Process for the manufacture of multi-layer circuits with dynamic flexing

Abstract

A multilayer through-hole contacted flexible circuit and method of manufacture thereof is presented having a laminar construction which is strictly symmetrical in the bending area; and which has no exposed adhesive. The flexible circuit is made by providing through-holes to a standard single sided laminate. Next, conductive material is vacuum deposited (e.g. sputtered or evaporated) into the through-holes and at the same time a conductive seed-layer is deposited on the polymer side of the standard laminate. Plating resist is applied to both sides of the material and the seed-layer side of the material is patterned such that circuit traces, pads, and through-holes can be electroplated with additional copper. The plating resist is stripped and the very thin layer of copper in the non-conductive areas is flash etched to produce semi-additive circuit features on the seed-layer side. Etch resist is then applied to both sides of the material and circuit patterns fabricated on the foil-side of the material using standard substractive processing techniques. A cover film coated with adhesive is then provided over the exposed circuit patterns.