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August 2017 • The PCB Magazine 49 Figure 2: Glass/copper process steps for preparing (A) a two-layer structure from a single piece of dielectric material and (B) the general technique for creating multiple layers. In (A), features (wires, pads, and through holes) are made on both sides of the substrate using a laser. Copper seeds are then planted using laser forward transfer of a thin foil. The copper droplets have good adhesion to the substrate but are too dispersed to make a conductive feature. The substrate is placed in an electroless copper plating bath and copper grows on the seeds, and excess copper can be polished off to make a smooth surface suitable for further layer build up or passivation. To make multilayer architectures (B), additional layers are laminated onto the completed construct from (A), and laser etching, seeding, and plating steps are repeated. LASER PATTERNING AND METALLIZATION TO REDUCE PROCESS STEPS FOR PCB MANUFACTURING