TO-263 Package
Transistor Package TO-263 Surface Mount style, 3-Terminal
TO-263 Plastic Case, Tab Mount
Tab mount. A type of package which provides a method of readily attaching one surface of the
semiconductor device to a heat sink to achieve thermal management of the case temperature. Other factors that may effect the mounting include using thermal grease.
When attached to a PWB a copper pad should be located underneath the thermal tab of the TO-263 with a minimum size detailed in the data-sheet. Heat dissipation is conducted from the junction by the metal tab.
Package 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.
3-Terminal TO-263 Package Drawing
Devices using the TO-263 package styles;
N-Channel FETs: 2N7558, 2N7559, 2N7560.
Note that because the table of dimensions was taken from a government document relating to a FET, the table also lists the pin out. Pin 1; Gate. Pin 2; Drain. Pin 3; Source. Pin 4 Drain.
As with many of the packages of this type; when only three pins are required than the tab [pin 4] is also electrically connected to the high current lead, which also is normally connected to pin 2. In other words, in many cases, pin 2 is normally connected to pin 4 [the tab]. However it is always possible for the tab not to be electrically connected to any terminal and just used as a heat sink, or a thermal connection to a heat sink [a copper pad on the PCB].
Always check the data sheet to determine the function of the pins. This page is intended to show the size and shape of a TO-263 semiconductor package. The function of the terminals could change depending on the semiconductor molded into the package.
