Hey, I have a question about the way the OMAP can/should be routed out
on the board. My fellow students and I are working on a device for a
school project that involves building a handheld console, and we chose
to use the OMAP for its speed and graphics capabilities. I've been
routing the main board out but have run into some troublesome issues
trying to stay within the budget afforded to us. First, is the trace/
space widths, we want to keep them at a minimum of 5 mils, and in
order to do so we have chosen to go with the CUS package as it allows,
and provides a guide for, the routing to be done in said spacing.
However, it seems their calculations of the pad sizes and via
diameters are larger than is physically possible unless some of the
vias are placed under the BGA pads. This isn't their suggestion,
albeit it seems the only option at the moment. I was wondering if that
is a bad idea to have them directly under the pads, as I fear the
solder might not make a secure connection. Also, the chip itself has a
ball size of 0.45 to 0.35 mm and so I made the pads for each ball 0.40
mm. Would it be safe to go to a smaller pad size, say 0.35 mm or 0.30,
in order to allow some of these vias to fit properly?
Any advice in this area would be greatly appreciated.
Thanks in advance!
~Wylder