Methods and Characterization of Pick and Place Microassembly

Abstract

Microassembly of MEMS structures using serial pick-and place has been demonstrated as a method for constructing complex three-dimensional microstructures. A new methodology to perform pick-and-place microassembly using a 3 DOF micromanipulator is demonstrated here. In this approach, the "pick" operation is performed on one chip, while the "place" operation is performed on a second chip mounted orthogonally to it under a microscope. This removes the need for the rotation of parts during assembly as required in previous works thus creating a significantly simpler assembly process. Also new in this work is the characterization of the contact resistance and the rigidity of assembled microstructures. The contact resistance of assembled microparts coated with 30nm of gold is measured to be approximately 12Ωusing a four-point measurement. The force required to pull out a micropart from a socket (into which it is assembled) is characterized along all three axes and found to be over 5mN in each case. The relationship between the force taken to engage the sockets and the force to pull out a micropart is measured to be linear. An electrostatic inchworm motor with extended range and a vertical thermal actuator are demonstrated which are manufactured using microassembly. Thus this assembly process with mechanically rigid assemblies is shown to have a number of potential applications.