EMI Noise, Part 5: EMI Suppression for Harsh Environments

Components utilized in harsh environment applications are typically subjected to excess mechanical stress, extremely hot or cold temperatures, the increased potential for electrostatic discharge, and/or high levels of radiation. As such, these components are manufactured with materials that are able to handle high temperature variations, and feature mechanically robust constructions. Dielectrics like ceramic NP0/C0G, for example, are able to handle temperatures up to 150o C with no change in capacitance, but lack the high dielectric constant required to make high capacitance devices. As a result of this limitation, dielectrics with higher constants, like X8R, have been developed to extend the temperature range of typical X7R dielectrics beyond their usual125o C limit. In fact, dielectrics that can withstand temperatures up to 250o C are already available, and dielectrics for applications with operating temperatures up to and beyond 300o C are currently being developed by several capacitor and filter manufacturers.

To meet extremely wide bandwidth filtering requirements in the exceptionally harsh space, military, and down-hole drilling industries, customers require high performance EMI filters with increased mechanical robustness and thermal performance custom tailored to the specifications of their application. For instance, components utilized in space applications must endure extreme temperature variations and effects like whiskering in tin terminations, and may also experience high levels of mechanical stress during a rocket’s takeoff and while in flight. Consequently, EMI filters designed for use in space applications typically feature high temperature dielectrics, lead or other alternate material terminations (to avoid whiskering), and especially robust mechanical constructions.

Figure 1

AVX high reliability SMPS capacitors

AVX high reliability SMPS capacitors

Similarly, down-hole drilling applications, like deep oil exploration, also expose components to extremely high thermal and mechanical stresses. These applications typically require leaded components that are designed and manufactured with high temperature dielectrics, unless circuit board miniaturization is a priority, in which case high temperature surface mount components are often employed. Additionally, due to the fact that specialized components for down-hole and other harsh environment applications are subjected to hundreds to thousands of temperature cycles and hundreds of hours of mechanical stress testing to ensure that they reliably perform to customer specifications, the qualification process can span weeks to months.

Military applications also employ specialized EMI filters designed to withstand harsh environments in various air, space, ground, and sea systems (e.g., jets, helicopters, missile and satellite systems, Humvees, tanks, handheld radios, submarines, aircraft carriers, and destroyer ships, among others). Regardless of what function they perform and where they’re deployed, today’s military systems employ an enormous number of highly sophisticated (and often top secret) electronic systems to improve performance and efficiency and reduce casualties in the battlefield. As such, these systems require extremely robust EMI filtering components tested and qualified to several military standards in addition to customer specifications to eliminate the risk of failure during normal operation.

Although qualification for such parts can be time-consuming, various EMI filtering component technologies designed to effectively protect against electrical noise in these and other extremely harsh environment applications are available from a host of suppliers. For more information about filtering components capable of handling high levels of electrical and physical stress — such as high reliability EMI filters constructed using discoidal capacitors inside a tubular sleeve and inductive elements used to create several different filter topologies (e.g., Tee, pi, and LC circuits) — please review the fourth post in this series, EMI Noise, Part 4: Box Level EMI Suppression

1 comment on “EMI Noise, Part 5: EMI Suppression for Harsh Environments

  1. CallieBaldwin
    July 13, 2015

    Very nice, Edgardo. This is a great series. 

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