Transistor Package

Transistor Package TO-220 Case style [5-Terminals, Staggered Leads]

TO-220 Transistor Package drawing, 5-Terminal Staggered Leads
TO-220 5-Terminal Package Drawing

There is no hard and fast rule for which component uses a staggered-lead or straight-lead package. For example one type of voltage regulator might be available in a bent-lead package while another type might use a straight-lead package.

There is also no difference between the power dissipation between package usage. That is either style might be found as a 3 amp voltage regulator. The staggered-lead is also not a package option, the part will be offered as a straight or staggered configuration.

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. In many cases a large heat sink is attached to the metal tab, in other cases the TO-220 is installed near the side of a PWB and the tab is attached to an infinite heat sink as in the panel of a metal chassis or case.
When attached to a PWB a copper pad or island should be located underneath the thermal tab of the TO-220. The staggered lead TO-220 package will aid with copper pad area on the PWB because the leads are moved apart allowing for an increased pad area.

Unlike the 3-Terminal TO-220 Package, the 5-lead package is used for semiconductors other than transistors or FETs; for example, Voltage regulators having control pins.

For what ever reason the staggered-lead TO-220 package seems to be more popular than the straight-lead TO-220 package. However it would appear that because the leads are staggered in this version it allows for larger copper pads on the Printed Wiring Board. Because ever other pin is off-set, each terminal pad may be larger because the next pin does not reside directly adjacent to it. So larger copper pads translate into a better heat transfer from the device and into the board, reducing the heat seen by the device.

5-Lead TO-220 Package Dimensions
5-Lead TO-220 Transistor Package Dimensions, Staggered Leads

The surface mount version of a 5-lead TO-220 is the 5-Terminal TO-263.
There are also other sizes of the TO-263 package, having more or less pins. The TO-263 component varies in number of terminals just like the TO-220 does.

The symbols in the dimension table and outline drawing and intended to be used together. A data sheet may use completely different symbols to indicate a dimension, so these diagram may not mate up well with a data sheet from some other company. However the actual dimensions should be the same, within the tolerances indicated within the data sheet, or the min. and max. numbers specified above.

Pre-bent lead Package

Metal Slide On Heat Sink
Slide-on Heat Sink

Related topics:
Transistor Derating Guidelines
Including Thermal definitions

Types of Transistor cases
Manufacturers of FETs and BJTs
Thermal Compounds

Related TO-220 Packages
3-Terminal TO-220 Package
5 Straight-Lead TO-220
7-Terminal TO-220 Package

This version uses preformed leads,
Referred to as staggered leads.

TO-220 Voltage Regulators:
Having staggered pins.
LM2575; Step-Down Voltage Regulator
LM2585; Flyback Regulator
LM2587; Flyback Regulator

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Modified 1/21/12
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