We use many BGA's on our boards. The majority
of them are on a 50 mil pad pitch. We are
just now starting to use the 1 mm pad pitch
devices. The 50 mil parts range from 192 pins
to 1088. the 1 mm parts range from 824 to
1270. All of our BGA's use a dogbone shaped
pad. One end of the dogbone is for device
attachment. The other end performs a via on
a stringer function. The designer never needs
to create a breakout pattern. As far as the
designer is concerned the BGA looks like a
through-hole part and I've controlled the
routing so that only the through-hole part of
the pin accepts a connect line. No connect lines
can go to the BGA pad. On the 50 mil parts the
bottom pad is large enough for test to use as
a test point. The 1 mm don't allow this convenience.

              O    BGA attachment pad section
            //     Copper connect section
            o      Through-hole section

This pad was designed to benefit rework, manufacturing,
design, and test.

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