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81 Interconnection options With many suppliers, connectors will come with pre-crimped lengths of wire running off them; at other times it is up to the end-user to do the wiring themselves. Either way, it is important to consider the many wire interconnection solutions available when integrating connectors in a vehicle. Crimping remains the most popular approach owing to its repeatability. Modern suppliers and integrators of connectors in the unmanned systems market increasingly use electromechanical systems for automated and calibrated control of crimp quality, depth and height. Connector suppliers always offer specifications for end-users to follow with their crimping tools and positioners, as these help ensure correct crimping of contacts and secure interconnections. However, not all end-users have access to the same quality of crimping equipment. If crimping tools are of poor quality, soldering the wire to the connector could give better results. Soldering is also common for PCB connectors as it is difficult to make a decent crimp in such small spaces. In fact, lack of access to good crimping equipment still prevents some UAV technicians from choosing connectors over hard-soldering their wires in place. That comes with many disadvantages though, such as making copper wire very brittle when applying solder metal to it. This makes soldered connections more likely to break under bending loads, and thus less suitable for the cramped subsystems bays and high- g manoeuvres that are increasingly typical in unmanned vehicles. A high-quality crimp, however, is secure enough to withstand significant bending loads, as well as similar tension loads to soldered joints; the copper wire will typically break before the crimp does. Also, crimped connectors are more prone to ‘popping’ out of their sockets rather than breaking, meaning repairs are limited to re-applying the crimp. Perhaps most important though, a crimp that successfully fuses the metals together will give a lower electrical resistance than a soldered connector That means soldering connections will cause them to heat up faster, making them potentially dangerous for high- current connections. And for UAS designers eyeing regulatory concerns, the FAA will not certify anything with solder joints in any part of the primary flight control system. The inherent risk perceived in unmanned vehicles not having a pilot onboard could extend this rule to other vehicles and subsystems. To improve the quality of the crimp, some connector manufacturers use Connectors | Focus A high-quality crimp is secure enough to withstand large bending loads: the copper wire will break before the crimp does Unmanned Systems Technology | February/March 2019 The growing specialisation of unmanned vehicles has prompted greater customisation and hybridisation of connector contacts and shapes (Courtesy of Omnetics) Crimping remains widely favoured over soldering as a means of connecting wires to contacts, and the FAA will not certify anything with solder joints in any part of the primary flight control system (Courtesy of Ulti-Mate)