Circuit Board Shielding: An Overview

Circuit Board Shielding: An Overview

Next time when you wonder why your brand-new electronics device is not working up to your expectation, blame it on the faulty design of its printed circuit board (PCB) – the part that mechanically supports and electrically connects its various components. However, poor PCB design is not the only factor to be blamed; electromagnetic interferences (EMI) – a kind of disruptive energy emitted from electronics devices- also play the spoilsport. Wondering how? Well, in a wireless system, almost every wire receives and transmits spurious signals, subsequently degrading the overall performance of your favorite gadget. In addition to a smart PCB design, you will also need the right shielding solutions to optimize the performance of your device. These protective shields are designed to prevent spurious signals from interfering with the electronic system’s operation, subsequently ensuring topnotch performance. Here is a brief overview of circuit board shielding solutions:

EMI Shielding – An Integral Part of PCB Design

Most of today’s wireless devices such as cell phones, tablets or laptops confront the electromagnetic radiations from two sources – the radio frequency (RF) front end that transmits the signal, and the internal digital circuits. Today’s designers are faced with the challenge of creating a circuit board that gives out minimal emissions. Once that is done, the designers have to shield the sensitive parts of the board in order to prevent radiation and to protect it from the exposure of emissions from other portions of the system.

Shield Varieties

Circuit board shields are available in many shapes and sizes. They are made of different types of material, which may range from metals such as stainless steel and tin to conductive foams and metal films. They may take the forms of gaskets, grounding pads, and low DC-resistant shields. Equipped with electrically conductive interfaces, these sophisticated shields can provide maximum shielding effectiveness for some of the most demanding applications including power amplifiers, handheld wireless devices and wireless base stations. For example, metal gaskets are often used to effectively shield as much of the enclosure as possible. They form a conductive barrier and help prevent the EMI from leaking out of the circuit board.

Ideally, an EMI shield should be a sealed container with no openings. However, this is not possible to achieve in real life, as the chips inside the container have inputs and outputs, and are connected to power source. Leaking can occur through these openings, and additional measures have to be taken to prevent this.

Factors Determining Shielding Abilities

The efficacy of shielding solutions depends on three properties of the shielding material – conductivity, permeability, and thickness. The permeability and conductivity of its materials determine the solution’s ability to emit or transmit EMI signals. Airflow and mechanical strength are two other factors that have to be considered while designing shielding solutions. Good quality solutions must have apertures or holes in their structures to allow air to flow through the circuit, helping cut down thermal buildup within the circuits. This helps prevent the wastage of significant amounts of power.

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