An active micro joining mechanism for 3D assembly

Abstract

An active joining mechanism for the construction of microstructures, comprising detethered microparts and locking actuators fabricated on a wafer, has been implemented. An active locking mechanism is a system on chip (SOC) type of actuator which is designed to control the socket's opening to allow insertion of a micropart with zero force. This allows the delicate micropart to be secured without the need of substantial forces that could cause damage to the micropart or the socket. Moreover, it enhances the assembly throughput, tolerance and yield due to the frictionless self-alignment of the micropart. The design concept, assembly and extensive characterization have been illustrated for 100 µm thick microstructures made of SOI wafers and patterned by deep reactive ion etching. Single-sided and double-sided electrothermal bent beam actuators are utilized for the socket to actively open during assembly and close to lock the micropart against the locking mechanism. Finally, the mechanical and electrical characteristics of the joints can be further enhanced by reflow of the deposited layers of the 80Au–20Sn solder alloy at the contact areas.