Page 12 - 2021 High-Reliability, Harsh Environment Connectivity eBook

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Discrete Wire Versus Flexible Printed Circuits for High-Reliability Systems
Wendy Jane Preston, Interconnect Specialist, Harwin
Today’s high-density electronic systems call for advanced interconnect solutions to unite the numerous PCBs and internal modules needed to facilitate complex functions. When we are talking about high-reliability applications, the requirements for the cables involved are especially demanding. Discrete wire arrangements and flexible printed circuits (FPCs) are both widely specified in this market, but it can be challenging to determine which product is the best choice. In a large number of standard applications, solid or stranded discrete wire cables are usually adequate. However, if a system is subject to space or weight constraints, interconnect solutions optimized for size, weight, and power (SWaP) should be considered.
The Benefits of FPCs
FPC cables feature intricate layers of circuitry etched directly onto an ultra-thin copper-clad polymer substrate. FPCs provide very low profiles, plus considerable weight reductions, which has made them a popular choice for scaled- down consumer electronics designs. As many military applications also become increasingly miniaturized, FPCs are experiencing exponential employment in satellite, robotics, and avionics designs.
A key attribute of FPCs is their ability to support substantially tighter bends than other types of cable. They are also better equipped to deal with dynamic motions while being subjected to bending, which is of particular relevance in relation to linear actuators, rugged laptops, and flight control surfaces, where movements repeatedly occur on a single axis. The flat form factor of an FPC also makes it capable of bending at right angles to the plane of the cable, but not in other directions. As such, specifying an FPC solution means that you will lose the ability to simultaneously bend in multiple axes.