Manufacturing methods for printed circuit boards

A method of forming a plurality of solid conductive bumps for interconnecting two conductive layers of a circuit board, said conductive bumps having upper surfaces, said method comprising the steps of

• (a) obtaining a first continuous homogenous metal layer disposed on a second metal layer, said first metal layer having a substantially planar exposed face and said second metal layer having an exposed face;
• (b) applying a first photoresist onto the exposed face of said first metal layer and a second photoresist onto the exposed face of said second metal layer;
• (c) imaging said first photoresist to define a pattern of remaining photoresist sections;
• (d) forming a plurality of conductive bumps by etching regions of the first metal layer not covered by said remaining first photoresist sections to a second desired height;
• (e) removing said first photoresist and said second photoresist;
• (f) applying a third photoresist onto the first metal layer and the second metal layer;
• (g) exposing and developing said third photoresist on said first metal layer to define a pattern of conductive bumps and circuit lines;
• (h) etching the first metal layer sections exposed by the development of said third photoresist to form a plurality of circuit lines in said first metal layer;
• (i) removing said third photoresist;
• (j) applying a dielectric layer onto said plurality of circuit lines, said dielectric layer defining a plurality of holes which expose the upper surfaces of said plurality of conductive bumps;
• and
• (k) removing said second metal layer.