Keith,

the IPC-SM-782 land pattern design standard outlines the principles to be
considered when designing a SMT land pattern. The committee provided a
complete description of the process so that new components, not yet listed,
can have land patterns designed in accordance with the recommended
principles. 

In addition to the standard, the IPC released the IPC-EM-782, which is an
electronic spreadsheet version of the calculations. It provides for you to
input the component dimensions and their respective tolerances, a fabrication
allowance, pick and place accuracy, and your choice for solder fillet sizes.
Once this step is completed, you have an opportunity analyze the results and
make any further changes. Once you have completed all these steps, it
calculates all you land pattern dimensions, and provides a final analysis
associated with the land pattern. 

The best part of the program, is that it follows the principles of reliable
land pattern design. It also allows the designer to create a land pattern
that matches his or her processes, or meets industry concensus.

Regards,

Gary Ferrari
IPC Staff

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