Mechanics of micromechanical clips for optical fibers

Abstract

The use of single-mode optical fibers in telecommunications is widespread. However, current laser pig-tailing methods employing either glue or weld to secure the fibers in place are costly and there are inherent problems such as initial fiber mis-alignment, movement during bonding and instability during the service life. An innovative mechanical solution using silicon or silicon nitride clips has recently been proposed to address the issue (Strandman and Bäcklund 1995 Proc. SPIE 2639 18, Strandman and Bäcklund 1997 J. Microelectromech. Syst. 6 35, Strandman and Bäcklund 1998 J. Micromech. Microeng. 8 39, Bostock et al 1998 J. Micromech. Microeng. 8 343, Liu and Lu 2001 J. Micromech. Microeng. 11 195). This paper analyses the mechanical properties of such clips, with special focus placed on crack initiation and propagation due to excessive loading. The singular stress fields near the corner of the clip and substrate are calculated by the method of finite elements, and theoretical models are developed to predict the initiation of failure for clip/substrate systems having various geometrical dimensions and material combinations. The orientations of the initial crack as well as crack growth processes are discussed. The predicted failure modes are compared with those observed in silicon nitride/silicon systems.