Method for plating a substrate to eliminate the use of a solder mask

Abstract

A novel process for plating a substrate without solder mask wherein the substrate is coated with a polymer catalyst to assist adhesion of conductive metal to the substrate. Next, a first plating mask photopolymer, or plating resist, is coated over the polymer catalyst, a circuit pattern is imaged onto the first plating mask and the first plating mask is developed to reveal windows, or circuit traces, in the first plating mask corresponding to the circuit pattern to be embodied on the substrate. Thereafter, a first conductive material such as copper is plated into the windows, and, thereafter, a second conductive material such as nickel may be plated into the windows on top of the first conductive material. Then, the first plating mask is removed from the substrate, leaving behind the conductive material in the form of the desired circuit pattern. Next, a second plating mask photopolymer is formed over the substrate and conductive materials, and an I/O interconnect mask corresponding to the I/O interconnect pads is photo-optically imaged onto the second plating mask and the second plating mask is developed to remove portions thereof, creating 'interconnect voids,' corresponding to the interconnect pads. Thereafter, a third conductive material such as gold is plated into the interconnect voids to create conductive I/O pads.