Reliable ultra-low-loop bonding approach on X2/X3 thin QFN

摘要

Smart mobile devices such as smart phones & tablets are gaining tremendous growth in the consumer market due to their ability to offer greater functionality and ease of use such as voice and SMS coupled with mobile internet applications, multimedia functionality, high speed data processing capabilities, and inbuilt GPS capabilities, not forgetting the cm mm-sized thickness platform that makes them easily transportable, readily accompanied or even wearable. These requirements for higher integration & miniaturization drive integrated circuits (ICs) to be packaged towards thinner, smaller or more complex configurations. Multidie within a package will most likely to be the configuration used to attain higher integration. With wirebonding as still the preferred interconnection method of choice, be it between die to leadframe or die to die, these in turn drive the interconnections towards various advanced looping trajectories such as multi-height loops, long wires or ultra-low-loop. When the wire loop height gets low as in the ultra-low loop, there would be potential of the neck damage as well as wire shorting/collapsing to the surface beneath it. Looping gets even more challenging when the wire length gets longer with ultra-low loop bonding at the same time. This paper will discuss on the forming of reliable ultra-low-loop for various configurations in the QFN thin packages, eg. X2 (max0.4mm package thickness) or X3 (max 0.3mm package thickness), through the selection of wires, shapes of the loop profile, supporting tools, while maintaining high quality and reliability at post-bond and post-mold conditions. Finally, full reliability testing and qualification will be performed on the ultra-low-loop for various configurations to ensure robustness of the looping.