BGA-272 and double side PCB

Wed Mar 30, 2005 12:53 pm   

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?

Thanks!

Thu Mar 31, 2005 8:32 am   

I agree with Leon.

2 plane layers : Power and Ground
and 4 signal layers.

The number of layers depends on the number of rows deep of the BGA you
want to tap into.
Top layer : 2 rows\
next inner layer : 2 more rows
every subsequent signal layer : 1 more row.

So first decide the number of rows you want to dig into and then
calculate the number of layers. Dont count the power/ground pins for
this since they will directly connect to the plane layers with vias.

Read applicatio notes on Xilinx and Altera about BGA layout. It is
tricky, dont do it unless you are certain.

TIP: Make sure the feedthrough vias near the BGA pads are tented. Else
the solder paste can get sucked into the via.