The invention relates to a welding pad structure arranged above an active circuit structure. The welding pad structure comprises a welding pad, a protective layer and an upmost metal layer in the active circuit structure, wherein the protective layer is covered on the welding pad and is provided with an opening exposing part of the welding pad; part of the upmost metal layer arranged below the opening is a supporting layer which is provided with at least one gap, and the upmost metal layer is electrically connected with the welding pad by a plurality of dielectric window plugs.