A bigger part *could* go there (as in, there's space for a bigger part) but that doesn't mean a bigger part *has* to go there.
It's pretty common when designing a PCB to tweak the design so that a range of different component packages can fit in, depending on what stock you have in/what's currently cheap to buy. Saves you redesigning the PCB every time you change supplier.
I'd still guess that those big pads are just to make for better heat dissipation.
They should be able to handle 2A each (the sticker on the box says it's rated up to 6A) so they probably will generate a bit of heat so you're probably right.
Interesting site about the PCB design. I'll have another look at that later .
I only started looking into PCB design last week, never made one before. Want to design an interface board for my floppy organ to make it a bit neater.
I like that page, even if it's just because everything looks really neat and tidy.
I've clicked about a bit more and it's made me want to design a PCB.
Are these things cheap to get made?
I think the answer is no from a quick search. £80-100 seems to be the figure for the size I might want.
Don't pull that out at the airport.
There's a few options for making the PCB.
You can order them from a PCB fab place, but it really doesn't make financial sense unless you're doing a fairly big run of boards. I read a while ago about a new service someone was setting up getting small batches done via China for pretty cheap (compared to normal prices, anyway). Can't remember what it was called.
Making your own: Simplest way is toner transfer to transfer the layout to a copper board, and then you chemically etch the rest of the copper off. Can be hit and miss (I've heard) with small traces - depends on your print quality/transfer quality.
An interesting alternative is to use a CNC mill to remove the unneeded copper, with precision being governed by the quality of your CNC machine.
(the other other method is to be at Uni, where they have proper PCB manufacturing kit that can do plated through-holes, multi layers, masks, type etc. )