EFFECTS OF FLOATING PLANES IN 3-DIMENSIONAL PACKAGING STRUCTURES ON SIMULTANEOUS SWITCHING NOISE

The effects of floating conductors in three-dimensional (3-D) packagin g structures are investigated. The simulations are based on a frequenc y-dependent integral equation formulation for the calculation of the m agnetoquasistatic current distribution in complex: interconnect struct ures. The calculated current distributions are used to develop an indu ctance/resistance equivalent circuit representation of the package tha t can be used as a subcircuit in SPICE for simultaneous switching nois e calculations. The model is frequency dependent and captures the Effe ct that multiple solid/meshed ground/power planes, pins, vias and trac es have on overall package inductive performance, The impact of floati ng planes, such as a heat spreader under a ball grid array (BGA) struc ture, on the mutual inductances of the structure is demonstrated. The frequency dependence of the floating plane effects is examined also. T he behavior of the induced eddy currents in the floating plane is inve stigated also, particularly in the vicinity of interconnect discontinu ities. Switching noise results obtained using SPICE simulation and the generated inductance/resistance equivalent package models show the ef fects of floating planes on switching noise.