Abstract
High-density 3D packaging technology for a CCD micro-camera system module consisting of an experimental wireless micromachine for inspection of 10 mmφ inner surface of tubes in electric power generators has been developed by applying high-density interconnection stack-unit modules that have fine-pitch flip-chip interconnections within copper-column-based solder bumps and high-aspect-ratio sidewall footprints for vertical interconnections. Copper-column-based solder bump design and underfill encapsulation resin characteristics were optimized to reduce the strain in the bump and to achieve fine-pitch flip-chip interconnection with high-reliability. High-aspect-ratio sidewall footprints were realized by the copper-filled stacked vias at the edge of the substrate. High-precision distribution of sidewall footprints was achieved by laminating multiple stack-unit substrates simultaneously. The fabricated 3D package has operated satisfactorily as the CCD imaging data transmission circuit module and it has been confirmed that the output CCD images have high resolution which enables 20μm objects to be distinguish inside 10mmφ tubes. The technology was confirmed to be effective for incorporating many devices of different sizes at far higher packaging density than it is possible to attain using conventional technology.
