PCB Shields: Types, Materials, and Benefits
Many electronic circuits require protection from electromagnetic interference. Without protection, they can suffer unusual issues leading to degradation of performance and even failure. Electromagnetic interference may also affect sensitive electronic components. For these reasons, Rush PCB UK suggests installing PCB shields onto printed circuit boards. This technology ensures the safety and longevity of the circuit board by blocking most types of radiation. This article deals with the type of PCB shields available and their benefits.
What are PCB Shields
Shielding for electromagnetic interference typically protects sensitive circuits and components from external electromagnetic signals. It also ensures that signals generated internally do not escape and disturb neighboring circuits and components. Some electromagnetic frequencies may interrupt a safety-critical signal or disturb a communication line. Typically, such safeguards work well with sensitive components, including ICs and interconnecting wires on PCBs. The shielding feature, therefore, prevents signal degradation, disruption, data corruption, component failure, and software defects in circuits and components on PCBs.
RF PCB Shields
Effective RF shielding typically blocks radio frequencies and electromagnetic radiation by reducing the coupling between electromagnetic fields and radio waves. These shields behave as Faraday cages, impeding electrostatic fields also.
Types of PCB Shields
Many types of shielding materials are available in the market, providing practical and straightforward solutions. Although traditional methods involving good layout practices and filters do help in reducing EMI/EMC issues, but may not be effective. To improve the situation, designers typically use:
Shielding cans: Typically made of metals, these custom-made shield boxes surround noise-generating circuits, thereby restricting electromagnetic radiation.
Electromagnetic Shielding Materials: These are elastomer materials applied to special components to limit electromagnetic radiation.
Ferrite beads, plates, and rods: Most ferrite beads, plates, and rods behave like EMI filters.
Mesh Materials: Rather than using rigid shielding cans, these flexible high-conductivity materials are useful for flexible and rigid-flex boards.
Uniform Ground Planes: These grounding planes can supply several grounding points while allowing the grounding of conductive shielding materials.
Combining shielding along with following best practices for PCB layouts can allow designs to pass EMI/EMC tests.
PCB Shield Materials
PCB shields are made from various ferromagnetic metals. The most popular are:
- Tin-Plated Phosphor Bronze
- Stainless Steel
- Nickel Silver
- Tin-Plated Copper
- Tin-Plated Cold Rolled Steel
For shielding electromagnetic waves below 100 MHz, tin-plated steel is the most recommended by Rush PCB UK. For shielding from signals higher than 200 MHz, tin-plated copper is a better choice. Tin plating on the shield material makes it easier to ground it by soldering to the PCB. Aluminum is not ferromagnetic and is not useful as a shielding material.
Benefits of PCB Shields
Using PCB shields on printed circuit boards offers many benefits. Apart from protection from EMI/EMC, these shields offer benefits like:
- Unlimited design possibilities
- Variable Footprints
- Surface mount or through hole
- Configuration can be low-profile
- Multi-cavity patterns
- Double security—cover and fence
- Input/Output holes
- Cutouts for connectors
- Ventilation holes
- Removable for easy access
- RF absorbers for extended shielding
- Protection against shock and vibration through a secure lock mechanism
- Insulation padding
- ESD protection
Read About: What are Optical Printed Circuit Boards?
Custom circuits can have the necessary protection with PCB shields. However, the designer must ensure that the circuit meets its requirements with the shield in place. They have the freedom to use a special material that works best for a specified frequency range. With RF shields, it is possible to block out unwanted radio frequencies and electromagnetic radiation. Various affordable materials for PCB shields are available in the market.