I want to ask a question:
I am doing a project which needs a DSP chip with BGA package. It has
272 pins. Is double layer PCB enough for routing?
If you need a DSP then presumably you need it because it needs to crunch
numbers. In that case you're going to need a good power and ground
plane and power distribution network. So two layers is certainly not
enough.
The number of layers you'll need depends on how the 272 balls are
configured on the package and how the signals go to those balls.
Analog devices has a 576-ball BGA in which there are only I/O signals on
the outer 4 layers around the outside of the BGA. The inside is all
ground and power pins. This makes breakout much easier. I was able to
lay that out with 4 signal layers. It could have been done with
2-layers with a few of the system requirements relaxed.
Other determining factors are what trace widths and separation rules you
can use/afford with your board shop and the pitch of the 272 balls, the
size of the overall board assembly, the pitch of the BGA balls, the via
drill size, the annular ring size, ....
If you could route the signals on two layers then at a bare minimum
you'll need 4-layers. I would imagine that will more than likely become
6-layers and quite possibly 8-layers. The board I did with 4 layers of
routing also had 4 layers of power/ground planes for a total of 8.
Take this as a reference only. Without knowing the rest of the details
I can only speculate. YMMV.
Cheers.
