Abstract: In order to form a (flexible) electrical interconnect structure a flexible dielectric substrate having a plurality of windows is laminated between a first, relatively thin flexible conductor layer and a second, relatively thick conductor layer. The first flexible conductor layer is patterned into a plurality of flexible conductor lines The second conductor layer is patterned into first and second pluralities of spaced apart terminals, which overlie the windows. Conductive vias are formed through the flexible dielectric substrate between the terminals and the flexible conductor lines, thereby connecting the terminals on one side of the flexible substrate to the flexible conductor lines on the other side of the substrate .