What is Transistor Outline (TO)?

There are various types of semiconductor and IC packages, such as Transistor Outline (TO) and Small Outline Transistor (SOT).

In addition, there are various types of Transistor Outline (TO). An example is shown below.

• TO-92: Used for low-power transistors, etc.
• TO-220: Used for components with relatively high heat dissipation
• TO-247: Even larger than TO-220
• TO-3: A package used in the early days of power transistors, similar in shape to a hat.

In this article, we have tried to explain "Transistor Outline (TO) Definition" and "Types and Features of Transistor Outline (TO)" in an easy-to-understand manner using diagrams. We hope you will find it helpful.

Transistor Outline (TO) Definition

TO stands for "Transistor Outline". Transistor Outline (TO) is a package often used for transistors, but it is also used for ICs and diodes.

There are various types of Transistor Outline (TO), which are denoted by a combination of TO and a number. For example, there are "TO-92 used for small power transistors", "TO-220 used for components with relatively high heat dissipation", and "TO-247, which is even larger than TO-220".

Package materials used for Transistor Outline (TO) include plastic, metal, and ceramic.

Next, I will explain "Types and Characteristics of Transistor Outline (TO)" in turn.

TO-92

TO-92 is an insertion-mount package with a lead pitch of 1.27mm. The longer package type is called "TO-92MOD". Alternatively, TO-92 is sometimes referred to as "TO-226AA" for JEDEC standard.

TO-92 is used for "3-terminal devices such as transistors and thyristors" and "ICs with a small number of leads such as voltage regulators".

The main advantages of TO-92 are its low manufacturing cost and small size. However, since it cannot diffuse much heat, it cannot be used in cases where power consumption is large.

TO-252

TO-252 is a surface mountable package by forming leads. TO-252 has various names such as DPAK, PPAK, and SC-63.

The lead pitch of TO-252 is 1.27 mm.

Some manufacturers refer to the long-lead type of TO-252 as SC-64.

Like TO-92, TO-252 is used for "3-terminal devices such as transistors and thyristors" and "ICs with a small number of leads such as voltage regulators".

TO-220・TO-202・TO-263・TO-218

Next, TO-220, TO-202, TO-263, and TO-218 with a lead pitch of 2.54 mm are explained.

TO-220

TO-220 is an insertion-mount package with a lead pitch of 2.54mm. TO-220 has a metal tab for mounting on a heat sink.

TO-220 has screw holes at the top of the package so that it can be screwed to a heat sink. Therefore, TO-220 is used for components that dissipate relatively large amounts of heat.

TO-220 has a "metal package" and a "full mold package" for the mounting part of the heat sink. In the full-molded package, the mounting part of the heat sink is covered with plastic. The full-molded product is sometimes referred to as TO-220FM.

TO-220 is available in 3-pin, 5-pin, and 7-pin versions, but the 3-pin TO-220 is most commonly used because this package is primarily used for transistors.

TO-202

TO-202 is an insertion-mount package with a lead pitch of 2.54mm.

TO-202 is characterized by a flat metal tab on the back.

TO-263

TO-263 is an insertion-mount package with a lead pitch of 2.54mm. TO-263 is shaped like a smaller metal tab of TO-220.

TO-263 has various names such as D2PAK and DDPAK.

Normally, TO-263 has formed leads to allow surface mounting.

TO-263 is available in 3-pin, 5-pin, and 7-pin versions.

TO-218

TO-218 is an insertion-mount package.

TO-218 has 2 to 5 pins. The lead pitch varies depending on the number of pins. For example, the lead pitch of 3 pins is about 5.2 mm, while that of 5 pins is 2.54 mm.

TO-218 features a flat metal tab on the back.

TO-247・TO-3P・TO-264

This section describes the TO-247, TO-3P, and TO-264 transistors, which are larger than the TO-220. The lead pitch of the TO-247, TO-3P, and TO-264 is 5.45 mm.

TO-247

TO-247 is an insertion-mount package with a lead pitch of 5.45mm.

TO-247 is a package used for components with large heat dissipation. TO-247 is similar in shape to TO-3P, which will be explained later.

TO-3P

TO-3P is an insertion-mount package with a lead pitch of 5.45mm.

TO-3P is a package used for components with large heat dissipation. TO-3P is similar in shape to TO-247.

TO-264

TO-264 is an insertion-mount package with a lead pitch of 5.45mm.

TO-264 has 2 to 5 pins.

TO-254・TO-257・TO-258・TO-259・TO-267

This section describes TO-254, TO-257, TO-258, TO-259, and TO-267, whose packages are made of metal.

TO-254

TO-254 is an insertion-mount package. The standard lead pitch of TO-254 is 3.81mm.

TO-254 has a metal body and a flat metal tab on the backside. TO-254 is more expensive than TO-220 and others due to its metal body and hermetic sealing, but it is more reliable.

TO-254 is similar in shape to the TO-257 described below, but is larger.

TO-257

TO-257 is an insertion-mount package. TO257 is packaged in a metal package with the plastic molded part of TO-220.

TO-257 is similar in shape to TO-254, but smaller than TO-254.

TO-258

TO-258 is an insertion-mount package. The standard lead pitch of TO-258 is 5.08mm.

TO-258 is similar in shape to TO-257.

TO-259

TO-259 is an insertion-mount package.

TO-259 is similar in shape to TO-258, but the metal tabs attached to the body are different.

The metal tabs attached to the TO-259 serve as heat sinks. The metal tabs also have screw holes so they can be screwed onto the heat sink.

TO-267

TO-267 is an insertion-mount package. The standard lead pitch of TO-267 is 5.08mm.

TO-3・TO-66

Next, we will discuss "TO-3, an early package of power transistors" and "TO-66, which is smaller in shape than TO-3". Both are shaped like a hat.

TO-3

TO-3 was an early package for power transistors. Today, TO-3 is almost never used.

TO-3 is a metal package whose cylindrical part has a diameter of 22.2 mm and a height of about 5.7 mm, and its shape resembles a hat.

It is designed to be fixed to the heat sink with screws using the two holes in TO-3.

TO-3 is similar in shape to TO-66, but has a longer diameter than TO-66.

TO-66

TO-66 is a metal package whose cylindrical part has a diameter of 12.4 mm and a height of about 5.7 mm, and its shape resembles a hat.

TO-66 is similar in shape to TO-3, but has a shorter diameter than TO-3.

It is designed to be fixed to the heat sink with screws using the two holes in TO-66.

The number of pins includes 3-pin, 5-pin, and 9-pin.

TO-5・TO-33・TO-39・TO-18・TO-72・TO-46・TO-52・TO-99・TO-100・TO-8

This section describes "TO-5, TO-33, TO-39, TO-18, TO-72, TO-46, TO-52, TO-99, TO-100, and TO-8" whose packages are metallic and cylindrical in shape. These packages are rarely used today.

TO-5

TO-5 is a metal package whose cylindrical portion has a diameter of 8.1 mm and a height of about 6.3 mm.

TO-5, TO-33, and TO-39 are similar in shape. TO-5 is similar in shape to TO-18 and TO-72, but the shape of the head part is slightly different.

TO-33

TO-33 is a metal package whose cylindrical portion has a diameter of 8 mm and a height of about 2.5 mm.

TO-5, TO-33, and TO-39 are similar in shape. TO-33 is similar in shape to TO-18 and TO-72, but the shape of the head part is slightly different.

TO-39

TO-39 is a metal package whose cylindrical portion has a diameter of 8 mm and a height of about 2.5 mm.

TO-5, TO-33, and TO-39 are similar in shape. TO-39 is similar in shape to TO-18 and TO-72, but the shape of the head part is slightly different.

TO-18

TO-18 is a metal package whose cylindrical portion has a diameter of 4.7 mm and a height of about 4.8 mm.

TO-18 and TO-72 are similar in shape. TO-18 is similar in shape to TO-5, TO-33, and TO-39, but the shape of the head part is slightly different.

TO-72

TO-72 is a metal package whose cylindrical portion has a diameter of 4.7 mm and a height of about 4.8 mm.

TO-18 and TO-72 are similar in shape. TO-72 is similar in shape to TO-5, TO-33, and TO-39, but the shape of the head part is slightly different.

TO-46

TO-46 is a metal package whose cylindrical portion has a diameter of 4.7 mm and a height of about 2.4 mm.

TO-46 is slightly lower in height than TO-52.

TO-52

TO-52 is a metal package whose cylindrical portion has a diameter of 4.7 mm and a height of about 3.4 mm.

TO-52 is slightly higher in height than TO-46.

TO-99

TO-99 is a metal package whose cylindrical portion has a diameter of 8 mm and a height of about 4 mm.

The bottom of the TO-99 has 8 pins arranged in a circular pattern. In addition, there is a protrusion of about 1 mm in the center of the 8 pins to raise the bottom surface above the PCB.

TO-99 is similar to TO-100 (TO-100 has 10 pins).

TO-100

TO-100 is a metal package whose cylindrical portion has a diameter of 8 mm and a height of about 4 mm.

The bottom of the TO-100 has 10 pins arranged in a circular pattern. In addition, there is a protrusion of about 1 mm in the center of the 10 pins to raise the bottom surface above the PCB.

TO-100 is similar to TO-99 (TO-99 has 8 pins).

TO-8

TO-8 is a metal package whose cylindrical portion has a diameter of about 14 mm.

The TO-8 is available in various heights. Due to the long diameter, the cylindrical part is short.

Other TO packages

TO-126

TO-126 is a package used for "3-terminal devices such as transistors and thyristors.

Generally, a metal plate is attached to the back of TO-126, and the body has holes so that it can be screwed to a heat sink.

TO-36

TO-36 is designed to be fixed to the heat sink with screws using the hole in the center.

Summary

In this article, the following information on the "Transistor Outline (TO)" was explained.

• Transistor Outline (TO) Definition
• Types of Transistor Outline (TO)

Thank you for reading.