Hi Eli -
     
     We have soldered TO 220s to organic substrates (FR4, BT, etc.)  with 
     very few problems. The reflow profile needs to be looked at for each 
     assembly so that you heat up the all of the components uniformly but 
     there is no "magic" in the process. I would not use any attachment 
     hardware unless your use environment (e.g. lots of vibration) requires 
     it - attachment hardware will increase your cost via assembly cycle 
     time and material costs.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: TO220 reflow soldering
Author:  [log in to unmask] at ccmgw1
Date:    6/26/96 11:37 PM


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