Electronic devices are a part of everyday life and hence it is essential that they have good quality PCBAs incorporated within for proper functioning. Often at device as well as PCB level, signals in the form of electromagnetic waves mix up which creates noise and may alter the functioning of the device. This interference must be removed. There are various techniques and solutions used to mitigate EMI such as board level shields which are be used to retain these waves within so that they do not interfere. With these solutions, electromagnetic interference as well as radio frequency interference can be controlled through either EMI filtering or board level shielding both of which are helpful in curbing EMI and RFI. This post discusses the differences between EMI filtering and board level shielding and also throws light on electromagnetic compatibility (EMC).
What is EMI Filtering?
These are devices featuring circuit boards, which comprise capacitors and inductors that are connected to the circuits. Through filters, EMI can be diverted and grounded, thus preventing any damage to the device. These inductors allow low frequency currents to permeate through while restricting the unnecessary and high frequency ones. Usually, EMI filters are useful for a frequency range of 9KHz to 30MHz. Beyond this range, shielding becomes essential. EMI filters are of two types.
- Active filters: This one has active components which detect and amplify EMI from the transformer and send the selected signals back after filtering.
- Passive filters: These do not have any circuit controlling components and hence are cost effective. They comprise capacitors and inductors which filter the unnecessary signals.
What Are Board Level Shields?
Board level shields are EMI shields which cover the printed circuit board in such a way that it restricts signals inside to prevent noise. Such boards and shields must be designed with a lot of thought pertaining to heat dissipation, ventilation, grounding connections, and so on. Shields are used for mitigating high frequency range signals. The good part is some types of EMI shields also work as heat sinks. Shields come in various thicknesses and can be custom made depending on the noise and heat generation requirements of the application. Plasticized metals are now used in constructing these shields as they reduce the weight and are flexible and easy to remove. These are non-conductive materials on the inside which help balance magnetic and dielectric permeability, conductivity, as well as physical stability.
What is EMC?
EMC stands for electromagnetic compatibility and is a standard designed for devices to be able to function in an EMI environment, without any issues. Shielding boards helps achieve EMC for most applications.
Differences Between EMI Filtering and Board Level Shielding
While EMI filters are helpful in controlling EMI, board level shielding is typically used for high frequency applications. At times, a combination of filters and shields may be used. Here are some differentiating pointers.
- Filters eliminate internal as well as external EMI with the help of conductors and other related tools. Shields mitigate EMI through air. They also protect the board against compatibility issues.
- A combination of filters and shields may be used to increase heat dissipation through the shield holes. However, shields can also act as a heat sink.
- Shields are especially useful for compact boards with multiple components and complex circuitry. These boards are much in demand owing to the miniature size of devices. These are multi-cavity board level shields which can be removed and fitted again easily in case of board inspection, solder reflow, and so on.
- These shields can fit the board of any size, shape, surface, and more.
- With such advanced shields available now, filters may not be required in at least some applications.
If you are an OEM or a PCB manufacturer, you would require good quality EMI shields for your boards. Ensure you partner with an expert player specializing in the design and manufacture of board level shields which resolve all the associated challenges. Also, these devices need to meet EMI regulation standards. XGR Technologies offers SnapShot ® EMI Shields that assures excellent shielding effectiveness from below 1 GHz to 12 GHz. They offer consistent isolation across a wide frequency range. These shields are made of plasticized metal and hence are flexible, lightweight, and can be removed and reinstalled easily. The shields have non-conductive interior surface which reduces electromagnetic coupling with traces of the circuit, thus increasing safety, efficiency, and device functionality. You can contact XGR Technologies team today to know more about these EMI shields or share your requirements.
