TO-18

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A drawing of a ZN414 IC in a TO-18 package.

In electronics, TO-18 is a designation for a style of transistor metal case. The case is therefore more expensive than the similarly sized plastic TO-92 package. The name is from JEDEC, signifying Transistor Outline Package, Case Style 18.

Construction and orientation

The tab is located 45° from pin 1, which is typically the Emitter. The lead diameter is nominally 0.45 mm, the diameter of the cap is 4.5-4.95mm (0.178-0.195 inches) and the overall width (not including the tab) is 5.4 mm.

Different manufacturers have different tolerances, and the actual form factor may vary slightly, depending on function.

Uses and variants

The 3-lead TO-18 is used for transistors and other devices using no more than three leads. Variants for diodes, photodiodes and LEDs have only two leads. Light-sensitive or light-emitting devices have a transparent window, lens, or parabolic reflectors in the top of the case rather than a sealed, flat top. For example, diode lasers such as those found in CD players may be packaged in TO-18 cases with a lens.

See also

Wikimedia Commons has media related to TO-18 transistor packages.
  • Chip carrier Chip packaging and package types list
  • TO-3 a large metal case for power semiconductors

References

    Diode
    Transistor
    Single row
    • SIP / SIL
    Dual row
    Quad row
    • LCC
    • PLCC
    • QFN
    • QFP
    • QUIP / QUIL
    Grid array
    Wafer
    Related topics
    Note: It's relatively common to find packages that contain other components than their designated ones, such as voltage regulators in transistor packages, etc.
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