patenting processes for printing and etching flat conductors on flexible base materials to replace wire harnesses. An advertisement from the 1950s placed by Photocircuits Corporation demonstrated their interest in flexible circuits. Flexible circuits are variously known around the world variously as flexible printed wiring, flex print, flexi circuits, are used in many products. Credit is due to the efforts of Japanese electronics packaging engineers who have found ways to employ flexible circuit technology. Flexible circuits are one of the fastest growing interconnection product market segments. One variation on flexible circuit technology is called "flexible electronics". It involves the integration of both active and passive functions in the device. Flexible circuit structures Flexible circuits display significant variation in their construction. Single-sided flex circuits Single-sided flexible circuits have a conductor layer made of either a metal or conductive (metal filled) polymer on a flexible dielectric film. Component termination features are accessible only from one side. Holes may be formed in the base film to allow component leads to pass through for interconnection, normally by soldering. Single sided flex circuits can be fabricated with or without such protective coatings as cover layers or cover coats, however the use of a protective coating over circuits is the most common practice. The development of surface mounted devices on sputtered conductive films has enabled the production of transparent LED Films, which is used in LED Glass but also in flexible automotive lighting composites. Double access or back-bared flex circuits Double access flex, also known as back-bared flex, are flexible circuits that have a single conductor layer, but allow access to selected features of the conductor pattern from both sides. While this type of circuit has benefits, the specialized processing requirements for accessing the features limits its use. Sculptured flex circuits Manufacturing sculptured flex circuits involves a special flex circuit multi-step etching method that yields a flexible circuit having finished copper conductors wherein the conductor thickness differs at various places along their length. (I.e., the conductors are thin in flexible areas and thick at interconnection points.) Double-sided flex circuits Double-sided flex circuits have two conductor layers. They can be fabricated with or without plated through holes, though the plated through hole variation is much more common. When constructed without plated through holes, connection features are accessed from one side only, and the circuit is defined as a "Type V (5)" according to military specifications. Because of the