FreeLists / si-list / [SI-LIST] Re: Split GND Plane on PKG

[Alan.Hiltonnickel@xxxxxxx]

Jongbae,

Your blanket statement, "most package designers split their ground 
planes in PKG" is not necessarily true, and is certainly not provable.

I can tell you what a GOOD package designer will do: they will structure 
their power and ground carefully in the context of the silicon they are 
connected to and the PCB environment they are planning to connect that 
silicon to. I have been know to reconnect isolated ground planes that 
others felt should be separate from regular "ground", with no ill 
effect. I have also been known to be very particular about how a 
separate ground is routed to provide a minimal noise coupling for, say, 
a PLL.

A designer who splits a ground plane should provide an adequate analysis 
(preferably with simulations) to back up such a drastic action, and 
should also have a strategy to minimize the impact on high speed signals 
and EMI.

Alan.

jbtera77@xxxxxxxxx wrote On 06/06/06 22:29,:

>Hi, all
>As i know, most PKG designers split their ground plane in PKG. It is
>usually for seperation of digital with analog. However, i think, even if we
>split GND on PKG, once the package is connected to board by BGA or
>wirebonding, the effect of split-GND on PKG will not be appear. Instead, the
>board design is much more dominate than pkg p/g design.
>So, in my opinion, we don't have to split its ground plane on PKG because it
>doesn't affect to overall p/g design including board (maybe a little) and
>splitting the ground plane may cause the signal integrity problem.
>
>Could you please let me know the reason designers split the ground plane in
>package.
>
>rgs,
>Jongbae.
>
>  
>

-- 
Alan Hilton-Nickel
Signal Integrity Engineer
Sun Microsystems Inc.
Netra Systems and Networking
Newark, CA

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