[SI-LIST] BGA Breakout.



Hello Gurus;

 

I am doing some preliminary calculations on the breakout of
a 1,400+  Ball  , BGA. Roughly one half of them are signal
connections which would need traces running up to them. The vendor claims you
can run two traces between Vias, my calculations are not adding up, I have a
few questions.

 

1. Generally, do the Vias have a pad even on the signal
layer it is not connecting to?.

 

2. Do the Vias have a larger pad on the inner layers?

 

3.  With a Ball pitch
of 1 mm (39 mils.) and an Antipad of 35 mils, there is hardly any room for one
trace between Vias, what am I doing wrong?

 

Thanks, 

 

Surita Chandani




      
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