Electronics Protection - June/July 2012 - (Page 12)

Feature Packaging Solutions for Critical Electronics Protection in Challenging Environments Marc Caiola, Channel & Marketing Manager, North America Pentair Technical Products, Schroff Brand High-speed data transfer, system availability and mission-critical reliability are crucial in the defense industry. More than ever, success depends on the capability to rapidly gather and distribute specific information, whether it be on ships, tanks, ground control stations, combat aircraft or on unmanned air vehicles. Communications equipment must provide rapid deployment and ensure interoperability with the existing platform even in the most extreme environments. To ensure consistent performance in harsh environments, communications equipment requires effective packaging solutions designed to accommodate factors such as dust, moisture, shock and vibration. Depending on the application, packaging solutions must adhere to specific levels of protection. In addition to providing the necessary levels of protection, these packaging solutions prevent critical electronic components from overheating. Implementing a proper cooling system assists in continued network equipment performance and overall system reliability. design applies no insertion and extraction force on the PCB, removing the risk of over tightening to prevent damage to the board and card-lok during installation. Card-lok retainers are available in various lengths, individual wedge dimensions, mounting configurations and finishes to satisfy diverse application requirements. Conduction-Cooled Assemblies Conduction-cooled assemblies (CCAs) are generally used when passive free air convection or active forced air cooling is not possible, such as in space applications or where creating airflow with moving parts might affect the reliability of the system. Featuring a robust, lightweight aluminum design, CCAs deliver high thermal conductivity, while ensuring By transferring heat away from critisufficient structural support. cal electronics, CCAs prevent premature wear and failure and deliver CCAs also assist in avoiding exposure of critical electronics higher retention force on the card. to dust or contaminants. To modify a standard board for conduction cooling, a machined-aluminum cooling frame is secured to the board to convect heat away from components to the card edges. By transferring heat away from electronics, CCAs prevent premature wear and failure, and deliver higher retention force on the card. CCAs also improve the structural rigidity of the standard commercial board, minimizing flexing and providing protection in the case of shock and vibration. The use of stiffening ribs also help to reduce board flexing during mechanical shock and vibration, lessening the susceptibility of the damage to the connector pins and housing. The best mechanical support is along the edges of the CCA, with better support near and along the stiffening ribs. Higher mass board components and high power heat dissipation parts should be placed in close proximity to the card edges or stiffening ribs. A vacuum plate can be also be added to the board, which acts as a heat spreader for board components. The under side of the plate can be machined to match the component heights and locations on the board. Heat is carried away to the card edges where a wedge-lok mechanism secures the board inside the chassis and provides a thermal interface to transfer the heat to the chassis and surrounding environment. If a vacuum plate is not used, vacuum thermal strips can be employed to provide the appropriate spacing to go into the chassis cold wall channel. CCAs are available in numerous configuration sizes and finishes to fit various platform and application requirements, including, but not limited to, VME, CompactPCI, VPX and AdvancedMC. Subracks A standard subrack consists of two side panels and at least four horizontal rails. For a benign environment, a simple subrack featuring a sheet of metal and snap-in plastic guides can be used. For areas requiring a more rugged solution, such as military and defense applications, a subrack with end plates offering thicker material should be employed to survive stressed environments. This type of subrack also contains more bars to support heavier card guides. Electronics Packaging Components While there are a variety of packaging components that aid in the protection of electronics, this article will focus on card-lok retainers, conduction-cooled assemblies, subracks and cabinets. Card-Lok Retainers A secure clamping force is essential in avoiding damage to board module assemblies or printed circuit boards (PCBs). When shock or vibration is present, the board channel will start to flex, which can result in Advanced card-lok retainers employ a system failure or acciden- screw-actuated wedge action that locks tal ejection of the board. the PCB in place with a hex wrench, establishing the secure hold required for Card-lok retainers are military two-level maintenance systems. designed to secure PCBs to the cold wall in cold plate-heat exchanger applications. They are typically mounted to the board or subrack. Providing retention to the card guide, the card-lok retainer clamps to the board edge to ensure secure clamping at the connector side, top and bottom edges and backplane side. There are two types of retainer configurations: primary-side placement and secondary-side placement. Primaryside placement retainers orient on the primary side of the PCB, situating the main thermal interface to the cold-plate slot through the secondary-side cover flanges. Retainers on the secondary side of the PCB present the main thermal interface to the cold-plate slot through the primary side cover flanges. This configuration provides a better thermal path from the PCB components to the cold plate. However, secondary-side placement also reduces the available PCB area. Advanced card-lok retainers employ a screw-actuated wedge action that locks the PCB in place with a standard hex wrench, establishing the secure hold required for military two-level maintenance systems. Eliminating the need for a torque wrench, this 12 June/July 2012 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - June/July 2012

Electronics Protection - June/July 2012
FLIR T-series Cameras Introduce Thermal Image Enhancement Technology
Renewable Raw Materials - The Future of Plastic Enclosures
Global Electronic Enclosure Resins and Markets
Ferrite Testing Reveals Significant Performance Variations
Packaging Solutions for Critical Electronics Protection in Challenging Environments
Fluid Submersion Technology for Green Data Center Cooling
TRTL BOT Unveils KidSafe Case for iPhone 4 and 4S
Curtiss-Wright Controls Defense Solution Releases New D2D ATR 3U OpenVPX Chassis
Stulz Introduces CyberRow Data Center Cooling Solution
Abbott Technologies Offers New Sealed Power Supply
New Engineered Multi-Cavity Shielding Solution
Gore Enhances Product Performance with new of Screw-in Vents
Industry News
Calendar of Events

Electronics Protection - June/July 2012