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°C. Precise alignment of the CCD chips, long-term thermal cycling between 25°C and -140°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°C to -138°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