Self-Assembly Techniques for Massively Parallel Packaging of MEMS Devices

Self-Assembly Techniques for Massively Parallel Packaging of MEMS Devices Jiandong Fang Chair of Supervisory Committee: Professor Karl F. Böhringer Electrical Engineering This dissertation investigates applications of self-assembly for massively parallel packaging of flat micro-components, the most common appearance of microelectromechanical systems (MEMS) or CMOS chips. Self-assembly assembles micro-components in parallel without any serial, one-bye-one manipulation of components. To satisfy various packaging requirements, we have developed and demonstrated four different self-assembly processes: capillary-driven self-organizing parallel assembly (C-SPASS), semi dry uniquely orienting self-organizing parallel assembly (semi DUO-SPASS), DUO-SPASS and vertical/horizontal self-organizing parallel assembly (VH-SPASS). The C-SPASS process assembles micro-components onto liquid covered receptor sites by minimizing interfacial energies until components align with receptor sites. We have demonstrated this assembly process by bonding PZT actuators for micro fluidic pumps (liquid adhesive polymerized for permanent bonding), and these pumps showed high performance uniformity: a low deviation ∼1.5% for pumping rates at resonant frequencies. The semi DUO-SPASS process is based on single-stage shape recognition between a part’s peg and a receptor site’s hole. Orbital shaking moves parts to be trapped. Unique in-plane alignment is achieved by minimizing potential energy based on pendulum’s principle (the peg is located offset from the center of mass of the component). Our demonstrated experiments resulted in ∼99% yields after 3 minutes’ agitation for 2mm square parts. The DUO-SPASS process relies on two-stage shape recognition between two pegs on a part and two recessed features in a receptor site. The 1 recognition by a tall circular peg anchors the part, and the 2 recognition by a shallow cross peg fixes the part to a specific in-plane orientation. Our demonstrated experiments resulted in ∼98% yields for 1mm square parts. The VH-SPASS process relies on single-stage shape matching and capillary forces. Driven by vibration, parts are trapped to apertures with an opening only for a vertically standing part. Horizontal and vertical assemblies are respectively achieved with and without additional capillary torques introduced by steam condensate. Assembly results showed ∼1% defect rates for 1000 receptor sites on a 4′′ substrate.