Structural Optimization of Curved Image Sensor

The use of curved image sensor is effective for the miniaturization of camera modules fitted to digital camera, mobile phone, etc. This paper describes the strength data of curved image sensor and describes the structural optimization of the elements using this data. The main results are given below. (1) The bending strength and surface strength of Si elements and image sensors were clarified through experiments, and the effects of stress relief method, dicing method and thickness on the basic strength were made clear. In particular, a new surface strength test method is suggested. (2) A three-dimensional, larges deformation FEM analysis was carried out to obtain the stress generated when curving the image sensor. It was made clear, judging from the measured strength of image sensor, that there were several breakage modes caused by 1) bending stress fractures at the periphery of the element, 2) Surface stress fractures at the center of the element and 3) buckling due to compressive stress at the periphery of the element. (3) In order to reduce the fracture rate of curved image sensors, it is effective to use a genetic algorithms and an information integration method based on several conditions limiting its structural design. The fracture rate was found to conform to the experimental result.