Diodes cover an extensive range, from small-signal diodes to power rectifiers. Working up from the low power end, the most likely package is a TO-236 outline package. As described in Figure 1, the die is mounted on a lead frame which is encapsulated in a transfer-moulded plastic package. The standard outline has three pins, so two diodes could be mounted, provided they share a common terminal. Alternative four-pin packages within the same outline would enable a double diode to be manufactured.
An alternative, for a single diode only, is the MELF package. Whilst a miniature version of this is sometimes used, it is not easy to mount at 100% yield, and bears only a polarity marking. For this reason, apart from the expensive method of manufacture, MELFs are not popular with assemblers. They will, however, dissipate substantially more heat.
For a medium-power device, a package of the DO-214 variety (Figure 4) would probably be best. The power rating is related to the package size, and more specifically the size of the internal metal heat sink to which the die is attached – the bigger the metal area, the higher the power of the die that can be accommodated.
For higher power, a range of specialist packages is available, although in practice power packages like the TO-220 are quite often used at the bottom end of the range.