Enabling curved hemispherical arrays with Quilt Packaging interconnect technology

Design, fabrication and assembly of curved imaging arrays is challenging. Optical design theory reveals the design challenge of a well-corrected image across a planar surface. As the field of view (FOV) is increased, deviation from the plane of best focus (Petzval surface) is increased. Reducing that deviation drives the power of lens elements higher, resulting in the increase of residual aberrations, especially zonal spherical aberrations. Wide FOV systems having customary planar focal plane arrays (FPA) require additional lenses to correct for distortions. The curved nature of a hemispherical imager minimizes off-axis aberrations and distortions throughout the FOV, and thus is of significant interest for increasing system performance while also reducing complexity, SWAP and cost. This paper will present an overview of hemispherical array development enabled by Quilt Packaging (QP) chip integration technology for creation of piece-wise curved arrays. QP is a direct edge-to-edge chip interconnection approach that can be implemented to enable hemispherical imagers created from the piecewise integration of 2D array ICs of varying geometries. The unique attributes of QP allow for an interconnection that is both robust mechanically and very low loss, high bandwidth electrically. Utilizing this approach allows for straightforward 2D wafer processing and design, reduces or eliminates the need for thinning/flexible chips, and can improve fabrication yields by reducing individual chip area. Indiana Integrated Circuits, LLC and Northrop Grumman Corporation are evaluating the potential performance, reliability and SWAP benefits of extending earlier Quilt Packaging imager work into the 3rd dimension for curved arrays.