IEC TR 63017:2015(E) specifies a compensation method of Cu linewidth according to impeadance reduction by using noise suppression materials (hereafter referred to as NSMs) for FPCBs. This Technical Report presents an optimum result for maintaining a designated performance of FPCBs by using NSMs. It also indicates a measuring method for an impedance variation of FPCBs using NSMs with the prevailing TDR (time domain reflectometry) method. This method is resticted to measuring only the variation of an impedance value in accordance with the variation of the Cu linewidth by using NSMs for FPCBs. This report, however, neither determines nor indicates the structure or material of FPCBs.