TO-220
The TO-220 is a style of electronic component package, commonly used for transistors, silicon-controlled rectifiers, and integrated circuits. The "TO" designation stands for "transistor outline". [1] TO-220 packages have three leads. Similar packages with two, four, five or seven leads are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. Components made in TO-220 packages can dissipate more heat than those constructed in TO-92 cases.
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[edit] Typical applications
The TO-220 package is an example of a through-hole design rather than a surface-mount technology type of package. TO-220 packages are heatsinkable, and thus can be used for applications where large amounts of power are dissipated as heat. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is often applied to further improve heat transfer from the package to the heatsink.
The metal tab is often connected electrically to the internal circuitry. This does not normally pose a problem when using isolated heatsinks, but an electrically-insulating pad or sheet may be required to electrically isolate the component from the heatsink if the heatsink is electrically conductive, grounded or otherwise non-isolated. Many materials may be used to electrically isolate the TO-220 package, some of which have the added benefit of high thermal conductivity.
In applications that require a heatsink, damage or destruction of the TO-220 device due to overheating may occur if the heatsink is dislodged during operation.
A TO-220 package that is not heatsinked typically dissipates around 1 watt (W), at a temperature 62.5C higher than the ambient temperature.
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[edit] Advantages
- Can be used in high-power and high-current applications where equivalent components of other cases may be susceptible to damage.
- Grounding area makes handling easier by reducing the possibility of damage from electrostatic discharge.
- Mounting with the tab ensures the component to be held firmly in place.
[edit] Disadvantages
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- More costly than equivalent components of other cases.
- Footprint requires considerably more surface area on a printed circuit board than other case styles, especially when heatsinks are used.
- In the case of chassis-mounting, space must be dedicated to the components and/or their heatsinks, thereby increasing production costs.
[edit] Variations
The standard TO220 outline is defined by the JEDEC organization. There are a number of variations on this outline [2], such as:
- TO-220F, which has an insulated tab and body, and typically has a higher thermal resistance than the metal tab versions.
- TO-220AB
- TO-220AC
Sometimes the designation is followed by the number of leads, as in TO-220AB-5L for five leads, etc.
[edit] Common components that use the TO-220 package
- 7805, +5-volt linear voltage regulator
- 7812, +12-volt linear voltage regulator
- LM317T, adjustable linear voltage regulator
- LM340, linear voltage regulator
- IRF510, N-channel MOSFET (5.6A, 100V)
[edit] See also
- TO-3, a metal case used for power semiconductors
[edit] References
- ^ List of semiconductor cases, http://malaysia.rs-online.com/web/generalDisplay.html?id=centre/eem_techref_semipack
- ^ List of package types, http://www.fairchildsemi.com/products/discrete/packaging/pkg.html
[edit] See also
- Chip carrier Chip packaging and package types list
