TO-66 Transistor Package

TO-66 Package

Transistor Package TO-66 Case style, 3-Terminal

TO-66 Package Outline
TO-66 Dimensions

3-Terminal TO-66
Dual-Base Darlington
Circuit example

TO-66 Lead Designation:
[Pin out]
Terminal 1, Emitter.
Terminal 2, Base [B1].
Terminal 3, Base [B2].
Case, Collector.

3-Terminal TO-66 Semiconductors;
NPN Power Darlington Transistor;
2N6352, 2N6353

TO-66 Package Diagram showing lead identification and Schematic
TO-66 Package, Package Details

The TO-66 style case is a through-hole flange-mount device in a metal package, similar to a TO-3 Case package, but with 3 terminals instead of two.
The diagram above shows the terminal locations for a 3-lead TO-66 package, with the case tied to the collector. The picture below shows the normal case attachment method for the TO-66 metal can. Note that the collector lead or metal case of the TO-66 is attached to a metal heat sink via two screws. Additional semiconductors may also use a TO-66 package [other than the schematic shown above]. A more common variant of the TO-66 case uses only two terminals; 2-Terminal TO-66. A 4 terminal TO-66 is also possible [but not shown].

Case mount. [Flange Mount] A style of package which allows the case to be attached to a heat dissipater or heat sink to achieve thermal management of the case temperature. The case of a 2-Terminal TO-66 device [and some 3-leaded TO-66] is connected to the Collector to aid in heat dissipation.

Case temperature. The component body or case temperature is that temperature measured at a specified point on the case of a semiconductor device.

TO-3 Transistor Package
Diamond Metal Case

The picture of the TO-3 is only shown to provide a relative shape, as the TO-66 package is a much smaller package but still in the diamond shaped metal package.

Normal TO-66 heat sinks are a Black Anodized Aluminum Alloy with 2 mounting holes. However any metal panel or metal plate may be used as a heat sink. In fact in many cases the TO-66 package is mounted external to a chassis to allow for better air flow [assuming a metal chassis.

Diamond Base
0.200 Pin Circle Spacing

TO-66 Package Outline
3-Terminal TO-66 Table of Package Dimensions

Related topics:
Types of Transistor cases
Heat Sink Manufacturers
Transistor Derating Guidelines
Manufacturers of FETs and BJTs

Editor Note:
Many semiconductors might use a TO-66
Part numbers are examples.
Terminal identifications are examples
Semiconductor schematics are examples

PC motherboard

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Modified 6/13/15
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