Electrical characterization of BGA packages

Abstract

For critical high speed applications, system designers budget electrical performance for each individual component within the integration. During the budgeting process, each component is treated as a black box, and is assigned target performance levels. Crosstalk and switching noise levels are specified and closely watched, since they can cause episodes of false switching. SPICE simulations are performed at the IC, package, and system level to track down any signal integrity problems or issues. Obtaining accurate package models, in particular for power and ground, are the key to overall simulation accuracy. Package power and ground inductance plays a major role in determining switching noise performance. Ball Grid Array (BGA) packages are constructed with laminate substrates that provide an efficient means for achieving minimal power and ground inductance implementation. A BGA that is strategically designed will yield further enhancements in crosstalk and switching noise performance. This is accomplished by optimal implementation and location of power, ground, and signal networks. By doing so, loop inductance created at critical locations in the BGA are reduced by mutual inductance. BGA packages use power and ground rings to provide low inductance access from Integrated Circuit (IC) bond pads to package planes. These connections are typically done using many bond wires equally distributed around the perimeter of the die. Rings are used in combination with via holes, planes, and solder balls to complete the power and ground network structures. Careful attention to how the currents flow in these structures in conjunction with signal traces will yield minimal effective inductance. This paper presents a characterization methodology for creating BGA electrical models. It addresses a class of BGAs that contain power and ground planes, and the Plastic BGA package is used as a vehicle. The measurements are performed in frequency domain using a vector network analyzer. Using these models, electrical performance of BGA packages is evaluated.