Connectors link multiple electronic components to transmit power and signals across one or many systems. This article details key connector design considerations, focusing on mitigating electromagnetic interference (EMI) and radio frequency interference (RFI). It also reviews criteria for selecting EMI/RFI-resistant connectors, discusses compliance and standards, and offers technical tips for testing and maintaining shielding.
Exploring the effects of EMI/RFI
EMI/RFI originate from various sources, such as internal system operations, transmission lines and towers, and atmospheric disturbances. Unprotected electronic systems may experience signal distortion or corrupt data transmissions, leading to critical malfunctions and even permanent failure. Essential for high-risk EMI/RFI environments, shielded connectors rely on metallic enclosures to significantly reduce or eliminate these risks.
To ensure a system-wide EMI/RFI-resistant design approach, key factors — such as material composition, shielding, and deployment scenarios — should be carefully assessed when selecting a connector.
Connector shielding: from gold to copper
Effective EMI/RFI connector shielding hinges on its metallic composition; these compositions can include:
- Gold: delivers the highest standard in electrical conduction and corrosion resistance for medical devices, precision instruments, and satellite communications.
- Zinc-nickel alloys provide extensive frequency shielding and corrosion resistance for aerospace, military, and marine electronics.
- Aluminum and stainless steel offer robust shielding to withstand challenging automotive and industrial environments.
- Nickel: contributes toughness and durability, which are essential for connectors in construction and industrial applications.
- Copper: targets telecommunications and computing, maintaining signal integrity with high electrical conductivity.
- Tin: is a basic and cost-effective shielding option in many consumer devices.
Adding a conductive layer to connector shielding
Plating adds a conductive layer to connector shielding — improving electrical performance and preventing corrosion. Although gold plating is common in high-frequency connectors for communication systems, medical imaging, and aerospace applications, other metals, such as nickel and copper, are used in less demanding scenarios to balance durability and cost.
Beyond shielding and plating, ensuring a streamlined and integrated design is essential for EMI/RFI-resistant connectors. For example, smooth, rounded connectors boost grounding capabilities and minimize signal leakage, while precise engineering of pin arrangement and enclosure configuration bolsters overall electromagnetic compatibility and accelerates system integration.
Backshells, which add mechanical strength and extra shielding, are another key design aspect of EMI/RFI-resistant connectors. Bolstering resistance to environmental stressors and electromagnetic interference, backshells incorporate cable management and strain relief. Equipped with multicore cables that feature braided metal sheathes, environmental backshells often adopt circular form factors and offer additional grounding measures. Meanwhile, high-performance backshell designs for military applications provide extra protection against water, sand, and shock.
Advanced shielding solutions for aerospace and defense
EMI/RFI poses a clear and present danger to mission-critical systems such as communication devices, radar, and avionics controls in the aerospace and defense sectors. Many military-grade EMI/RFI-resistant connectors feature integrated connector shields and black zinc nickel plating to safeguard these systems.
Moreover, advanced filtering techniques, such as chip-on-flex (CoF) technology and sophisticated cable assemblies, establish multiple layers of defense against EMI/RFI to ensure system integrity.
Choosing an EMI/RFI-resistant connector
EMI/RFI-resistant connector selection includes a comprehensive analysis of where and how it will be used, including:
- System design and layout: space limitations influence connector size and shape. In low EMI/RFI risk areas, simpler connectors suffice.
- Application and frequency: detailed power and signal analysis help match connector specifications with system frequency and shielding requirements.
- Exposure to corrosives and stress: material and coating choices are made after determining resistance to environmental wear.
- Backshell and plating: high-risk environments require sturdy backshells for additional protection and shielding, while plating options are selected for their balance of conductivity, resilience, and cost.
- Electrical specifications: accurately assessing current carrying capacity, voltage rating, and insulation properties ensures performance and safety.
Testing and verifying EMI/RFI-resistance compliance
After selecting connectors based on the outlined criteria, system designers should conduct EMI/RFI shielding tests to verify adherence to widely adopted industry standards formulated by organizations such as the International Special Committee on Radio Interference (CISPR) and the Institute of Electrical and Electronics Engineers (IEEE).
Design validation and testing involve laboratory signal analysis and environmental and operational stress evaluations. Notably, real-world compliance assessments help determine filter selection by highlighting optimal design options that minimize interference while ensuring signal flow.
Maintaining and optimizing shielding
Routine maintenance of EMI/RFI-resistant connectors, such as impedance assessments, visual inspections, and continuity checks, helps ensure structural integrity and prevent signal disruption. However, additional in-field assessments are crucial to proactively detect and correct vulnerabilities, ranging from loosened connections and corroded contacts to compromised insulation materials. This process involves meticulously examining connectors for defects that could lead to shielding deterioration and early replacement.
Summary
Connectors facilitate the seamless signals and power transmission between different components and systems. When designing or selecting EMI/RFI-resistant connectors, engineers should carefully consider metal shielding and plating composition, conduct a thorough analysis of where and how they will be used, and perform rigorous testing to ensure compliance with CISPR and IEEE standards.
References
Design Considerations of EMI Resistant Connectors, Electronic Specifier
A Basic Overview of RF/EMI Filters and Filtered Connectors, In Compliance Magazine
Factors to Consider When Selecting Shielded vs Unshielded Electrical Connectors, Energy5
Key Considerations When Selecting a Connector Solution, TechBriefs
Discover High-Performance EMI/RFI Shielding & Cable Assemblies, PEI-Genesis
Use Shielded Connectors to Achieve Reliable High-Speed Connectivity in Dense, Compact Form Factors, DigiKey
How to Deliver a Reliable Connector Design, NewElectronics
Three Key Considerations When Selecting EMI/RFI Shielding Solutions for Aerospace and Defense Applications, Connector Supplier
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