1. A flexible circuit board comprising:a first conductive substrate comprising a first insulating layer, a first signal line, a second signal line, and a plurality of first conductive posts; the first insulating layer comprising a first surface and a second surface opposite to the first surface; and the first signal line forming on the first surface, the second signal line forming on the second surface, and the first conductive posts extends through the first signal line and the first insulating layer, the first signal line being electrically connected with the second signal line via the first conductive posts;
an outer layer being formed on the first signal line; the outer layer comprising a first pad and a second pad;
a second conductive post being electrically connected the first pad and the first signal line; and
a third conductive post being electrically connected the second pad and the second signal line.