Direct electroless plating of conductive thermoplastics for selective metallization of 3D printed parts

Electroless plating is a promising approach for metallizing plastic 3D printed parts, but current approaches rely on surface activation with expensive precious metal catalysts such as palladium. In this work, we demonstrate conductive composite filaments loaded with metal or other conductive particulate can be electrolessly plated directly, without prior activation, with exposed particles serving as nucleation sites. Several commercially available filaments based on different particulate loading were plated, with both carbon black and copper particulate shown to nucleate in an electroless copper plating bath. Flash ablation metallization, the use of a flash of high energy white light to ablate the polymer on the surface and expose a higher density of metal particulate, was also shown to accelerate the plating process. Selective plating was then achieved through use of a dual extruder 3D printer to define conductive composite regions for plating on a non-conducting thermoplastic. Trace resistances were reduced by as much as five orders of magnitude after copper plating. A toroidal inductor was printed and shown to drop in resistance from 24 kΩ before to 2.3 Ω after plating, with post-plating inductance and quality factor 315 nH and 10.3 respectively. A 555 timer circuit demonstrator was also plated.