(A) toroidal current probe design for analysis of electro-static discharge (ESD) current distribution in multi-layer PCBs

Abstract

Electrostatic discharge (ESD) problems have attracted a lot of attentions in these days because ESDs causes severe damages on chips such as melt of interconnect and junction breakdown. To reduce the damages and protect chips from ESD damages, previous researches introduced chip-level protection methods. However, it is getting more difficult to protect chips from ESD damages because the protection capacity of on-chip ESD circuit is significantly reduced as scaling down of chip technologies. To make up for limitation of on-chip ESD protections, board-level ESD protection is required. In previous researches, bulk current probes or near-filed sensor are used for analysis of ESD current paths. The bulk current probe has been used for sensing ESD currents, however it is difficult to be used when we measure the ESD current generated inside PCBs because the bulk current probe needs additional lines or structures. For a specialized ESD current detection, We propose a novel toroidal current probe embedded in multi-layer printed circuit boards (PCBs) for electrostatic discharge (ESD) detection. The proposed current probe adopts toroidal coil concept. Toroidal coil is implemented by through-hole via array and transmission lines. The proposed current probe consists of an inner via-array, bridge lines, and an outer via-array, which surround an ESD current path and form a toroidal to detect an ESD current. It captures magnetic field generated from ESD current flowing at the center via. The captured magnetic field is measured as a form of voltage and converted to the current through a simple math operation. A transfer impedance between a port injected an ESD current and the proposed current probe is used for analysis of an ESD current coupling. Through experimental measurements, we verified the proposed current probe by comparison with a conventional current probe. By embedded in PCB, the proposed current probe can provides accurate and high reproducible measurement. Further...