[SI-LIST] Re: Placement of power/ground balls in BGAs
- From: "DAVID CUTHBERT" <telegrapher9@xxxxxxxxx>
- To: weirsi@xxxxxxxxxx
- Date: Mon, 7 Jan 2008 06:19:10 -0700
The return current will travel equally in the power pins and the GND pins.
So the placement of the power pins is as important as the GND pins.
Dave Cuthbert
Consultant, SI, EMC, power electronics, everything analog
NARTE Certified EMC engineer
On Jan 7, 2008 5:47 AM, steve weir <weirsi@xxxxxxxxxx> wrote:
> Alaa this is not something to which there is a simple answer. Package
> design involves trading off performance and cost. What you need to
> begin with is a definition of the performance that you require and the
> cost within which you must live. Then you can seek out design
> alternatives that are within your cost requirements and determine if any
> of them will satisfy your performance needs.
>
> It is unlikely that you will be able to successfully design a
> high-performance cost-effective package without access to good
> simulation software. Also this is your first time through then I highly
> recommend you find someone within your organization with suitable
> experience to help guide you.
>
> Ground balls in the center of the package are very useful for removing
> heat. Ground or power balls must be meshed at sufficient density
> through the pin field to meet return impedance requirements. Those
> requirements depend a lot on signal edge rates and how the power and
> ground nodes are bound inside the package and on the PCB.
>
> Steve.
> Alaa Alani wrote:
> > =20=0D=0AHi,=0D=0A=20=0D=0AI am looking into the placement of power and
> gro=
> > und balls in BGA=0D=0Apackages. In Xilinx's Virtex-II handbook, it is
> shown=
> > that GND balls are=0D=0Aplaced in the centre island (beneath the die)
> and =
> > also arranged radially=0D=0Atowards the four corners of the package.
> Power =
> > balls on the other hand,=0D=0Aare surrounding the die on four sides. Are
> th=
> > ere any guidelines for=0D=0Aplacement of pwr/gnd balls in BGA=3F Should
> the=
> > number of power and ground=0D=0Aballs be the same or should we allocate
> mo=
> > re ground balls in order to=0D=0Areduce ground
> bounce=3F=0D=0A=20=0D=0AThan=
> > ks,=0D=0AAlaa Alani=0D=0AImagination Technologies=0D=0A=0D=0A-=0D=0AThis
> me=
> > ssage is subject to Imagination Technologies' e-mail terms:
> http://www.imgt=
> > ec.com/e-mail.htm=0D=0A-=0D=0A
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