Electromagnetic radiation has remained a significant challenge for almost all electrical devices,especially those devices with wireless features.Added to this is the latest craze for miniaturization of handsets. This means high frequency components are now crammed into very tight spaces, which in turn shrinks the size of the printed circuit boards (PCBs) required. Therefore, the EMI shielding solutions of today must have a greater capability to perform and suppress radiation from portable devices without adding extra costs due to the increased complexity involved with manufacturing such miniature shields.
In a recent study, when the traditional test methods were applied for understanding the shielding requirements in battery-powered portable wireless designs, some shortcomings were identified. Most of the test methods available today were developed to identify the materials that would comprise an EMI enclosure.However, there remains no formal published test methods to study the shielding effectiveness (SE) of an assembled shield on a PCB of a portable wireless device. Currently, in order to enhance the PCB shielding, two primary approaches are used for cell phones – soldered perforated cans and plated covers with EMI gaskets. It is critical that the portable device performs without interference, and that EMI regulations and standards are maintained.
An EMI shield is essentially a six sided enclosure, consisting of a five-sided metal can (Faraday cage) with the ground plane of the printed circuit board (PCB) being the sixth side.The EMI shield must be placed around and in close proximity to the electronic components on a PCB.This greatly reduces any chances of a RF or EMI leakage. In order to be effective, the design should be lightweight and low cost, and meet mechanical and electrical demands.
Effectiveness of PCB shields in wireless devices can be tested in three ways:
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Compliance testing – evaluating the final product and checking whether it meets the industry-standard test methods as well as acceptance levels
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Functional testing – Evaluating the functionality of the device as set by the manufacturer
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Indirect testing – Characterizing the constituent properties of a shield
Engineers may need to customize features to minimize the shielding impact in portable devices. Phenomenon such as cavity resonance and radiation through apertures should be kept in mind when designing PCB shielding enclosures. If you are looking for circuit board shielding, consider checking out our wide array of products. Contact us for both off-the-shelf and customized EMI solutions.
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