Patent ID: 7485812

Claim:
A multi-layer circuit board apparatus comprising: a plurality of circuit boards, each circuit board comprising an electrically conductive sheet coated with a conformal insulating top layer covering one surface of the conductive sheet, a conformal insulating bottom layer covering another surface of the conductive sheet, a conformal insulating edge layer covering an edge of the conductive sheet and a circuit pattern defined on an outward facing surface of at least one of the top layer and bottom layer; and an insulating interlayer sandwiched between the top layer of a first circuit board of the plurality of circuit boards and the bottom layer of a second circuit board of the plurality of circuit boards; wherein a circuit pattern of one of the plurality of circuit boards includes at least one electrical conductor on the top layer of the one circuit board and at least one electrical conductor on the bottom layer of the one circuit board; and a through-hole or via extends through the one circuit board, the though-hole having an electrical conducting interior surface extending therethrough electrically connecting the one electrical conductor on the top layer of the one circuit board and the one electrical conductor on the bottom layer of the one circuit board, the electrical conducting interior surface electrically isolated from the electrically conductive sheet by an insulating through-hole layer, with opposing sides of the interior surface of the through-hole having an outline generally in the shape of a hyperbola.