![TO-5 Heatsinks](https://upload.wikimedia.org/wikipedia/commons/b/b5/TO-5_Heatsinks.jpg)
In electronics, TO-5 is a designation for a standardized metal
semiconductor package
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...
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 JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States.
JEDEC has over 300 members, including some of the w ...
.
The first commercial silicon transistors, the
2N696 and 2N697 from
Fairchild Semiconductor, came in a TO-5 package.
Construction and orientation
The tab is located 45° from pin 1, which is typically the emitter. The typical TO-5 package has a base diameter of , a cap diameter of , a cap height of .
The pins are isolated from the package by individual glass-metal seals, or by a single resin potting. Sometimes one pin is connected directly to the metal case.
Variants
Several variants of the original TO-5 package have the same cap dimensions but differ in the number and length of the leads (wires). Somewhat incorrectly, TO-5 and
TO-39
In electronics, TO-5 is a designation for a standardized 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 JE ...
are often used in manufacturer's literature as synonyms for any package with the cap dimensions of TO-5, regardless of the number of leads, or even for any package with the diameter of TO-5, regardless of the cap height and the number of leads. Compared to TO-5, for the other variants (except
TO-33
In electronics, TO-5 is a designation for a standardized 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 J ...
and
TO-42) the minimum length of the leads was shortened from to which is sufficient for
through-hole technology
In electronics, through-hole technology (also spelled "thru-hole") is a manufacturing scheme in which leads on the components are inserted through holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side, either ...
and leads to a cost reduction, whereas the longer leads were needed for
point-to-point construction
Point-to-point construction is a non-automated method of construction of electronics Electronic circuit, circuits widely used before the use of printed circuit boards (PCBs) and automated assembly gradually became widespread following their intr ...
. Lead lengths of and are quite common but were not standardized separately by JEDEC. There are variants with between 2 and 12 leads. The leads are arranged in a circle with a diameter of (except TO-96, TO-97, TO-100, TO-101). Before the introduction of
dual in-line packages in 1965, integrated circuits were packaged mostly in metal can packages such as the TO-5 variants with more than 3 leads.
TO-39 / TO-9 / TO-16 / TO-42
The TO-39, TO-9, and TO-16 packages have 3 leads and differ in the shortened leads mentioned above from TO-5. Additionally, the TO-9 and TO-16 packages do not have a tab. The TO-42 package is almost identical to the TO-5 package (including the long leads) but has four stand-offs at the bottom of the base that keep the base about 0.5 mm above the circuit board. Possibly the TO-16 and TO-42 designations were not actually used.
TO-12 / TO-33
![Perkin Elmer VTL2C1 cm](https://upload.wikimedia.org/wikipedia/commons/7/72/Perkin_Elmer_VTL2C1_cm.jpg)
The TO-12 and TO-33 packages have 4 leads. TO-33 has leads like TO-5 while TO-12 has leads. For transistors, the fourth wire is typically connected to the metal case as a means of
electromagnetic shielding
In electrical engineering, electromagnetic shielding is the practice of reducing or blocking the electromagnetic field (EMF) in a space with barriers made of conductive or magnetic materials. It is typically applied to enclosures, for isolatin ...
for
radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...
applications.
TO-75
The TO-75 package has 6 leads (at most one of those may be omitted). The minimum angle between two adjacent leads is 60°.
TO-76 / TO-77
![Tesla MAA723](https://upload.wikimedia.org/wikipedia/commons/c/c8/Tesla_MAA723.jpg)
The TO-76 and TO-77 packages have 8 leads (up to three of those may be omitted). The minimum angle between two adjacent leads is 45°. The TO-77 package differs from the TO-76 package only in that the bottom of a TO-77 package can sit directly on a
circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struc ...
whereas the TO-76 package requires a distance of up to between circuit board and package.
TO-78 / TO-79 / TO-80 / TO-99
![Tesla MAC198](https://upload.wikimedia.org/wikipedia/commons/b/bb/Tesla_MAC198.jpg)
The TO-78, TO-79, TO-80, and TO-99 packages have 8 leads (up to three of those may be omitted). The minimum angle between two adjacent leads is 45°. These packages differ from other variants in the height of the cap. Instead of the cap height is only for TO-78 / TO-99, for TO-79, and for TO-80. The TO-78 package differs from the TO-99 package only in that the bottom of a TO-78 package can sit directly on a
circuit board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struc ...
whereas the TO-99 package requires a distance of up to between circuit board and package.
TO-74
The TO-74 package has 10 leads (at most one of those may be omitted). The minimum angle between two adjacent leads is 36°.
TO-96 / TO-97 / TO-100
The TO-96, TO-97, and TO-100 packages have 10 leads (at most one of those may be omitted). The minimum angle between two adjacent leads is 36°. For these packages the diameter of the circle of leads is increased from to . This allows a slightly increased chip area in a cap of unchanged diameter. TO-96 has the standard cap height of , while TO-100 and TO-97 have reduced cap heights of (like TO-78) and (like TO-79), respectively.
TO-73
The TO-73 package has 12 leads (at most one of those may be omitted). The minimum angle between two adjacent leads is 30°.
TO-101
The TO-101 package has 12 leads (at most one of those may be omitted). The minimum angle between two adjacent leads is 30°. For this package the diameter of the circle of leads is increased from to . This allows a slightly increased chip area in a cap of unchanged diameter. TO-101 has a reduced cap height of (like TO-78).
TO-205
![NatSemi LH0070](https://upload.wikimedia.org/wikipedia/commons/2/25/NatSemi_LH0070.jpg)
TO-205 is intended to replace previous definitions of packages with leads arranged in a circle with a diameter of .
The different outlines are now defined as variants of TO-205: TO-5 is renamed to TO-205-AA, TO-12 to TO-205-AB, TO-33 to TO-205-AC, TO-39 to TO-205-AD. A new package with 3 leads and a cap height of (similar to TO-78 / TO-99) is added as TO-205-AF.
National Standards
}
, rowspan=2, —
, rowspan=2, KT-2-7
, rowspan=2, —
, -
,
Rosstandart
Federal Technical Regulation and Metrology Agency (Rosstandart) (russian: Федеральное агентство по техническому регулированию и метрологии (Росстандарт)) is the Russian federal ...
,
GOST
GOST (russian: ГОСТ) refers to a set of International standard, international Technical standard, technical Standardization, standards maintained by the ''Euro-Asian Council for Standardization, Metrology and Certification (EASC)'', a region ...
R 57439
, -
, rowspan=2,
Kombinat Mikroelektronik Erfurt
VEB Kombinat Mikroelektronik Erfurt was an important manufacturer of active electronic components in East Germany. It should not be confused with the more well-known VEB Kombinat Robotron Dresden which used integrated circuits from Kombinat ...
, TGL 11811
, —
, —
, —
, B3/15-3a
, —
, -
, TGL 26713/07
[
, —
, —
, —
, F1BC3
, —
]
References
External links
TO-5 package
from EESemi.com
{{Semiconductor packages
Semiconductor packages