[SI-LIST] Re: BGA Vs QFP
- From: "Bush, Walter" <Walter.Bush@xxxxxxxxx>
- To: <starsilic@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 23 Apr 2007 19:03:28 -0700
Hi Canes
If the BGA has planes, your PDS is better then the One Layer QFP
package. Can you just remove Power ground leads from the BGA, not so
simple.
Let's look at these two packages;
JEDEC-MS-034b.pdf BGA 256 lead, Body size 17x17mm
JEDEC-MS-029A.pdf QFP 256 lead, Body size 28x28mm
1. Dose the QFP meet PDS budgets as is?
2. Dose the QFP meet SSO/SSI requirements?
3. If Powers are removed from BGA will PDS be met?
4. If grounds are removed from BGA will PDS be met?
5. If return paths are remove from BGA will SSO/SSI be met?
6. For NEXT and FEXT on the QFP I will see two aggressors within 1.0mm
on either side of the victim, on the BGA I will see eight aggressors
with in 1.0mm, But the BGA has a return path that can reduces over all
coupling.
Assuming four quadrants on QFP Package, 12 powers, and Ground (6 GND, 4
VDDI 2 VDD) per quadrant this leaves 52 IO, 4 IO per return path, add 4
Ground, or 2 Ground and 2 power, this leaves 48 * 4 =3D 192 lead for
signals (or approximately 4 IO per return path), This should be the same
for the BGA, although, if Number 3-6 are not an issues, then yes can
reduce the PDS on the BGA.
Just my thoughts, Thanks, Walter
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Canes Venatici
Sent: Monday, April 23, 2007 6:40 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] BGA Vs QFP
Hi all,
I'm having some confusion related to BGA. I believe BGA can have planes
for ground, core vdd, io vdd etc.
Since the planes are equipotential, can I assume for same number of
power pin count in QFP, I can reduce balls in BGA.
For ex.,=20
I have a common die for two packages say, QFP and BGA with same number
of pads for both packages.=20
But I want to reduce the power pin count by taking advantage of planes
in BGA. Is it possible?
Could anyone throw some light on it?
Regards
Canes
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