RF Shielding
Radiofrequency (RF) shielding is the practice of blocking radiofrequency electromagnetic signals that cause radio frequency interference (RFI). The use of RF shielding is a measure to safeguard our devices and equipment from the harmful effects brought by RFI.
Kristeel shields are used in various industries including:
- Military and Aerospace
- Electronic Industries
- Medical Applications
- White Goods
- Telecommunications
- Office Automation
- Train control and propulsion systems
Popular Metals Used in RFI Shielding
- The most common metals used by Leader Tech customers for RFI/EMI shielding are pre-tin-plated steel in both bright and matte finishes and copper alloys, known as nickel silver or German silver.
- For development stages to reduce customer initial costs, Kristeel offers RF shields with optional temporary bending fixtures at a lower cost. Bending tools for the production stage are also available.
- Here is a quick look at how each one of them works:
Tin-Plated Steel
Tin-plated or pre-tin-plated steel is an ideal low-cost solution that works well from lower frequencies in the kHz range through frequencies into the lower GHz range. Carbon steel has a permeability value in the lower hundreds range, providing the low-frequency magnetic shielding property missing in alloy 770, copper, or aluminum. Tin plating offers corrosion protection for the steel to prevent rusting and provides a solderable surface to attach the shield to the traces on the surface board during assembly. This is used when large quantities are required, and the process used is blanking.
Nickel Silver – Commercial, Copper Alloy 770, 752, 757:
Commercial-grade nickel silver is a widely used metal for RF shields. Copper alloys, also known as alloys of copper, nickel, and zinc, are used in EMI shielding applications mainly for their corrosion-resistant properties. The base material is inherently aesthetic and does not require post-plating to make it corrosion-resistant or solderable. The material works well as an EMI shield from the mid-kHz range up into the GHz. The permeability is 1, making it ideal in MRI-related applications where no magnetic materials are permitted. Commercial nickel silver is also used widely in the industry for prototype and production. The process used is Photo Chemical Machining (PCM) for quantities up to 50,000 units, and for large quantities, a press tool is recommended.
Copper and Brass:
Copper is the most reliable metal in EMI shielding because it is highly effective in attenuating magnetic and electrical waves. From hospital MRI facilities to basic computer equipment, the use of copper in RFI shielding serves the purpose effectively. Due to the versatility of this metal, it can be easily fabricated along with its alloys brass, phosphorous bronze, and beryllium copper. These metals typically cost more than the alternative shielding alloys of pre-tin-plated steel or copper alloy 770 but, on the other hand, offer higher conductivity. Phosphorous bronze and beryllium copper are more commonly used in contact applications for batteries or springs due to their elasticity. Brass with tin plating is economical for both prototypes and production use.
Aluminium:
Although aluminum poses a few fabrication challenges, it is still an excellent choice for several applications, mostly due to its non-ferrous properties, its strength-to-weight ratio, and its high conductivity. Aluminum has nearly 60 percent of conductivity when compared with copper. However, using this metal requires precise attention to its galvanic corrosion and oxidation properties. The material will form into an oxide over time and has poor solderability on its own.
