Flexible circuits (also variously referred to around the globe as flex circuits, flexible printed circuit boards, flex print, flexi-circuits) are members of electronic and interconnection family. They consist of a thin insulating polymer film having conductive circuit patterns affixed thereto and typically supplied with a thin polymer coating to protect the conductor circuits. The technology has been used for interconnecting electronic devices since the 1950s in one form or another. It is now one of the most important interconnection technologies in use for the manufacture of many of today’s most advanced electronic products. Flexible electronics, also known as flex circuits, is a technology for assembling electronic circuits by mounting electronic devices on flexible plastic substrates, such as polyimide, PEEK or transparent conductive polyester film. Additionally, flex circuits can be screen printed silver circuits on polyester. A printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it. Printed circuit boards are used in all but the simplest electronic products. They are also used in some electrical products, such as passive switch boxes. PCBs can be single-sided (one copper layer), double-sided (two copper layers on both sides of one substrate layer), or multi-layer (outer and inner layers of copper, alternating with layers of substrate). Multi-layer PCBs allow for much higher component density, because circuit traces on the inner layers would otherwise take up surface space between components.