Transistor Package TO-220 Case style [3-Terminals]
TO-220 Plastic Case, Tab Mount
Case mount. [Tab Mount] A type of package which provides a method of readily attaching one surface of the
semiconductor device to a heat dissipater [heat sink] to achieve thermal management of the case temperature. Other factors that may effect the mounting include using a Mica washer, copper washer, and thermal grease.
When attached to a PWB a copper pad should be located underneath the thermal tab of the TO-220.
Case temperature. Case temperature is that temperature measured at a specified point on the case of a semiconductor device. The JEDEC specification will define the location of the thermocouple on the case.
Heat dissipation is handled by the metal tab; however during thermal measurements the case might be restrained with a metal clip holding the plastic body or a screw through the metal tab. Which ever mounting method is used will result in two completely different values in thermal impedance. As does the location of the thermocouple, under the die [hottest], next to the die [JEDEC], or on the tab [coolest].
TO-220AB 3-Terminal Package Drawing
Note the location of the Thermal Pad in the picture above.
The bottom tab [term 4] may be electrically connected to the Drain.
The surface mount version of a TO-220 is the TO-263 [D2PAK].
Note that part of the TO-220 body may lift off the mounting surface as pressure is applied to the tab by the mounting bolt, use conductive epoxy to secure the body of the TO-220 to the mounting surface, normally the printed wiring board [PWB].
