High Yield Assembly of Compliant MEMS Snap Fasteners

Heterogeneous assembly at the microscale has recently emerged as a viable pathway to constructing 3-dimensional microrobots and other miniaturized devices. In contrast to self-assembly, this method is directed and deterministic, and is based on serial or parallel microassembly. Whereas at the meso and macro scales, automation is often undertaken after, and often benchmarked against manual assembly, we demonstrate that deterministic automation at the MEMS scale can be completed with higher yields through the use of engineered compliance and precision robotic cells. Snap fasteners have long been used as a way to exploit the inherent stability of local minima of the deformation energy caused by interference during part mating. In this paper we assume that the building blocks are 2 1/2 -dimensional, as is the case with lithographically microfabricated MEMS parts. The assembly of the snap fasteners is done using μ³, a multi-robot microassembly station with unique characteristics located at our ARRI’s Texas Microfactory lab. Experiments are performed to demonstrate that fast and reliable assemblies can be expected if the microparts and the robotic cell satisfy a so-called “High Yield Assembly Condition” (H.Y.A.C.). Important design trade-offs for assembly and performance of microsnap fasteners are discussed and experimentally evaluated.