Thermal modeling and analysis for a novel packaging structure of CMOS image sensor

In this paper, a novel new package solution for CMOS image sensor (CIS) based on molding compound interconnect substrate (MIS) is proposed. First, a 13 million pixel CIS packaged by quad flat no lead (QFN) is chosen as a reference. Considering the design parameters, a new package structure based on MIS is designed. Second, Two kinds of three-dimensional finite element models of CIS package are respectively established by ANSYS Workbench. One is packaged by QFN, and the other one is packaged by MIS. Then the thermal-mechanical property of the two package structures during the cooling process just after molding is analyzed. In the initial simulation, warpage of new package structure based on MIS is 22.915µm, which is less than it in QFN model. However, the peak equivalent stress in CIS chip of QFN is 74.307Mpa much less than 335.53Mpa in MIS model. Third, as the geometry parameters and epoxy molding compound (EMC) characteristics influencing the reliability of the package, a series of comprehensive parametric studies are conducted in this paper. From the simulation, the opening size and the CTE of EMC are found to be the most critical factors, which affect the warpage of package and equivalent stress in CIS chip.