The High-Flatness Mounting Process of Image Sensor Splicing Units with Ultra-Large Format Focal Plane

Image sensor chip splicing technology plays a crucial role in enhancing the imaging capabilities of current ultra-large-format focal plane imaging systems for both space-based and ground-based ultra-large-format focal plane imaging systems, where the imaging performance heavily relies on the flatness of the chip mounted on the substrate within the splicing unit. Based on the analysis of the influencing factors of chip-mounting flatness, this research developed a high-flatness mounting methods for packaging structure of chip-adhesive-substrate, irrespective of focal plane size. Through the coordinated optimization of packaging materials, structural dimensions, and mounting processes, high-flatness mounting of image sensor chips can be achieved. The substrate material and thickness, along with chip thickness exert a more pronounced impact on chip-mounting flatness compared to mounting process variables like dispensing pattern, adhesive thickness, and curing curve. Furthermore, for substrate and chip with specific size, there exists an optimal chip thickness that yields the best flatness for chip mounting. Based on this method, this research successfully achieved superior flatness mounting of a 50 mm × 96 mm sized large-format focal plane on an AlN substrate by employing both large-sized single-chip mounting and multi-small-sized chip splicing mounting techniques. Specifically, the flatness of the large-sized single-chip mounting reached 2.8 μm, while the flatness of the 2 × 3 chip splicing array attained 11.6 μm; the flatness of these samples did not show significant change after consecutive tests of 100 h aging at 100 °C and 100 times thermal cycling (−55 °C to 100 °C).