Shielding RF Circuit Boards
RF signals are everywhere in our lives, from the radios used by drivers on the road to the mobile phones that connect us with family and friends. But RF interference from these devices is not just annoying, it can also cause malfunctions. This is why it’s so important to shield RF circuit boards from unwanted interference from EMI and RFI. Shielding can reduce the size of loop antennas to significantly attenuate the EM energy that could otherwise interfere with signal integrity and performance.
There are a variety of techniques for shielding rf circuit board, including metal boxes, conductive foams, and conductive film. Using the right material for the application is critical, as it should have both high electrical conductivity and magnetic permeability. Typically, copper is used for these applications due to its ability to both absorb and reflect EMI signals.
PCB level EMI shields are often used to control the amplitude of high-threat noise from noisy components like power amplifiers and voltage regulators. But even when this technique is employed, other EMI suppression techniques should be considered, such as grounding and filtering, to keep the overall noise from a system to a minimum.
The “ideal” shield is a continuous conductive box with no openings. However, this is not a practical solution since whatever is inside the shield has inputs and outputs and requires power and ground connections – all of which will leak RF energy unless additional protection is included.
A simpler option is to use an insulating material, such as plastic or FR4, around the circuit board. This is inexpensive and effective for low-threat, low-frequency applications. For higher-threat signals, however, it is necessary to use a more robust solution.
Techniques For Shielding RF Circuit Boards
One such method involves etching a layer of conductive copper onto the insulating material. The copper layers, either solid or cross-hatched, are then linked to the circuit’s ground plane through stitched vias. This solution is more durable than the plastic approach and can be utilized in rigid PCB designs as well as flexible ones.
Another PCB level EMI shielding solution is to use silver ink. Silver ink utilizes selective perforations within the main coverlay to expose the ground or signal layers. This allows a conductive glue to bind through the holes and establish an electrical connection between the ground planes and the signal/ground layers.
For more complex or sensitive applications, it’s possible to use a conductive copper sheet as the entire shielding structure. These structures are more robust than a traditional metal box, but they require that the entire circuit board be in contact with the shield to provide adequate protection.
When choosing a manufacturing partner to design and produce an RF shield for your circuit board, it’s best to work with someone who has experience in the field. They should be able to demonstrate the manufacturability of their products with specific examples from previous projects and customer testimonials. It’s also a good idea to work with partners who can handle more of the process in-house, as this helps to keep costs down and improve quality.