I am making my first pcb with a xilinx fpga device(256 pin BGA package).I am simply connecting the all I/O's to 4 standard 40 pin connectors.Are padstacks necessary for PCB routing??.I have drawn the schematic in Capture imported it to Layout_Plus and autorouted it.
But after 3 hours of autorouting it did not converge(couldnt route the board fully).Then i tried to route it in Spectra still it didnt converge.Increasing the number of layers didnt help.What is wrong?? Is it because of BGA package? Or is it because I did not use padstacks.
You are going to need some sort of via...
I suspect you have some clearance issues that Specctra is adhering to. This is most likely the cause of the failure.
If you try to hand route from any pin on the BGA do you get errors (in Specctra)? If so these will prevent the autorouter from completing.
There are some good "do" files on the Cadence sourcelink to help you get started routing...
thanx for the advice.can you plz give the link of "do" files which you were telling about. Also it seems that one has to manually fanout a BGA package first with proper vias.For example, the document "xapp157" from xilinx gives the dimension of vias,land pad diameter etc.After fanout it wil be routable i guess.Please correct me if i am wrong
bennyn1 said:Also it seems that one has to manually fanout a BGA package first with proper vias.
Definitely do NOT have to add manually. You have a clearance issue if Specctra is not fanning out the BGA properly. Like I said in my previous post, you need to test this by routing by hand to see if you are getting errors. If your clearances are correct then you would not be asking.
DO files are on Cadence's customer support website sourcelink.cadence.com