It was to make a transistor case in the 1960s for high power transistors that needed to dissipate a lot of heat and possible physical damage as they guzzled large amounts of elecctrical power.
TO-3 power transistor packing unit shellEdit
In electronics, TO-3 is a designation for a standardised metal semiconductor package used for transistors and some integrated circuits. The TO element stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC.
The TO-3 metal can package is commonly used for power transistors, silicon-controlled rectifiers, and, occasionally, integrated circuits. TO-3 packages usually have two leads, the case being the third connection, though devices with four leads exist and more leads are possible. The TO-3 case has two mounting holes. The design originated at Motorola around 1955. The lead spacing was originally intended to allow plugging the device into a then-common tube socket.
The metal package can be attached to a heat sink, making it suitable for devices dissipating several watts of heat. Thermal compound is used to improve heat transfer between the device case and the heat sink. Since the device case is one of the electrical connections, an insulator may be required to electrically isolate the component from the heatsink. Insulating washers may be made of mica or other materials with good thermal conductivity.
The case is used with high-power and high-current devices, on the order of a few tens of amperes current and up to a hundred watts of heat dissipation. The case surfaces are metal for good heat conductivity and durability. The metal-to-metal and metal-to-glass joints provide hermetic seals that protect the semiconductor from liquids and gases.
Compared with equivalent plastic packages, the TO-3 is more costly. The spacing and dimensions of the case leads make it unsuitable for higher (radio frequency) devices.
The semiconductor die component is mounted on a raised platform on a metal plate with the metal can crimped on top of it, providing high heat conductivity and durability. The 2 leads pass through the metal base plate and are sealed with glass. The metal case is connected to the internal device and the leads are connected to the die with bonding wires.
Common components that use the TO-3 packageEdit
- LM317, voltage regulator.
- LM78xx, voltage regulator.
- LM340, voltage regulator.
- 2N3055, NPN power transistor.
- 2N2955, PNP power transistor.
- KD503, NPN power transistor.
Soviet КТ819ГМ NPN power transistor packing unit shellEdit
The Soviet КТ819ГМ NPN power transistor was a Soviet 2N3055 transistor copy inside in a copied TO-3 package. It was one of many technological rip-offs the Soviets did against the West.
TO-66 power transistor packing unit shellEdit
TO-66 is a type of semiconductor package for devices with three pins, such as transistors. The shape is similar to the TO-3 package, but the size is smaller.
TO-66, TO-3 and КТ819ГМ NPN have 2 legs since the metal case acts as the 3rd.
TO-220 power transistor packing unit shellEdit
The TO-220 is a style of electronic component package, commonly used for discrete semiconductors as transistors and silicon-controlled rectifiers, as well as integrated circuits. The "TO" designation stands for "transistor outline". TO-220 packages have three leads. Similar packages with two, four, five or seven leads are also manufactured. A notable characteristic is a oblong metal tab with a hole used in mounting the case to a heat sink, atached to the back of the squaire 3 legged epoxy or plastic case. Components made in TO-220 packages can dissipate more heat than those constructed in TO-92 cases.
The TO-220 package is a "power package" intended for power semiconductors and an example of a through-hole design rather than a surface-mount technology type of package. TO-220 packages can be mounted to a heat sink to dissipate several watts of waste heat. On a so-called "infinite heat sink", this can be 50W or more. The top of the package has a metal tab with a hole used in mounting the component to a heat sink. 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 heatsinked, dissipating 1W of heat, will have an internal (junction) temperature typically 2 to 5 °C higher than the package's temperature (due to the thermal resistance between the junction and the metal tab) and the metal tab of the TO-220 package will typically have a temperature of 1 to 60 °C higher than the ambient temperature, depending on the type of heatsink (if any) used.
The junction-to-case thermal resistance of a TO-220 packaged device (which typically matters less than the case-to-ambient thermal resistance), depends on the thickness and the area of the semiconductor die inside the package, typically in a range between 0.5 °C/W and 3 °C/W (according to one textbook) or 1.5 °C/W and 4 °C/W (according to another).
If more heat needs to be dissipated, devices in the also widely used TO-247 (or TO-3P) package can be selected. TO-3P has a typical junction-to-ambient (heatsink) thermal resistance of only about 40 °C/W, and its TO-3PF variant a slightly lower one. Further increase of heat dissipation capability is possible with power modules.
When a TO-220 package is used without a heatsink, the package acts as its own heatsink, and the heatsink-to-ambient thermal resistance in air for a TO-220 package is approximately 70 °C/W.
- TS7805 linear voltage regulator in a TO-220 variant package with electrically isolated tab.
The standard TO-220 outline is defined by the JEDEC organization. There are a number of variations on this outline, such as:
- TO-220F, which has an insulated tab and body, and typically has a higher thermal resistance than the metal tab versions.
Sometimes the designation is followed by the number of leads, as in TO-220AB-5L for five leads, etc.
There also some vendor-specific variations such as International Rectifier's SUPER-220, which dispenses with the hole in favor of clip-mounting, thus claiming TO-247-like thermal performance in a TO-220 footprint.
Common components that use the TO-220 packageEdit
- 7805, +5 V linear voltage regulator.
- 7812, +12 V linear voltage regulator.
- LM317T, adjustable linear voltage regulator.
- LM340, linear voltage regulator.
- IRF510, N-channel MOSFET (5.6 A, 100 V).
Related packages Edit
- TO-257 is a hermetically sealed metal package that is otherwise considered equivalent to TO-220.
- TO-220F also known as the SOT186 and SC67 is TO-220 like package, where the heatsink mounting tab has been encased in the plastic.
Soviet КТ819Г power transistor packing unit shellEdit
The КТ819Г\KT819G transistor was the Soviet to several types of Western power transistors. The package is the Soviet version of the Western TO-220 package.
Single in-line (pin) package (SIP or SIPP)Edit
A single in-line (pin) package (SIP or SIPP) has one row of connecting pins. It is not as popular as the DIP, but has been used for packaging RAM chips and multiple resistors with a common pin. SIPs group RAM chips together on a small board either by the DIP process or surface mounting SMD process. The board itself has a single row of pin-leads that resembles a comb extending from its bottom edge, which plug into a special socket on a system or system-expansion board. SIPs are commonly found in memory modules. As compared to DIPs with a typical maximum I/O count of 64, SIPs have a typical maximum I/O count of 24 with lower package costs.
One variant of the single in-line package uses part of the lead frame for a heat sink tab. This multi-leaded power package is useful for such applications as audio power amplifiers, for example.
Multi-leaded power packageEdit
The multi-leaded power package is a style of electronic component package, commonly used for high power integrated circuits, especially for monolithic audio amplifiers. It was derived from single in-line package. The difference is the lead arrangement; multi-leaded power packages usually have the lead bent to zig-zag pattern. Multi-leaded power packages commonly have more than three leads; nine-, thirteen- and fifteen-lead units are common, units with five or seven leads with TO-220 style are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. The physical view of multi-leaded power packages are simply stretched TO-220 packages. Components made in multi-leaded power packages can handle more power than those constructed in TO-220 cases, or even TO3 cases with thermal resistance no less than 1.5 C/W.
- One well-known STMicroelectronics brand of this type of package is Multiwatt.
- A well known 5 legged version of the TO-220 is the Pentawatt.
Multi-leaded power packages are heatsinkable, and thus can be used in projects where a large amount of power is being drawn. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is also used to provide greater heat transfer.
The metal tab is often connected electrically to the internal circuitry, ground and supply connection are common. 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 grounded or otherwise non-isolated. Many materials may be used to electrically isolate the multi-leaded power package, like mica plastic, some of which have the added benefit of high thermal conductivity.
In applications where vertical clearance is at a premium (such as ISA cards in computers), it is often feasible to bend the leads at a right angle and mount the component flat to the printed wiring board using a screw and nut. This often provides enough surface area to heatsink the component when power dissipation is moderately high.
Common components that use the Multi-leaded power packageEdit
Monolithic audio amplifiers:
- TDA 2030, 20 watt audio amplifier with 5 leads, TO-220 style.
- TDA 2052, 50 watt audio amplifier with 7 leads.
- TDA 7294, 100 watt audio amplifier with 13 lead arrangement.
- IC and transistor in line packaging
- Transistor and IC packages
- Integrated circuits
- LM317 adjustable linear voltage regulator
- 2N3055 silicon NPN power transistor
- Heat sink
- Useful metals
- TO-5, T0-18 and other related related package sizes