Abstract: A method of predicting the three-dimensional topography of a surface of a semiconductor device including a flowable material includes establishing reflow process conditions including a total process time; establishing a grid of three-dimensional cells encompassing at least part of a semiconductor device and including a flowable material; specifying the concentration of a flowable material in each cell; establishing polygonal surfaces of constant flowable material concentration that extend amongst the cells; calculating the chemical potential of each constant concentration polygonal surface; calculating the surface flux of flowable material between adjacent polygonal surfaces; calculating the material flow between cells for a time interval .increment.t less than the process time by multiplying the surface flux by the time .increment.