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The Tolerance Deviation of -0.10 mm to +0.30 mm does not play into the mathematical model of the IPC-7351 land pattern calculation for the resulting pad size. You can enter -0.10 mm to +0.30 mm or +/- 0.20 mm and get the same results. Also, it makes no difference if a component manufacturer only provides Nominal package dimensions. There still is a minimum of 0.10 mm +/- tolerance on every dimension. No manufacturer can produce component packages that are 100% perfect every time. i.e.: no one should ever put 0.00 for a tolerance. We've been creating land pattern calculators since 2001 and while we really appreciate users to challenge the standard to find flaws or suggest a better solution. We know that some mfr. tolerances are uneven and you can put them in the calculator uneven, but the program will make them even. Maybe this is something we need to look into for the V2016 Library Expert rewrite. The code is getting old and we need to create a brand new tool to make it look like 2016 to work with Windows 10 coming this October.
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