Detecting counterfeit electronic circuits: the effect of PCB thickness and dielectric permittivity on the electromagnetic fingerprint

Printed circuit boards (PCBs) are essential in electronic systems, providing mechanical stability and electrical connectivity. Their selection must align with the mission profile to ensure longevity and resistance to environmental degradation. In critical applications, unexpected variations in PCB characteristics can compromise system reliability. Counterfeit PCBs pose significant risks, potentially leading to failures and system outages. The globalization of the supply chain has increased PCB vulnerability to counterfeiting, which includes cloning, over-producing, refurbishing used boards, illegally repurposing rejected PCBs, and tampering for malicious purposes. Current detection techniques often focus on verifying key electronic components rather than the bare PCB, and therefore do not allow for detecting whether genuine components are mounted on a counterfeit PCB. Many inspection methods require direct access to the PCB, whereas nondestructive approaches offer clear advantages. A promising nondestructive technique involves analyzing the electromagnetic (EM) fingerprint of integrated circuits (ICs) and boards. EM emissions depend on factors such as clock frequency, circuit architecture, and material properties. Any deviation in these parameters may indicate counterfeit activity. This study investigates how variations in PCB substrate thickness and dielectric permittivity affect near-field EM emissions. Using a low-power microcontroller mounted on custom-designed PCBs fabricated using different substrates, we explore how these variations can be detected, providing a reliable and noninvasive method that constitutes a valuable support for identifying counterfeit PCBs.