The miniaturization of a micro-ball endoscope by SiP approach

The use of capsule endoscope greatly contributes to the painless and hygiene diagnoses of the small intestine, which cannot be reached easily by traditional upper endoscopy or colonoscopy. However, most of current commercial capsule endoscopes only carry one or two cameras, which may lead to missing some interesting spots due to the limited field of view. A micro-ball endoscope with six CMOS image sensors mounted on a cubic carrier could reduce the miss rate. Some initial prototypes were built with PCBs and connectors. The minimum size of initial prototypes was 22mm×22mm×22mm, which limited the practical use in human medicine. Thus, it is essential to minimize the prototype cube size. In the present work, a SiP (System in Package) approach was proposed to promote the miniaturization of the micro-ball endoscope. Utilization of rigid-flex substrate of special configuration, which is bendable other than PCBs and connectors, achieved seamless connection between adjacent boards and higher package density by employing three-dimension (3-D) space. The technology of multi die stack was also applied to lower the footprint. With this new SiP design, the size of complicated micro-ball endoscope, which involves ASIC (Application Specific Integrated Circuits) chips, image sensors, Flash chips, and wireless transceiver module, was successfully reduced to 16mm×16mm ×16mm.