Optimum Number Density of Blocks Released in Fluidic Self-Assembly of Microelectronics

An experimental study was conducted to demonstrate the existence and estimate the value of an optimum number density of silicon plates (blocks) in a fluidic self-assembly process used for parallel assembling of microelectronics. Blocks ranging in size from 350 to 1050 microns were released under water over an inclined substrate and allowed to move gravitationally to fill indentations (receptors) of matching shape. The performance of the process was evaluated in terms of the time necessary to achieve filling. Results indicate that there is an optimum block density for which the filling time is minimum. If the density is too high, blocks in contact with each other form agglomerations that reduce the mobility of individual blocks and prevent them from aligning properly with the receptors to fill them. The optimum area fraction covered by blocks was relatively similar for the three sizes of blocks considered. The findings amend a common belief that the FSA performance increases indefinitely with the density of blocks released. Economic advantages of a limited block density at industrial scale are discussed.