Patent ID: 8198542

Claim:
A flexible printed circuit board comprising: a first dielectric portion subjected to tension in response to bending; a second dielectric portion subjected to compression in response to bending; and a conductive portion conducting electrical signals, and having a neutral plane, the neutral plane being within a predetermined range of the thickness of the conductive portion, and forming a substantial interface of tension and compression between the first and second dielectric portions, wherein each of the first and second dielectric portions includes at least one dielectric layer, wherein a geometric center, obtained by converting the thickness and the width of respective layer of the flexible printed circuit board using same elastic modulus, is located in the predetermined range of the thickness of the conductive portion, and wherein the neutral plane is located according to: Y n =(Σ( T i *E i *Y i ))/(Σ( T i *) E i )), and Σ T x <Y n <(Σ T x +T c ), where Y n is a distance normally extending from a reference plane to the neutral plane, T i is the thickness of a respective layer of the flexible printed circuit board, E i is an elastic modulus of a material placed in the respective layer of the flexible printed circuit board, Y i is a distance normally extending from the reference plane to the geometric center of the respective layer, T x is the thickness of the respective layer under the conductive portion, T c is the thickness of the conductive portion, and the reference plane is an underside of the flexible printed circuit board.