Transistor Packages

Vertical Heptawatt Package Style

Transistor Package TO-220 Case style [7-Terminals]

TO-220 Transistor Package drawing, 7-Terminal front and back view
TO-220AB 7-Terminal Package Drawing

Case mount. [Tab Mount] A type of package which provides a method of attaching one surface of the semiconductor package to a heat dissipater [heat sink] to achieve thermal management of the case temperature. One of the characteristics of a power package is the large heat conductive slug integrated into the body of the package. Other factors that may effect the mounting include using a Mica washer, copper washer, and thermal grease. A vertical heat sink for a TO-220 is shown above, other examples are shown on related pages. This particular style is produced with a board mounting tab.
When attached to a PWB, a copper pad should be located underneath the thermal tab of the TO-220. The bottom tab should be electrically connected to ground.

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, when comparing parts, check that the location of one measurement from one company is the same location used by another company [otherwise it's not a fair comparison of components]. Heat dissipation is handled by the metal tab, which is usually in close contact with the semiconductor die inside the package. Which, by the way is why the tab should be attached to a heat sink; because it directly removes heat away from the semiconductor die, and of course cools down the part.

Unlike the 3-Terminal TO-220 Package, the 7-lead package is used for semiconductors other than transistors or FETs; for example, Voltage regulators having control pins.

The surface mount version of a TO-220 is the TO-263 [7-Terminal].

7-Lead TO-220AB Package Dimensions
7-Lead TO-220 Transistor Package Dimensions

The outside case dimensions are provided here for convenience, but the dimensions are identical to the other TO-220 packages regardless of the number of terminal on the package. Of course the body width is changing or increasing to accommodate the additional pins. In fact that why this package belongs to the TO-220 family.

Note that the package normally sets the maximum die size used within the package. The increase in the number of leads on this package means that there are more bonding pads on this semiconductor than on the 3-terminal or 5-terminal packages.

The 7-terminal TO-220 package is normally found being used power regulators and related circuit functions. As with the other TO-220 package variations, the staggered leads assist with circuit routing. The increased routing area allow both a larger copper pad for each terminal and larger copper traces running between the terminals. Of course if the traces run directly to the pins and not between them, than staggering the leads doesn't assist in board routing.

Because this page only covers the generic package type, the basics of a package outline and a general description of the package type; the data sheet should still be consulted to determine any special mounting requirements based on the package type and the specific semiconductor used within the package. The data sheet may recommend a particular mounting method or insist on the requirements of a heat-sink and/or how the heat-sink should be mounted or attached. More importantly the data sheet might indicate the minimum size of a heat-sink, or in many cases a metal plate that the component is attached to.

Vertically Mounted Metal Heat Sink with Fins and Mounting Tabs
TO-220 Heatsink

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
5 Staggered-Lead TO-220
5 Staggered-Lead TO-220 [listed here]
11 Staggered-Lead TO-220
15 Staggered-Lead TO-220
27 Staggered-Lead TO-220

The case is molded epoxy.
Defined by the dimension table.

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Modified 1/21/12
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