December 28, 2017
Today’s electronic systems are evolving to ever-portable, present, continuous operation devices that work in nearly every kind of environment. They’re often lightweight, miniaturized versions of older electronics that must work harder, run faster, and be immune to outside effects like solar and electromagnetic fields. They must also perform well during high physical shock, vibration, and temperature extremes. Lead designs, in this evolution, have included applications in military instruments, portable soldier electronics, space technology, unmanned vehicles, robotics, and down-hole drilling in the petroleum industry. NASA and satellite ruggedness requirements include unique specifications from radiation protection to preventing outgassing of polymers used to construct the device itself. Ruggedized systems are also being applied in surveillance systems, factory equipment, and remote surgical systems.
Oftentimes, the most exposed and vulnerable portions of electronic systems are the extended cables, connectors, and interconnections used to route signals and power from one portion of the system to another. Ensuring product reliability requires a combined focus on material selection, physical design, and electrical processing capabilities. To ensure new designs survive and perform to expectations, a range of specifications and guidelines are established early in the process of development.
Additional benefits of designing ruggedized miniature interconnects is that they lend to expanding their use in ever-broadening applications:
1. Automotive Sensor and Detector Systems
Automotive sensor and detector systems contain highly portable electronics used to predict and protect collisions and/or offer design improvements in the auto interior to protect passengers. Crash test dummies are designed with multiple electronic capabilities including measuring and direction of impact, even relax-mode after the impact. The sensor systems are extremely small, lightweight, and ruggedized to withstand multiple tests.
2. Ground Troop Electronics
Ground troop electronics will often require reliable devices like highly flexible cabling and connectors that will be exposed to water splash, immersion, along with intense exposure to solar radiation and heat. They must also be rugged enough to handle travel through rough terrain, along with being quickly plugged and unplugged through many cycles. Cable materials like polyurethane jacketing with over-molded connectors that tightly seal and don’t deteriorate, are mandatory to meet specifications like IP-67/68.
This Ingress Protection Code (IP), consists of the letters IP followed by two digits and a letter. The international IEC 60529 standard lists the degrees of protection provided against intrusion of solid objects like dust, accidental contact, and water in electrical enclosures. The first digit number for example, refers to solids and the second digit refers to liquids. Additionally, one can follow the standards chart and specify true water protection based upon time and depth of immersion or amount of splashing. Alternatively, one can specify how much dust or dirt exposure an electrical device can be exposed before it harms the circuit.
3. Unmanned Vehicle Ruggedized Electronics
Ruggedized electronics for unmanned vehicles require somewhat different protections. Most often, the circuits are inside the machine body of fuselage, must be very small, and lightweight. Cable material is less of a concern, but the connector pin to socket mating design is critical. Pin to Socket designs must “hold tight” continuously during use, along with meeting shock and vibration specifications. Most designers use spring contact material of 17,200 ksi tempered Beryllium Copper per ASTM B194, followed by nickel that is hard gold plated to ASTM B488 standards.
4. UAV Advancements
Unmanned aerial vehicles (UAVs) push the designer to use very small, lightweight electronics in order to extend unit payload and flight time availability. Hand-launched and crash-landed vehicles need to be ruggedized to perform in their uniquely rough conditions. During flight operations, however, long-term continuous vibrations occur, which is an effect called “fretting.” Very slight movement back and forth within the interconnections tends to slowly wear through the gold plating until the nickel becomes exposed and serves as the main contact metal between the pin and socket. When this happens, the contact resistance increases dramatically and damages circuit performance. Very firm locking or latching mechanisms are required in preventing this movement during service to avoid fretting. Jacking or locking screws can help mate and secure the connectors in mind. When faster change over and space is limited, there are squeeze latching mechanisms that replace the screw systems and meet or exceed the clamping and holding strength of the lock screws.
5. Down-Hole Drilling
Down-hole drilling technology involves electronics that go down inside the drill bit to guide direction, and these drill bit sensors require nearly all the demands listed above plus the need to function in extremely high temperatures. Many military interconnections are specified to function from -55° C to +125° C. While drilling deep down inside earth for petroleum or gas, we must increase these design requirements so that the materials can withstand temperatures of +200° C for long periods of time. In unique cases, the temperature can exceed 240° C. Geothermal research devices see much the same environment. The electronics are inside the drill bit casing near the grinding and pounding system cutting away the earth, so they experience constant vibration and shock. Robust housings and lead material protect the electronics from wear and tear, in addition to metal back-shells, strain-reliefs, braided shields, and special cables.
Heavy use of electronics at point-of-source data has greatly expanded our effectiveness and capabilities. Modern chips are designed to be used where the action is occurring. Rugged designs are providing that capability, increasing our use of higher speed electronics, and spreading its functions from consumer Internet of Things (IoT) systems to deep space satellites. Older standard interconnection electronics have their place and serve as good examples to grow. Rapid design, rugged requirements, and modern materials have paved the way for systems to fit and survive in extreme environments. We can now see farther and deeper, collect data from sources on Mars to inside our brain. We can drive unmanned aircraft from different continents and not drive our car as we race down the highways. All this comes with improved and ruggedized electronics.
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From : https://www.ecnmag.com