Conductive Composition for Low Frequency EMI Shielding
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Solution Overview
Problem
Current EMI shielding solutions, such as metal lids and conformal shielding technologies, fail to provide effective shielding at low frequency ranges (5MHz to 200MHz) while maintaining high frequency shielding effectiveness, and are not suitable for miniature devices due to space constraints and process limitations.
Innovation Solution
A conductive composition comprising a thermoplastic or thermoset resin, a reactive diluent, and a mixture of magnetic and electrically conductive particles, with ≥10% magnetic particles by weight, which provides both high electrical conductivity and magnetic permeability for effective EMI shielding across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal lids or cans are used for EMI shielding, then EMI shielding effectiveness is improved, but device miniaturization and packing density are worsened due to space requirements
Solution Approach 1:
The patent employs a thin-film conductive adhesive composition that can be applied as a conformal coating on package substrates. This replaces bulky metal enclosures with a thin, flexible adhesive layer containing conductive and magnetic fillers, achieving effective EMI shielding while minimizing packaging volume and enabling device miniaturization.
Solution Approach 2:
The patent substitutes the mechanical metal enclosure system with a chemically-based conductive adhesive system. The adhesive forms an electrically and magnetically conductive barrier through chemical composition rather than physical metal structure, eliminating the need for separate metal shielding components and reducing overall device volume.
2Reliability
If sputtering process is used to form metal shield, then EMI shielding effectiveness is improved, but manufacturing productivity and process efficiency are worsened due to vacuum requirements and slow deposition rate
Solution Approach 1:
The patent replaces the physical vapor deposition sputtering process with a chemical-based adhesive application process. The conductive adhesive can be applied using conventional techniques such as screen printing, dispensing, or dip-coating, eliminating the need for vacuum equipment and enabling faster, more scalable manufacturing while maintaining EMI shielding performance.
3Reliability
If plating process is used to form metal shield, then EMI shielding effectiveness is improved, but device complexity and process difficulty are worsened due to multiple steps and masking requirements
Solution Approach 1:
The patent extracts and eliminates the complex multi-step plating process (surface pre-treatment, masking, plating, rinsing, drying) by using a pre-formulated conductive adhesive composition. The adhesive contains all necessary functional components (resin, conductive particles, magnetic particles, solvents) in a single applicatable formulation, reducing the shielding process to a single application and cure step.
Solution Approach 2:
The conductive adhesive composition serves multiple functions simultaneously: it provides electrical conductivity for high frequency shielding, magnetic permeability for low frequency shielding, adhesion to substrates, and conformal coverage capability. This multi-functionality eliminates the need for separate processes for each function, simplifying the overall manufacturing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition achieves EMI shielding effectiveness of ≥20 dB, with volume resistivity <5E-02 ohm·cm and relative magnetic permeability >1.1, suitable for use in miniature devices and applicable through various application methods like spray coating, dispensing, or printing.
Implementation Method 1
the primary mechanism for low frequency (MHz or lower) EMI shielding is adsorption, which is in turn primarily determined by magnetic permeability of a shielding layer
Implementation Method 2
the primary mechanism for high frequency (GHz or higher) EMI shielding is reflection, which is primarily determined by electrical conductivity of shielding layer
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a conductive compositions for low frequency EMI shielding. An EMI shielding composition according to the present invention comprises a resin comprising a thermoplastic resin and/or a thermoset resin, a solvent and/or a reactive diluent and particles, wherein said particles comprise a mixture of magnetic particles and electrically conductive particles or magnetic particles coated with electrically conductive material or a mixture of magnetic particles coated with electrically conductive material and electrically conductive particles and wherein, said composition comprises ≥ 10％magnetic particles by weight, by total weight of the composition. The EMI shielding composition according to the present invention has good electrical and magnetic conductivity and is suitable as a drop-in solution for EMI shielding in a wide frequency range, and especially at low frequency ranges.