[SI-LIST] Stack up for EMI reduction
- From: "Nima Lotfi" <lnima@xxxxxxxxxxxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 30 Jan 2004 18:11:55 -0500
Hi,
I'm looking at re-layout of a 10 layer board because of EMI problems. The
board contains 4 differential serial signals a ~700Mhz, and about 20 single
ended signals at 70 MHz. The main problem frequencies are around 350 Mhz.
There are 4 large BGA components on the board.
I would ideally like to move into a 12 layer board, however there is quite a
bit of (non technical) resistance to doing that.
I like to eliminate 2 signal layers, by making my other 2 signal layer
denser. Then I'll use the eliminated signal layers as ground/power layers,
but I will need to use these new gnd/power layers to assist with breakout of
4 high density (500pins) BGA.
My question is can any one comment on whether I should in theory get an EMI
improvement? What should I look out for?
My current stack up is:
1 Mainly GND with some breakout
2 Signal
3 Gnd
4 Signal
5 Power
6 Gnd
7 Signal
8 GND/Power (mixed)
9 Signal
10 mainly GND with some breakout
New proposed stack up
1 GND with some breakout
2 power with some breakout
3 Gnd
4 Signal
5 Power
6 Gnd
7 Signal
8 GND/Power (mixed)
9 Power with some breakout
10 mainly GND with some breakout
Thanks,
Nima
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