Power Transistor Outline (TO) Packages

The Power transistor Outline (TO) Package is a type of “transistor outline” package that features a metallic body with two flat metal tabs which enable it to dissipate large amounts of heat. TO packages are hermetically sealed to protect the device from environmental factors such as contaminants and moisture. The leads protrude from the bottom of the package through glass and ceramic feed-throughs that insulate them from the metal body. These packages are mostly used for transistors, thyristors, and integrated circuits with low lead counts such as voltage regulators that are intended for high-reliability and mission-critical circuits. The metal tabs perform as heat sinks themselves, but they each have a hole so that they can easily be screwed onto a larger heat sink if higher power handling capability is required. The tabs are located on opposite corners of the back of the body.

Advantages of Power Transistor Outline (TO) Packages

Used for packaging high-power and high voltage devices
Excellent thermal properties from Cu/W heat sinks than can include BeO and ALN inserts
Packages meet Military and Space specifications
Open tooled designs such as TO254, TO257 and TO258
Full Hermiticity 1×10-8
Metal seal ring for seam sealing

Part Type	Leads	Drawing No
TO-3		Power PKG	RFQ
TO-66	2 LD	POWER PKG	RFQ
TO-254	3 LD	POWER PKG	RFQ
TO-257	3 LD	POWER PKG	RFQ
TO-258	3 LD	POWER PKG	RFQ
TO-259	3 LD	POWER PKG	RFQ
TO-267	3 LD	POWER PKG	RFQ