[SI-LIST] Re: Placement of power/ground balls in BGAs
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Alaa.Alani@xxxxxxxxxx
- Date: Mon, 07 Jan 2008 04:47:40 -0800
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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