Re: 320pin BGA Pin Layout suggestions

..5MM BGAs tend to be a whole new ball game.
From .75mm pitch on up you can do a conventional "Dog Bone" approach to fanning them out. For .5mm the drill/pad/land size is not manufacuturable for Dog Bone fan outs. So you need to do Via in a Pad.
Step one, then is to make sure your PCB vendor can do via in a pad (with plug and fill of course).
That said you "may" not have to do that for this part depending on what signals you are actually using and what is power and ground. That is because this is only a 4 row part. You may be able to squeeze row AC between AD and AB between AA and get it fanned out with say a .2mm drill in a .45mm-.50mm pad or some such away from the balls.
To fan out a .5mm BGA this way you are going to need .083mm (3.28 mills) trace and space which is still way small, so again start with your fab house to see what they can do.

If your using PADS you may want to hit the PADS newsgroup where there are lots of people with experience in this kind of stuff hanging out.
PADS is NNTP server - listserver.pads.com with the newsgroup "Talk"

Hawker


On 3/19/2007 3:35 AM, The digits of Joe G (Home)'s hands composed the following:
Hi All,

I am looing at laying out 320pin BGA on a PCB like this one.

http://www.standardics.nxp.com/packaging/package.outlines/pdf/sot824-1.pdf

The pitch between balls is 0.5mm. The internal cpu speed is 220MHz but the external I think is ~60MHz.

It has a JTAG port

Questions
Q1
How many PCB layers would you recommend and why

Q2
Is there anything else I should watch out for?


Any other pointers on this beast would be appreciated.


Regards
Joseph


.

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