we want to use FR4 
boards . Our intention was to bend the TO220
leads and insert them in pths and reflow solder the body  of the 
transistor to the board on a suitable land and later wave solder the 
leads . But I was told that in pcbs it is customary to use screws and 
nuts or eylets instead of soldering .One explanation was that there is a 
big thermal mismatch but no one seemed to know for sure .
What I would like to know if anyone has any experience in reflow 
soldering TO220 s to pcbs and if anyone knows why  it should not be 
done.
 thanking you 
Eli Dallal
process engineer 
Tadiran telecommunications