Thermal and Mechanical Analysis of Imaging Ball Grid Array Image Sensor Package

Abstract

The growing demand of mobile phone, cameras and automotive pushes development of image sensor packaging in a trend of shrank form factor and more complex substrate design. To cater to the demand, the next generation image sensor package, Imaging Ball Grid Array (iBGA), was developed by UTAC. iBGA packages use organic substrates instead of ceramic carrier used in previous image sensor packages, for example, CLCC (Ceramic Leadless Chip Carrier) package. iBGA allows image sensor to become smaller, more advanced routings and alternative bill of materials to address specific material lead-times. When a new packaging is developed, characterizations of the package are crucial. Finite element modeling and simulation approach is proven to be the most efficient and enable shorter time to market by elimination numerous engineering DOE and design-prototype-test cycles. Firstly, for any IC packaging, thermal performance is one of the factors needs to be considered as the new packaging type should not be so warm that will have negative impact on overall performance and reliability of the device. Secondly, as image sensor's essential part is a glass and glass is a brittle material, thermo-mechanical stress due to CTE miss-match to be resolved when developing the package. In this paper, the characterization of UTAC image sensor package imaging ball grid array (iBGA) is studied. The structure and the packaging process of iBGA are illustrated. Thermal simulation is done using Computational Fluid Dynamic (CFD) simulation software to study heat dissipation and thermal performance under steady state condition with JEDEC standard. Moreover, mechanical simulation for warpage is conducted using Finite Element Analysis (FEA) simulation tool and correlated with Shadow Moiré measurement. Lastly, reliability examination is also done for iBGA. Studies will reveal the mechanical characteristics and thermal performance of the package in depth.