Electromagnetic Interference (EMI) of System-on-Package (SOP)

TLDR

Electromagnetic interference is a critical concern for next‑generation system‑on‑package designs, where high‑performance digital LSIs generate EMI that can impair nearby RF and analog circuits. The paper outlines key EMI aspects in SOPs—die/package and substrate levels, electromagnetic modeling and simulation, and near‑field measurement—and aims to guide designers in incorporating EMI mitigation. It examines LSI radiated emission sources such as signal‑return loops and switching currents, substrate coupling paths, return‑current path design, DC bus resonance suppression, and presents simulation and near‑field measurement techniques to validate EMI‑free designs.

Abstract

Electromagnetic interference (EMI) issues are expected to be crucial for next-generation system-on-package (SOP) integrated high-performance digital LSIs and for radio frequency (RF) and analog circuits. Ordinarily in SOPs, high-performance digital LSIs are sources of EMI, while RF and analog circuits are affected by EMI (victims). This paper describes the following aspects of EMI in SOPs: 1) die/package-level EMI; 2) substrate-level EMI; 3) electromagnetic modeling and simulation; and 4) near electromagnetic field measurement. First, LSI designs are discussed with regard to radiated emission. The signal-return path loop and switching current in the power/ground line are inherent sources of EMI. The EMI of substrate, which work as coupling paths or unwanted antennas, is described. Maintaining the return current path is an important aspect of substrate design for suppressing EMI and for maintaining signal integrity (SI). In addition, isolating and suppressing the resonance of the DC power bus in a substrate is another important design aspect for EMI and for power integrity (PI). Various electromagnetic simulation methodologies are introduced as indispensable design tools for achieving high-performance SOPs without EMI problems. Measurement techniques for near electric and magnetic fields are explained, as they are necessary to confirm the appropriateness of designs and to investigate the causes of EMI problems. This paper is expected to be useful in the design and development of SOPs that take EMI into consideration.