Wirebond Vs. Flip Chip Design of High Speed 3D Stacked Memory Packages

Farhang Yazdani

BroadPak Corporation


3D Memory package-on-package stacking has gained popularity due to increase in demand for bandwidth, higher density and miniaturization. Challenges in design of high performance 3D stacks have increased with amplification in speed and signal integrity issues. This paper dissects the design elements of 3D memory stacks architecture and characterizes the signal integrity and trade off of wirebond and flip-chip stacks for high data rate applications. Signal integrity characterization of up to 10 stacked packages in both wirebond and flip chip configurations are presented. Effect of BGA stacking, transmission line and wirebond vs flip chip in both time and frequency domains are analyzed and presented. It is shown that the effect of very short wirebonds used in cavity down packaging and solder ball stacking is minimal at 10GB/s.