Solderjet Bumping as a Versatile Tool for the Integration of Piezoelectric Deformable Mirrors

A deformable mirror (DM) is a device that aims to compensate laser-induced mirror deformation and thermal lensing in the optical system. The mounting of membrane based DM with screen-printed actuators is crucial, as stress may deform the membrane and change their characteristics (shape, piezoelectric deflection, natural frequency). We present the laser-based Solderjet Bumping (SJB) technique to assemble mounts for piezoelectric-activated DM. The discussed polymer-free joining offers advantages, such as improved temporal stability and low outgassing, over adhesive bonding. We evaluate the optimum number of solder joints with respect to resonance behavior by finite elements analysis and experimental measurements. Long-term evaluation over a period of more than four years shows no significant change of resonance behavior. Thus, we prove the SJB bonding technique to be stable for dynamic applications over several years, and consider it a versatile tool for integration of DM.