The term Transistor Outline package (more commonly referred to as TO packages) has been used for several decades. It is an industrial standard that governs the design and size of current-conducting microelectronic packaging and housings. A TO package always consists of two components: a TO header and a TO cap. While the TO header makes sure that the encapsulated components are provided with power, the cap ensures the smooth transmission of optical signals. This includes the transmitters (e.g. laser diodes) as well as the receivers of the optical signals (e.g. photodiodes).
The TO header provides a mechanical basis for the installation of electronic and optical components such as semiconductors, laser diodes or simple electronic circuits, while at the same time providing power to the encapsulated components with the aid of pins. Optical components in TO packages such as photodiodes and laser diodes are particularly susceptible to damage from their environment. Humidity, in particular, can cause semiconductor elements to corrode rapidly, leading to failure of the entire component. This is why these TO header components require reliable and permanent protection.
In general, there are three different types of TO headers which are distinguished based on the production technology used in their manufacture:
- Shelled TO headers consist of a metal foil that was shaped using thermoforming and in which the pins are fixed using glass.
- Stamped TO headers come with raised heads (Stamp A) or flat heads (Stamp B):
In opto-electronics, TO headers are used in nearly all conventional areas of microelectronic packaging applications - on both the transmitter side (TOSA) and on the receiver side (ROSA) of transceivers, as well as in the area of high-speed data transfer, infrared applications etc... The new TO PLUS® is also suitable for use in high frequency applications.
Micro-Electro-Mechanical Systems (MEMS) represent a new area of microelectronic packaging applications with great potential for growth. These systems enable optical signals to be switched using a range of small, mobile mirrors. At the present time MEMS are predominantly used in the high-tech sector, but are becoming increasingly used in mass applications such as LCD projectors and other image projectors. While data communication applications use only stamped TO headers, shelled TO headers are used primarily on the receiver side of sensor technology applications.
Generally, we can manufacture all standard stamped and shelled TO header designs. As shown in the table below, there is a range of different international standards that have been established over the years.
|TO 5||Shelled||7.6||9.1||TO 5|
|TO 8||Stamped A||11.7||13.9||TO 8|
|TO 18||Shelled||4.2||5.4|| TO 18
|TO 38||Stamped B||n⁄a||3.8||TO 38|
|TO 39||Stamped A||7.5||9.1||TO 5|
|TO 41||Stamped A||3.1||4.1||TO 56|
|TO 46||Stamped A||4.2||5.3|| TO 18
|TO 56||Stamped B||n⁄a||5.6||TO 56|
The types of metal used in the manufacture of TO headers depend largely on the production methods used. Compression glass seals are generally manufactured using cold rolled steel (i.e. AISI 1010), while matched seals are primarily manufactured using Kovar®(ASTM-F15) and Alloy 52 (ASTM-F30).
The TO headers can be plated with various materials (nickel, nickel-gold, nickel-silver), and can also be coated in additional metal layers when required.
For more information about our glass-to-metal sealing technology, please refer to our Glass-to-Metal Seals technology page.
All products can be supplied in loose form or packaged individually and supplied on trays.