Structural Optimization of Curved Image Sensor

The bending strength and surface strength of thin silicon devices and structural optimization of the curved image sensor were investigated in order to achieve high quality and thin camera module with high reliability. A new surface strength test method was proposed and the effects of the stress relief treatment method, the dicing method and the thickness on the bending and surface strength were clarified through experiments. A three-dimensional large deformation finite element method (FEM) analysis was carried out to obtain the stress generated when curving the image sensor. It was made clear, judging from the measured and analyzed strength of the curved image sensor, that there were three failures modes caused by 1) bending stress at the periphery of the device, 2) surface stress at the center of the device and 3) buckling due to compressive stress at the periphery of the device. Structural optimization of the curved image sensor was carried out by the newly developed genetic algorithm and the information integration method. The optimum solution of the thickness of 51 μm, a curving radius of 20 mm, and a fracture rate of 2% was obtained for a high resolution image sensor.