Functional metallic circuitries created by laser-activated selective electroless plating for 3D customized electronics

Abstract

Laser-activated selective electroless plating (LASELP) is a promising complementary manufacturing process employed in hybrid additive manufacturing (HAM) technology for the fabrication of customized 3D electronics. However, to the best knowledge of the authors, most current LASELP technologies could only enable copper deposition on/within the polymer matrix, which largely limited the application scope of this technology. Accordingly, an advanced LASELP technology combining catalyst exchanging process is proposed to pattern diverse functional metals on the photopolymer to fabricate 3D electronics. Two kinds of catalyst systems are selected in this HAM technology: (1) Cu₂(OH)PO₄; (2) antimony tin oxide (ATO) and titania (TiO₂). Silver and nickel-phosphorus (Ni-P) alloy are selected as the representatives of direct- and indirect-ELP metals, respectively. Silver could be directly plated on the laser-activated surface to deposit a dense and highly conductive layer, while for the Ni-P layer an inevitable catalyst exchange step is applied here to induce Pd⁰ plating seeds on the laser-activated substrate. Finally, a variety of customized electronics, such as conformal circuit boards, smart structure with strain sensor, embedded structural thermometer, Internet of Things bottle cap, and gas tube integrated with 3D conformal NO₂ sensor are fabricated and fully verify this HAM technology.