Semiconductor QFN Package with Advanced Interlocking Design

Abstract

The mechanical interlocking structure for quad-flat no-lead (QFN) assembly for densified leadframe degrades as the package becomes thinner. Detractors such as package reliability and design requirement hinder further qualification of leadframes with increased number of input/output (I/O) pins. In this paper, a new and advanced design of leadframe is discussed and presented with improvement in mechanical interlocking structure of high stress areas such as lead and pad junction. The leadframe is re-designed having lead lines on the lead and pad that will be etched away after molding process replacing full copper base frame. Through application of the design, the effective mechanical interlocking is improved from 60% to 100% for mold-lead and mold-pad interface.