Shielding for electromagnetic interference (EMI) is critical to military electronics systems operating in demanding environments requiring low emitted electronic signatures and protection from electromagnetic radiation. In mobile military applications, EMI shielding must be maintained during storage, transport and operation in a wide variety of demanding and corrosive environments.
An integral part of the EMI shielding system is an EMI shielding caulk that seals the seams on external structures from panel to panel to ensure conductivity around the entire system. The caulking maintains a faraday cage that protects the internal electronic components against external electromagnetic interference and/or electromagnetic pulses (EMP). This prevents a possible failure mode of the EMI shielding enclosure when two metal panels are joined together without protecting the seam with a reliable caulking. If there is no caulking or if an inferior caulking fails, there is a significant opportunity for EMI emissions/susceptibility.
Parker Chomerics has developed the next generation EMI shielding caulk for use on military radar shelters. The new CHO-BOND® 1019 provides a substantial increase in performance over existing legacy materials by improving EMI shielding performance, corrosion resistance and by reducing application time. In addition, the new CHO-BOND® 1019 is paintable, eliminating the need for expensive intermediate layers. Along with better shielding performance, these features translate to significant savings by reducing manufacturing and material cost, increasing throughput, increasing the working life of the shelter and reducing maintenance costs.
To learn more about the science applied, trial formulations subjected, rigorous testing standards and results obtained, download our whitepaper: EMI Shielding Caulk Delivers Superior Performance in Military Radar Systems.
Military systems require rugged performance
EMI shielding plays a major role in military applications. The U.S. military has utilized EMI shielding caulks for decades on electronics’ housings such as radar shelters, radar test facilities, etc. A popular example, the AN/MSQ-104 Engagement Control Station (ECS), the command and control unit of the Patriot Missile firing battery, is housed in an EMI shielded radar shelter mounted onto the bed of a cargo truck or similar vehicle. Whether the ECS is being transported or operated under battle conditions, it experiences jolts and vibrations that can fatigue the rivets holding the aluminum shelter panels together; any loosening of the rivets will compromise the integrity of the EMI Shielding system around the command and control electronics inside the unit.
This would result in the system being vulnerable to EMI, thereby risking the proper operation or exposure to enemy anti-missile systems. This risk must be minimized since the U.S. Army and allied nations rely on the Patriot as their primary anti-ballistic missile system in the mission to protect strategic areas. Systems such as the AN/MSQ-104 have advanced technologically and increased in usage over the years. Furthermore, newer electronic components require even more EMI shielding levels that legacy caulks cannot attain.
Legacy EMI shielding caulks failure modes
Legacy EMI shielding caulks are single-component, non-hardening compounds made of traditional materials such as silicone filled with silver-plated copper. A key vulnerability of these materials traditionally has been corrosion issues. These legacy formulations have shielded against EMI but now fall short in applications where modernized high speed and high energy electronics are concerned. These advanced electronics are more sensitive to EMI and operate in a wider range of frequencies and, therefore, require improved shielding across the frequency range to receive proper protection. In order to provide improved shielding and corrosion resistance, it is necessary to use conductive fillers that deliver higher levels of shielding typically provided by silver-plated particles while improving upon the relatively poor corrosion resistance typically experienced with copper-based particles. Additionally, there are application issues that need to be addressed:
Often, epoxy-based paints applied to radar shelters will not adhere to silicone compounds. In this case, it is necessary to apply a polysulfide environmental sealant over the caulk to provide a paintable surface. The caulk and the polysulfide each require seven days (fourteen days total) to cure and must be applied in a temperature-regulated environment to ensure proper final-cured properties. In manufacturing, the fourteen days of waiting are logistically time-consuming and costly. Maintaining acceptable warehouse temperatures for application is also challenging. CHO-BOND® 1019 cures quickly and requires less time in narrow temperature ranges after application. Legacy caulks regularly experience cracking and corrosion over time, which leads to costly field repairs. CHO-BOND® 1019 resists cracking and corrosion significantly over those legacy products.
Optimize your process with CHO-BOND® 1019 Caulk
The next-generation CHO-BOND® 1019 is a fast-curing, paintable caulk that provides improved shielding and corrosion properties over the traditional caulks. It also has an improved application temperature range. In this product, we combine our metallic filler technology with cutting-edge base polymers to provide a unique formulation. This new technology transcends the legacy EMI shielding caulks as well as those compounds recently developed for similar modern military applications.
Our resulting CHO-BOND® 1019 EMI shielding caulk achieves superior results including:
Substantial cost savings
Our R&D engineers are experts at filler-resin combinations that will deliver the performance improvements necessary for the latest technologies.
Article contributed by Nick Pascucci, product development engineer, Parker Chomerics Division.
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