Tech Updates

Why and How to Use Cans for EMI Shielding on Your PCB

As you know, every electronic device produces some unwanted electromagnetic energy that can interfere with the operation of other nearby electronic equipment. As such to prevent both ingress and egress of electromagnetic energy, EMI shielding plays a vital role. Shielding is, in fact, the most common technique for controlling EMI radiations as the metal enclosures help keep harmful interference out and also unwanted emissions inside the equipment.

There are highly sensitive electronic circuits which need optimal protection against unwanted electromagnetic and radio frequency interference (EMI and RFI). This is because for the proper functioning of your PCB design, putting off electromagnetic interference is crucial. As such, ‘can shields’ are used to isolate sensitive components. The metal shields or ‘cans’ are mounted directly to the PCB to completely cover the required circuitry. PCB shielding cans are simple metal boxes that are easily soldered in place for tackling EMC problems. To prevent components from emissions, these shielding cans are applied selectively to the problem areas of a circuit.

What is a shield can?

EMI can shields are basically metal boxes that are attached to your PCB to enclose part of the circuitry on the surface. The purpose of the can is to prevent EMI from entering or leaving the covered region. Also known as cans, cages, covers, or lids, these are available in different metals. Depending on your application and budget, it is important to choose the right material for your shield can. Typically, available can materials include steel, aluminum, silver, brass, copper alloys, nickel, and tin plated plastic.

The right shield for your application is one that completely encapsulates your components. However, this doesn’t provide any option for inputs and outputs, or power and grounding. When you need to eliminate chances of can leakages, there is an option to provide additional shielding with gaskets, mesh, and films. To ensure proper thermal management, some can shield are also designed with a grid of holes in the metal.

Why you need a Shield Can

If your application requires putting a barrier to components against EMI that might occur on the PCB, shielding can is for you. The RF output, or inputs and amplifier stages in a circuit are most likely to be affected by/cause Electromagnetic Interference. As such, shielding the RF module and amplifier to isolate them from other noise in the circuit is a good option. Moreover, high-speed components like oscillators can also be shielded to avoid producing interference across the board.

In the process of designing a PCB, the step of good board design for EMI management should be followed by shielding. While designing your board, steps should be taken to minimize emissions such as short traces, proper grounding, and component placement to curtail emissions.

How to integrate can into the design

It is important to know how to properly integrate shield can into your design. This might be somewhat complex because manufacturers only provide external dimensions and you require information about internal clearance so that it fits around your components. Thus, first, you need to identify the components or subassemblies that need to be shielded. Next, determine the shield size you need and make sure your can has enough clearance for the components it’s shielding.

Once you have the right can for your application, it’s time to attach the can to the board. For doing this, adding solder pads around the intended components on your PCB is one option. Another way is using clips or frames to hold the can onto the PCB. It is better to attach shield or clips during automated fabrication processes by soldering the shield to surface mount pads. It is also possible to get custom-made PCB shields when a non-standard area needs to be shielded.