The
TO-220
is
a
type of plastic-molded package that features a flat metal tab at its
back (see Figure 1) to enable it to dissipate relatively large amounts
of heat. The TO-220 is commonly used for housing
transistors, thyristors, and
integrated
circuits with low lead counts.
The metal tab at the back of the TO-220 serves as a heat sink itself,
but it has a hole so that it can be screwed onto a larger heat sink if
higher power handling capability is required. Since this metal tab is
usually electrically connected to the device's internal circuit,
an
insulating pad or sheet must be inserted between it and the external
heat sink if no electrical connection between the heat sink and the
device circuit is desired.
A typical TO-220 package has 2 to 7
leads, although TO-220's with 3 leads are most commonly encountered
because this package is primarily used on three-terminal devices such as
transistors. The typical lead pitch (distance between leads) of a
TO-220 package is 2.54 mm.
Table 1.
Properties of a Typical TO-220
|
Body Size
(HxW)
excl.
Metal Tab |
Body Size (HxW)incl.
Metal Tab |
Body Thickness |
Metal Tab
Thickness |
Lead
Length |
|
9.2 mm x 9.9 mm |
15.7 mm x 9.9 mm |
4.5 mm |
1.3 mm |
13.1 mm |
