Dennis Saputelli wrote:

> are you sure you don't want the bottom pads untented?

> a recent customer specifically wanted the bottom via fanouts to be
> untented for test probing

> (i realize yours are in pad)
> your via in pad only goes to the layer below, right?
> 
> in my understanding this is the only way it can be small enough to not
> louse up the paste reflow


The Fab/Assembly shop (picked by client) gave me these specifications.
The holes are through the board, but plugged in the Fab process.

> what is the ball count and pitch of your chip and why exactly are you
> doing via in pad?


Multiple BGAs including 957 (31x31), 680 (34x34) and 432 (31x31) pitches 
vary from 50 mil to 0.8mm

Via in pad is a customer request ... er, ehh, demand. I have done 
"dogbones" in the past but this is the first VIP design.

> what are the various dimensions you are using?
> (just curious)


Depending on the BGA, 30 mil pad, 9mil hole (finished, plugged)
                       25 mil pad, 9mil hole (finished, plugged)
                       23 mil pad, 9mil hole (finished, plugged)
                      16 mil pad, 6mil hole (finished, plugged)

David W. Gulley
Destiny Designs


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