Near-Field Shielding Analysis of Conformal Coating Materials for Integrated Circuits

This article analyzes a near-field shielding performance of conformal shielding materials for integrated-circuits (ICs) by experiments. Two test boards with loop-type and patch-type patterns are designed to generate magnetic-field and electric-field, respectively. These sources mimic typical electromagnetic radiations from actual ICs. For shielding analysis, single-layered conductive materials, multilayered conductive and magnetic materials, hybrid materials with a mixture of conductive and magnetic pastes are considered as conformal shielding materials, which are coated on the test boards for measurements. Magnetic-field and electric-field shielding effectiveness (SE) of the materials evaluate by measurements using loop-probe, strip-line, and gigahertz transverse electromagnetic cell at the frequency range from 300 kHz to 3 GHz. Near-field SEs measured by three methods correspond generally well with each other at the frequency range up to a few hundred MHz. At the higher frequency, the ambient EM environment can affect the accuracy of the near-field measurements by the loop-probe and strip-line. For validation, numerical simulation is fulfilled and compared with measured results. Theoretical interpretation based on the Schelkunoff's SE decomposition is also addressed.