Multichip thin-film technology for low temperature packaging (CCD image sensors)

An advanced astrometric sensor array (AASA) of charge coupled device (CCD) chips has been constructed using hybrid multichip packaging technology for operation at -140 degrees C. Precise alignment of the CCD chips, long-term thermal cycling between 25 degrees C and -140 degrees C, and electrical signal coupling were challenges in the construction of the AASA. A series of AASA prototypes was fabricated with various epoxies, circuitry layouts, and substrate thicknesses in order to obtain materials, fabrication processes, and a structure suitable for construction of the AASA. A silicon template was fabricated by anisotropic etching and used to align the CCD sensors. The AASA samples were evaluated by thermal cycling (27 degrees C to -138 degrees C) and die shear tests. Computer modeling was used for thermal stress analysis of the mechanical behavior of the AASA as a function of temperature. The coupled noise between long parallel lines (1.5 cm) on the AASA was investigated by circuit simulation and experimental measurements. The experimental and modeling results are presented.<>