A lead frame assembly having a lead frame made of a single layer, a housing substantially surrounding the lead frame, and a plurality of leads formed as part of the lead frame. A discrete element model of the subsurface region is initialized, wherein the model comprises a model volume including a base, periodic horizontal boundaries, and soft objects representative of particles of the first grain distribution at a predetermined porosity. The at least portion of the current picture may comprise, for example, a block, a slice, a tile, a wavefront, or the entirety of the current picture. A reactive ion beam etching process removes the filler material at the side edges of the write pole and thus widens the opening at the side edges.