Re: What software do you use for PCB with FPGA ?

On Wed, 28 Jan 2009 00:49:17 -0800 (PST), rickman <gnuarm@xxxxxxxxx>
wrote:

On Jan 28, 3:01 am, secure...@xxxxxxxxx wrote:
Hi Brian Drummond

It may be worth looking athttp://www.freepcb.com/
I tried this last year and it looked OK for a 676 pin 1mm BGA.
(If you cross-check the Gerber output carefully!) I didn't get as far as
finishing the board though.

But with CS486, the pins are very close, 0.8 mm ...

That doesn't really affect a choice of design software. 0.8 mm is
actually fairly large in terms of the layout tools and PCB
technology. It will be the via sizes and track widths that challenge
the board makers (although there are plenty who can makes these
boards). The PCB tools are selected more on ease of use and "special"
features you may need. A 0.8 mm BGA does not require any "special"
features from the software.

It does matter in PCB123 software because that's tied to a specific
low-cost PCB manufacturing flow where small holes aren't available.
Otherwise Rickman is correct.

Be sure to check with the chip maker for the details of the pads and
included vias. They want your design to work and have lots of info on
how to do that.

And THAT's the important point. With 0.8mm BGA you will have to get a
via between 4 adjacent balls, with a pad large enough to maintain a
recommended annular ring around the smallest hole they can drill
(usually around 0.3mm) yet small enough to maintain a recommended
clearance from the pads. Inner layers can be harder - you might need to
get a track out between adjacent vias.

Draw it out on paper, add up the manuf's recommended sizes, and see if
it'll all fit.

http://www.sunstone.com/pcb-capabilities/manufacturing-capabilities.aspx
is one example; talk to your own local guys too.

From memory, 1mm BGA would JUST fit their full featured flow; I think
0.8mm would be well into their "custom quote" regime...

Xilinx also have app notes on PCB layout.

(FWIW I started out looking at CS484 but backed off to 1mm FG676.)

- Brian
.

Relevant Pages