Development of Robust Cu Wire Looping for Small Sensor QFN Package with Higher Dual Die Stack

Complex requirement for automotive accelerometer sensors new product development requires continuous innovation in QFN Cu wire bonding process. In this paper, an innovative thorough method to develop wire loop height and loop shape was developed to meet small QFN with package size 3x3mm with >40% dual die stack height increase vs. conventional product. Long wire length in terms of x, y, z direction has been studied on various loop type including forward and reverse bonding. The result of this study showed an optimized wire loop recipe can be achieved with zero wire short versus less optimized version which can cause as high as 36% wire short. The optimized wire loop recipe has been established and validated by T0 post mold test thus enabling a robust assembly process for small QFN sensor packages with significantly higher stacked die height.