Flexible printed  circuit (the brief name is FPC), also known as soft circuit board, flexible circuit board, its light quality, thin thickness,  freely bend it.  It can be  folded and other excellent characteristics and favored..., is a polyester film or polyimide as the substrate made of a highly   reliable, excellent flexible printed circuit, through flexible thin  plastic sheet, embedded circuit design, make in narrow and limited  space in a   large number of precision  components, thus forming flexible flexible  circuit. This kind of circuit can be bent , folded and overlapping with light weight, small volume, good heat dissipation, easy installation, and broke through the traditional interconnection technology.

      And it usually be made in irregullar shape to the different needs. also it can be made the different pitch.

       In the structure of the flexible circuit, the component material is the insulating film, conductor and adhesive. 

 

https://img.diytrade.com/seimg/206111/51324543.jpg

                                         irregullar shape and the  different pitch.