Omnetics Fall 2017 Newsletter

SMT and High Density Connectors

Starting with Micro-D Connectors in a New Era

Today’s circuits are used in applications that require high quality rugged performance, portability, and lighter and smaller components.  Surface-Mount Technology (SMT) for components is a significant method on PC boards and is now being pushed further for connector and interconnect methods. In addition, newer circuits are expected to perform during or after exposure to high moisture and a wide range of temperatures.  Many new applications also require increases in the number of signal lines than older circuits. The SMT chips are increasing circuit speed and moving to digital, but running on lower voltage and current levels.  The applications are also demanding lighter weight, more portability, and high-use reliability.   Circuit modules in those applications are being crammed together from module to module while meeting form, fit, and function to meet extreme combination of demands. The Micro-D connector still serves as a major contributor to the industry within the interconnection systems.  More often, circuits only require less than one ampere of current for signals running less than 15 volts.  Chips are often on modules crammed into tight spaces or out at the end of a probe or module.  Signal speeds are also creeping up. One key solution is the Micro-to-Nano interconnect system.  That is, the larger Micro-D connector acts as the interface to a system on the edge or outside of the box and is then connected to one or more Nano-D connectors inside the circuit system.  Critical to the system is the Micro-D’s ability to handle the outside environment, and the match of proper cabling to the Nano-D connectors at each individual module inside the box. Big problems can arise as the quantity of signals increase, the speed of the signals increase, and the space available decreases.  Electromagnetic interference (EMI), or electrical noise, begins to build in the design and then methods such as shielding, or shunting must be used to protect neighboring systems within the box. The keys to higher speed, especially in digital circuits, are impedance and attenuation control. Signal rise-time can be slowed or digital signal height can be reduced that would cause low circuit performance (similar to seeing pixels on digital TV when the signal is low). Managing the design of the link from the Micro-D into the rest of the system is critical.  With today’s solid modeling and fast turn shell manufacturing, a Micro-D connector can be quickly designed and built to mount in crucial points in the instrument.  Micro-D back-shells and shielded cable systems are designed to match the impedance of the circuit and shielded or drained to retain high performance in key applications. Standard military designs in applications such as rocket launchers can now use Micro-D designs to meet the rugged environment while consuming low space on the release pod.  Break-away cables can be placed into robotics and remote systems.  Micro to Nano systems are used to help control UAV technology that require the larger Micro-D as a ground interface, but has only room for Nano-D connectors inside the systems. Best designs are beginning to look at standard Micro-D designs as a beginning building block, but with an eye to modified shells for custom fit into the ever increasing complexity and density of remote and portable electronics used in remote control technologies.   The Nano-to-Micro cable harness system is becoming more often the final choice to fit all into-the-box. Micro-D Upgrades that still meet the Military ruggedness and quality standards include the Latching Micro-D connector family.  Quick latches for plug to socket mating has been installed in many new military products and the strength of latching as well as performance in shock and vibration testing exceeds requirements specified for the old jack-screw methods.