Chip Scale Package for Image Sensor Device

Abstract

Chip on glass (COG) and chip on film (COF) package solutions for image sensor are introduced in this study. These packaging solutions are based on high precision, high reliability bumping and flip chip bonding technologies. To apply connection bumps on image sensor wafer, three bumping technologies are investigated; including gold stud bumps, electroless bumps and electroplated bumps. The issue of bumping technology on image sensor device is how to prevent damages and contaminations on microlens and sensing area. As a result, a series of well-controlled sputtering and stripping electroplated bumping process is developed and verified. The verified electroplated bumping process is also applied to produce RDL trace on 8” optical glass wafer. The gold stud bump is also an alternative low cost solution for image sensor package. The NCP and flip chip bonding technologies are used to bond the chip onto optical glass substrate and polyimide film. The lower processing temperature could ensure the microlens and color filter on image sensor will not be damaged during the assembly process. An innovative concept of image sensor with metal sealing ring is also investigated. The metal sealing ring could provide higher reliability and easy assembly process to reduce the risk of adhesive overflow to image sensing area. The reliability testing result show COG/COF image packages are low cost and high image quality solutions.