Component obsolescence and unavailability is hitting everyone quite hard this past year and a lot of my PCB layout work is now helping out companies with these problems.
Some companies don't even have credible second sources for critical components, but even those that do have still hit supply problems. A replacement part can usually be found eventually BUT more often than not it has a different PCB footprint. Cue re-design, re-evaluation, delays, stress, etc...
I hate to suggest this (because it makes my life harder!) but in this current climate designing footprints specifically to take multiple parts/packages is a VERY good idea.
Obviously this is a 'where-possible' kind of deal, and you'll need to watch out for potential changes to the impedance and capacitance of critical nets caused by larger pad sizes but there's not much to lose here, and plenty to gain. Double and even triple-padding has been around since PCBs first appeared but I see a lot less of it than I used to, and that might be because component availability has been so good for so long. But times are changing.
It may look a little ugly, but this FET footprint below can take compatible parts in DFN5, DPAK and D2PAK footprints. Flexibility!
The diode footprint can take an SMB or SMC. The resistor an 0603 or 0805 and R241 can take a 2010 or 1206.
Now that component package sizes are fairly stable and the rapid miniaturisation seems to have slowed considerably, the extra choice that this will give you when trying to find an alternative part is considerable. It might be that you'll need a second paste screen generated for assembly but in most cases even this would not be necessary, especially not for discrete components. Just talk to your assembler.
Of course you'll need a good, creative PCB designer - like here at Vital Sines! - who will ensure that you'll not run into any problems. Here are a few more very successful multi-package footprints that Vital Sines has done recently, to get you thinking.
So if you want to look like a genius soothsayer when Purchasing ring you up to say a critical part is now unavailable, you know what to do!
