  In designing an ion trap, geometry and rf source should be optimized such
that the trap depth is maximized while the ion remain stable. In a quadrupole
linear trap, stable parameters $a$ and $q$ are utilized frequently in
describing the stability. However, in a surface trap, the trap have to be
mapped to the linear quadrupole trap so that $a$ and $q$ can be evaluated. This
work explains how to handle them for surface trap designing and how the
geometry and rf source affect it. We conclude that the $q$ parameter should be
0.2~0.22 so that the trap is stable.
