Patent ID: 7514298

Claim:
A method of forming a high density printed wiring board for mounting a semiconductor, said method comprising: providing a substrate having upper and lower surfaces, with an upper conductive layer on the upper surface and a lower conductive layer on the lower surface; forming a plurality of taper-shaped passages through the substrate and the upper and lower conductive layers, each of the taper-shaped passages having a center axis, an internal wall surface, a small-diameter end having an opening diameter of 10-50 μm, and a large-diameter end having an opening diameter that is greater than the opening diameter of the small-diameter end and 100 μm or less; applying a metallic plating in each of the taper-shaped passages so as to plate the internal wall surfaces and seal the small-diameter ends in a manner so as to form a plurality of taper-shaped, electrically conductive through holes having a center axis, a small-diameter end, and a large-diameter end; and providing at least one of the through holes with a connection pad having a center axis, such that the connection pad is provided at least one of the small-diameter end and the large-diameter end of the through hole, and the center axis of the through hole is within 100 μm of a peripheral edge of the connection pad, but offset from the center axis of said connection pad.