Product-internal assembly functions

Abstract

In this project, the technical feasibility of a novel assembly concept was explored, in which microsystem-based self-assembly functionality is added to an existing product. The case considered is the accurate alignment of an optical fibre relative to a telecommunication laser source. In the most demanding cases this requires alignment accuracies down to 0.1 µm to achieve adequate optical coupling. This is very difficult to achieve using conventional assembly, making the assembly cost up to 50 - 80% of the overall device cost. Project goal was to develop a chip for aligning and fixing the fibre using microsystem technology (MST), comprising lithography-based techniques from the integrated circuit domain for selectively depositing and removing material on wafers. Advantages of this technology are the high attainable accuracies and the potential of batch-wise fabrication. Two functionalities were developed: 2-D positioning and clamping. Positioning of the fibre is achieved by two oblique contact surfaces, which can each be moved by a thermal V-shaped silicon actuator. Fibre tip displacements in a diamond shaped positioning window of over 25 by 40 µm were demonstrated with positioning resolutions smaller than 0.1 µm. When the fibre position is correct, which is determined by measuring the coupled light, it is fixed by an internal mechanical clamping device. Powering down both clamp and positioning actuators showed a fibre shift of less than 0.1 µm, thus reaching the target value for the project. Initial vibration measurements showed no additional position shifts, thereby demonstrating the stability of the system.