With the growing trend toward smaller, faster and more integrated electronic equipment the need for highly effective electromagnet interference protection (EMI) has increased greatly. EMI gaskets are essential to the electromagnetic compatibility (EMC) part of the automotive electronics testing, by keeping interference in and out of a device at a minimum so that it does not disrupt equipment in the immediate vicinity. But to guarantee that they perform in the field, EMI gaskets have to be put to the test—especially when it comes to shielding effectiveness and strength. Theis two parameters are the basic criteria in evaluating gasket performance in aerospace, automotive, telecommunications and medical equipment industries.
Shielding Attenuation: The Heart and Soul of EMI Performance
Shielding Effectiveness (SE) evaluates an EMI gasket’s capacity to reflect or attenuate electromagnetic radiation. This is generally given in dB, which tells to what extent the signal is attenuated by the gasket. The higher dB value, the better the shielding Performance. In the laboratories, SE is evaluated through different standard procedures (MIL-STD-285, IEEE 299, ASTM D4935, etc.). These tests place the gasket down between a source and a receiver to determine how much energy is leaking through the shielding.
In practice, the measurement of shielding effectiveness also needs to consider parameters such as frequency range, compression force, and material conductivity. EMI gaskets for low-frequency power electronics may have distinct shielding requirements from high-frequency RF applications. This is the data that engineers and manufacturers use to determine which gasket materials and designs are appropriate for certain environments.
What is durability in the context of long-term reliability?
Durability testing is just as important to consider for gasket EMI, especially for products that will be subject to environmental factors. One example is aging: a seal may work fine at first, but subsequent exposure to variable temperatures, moisture, vibration, and periodic mechanical strain challenges it. Typical durability measures include compression set, corrosion resistance, thermal aging and mechanical wear.
Compression set tests look at how well rubber gasket holds to its shape and functions after repeated compressions. In addition to the risk of excessive compression set resulting in low contact pressure, the shielding effectiveness also will be compromised. Thermal aging to determine if the gasket maintains its physical and electrical properties, gaskets are subjected to heat over time. This kind of data is more important in applications like aerospace or automotive electronics where thermal cycling is, indeed, a part of the operating environment.
Resistance to corrosion is also significant, particularly when gaskets are formed of or include metal filled materials. Moisture, salt spray, or exposure to harsh chemicals can result in corrosion that impairs conductivity and shielding capabilities. Testing in these simulated environments allows EMI gaskets to withstand their operating environments.
Comprehensive Analysis for Application-Customized Requirements
Testing for shield effectiveness and durability helps manufacturers and engineers select EMI gaskets that most closely meet their particular operating criteria. Although some of these gaskets may be suitable to shield high frequency emissions, the gaskets may not meet other environmental specifications. The others may have excellent resilience but not work well in narrow frequency bands.
Finally, by integrating these two in a holistic assessment we can guarantee that EMI gaskets provide constant performance throughout their life. Such thoroughgoing testing is not just a quality control concern — rather, it is key to achieving regulatory approval and long-term device reliability with a growing constellation of electronic ecosystems.