Measurement of Via Currents in Printed Circuit Boards Using Inductive Loops

Understanding the AC current flowing through BGA package pins is critical to create accurate models of the power distribution network. We show that these currents can be experimentally measured by inserting small induction loops next to the vias carrying the pin currents. Small induction loops were constructed which gave a measurement upper cutoff frequency of 2 GHz, and a sensitivity of about 0.14 mV/mA/ns This system allowed us to measure currents with an average accuracy of about 10% and a dI/dt as small as 6 muA/ns with averaging when measuring calibrated test structures