Eli,

We have been reflowing TO-220 pkgs to FR4 boards totally surface mount since 
1987. The front leads are cut and preformed to butt mount to the pwb. There 
is a pad designed to solder the heat sink area to the pwb. 

National Semiconductor does offer a lead option on their TO-220 pkgs which 
preforms the leads into a gull wing shape. We use one part from National 
like that.

Good Luck

Dan Shea
Sr. Process Engineer
The Foxboro Co.



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Date: Thu, 27 Jun 1996 07:23:42 -0700
From: Eli Dallal <[log in to unmask]>
Organization: Tadiran Telecommunications Ltd.
To: [log in to unmask]
Subject: TO220 reflow soldering

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


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