Signal Integrity Analysis and Validation of GHz I/O Interface on Wire Bond Ball Grid Array Technology Package

Wire Bond Ball Grid Array technology is widely used in the Intel® South Bridge, or I/O Controller Hub (ICH) for a few generations. With the continuing scaling speed of the I/O interfaces, ICH has SATA Gen 2 links and PCI Express links operating at 2.5Gbits/s and 3Gbits/s respectively within one chip. Due to the heavy traffic and new features, it pushes the electrical performance of Wire Bond Ball Grid Array technology to the limit. Comprehensive analysis and measurement covering high volume manufacturing is desired to ensure the product can meet industry electrical performance spec and operate without failure. Due to complexity level in the package, each package interconnect segment is required to be modeled in 2D or 3D models. The paper discusses the package electrical modeling methodology used in GHz I/O device modeling in more robust and accurate way to support high volume manufacturing and signal integrity design. The package models are then evaluated across frequency and timing analysis to find out the optimized design to signal integrity performance. S-parameter technique is used for frequency analysis while Eye Diagram for timing analysis. The relationship between S-parameter and Eye Diagram helps in understanding the contribution to the I/O performance from each package attributes including wirebonds, ballmap pins, traces and plating bars. The paper also describes the measurement setup and result using Time Domain Reflectometry (TDR) methodology for the I/O channel characterization.