Patent ID: 7968803

Claim:
A wiring substrate comprising: an electrical insulation substrate; a through-hole formed in the electrical insulation substrate; an electrically conductive paste filled inside the through-hole, the electrically conductive paste having conductive particles; and wiring traces disposed on one or both surfaces of the electrical insulation substrate and electrically connected with the electrically conductive paste; wherein interfaces of the wiring traces in contact with the electrically conductive paste have an asperate surface constituted by projections and recesses; wherein the asperate surface has a mean curvilinear asperate interval at least two times longer, but no more than ten times longer, than an average particle diameter of the conductive particles contained in the electrically conductive paste; and wherein a plurality of granular bumps are formed on said asperate surface such that a density of said granular bumps is greater at tips of the projections of the asperate surface than in the recesses of the asperate surface.