6 EMI Shielding Tips and Tricks

Posted by Irene Simpson on November 30th, 2017

Electromagnetic interference (EMI) poses a threat to the electronics industry. Disruption of electronic devices and equipment can cause anything from temporary disturbances to system failures and data losses. And with global electronic usage increasing rapidly, manufacturers are doing their best to come up with valuable solutions. This explains why one should take EMI shielding seriously. Below are a few tricks that engineers use to integrate suitable shielding in electronics systems:

1. Surface Treatment

At the fundamental level, shielding is all about creating a conductive layer that surrounds the object to be shielded. Known as a Faraday Cage, this system is quite effective against interruptions. Unfortunately, it is not resistant to the effects of corrosion and oxidization. And that is where surface treatment comes into the picture. It is only by painting or plating the metal enclosure and finishing flange surfaces can an engineer ward off corrosion. But here’s the catch: most manufacturers stop at a single coat. It could be due to budgetary constraints or a tight production schedule – irrespective of the reason, it leaves the system vulnerable to corrosion in marine or high-humidity environments. You need to add an additional coat to bypass this threat.

2. Material Thickness

Whether a particular frequency is blocked an entry or exit from a Faraday cage depends upon both thickness and material.  For example, low frequencies of 10 kHz or less can be rebuffed by up to 80 dB using a mild steel layer of 6 mm while a 30 MHz frequency requires only a 0.03 mm ultra-thin copper foil.

On the other hand, very low frequencies and direct current have a more dominant magnetic field, thereby requiring something more than thick layers. This ‘something’ is a special material like Mu-ferro alloys or HyMu 80. Plus, combinations of multiple layers may be necessary to achieve the right amount of shielding performance. So, material thickness plays a prominent role in the outcome.

3. Wires

If a wire penetrates a shielding that is not wholly connected to the shield, it acts as an antenna, reducing the shielding performance of a Faraday cage. This holds true even more in the case of higher frequencies.

4. Cost-Efficiency

What if a certain electronics manufacturer wants to implement shielding for its products but lacks a huge budget? Should they forego shielding? There is an alternative – shielding at the source. This is a more cost-effective method that involves the use of a can to shield the component(s) on the printed circuit board. The application of shielding minimizes radiation directly at the source.

5. EMI Gasket

The right EMI gasket is capable of minimizing the difference in electrochemical potential relative to the structural metal, thereby ensuring a lower galvanic current and slowing down corrosive effects. Plus, the component affects EMI shielding performance as well. That’s why the selection of the correct EMI gasket is so important. Ideally, designers should opt for an elastomeric EMI gasket that contains conductive filler particles. When such a component comes in contact with metal, it provides both EMI shielding and corrosion resistance. Some of the suitable shielding materials include silver-plated copper, nickel-plated aluminum, silver-plated aluminum, and pure silver.

6. Shielded Door

The closing force of a Faraday cage is an important factor that determines how easily a shielded door can be opened using one’s hands. And unless the door is opened, any problems with the vent panels, housing, windows, or entry panels cannot be fixed. Ultra-soft gaskets limit the closing force and bending of the door. Moreover, for a gasket to have the right degree of stability, the width of the piece must be more than its height. High-closure force can be avoided by using V-shaped gaskets that clamp the door in the direction opposite to the opening. Thus, the closing force is the sole friction force.

Electronics engineers put in a lot of thought towards EMI shielding. As new technology becomes more widespread, the need for shielding increases considerably. Thus, designers must resort to advanced techniques to ensure the products are suitably resistant to interference.