How to select MOSFET Package ?

The selection of the MOSFET package mainly depends on the following parameters.

Power dissipation/cooling

Power losses of the MOSFET have a great impact on the selection of the package.

SMD packages can be used for lower power dissipation:

DPAK for approximately 0.5 W (depending on pad size)

D2PAK for approximately 1 W (depending on pad size)

The through-hole packages like TO-220 and especially TO-247 with attached heat sink and forced cooling can dissipate much more power.

Creepage distance

The creepage distance between the legs of the package should correspond to the voltage requirements in the given application field.

Space/volume 

The size of the package can be also influenced by the available space/volume/height in a given case of SMPS/lamp ballast. For example, notebook adapters use I2Pak in order to reduce the height of the device.

Cost 

Smaller packages are usually less expensive than bigger ones. Also, SMD mounting technology can be more cost-effective during the manufacturing process. A fully isolated package helps to reduce the cost of heat sink assembly by skipping the manufacturing step of putting the isolation pad between the package and the heat sink.