A gasket can be defined as a mechanical seal that assists in filling gaps between two or more adjacent components in order to prevent leakage or any form of interference that can make its way through the spaces. Upon hearing the word "gasket," one may immediately think of a gasket within an automotive or industrial setting. However, there are other types of gaskets available. RFI gaskets, which can also be referred to as EMI gaskets, are utilized to reduce radio frequency interference in order to keep electronic devices functioning efficiently. Without the aid of RFI gaskets, electromagnetic and radio waves are able to travel through any gaps or slots in an electrical component or a magnetic shield.
There are numerous industries that utilize RFI gaskets, including aerospace, data communications, automotive, computers, military, network equipment, telecommunications, and medical. RFI gaskets are typically constructed with a rigid surface, and are designed to be as conductive as possible and closely fit the components it protects. In order to accommodate for a variety of components, RFI gaskets can be fabricated into countless configurations using a variety of materials. Each of the configurations in which gaskets are available have their own set of advantages. Several examples are as follows:
Fingerstrip gaskets generally have the largest physical compression range, and are capable of absorbing a wide frequency range. These gaskets are highly versatile in how they can be designed, are highly customizable, and are ideal for high-cycling, frequent-access applications.
Form-in-place gaskets are recommended for applications that require precision fitting. These gaskets can be applied to any metallic, plated, or painted surface that requires environmental sealing in addition to electromagnetic interference. Wire mesh and knitted gaskets can be constructed from metal wires such as aluminum, clad steel, tin-plated copper, and monel. Several advantages of a wire mesh gasket is that they can provide shielding from a broad range of frequencies, are cost effective, resilient, and are available in a broad range of sizes, shapes, and mounting options.
Oriented wire gaskets involve conductive wires that are encompassed by either sponge or solid silicone, and they are capable of providing adequate protection against rain or moisture as well as EMI radiation.
Electrically conductive elastomers are recommended for environmental sealing and EMI shielding, and can be made with a variety of conductive fillers, which include carbon, silver, and passivated aluminum, and elastomers such as silicone rubber, flourosilicone rubber, and ethylene propylene diene momomer (EPDM).
Since RFI gaskets can be made in an overwhelming variety of ways, there are quite a few considerations that must be made in deciding which gasket is appropriate for the desired application. For instance, there are materials that are used to make gaskets that are more sensitive to extreme temperatures than others. For example, a material that has been recently developed to manufacture gaskets is conductive plastic, which is made by adding steel fibers and carbon nanotubes or adding a conductive filler to a plastic in order to make it electrically conductive. Conductive plastic has been proven to be highly advantageous, as it is lighter in weight, more reliable, and more cost-efficient. However, one drawback to the material is that it is highly sensitive to extreme temperatures, and may crack or melt from prolonged exposure.
There are three main steps in evaluating an application to determine the right type of RFI gasket and shielding equipment to use. First, you must determine the source of the interference, which can be external or internal. External interference can come from a source outside the device. Therefore, in addition to gaskets, an enclosure, chamber, or walls may be utilized to protect the device. Internal interference can be generated by components within the device and affect each other. Therefore, the components must be shielded with an enclosure and gaskets to confine the electromagnetic waves they generate. Second, you must determine the interference's location and its magnitude, or strength, as these factors help determine the material of the gasket. You can obtain these measurements by way of field mapping and the use of a tool known as a Gaussmeter and other lab equipment sold in lab kits. The third and final step is calculating the shielding requirements using your data.
The electrical engineers who design these gaskets are required to familiarize themselves with the concepts of electrodynamics such as electromagnetism and the nature of electricity. Understanding radio waves is crucial in deciding the appropriate courses of action to shield a particular device from electromagnetic interference, and has played a pivotal role in the development of RFI shielding technology as we know it today.
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