Susceptibility Scanning as a Failure Analysis Tool for System-Level Electrostatic Discharge (ESD) Problems

Susceptibility scanning is an increasingly adopted method for root cause analysis of system-level immunity sensitivities. It allows localizing affected nets and integrated circuits (ICs). Further, it can be used to compare the immunity of functionally identical or similar ICs or circuit boards. This paper explains the methodology as applied to electrostatic discharge and provides examples of scan maps and signals probed during immunity scanning. Limitations of present immunity analysis methods are discussed.

I. Introduction

Near-Field electromagnetic interference (EMI) scanning techniques have been used for analyzing the fields above integrated circuits (ICs). The collection of near-field measuring data [6] is motivated by the desire to predict or analyze the EMI from electronic systems or to reconstruct the currents that flow from the IC or through its lead frame. Using near-field probing—as an injection tool—is a direct extension of the near-field scanning emission measurements mentioned before. However, a set of important differences need to be considered to successfully apply near-field scanning as a tool for analyzing immunity. Three important challenges need to be understood: 1) The scanning system needs feedback from the equipment under test (EUT) to recognize if a malfunction or degradation has occurred. 2) EMI scanning measures the field strength at a given frequency. However, in immunity testing, a wide variety of different noise types can be introduced during the scanning; thus, the user needs to determine the most appropriate type of noise. 3) The relationship between the setting of the disturbance source strength and the noise caused during a system test is highly complex; thus, it is difficult, and sometimes impossible, to directly relate system-level test results to local scanning results.