Hello there,

I was working on some analysis work on BGA pad diameters and its
correlation to other factors when I come across this Table 6 in
IPC-7095. I cannot explain the differences found which I highlighted in
bold.  The table specifies :

Nominal ball szie    Reduction    Nominal Land Dia.     Land Variation
0.75                            25%                0.55 (27%)
         0.60 - 0.50
0.60                            25%                0.45 (25%)
        0.50 - 0.40
0.50                            20%                0.40 (20%)
        0.45 - 0.35
0.45                            20%                0.35 (22%)
        0.35 - 0.25
0.40                            20%                0.30 (25%)
        0.35 - 0.20
0.30                            20%                0.25 (17%)
        0.25 - 0.20

Anyone care to shed a light on the difference in the two percentages or
how the Nominal Land Dia. value come about or agreed upon. Your answers
will be deeply appreciated.

Regards,
Wee Mei




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