TO-218 Package


The TO-218 is a type of plastic-molded "transistor-outline" 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-218 is commonly used for housing power transistors, thyristors, and integrated circuits with low lead counts.


The metal tab at the back of the TO-218 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.


A typical TO-218 package has 2 to 5 leads.  The lead pitch (distance between leads) of a TO-218 package varies, depending on the number of leads. For example, the 5-lead TO-218 package in Figure 1 has a lead pitch of 2.54 mm but an equivalent 3-lead TO-218 package can have a lead pitch of 5.1 mm.


Table 1. Properties of Typical TO-218 Packages

No. of Leads

Body Size (HxW)

 excl. Metal Tab

Body Size (HxW)incl. Metal Tab

Body Thickness

Metal Tab Thickness




12.5 mm x 15 mm

20.5 mm x 15 mm

4.85 mm

1.5 mm

15 mm


12.5 mm x 15 mm

20.3 mm x 15 mm

4.9 mm

2 mm

14 mm


Figure 1.  Example of a TO-218 Package


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