Study of micro-scale limits of solder self-assembly for MEMS

Solder self-assembly of MEMS has been shown to be an excellent approach for assembling three-dimensional MEMS structures by allowing more precise alignments and vastly increased complexity. This paper investigates if solder self-assembly could be applied at the sub-micron scale. Experiments studying the surface energy minimization properties of molten solder demonstrate that surface energy minimized solder spheres as small as 5 nm are possible. However, the intermetallic formation may limit our ability to reach the nano-scales. Nevertheless, even with intermetallic formation, it should be possible to use solder self-assembly at sub micron scale.