Assembly of high-aspect ratio optoelectronic sensor arrays on flexible substrates

Nowadays, most commercial optoelectronic sensor concepts are based on planar photodiode arrangements that originate from an integrated lithographic fabrication and include various filter functions. To enlarge the limited field of view to a certain extent (micro)-optical lenses can be attached by hybrid mounting. Moreover, there are strong interests in small lightweight systems for the complete 360° optical monitoring of the environment. Fields of application are navigation sensors for autarkic moving or flying robots as well as hand-held motion controller or protection equipment. To achieve optoelectronic sensors with a boundless field of view, the introduction of flexible photoreceptors or photoreceptor arrays is a reasonable approach. The present paper describes one promising technology value chain for manufacturing optical sensor arrays which are bendable within wide limits. The aligned chip-level mounting of multichannel optics leads to stacks with a comparably high-aspect ratio. Therefore the following assembly tasks are executable with restrictions only. The application of wire bonding versus flip-chip bonding as electrical joining techniques is discussed, just as the stability of the sensor stack during the separation process. As result, prototypes of curved optical flow sensors, which are fabricated by using the described techniques, are presented.