Equilibrium of hinged and hingeless structures rotated using surface tension forces

Two different geometries for the rotation of microstructures by the surface tension force of molten solder are investigated theoretically and experimentally. The geometries are based on structures with and without a hinge acting to constrain the motion of a flap to pure rotation. The equilibrium geometry of a hinged structure is first found analytically by considering the surface energy of the solder. An analysis of hingeless structures is then performed that shows a hinge to be unnecessary under certain conditions. Macroscopic experiments performed using printed circuit board parts are then described; the results show that the behaviors of hinged and hingeless structures are similar