gEDA-user: BGA package prototyping

[John Griessen <john@xxxxxxxxxxxxxx>]

Some feature packed chips are coming in 0.5mm pitch BGAs where there are
four rings of balls to connect.   How do you connect those to vias so you can
use middle layers to get out of the grid zone?  One could go to the outside formthe first two rows,
and toward the inside from the 3rd and 4th rows, then to vias, then outside by way of middle layers.

Sounds like the center would get crammed.  Can vias in the BGA pads be made so they don't wick out
BGA ball material?   Does a BGA ball melt during reflow, or just get near it?

What fabs can do
3 mils/3 mils (track/space) rules, cover the backof the vias with epoxy or soldermask?

Can you get one to assemble by toaster methods for prototyping?

Thanks,

John Griessen
-- 
Ecosensory   Austin TX


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