PCB routing

Hi i would like to know anyone about PCB routing experience with
Altera/Xilinx FBGA.
My aim is to know if which is easier to route, and w/c one has lower
layer count for 676-Ball

Thanks.

 

dear sir/madam

I am a pcb designer in high frequencies in texas university of
technology. please give me more information to help.

high hopes.
M.Darvishi

 

Don't know about them.....

If they both have 676 balls with the same dimensional spacing and size and
you apply the same PCB layout design rules to them then they will be
'Exactly' the same.

Your mission, should you accept it, is to 'think' about how you might play
with your internals, and externals, to iterate the final solution. Do not,
under any circumstances, give it to a PCB monkey. Do the job yourself.

I assume that since you know about beginning sentences with capital letters
the word 'iterate' will not be a problem.

I think it might be called Engineering.

DNA

 

Figure that you can get the outer two rows of balls out on layer 1,
and the next two rows on layer 2, and one more row per layer after
that. Then you need a ground plane and probably two power planes. The
Alterx/Xilinx thing depends on the details.

We did a Xilinx FG456 on an 8-layer board, with 6 rows deep of signal
balls all around. I could post pics.

John

 

Layer count is going to be about the same for both. They both use a
full grid approach, rather than leaving the centre zone clear.

I've put both of them down on different boards and from a PCB layout
perspective there's not really any difference between them. The biggest
single thing is being able to route the signals you need to the
external balls, but if you need all of them (otherwise you wouldn't be
in a 676) then figure 8 layers at a minimum.

I had (on both those designs) 16 layers for other reasons, so layer
count was not an issue for me.

In any case, for both devices, use non-SMD (solder mask defined) pads.

Cheers

PeteS

 

Genome,
Application Notes tells that Xilinx 676 BGA was routed with 6-layers,
while the competing 672 BGA was routed in 10-layers, have you tried any
of these? Just want to make sure.

 

Thanks can you show some?

 

Hi PeteS,
I have a gerber of an Altera 672-ball 8-layers, but Xilinx
Applications notes says that their 676-ball can be routed with 6-layers.

 

Can you see posts to a.b.s.e.? I could post there.

John

 

To misquote Archimedes.

"Give me tracks thin enough and vias small enough and I'll do it in two
layers."

 

Application notes are the greatest lies in the electronics universe,
and can be the greatest truths.

What was being routed? What were the signal definitions? What impedance
controls were required? What power? There are so many variables even
for a single device that it's not possible to say how many layers are
required without knowing the specifics of a design.

Cheers

PeteS

 

With tracks thin enough, you could get all the signals out on one
layer, with no vias. For my FG456, about 2 mil design rules would do
it, but I'd still want power and ground planes with vias.

John

 

Xilinx has an application note on suggested routing. In fact, the
Xilinx PCB routing application note is informative for people doing
BGA PCBs. I doubt that you will be using all the I/O pins, so you can
adjust your number of layers accordingly. The Xilinx parts have most
of the power/ground pins near the center. I would assume that the
Altera part is similar which means that the number of layers and
routing strategy will be similar. If the Altera part has a significant
number of power pins towards the outside, that can cause routing
problems.

 

Hi,


Did you use blind vias on the pads, or vias "between" the BGA pads?
I know it costs extra to have blind/buried vias, but also it could allow
you to use fewer layers possibly. Do you guys autoroute or manually
route? Thanks!

cheers,
Jamie

 

We use dogbones, undrilled pads for the bga balls with a very short
trace to a thru via, for all pads except the two outer rows, which are
the undrilled pads alone.

We mostly manually route, since autorouters usually make a bigger mess
than they're worth. But we do assign all the fpga pins to make routing
easy, with minimum crossovers. I usually let my layout guy assign the
fpga pins.

John

 

South Africa of all places.

In looking around I found a reference on Digg that claims they are making
Copper Indium Gallium Diselenide (CIGS). The breakthrough doesn't produce
that much more power for the same area just (supposedly) a much lower cost
for the Solar Panel. A factor of 4-5 is quoted in the second reference.

http://digg.com/tech_news/Newly_created_high-efficiency_solar_panels_from_South_Africa This link has some details at the bottom. http://www.engineeringnews.co.za/eng/news/today/?show=92093

 

AFAIK these panels are still at the 'lab' stage.

If they perform as advertised it will indeed be a major breakthrough. Since they're using Germanium I'd be concerned over their ability to take much in the way of high temperatures though.

Graham

 

Don't bother. Doing the math (50 watt panel costing $70 to build, $100
retail), show the panel makes about $1 of electricity a year, the cost
of borrowing the money, at least $7.

And that doent include the cost of installation, maintenance,
batteries, inverters, etc.

 

Germanium?

I see a bunch of materials quoted but no Germanium.

Perhaps you meant the Gallium?

Quoting:
"As it uses no silicon, costs are dramatically lower. It makes use of normal
window glass as a substrate, with - and this is where it gets complex -
molybdenum applied as back contact, followed by the core component, being a
compound semiconductor comprising five elements - copper, indium, gallium,
selenium and sulphide, replacing the silicon - with cadmium sulphide as a
buffer layer, followed by an intrinsic zinc oxide layer and, finally, a
conductive zinc-oxide layer."

They mentioned a Production Plant (verified) of 25MW. That's certainly small
compared to a commercial generation plant but I don't know if it's still in
the "Lab" stage. If you can believe what they say.

Robert

 

Since they quote a cost of 4 to 5 times larger for imported Solar Panels,
and say there is a thriving Solar Industry using them, I certainly think the
new panel will make a lot of changes in the current Industry. No one ever
said they were a replacement for the Power Grid in First World Countries.
And that's if you can believe what they say.

Robert