Landpattern Calculator: Component Dimension Cells

[CurtS]

I am using the Landpattern Calculator spreadsheet for SO family ICs to generate a landpattern for the MIL-STD-1835, F-18, cfg B case outline. The spreadsheet calls for a nominal dimension for dimension B (Cell E21). The dimension data provided by MIL-STD-1835 does not list a NOM dimension, only a MAX. How should I go about determining a suitable value for cell E21?

Thanks
Curt S.

[Tom]

Curt,

For Mil Spec applications it is perfectly fine to use the Max Value. The only reason why we specify Nominal for the body length is because we add a Courtyard that is 0.5mm larger than the Nominal Value to compensate for the Maximum Value. I hope this makes sense.

When it comes to the component body dimensions, it's always OK to use the Maximum Values, even if you do add a placement courtyard, the courtyard probably could be adjusted smaller because you already compensated for the Maximum Material Condition.