two layer PCB can do this?

[jigdo]

cyclone fpga two layer pcb

Hello:

Now I want to make a customer develop board.There are a 1C12 cyclone fpga 256 pins,a sdram 54 pins ,a flash 48 pins and other components.I think if
the four layers it will be easy,but much expensive.So I want to ask the two layers
can do this? the VCCand the GND how to route?



Best regards

jigdo

 

[amjad]

You can trace VCC with 60mil width it top and bot. layers and pour GND, making top and bot as composite layers in the sense, making coplanar waveguide in all the empty areas not occupied by traces with 20 mil clearance trace to copper and pad/via to copper.

 

[jigdo]

Hello amjad:

I am a newbie.Can you explain the sentense: "making coplanar waveguide in all the empty areas not occupied by traces with 20 mil clearance trace to copper and pad/via to copper ". Do you think that two layers PCB can finish the project? I don't have enough confidence.

 

[amjad]

Hi,

You can finish this project in 2 layers if your fpga pin pitch allows to take enough traces and based on your manufacturing and assembling capability. Check with your customer whether traces are allowed beneath fpga and other components on mounting side. To make the signals have ground reference, you can add copper i.e, positive plane in top and bot. layer and connect it to ground. Make sure you have clearance of 20mil from pads and traces with this ground plane. And you have to use 60mil trace width to route VCC. Which software are you using for this design ?

Regards.

 

[jigdo]

Hello

I use PADS2005,studing use the HyperLynx simulation.I think I have many
work to do.studing.......


Best Regards

jigdo

 

[amjad]

In PADS2005, you can make top and bot. layers as Split/Mixed plane and pour copper(gnd).

 

[cyberrat]

Quite difficult for a newby, but persist, rip up & retry again & again till it gets done, you'll get there.

Although as for cost, have you actually looked at the cost? having 4 layers can help make the board size smaller & may then make it more cost effective to have more layers as this also allows improvements in EMC & DFT etc.

I had a large double sided board (£27) that I reduced in size, went up to 4 layers & get it for £13 from the east now.

For that many pins I for see lots of links, via's etc on double sided.

 

[lydu]

2layer board will bring you EMC problem. Maybe the specification can't come true.

 

[kejitongxin]

i advise you to use 4layer board,2layer board will inevitably have emc problem

 

[funster]

two layer board are far not enough,

you'd better use four layer board

for better signal integrity and lower EMI.

four layer board is a little more expensive than two

layer board.


best regards

Hello:

Now I want to make a customer develop board.There are a 1C12 cyclone fpga 256 pins,a sdram 54 pins ,a flash 48 pins and other components.I think if
the four layers it will be easy,but much expensive.So I want to ask the two layers
can do this? the VCCand the GND how to route?



Best regards

jigdo