The Ultimate Guide to EMI/RFI Shielding

When it comes to performance in aerospace and defense systems, properly protecting against  electromagnetic interference (EMI) and radio frequency interference (RFI) is critically important. During material selection, engineers must balance EMI/RFI performance requirements with physical, chemical, and mechanical properties to find the best option for a given application.

In this resource, you’ll find optical coverage and transfer impedance guidance, material selection matrices, and a quick-selection checklist to help you determine the best EMI/RFI shielding for your application.

EMI vs. RFI at a Glance

Factor	EMI	RFI
Frequency Range	Entire EM spectrum	20 kHz – 300 GHz
Common Sources	Motors, power converters, lightning	Radios, radar, wireless devices
Typical Impact	Signal corruption, equipment malfunction	Data loss, communication disruption
Best Shielding Types	Braided sleeves, solid enclosures	Foil, coated fabrics

How EMI/RFI Shielding Works

Shielding materials prevent interference through:

• Reflection – Conductive surfaces bounce EM waves away.
  
  
• Absorption – Magnetic materials convert EM energy into harmless heat.
  
  
• Grounding – Safely routes unwanted currents to earth or chassis ground.
  
  

Optical Coverage & Transfer Impedance: Key Metrics for EMI/RFI Shielding

In braided cable shielding, optical coverage is the percentage of the underlying cable or component surface that is physically covered by the braid. It’s calculated using the braid’s weave angle, wire diameter, and spacing, collectively known as the fill factor.

The higher the optical coverage, the fewer gaps in the shield, which improves its ability to reflect and absorb electromagnetic waves. For example, a braid with 95% optical coverage provides denser EMI protection than one with 85%, making it a better choice for high-security communications or avionics where signal integrity is critical.

The optical coverage required varies for different applications:

• Avionics/sensitive comms: 90–95%
  
  
• General aircraft harness: 85–90%
  
  
• High-flex UAV routing: 80–88% 

Optical coverage is typically your first checkpoint when comparing shielding options but another metric that’s even more important in determining the right EMI/RFI shield for your application is transfer impedance, a topic so important we wrote a whole separate article about it that you can check out here: Selecting Shielded Cables: Why Transfer Impedance Matters

Shielding Material Selection Matrix

Material	Conductivity	Weight	Corrosion Resistance	Flexibility	Ideal For
Tin-Plated Copper (e.g., Roundit EMI DW Cu/Sn)	Excellent	Medium	Good	Medium	High EMI attenuation, aerospace harnesses, data cables
Nickel-Plated Copper (e.g., Roundit EMI DW, Roundit EMI FMJ, FMJ Space)	Very Good	Medium	Excellent	Medium	Harsh environments, high-temp EMI applications, aerospace & defense
316L Stainless Steel (e.g., Roundit 2000 S EMI)	Good	Heavy	Excellent	Low	Corrosive environments, marine, rail, industrial
Tinned Copper + Polyester (e.g., Roundit 2000 Cu EMI, Cu EMI D)	Good	Light-Medium	Good	High	Balanced EMI protection + flexibility for automotive & telecom
PPS/Nomex Hybrid with Metal Braid (e.g., Roundit NP EMI, Roundit 2000 NX EMI A/B)	Good	Light-Medium	Excellent	Medium-High	Mechanical + EMI protection, oil and water resistance

Choosing the Right Shielding Type

When selecting EMI shielding, it’s not just about blocking interference, other functional needs matter too.

Your shielding can also provide mechanical and abrasion protection when designed with the right materials and construction. Features to consider include:

Feature	Why It Matters	Options Available
PTFE Layers	Prevents direct contact between the braid and component, reducing abrasion and adding dielectric insulation.	Ideal for harnesses routed through vibration-prone areas.
Weight & EMI Optimization	Balances shielding effectiveness with total system mass—critical for aerospace and UAV applications.	Choose braid density and material for optimal trade-off.
ASTM B-355 Tracers	Identifies the class of metal used in the braid for faster maintenance and compliance checks.	Standard tracers for tinned copper, nickel-plated copper, etc.

Quick Selection Checklist

The following checklist contains the most important questions to answer before ordering EMI/RFI shielding for your application.

• What frequency range are you protecting against?
  
  
• Are weight restrictions a significant factor?
  
  
• Is the application in a harsh environment?
  
  
• Will the shielding need to flex with movement?
  
  
• Are there compliance standards (e.g., MIL-STD, AS9100 Rev D, ISO 9001:2015) to meet?
  
  

Let Titan Be Your Source for EMI/RFI Shielding

Shop our extensive range of EMI shielding products for physical and electromagnetic interference protection or contact us today to speak with one of our product specialists for assistance finding the right EMI/RFI shielding solution for your application.

About The Author

Joe Wigginton is a seasoned Sales Manager with a rich background in the aerospace and defense industries. With over 20 years of experience in the cable and cable protection sector, Joe initially served as a manufacturers' representative for 5 years before taking the entrepreneurial route. For the past 15 years, he has successfully owned and operated a business dedicated to supporting customers with top-quality products and solutions.

Beyond his professional achievements, Joe has traveled extensively worldwide to forge meaningful relationships and source the best products to meet our customers' needs. His global perspective and commitment to excellence make him a valuable asset to our team and clients alike.