Richard Sumner wrote:

> David,
> 
> Talk to your assembler before you invest time in this. The paste mask 
> becomes a metal stencil for applying the solder paste. So donuts will 
> not work (the donut hole is unsupported).


Actually my idea was to make the width of the track greater than 2x the 
radius of the arc so I would end up with a "filled donut". (For example 
if I want a 30 mil opening in the paste mask, I could use a 20mil wide 
arc with a radius of 5mil.)

However, what I have just tried that seems a bit simpler is to use a pad 
and a via (gee a via in a pad!) where the pad is TopLayer only and the 
via is set for tenting. Do an update free primitives after import to the 
PCB and viola...

> Big BGA's are a pain. If you could only get the designer

> to use only the two outer rows .......

   Unfortunately, I am the designer on this one and I have to go 10 rows 
deep (31x31 with all positions used! At least the inner most pins are 
power and GND. Actually the 4 corners are missing so its only 957 pins.)

In the past I have always used "dogbone" connections between BGA pad and 
via, but this time there are requirements for via-in-pad (which I do not 
like or trust, however the customer is "always right" if he persists in 
a decision that he has been warned against!).

But, I really wish for better control of the pad stacks (including ALL 
layers).


David W. Gulley
Destiny Designs


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