Quantitative Interpretation of Electromagnetic Interference Shielding Efficiency: Is It Really a Wave Absorber or a...

Area of Science:

• Materials Science
• Electromagnetics
• Physics

Background:

• Increasing electromagnetic (EM) pollution necessitates effective electromagnetic interference (EMI) shielding materials.
• Current evaluations often confuse EM wave reflection with absorption, leading to misclassification of materials.
• Shielding effectiveness (SE) metrics, including transmission (SE_T), absorption (SE_A), and reflection (SE_R), are complex and prone to misinterpretation.

Purpose of the Study:

• To differentiate between EM wave reflection and absorption mechanisms in EMI shielding materials.
• To establish a clear criterion for identifying true EM wave-absorbing materials.
• To provide a framework for accurate evaluation and development of EMI shielding solutions.

Main Methods:

• Analysis of the theoretical definitions of EMI shielding effectiveness (SE).
• Derivation of a quantitative condition for absorption-dominant shielding (A > 0.5).
• Establishment of a relationship between SE_R and absorption capability (SE_R < 3.01 dB).

Main Results:

• Many materials reported as EM wave absorbers exhibit over 50% reflection, not absorption.
• A critical threshold of SE_R < 3.01 dB is identified for absorption-dominant EMI shielding.
• A classification system for EMI shielding materials based on their dominant shielding mechanism was developed.

Conclusions:

• Accurate classification of EMI shielding materials requires distinguishing between reflection and absorption.
• The proposed criterion (SE_R < 3.01 dB) enables precise identification of absorption-dominant materials.
• This methodology offers significant insights for the future development of advanced EMI shielding technologies.