Hey, Kim, thanks!
This is good info. To make it easier to find for others who may be
interested, I have included a direct link to the document with the pad
design information for a .5mm pitch design. Look at the Reliability
section also. Lots of good information.
http://focus.ti.com/lit/an/ssyz015b/ssyz015b.pdf 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Haynes, Kim
Sent: Friday, March 02, 2007 10:42 AM
To: [log in to unmask]
Subject: Re: [TN] BGA footprint

Check www.ti.com and enter microstar in the text search box.  There are
several papers on small pitch BGA devices and the PCB designs to make
them usuable.  The thermal issues may also be important in a CSP.
Good luck,
Kim

________________________________

From: TechNet on behalf of Bob Perkins
Sent: Thu 3/1/2007 6:36 PM
To: [log in to unmask]
Subject: [TN] BGA footprint



Hi

I am working on a new board with a 0.5mm pitch BGA and I am wonder if
someone can advise me on the footprint.

1) the datasheet says the solder ball is 0.3mm +/-0.05mm
2) IPC recommends to use 80% of ball diameter for the pad which would be
0.24mm
3) Would it be OK to use a 0.2mm pad? I am hesitant to go against
recommended size without some corroborating documentation. The reason I
would want to use 0.2mm pad is to avoid using via-in-pad.

I am curious if IPC defines footprints based on what is good for
manufacturing or is it simply theoretical?

Thanks
Bob

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