Hi Earl,

                Across an 18 x 24 panel, the minimum registration
                tolerance of clearance  to pad is +/- 0.002".
                Isolated features can be
                held to +/- 0.001" if essential.

               We recommend a minimum solder mask web
                width of 0.004".  An absolute minimum of 0.0025"
                can be maintained in isolated areas.

                Hope this helps.


Best regards,

Keith Larson
Circuit Technology Inc.


[log in to unmask] wrote:

> I've been afronted with the latest BGA schemes dreamed up by someone not looking at, or willing to
> follow relatively simple design rules. That's my story.
>
> I remember LPI could hold fairly tight registration dimensions and tolerances across a panel. I just
> don't remember all I forgot concerning how tight these parameters might be.
>
> The best way to describe this dilemma is to say someone designed a 432 ball permiter BGA with some
> outer layer traces within 5 mils of the inside balls when 50 mils was available. With all things
> considered, without redesigning, there often are traces open to the aforementioned pads. Wonder why?
>
> The real question is what currently is reality without special "tweaking"? I mean, what are the
> practical process capability limitations concerning how tight will LPI S/M cover the distance
> without shorting - routinely - over say an 18 by 24 panel?
>
> Earl Moon
>
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