Laser sintering of copper conductive traces on primer pre-treated additive manufactured 3D surfaces

Abstract

This paper introduces a novel process for creating conductive copper traces on 3D surfaces from different additive manufacturing technologies by employing printed electronics techniques. An essential step in this process was the dip-coating pre-treatment with a primer to reduce the surface roughness below 100 nm, seal pores if present, and increase the thermal stability. This was followed by a dip-coating with copper nanoparticle ink, drying using a heat gun and thermal curing by laser sintering. The experiments determined the optimal laser peak intensity for achieving conductors with the lowest electrical resistance possible. The laser parameters' processing window provided conductive traces on 3D surfaces with properties comparable to photonic sintering on planar substrates. Thereby, the conductive traces reached electrical specific resistances lower than 18 µΩ cm (elemental copper: ρ = 1.8 µΩ cm) and a copper material percentage higher than 90 atom %. Shear tests validated the assembly with surfacemount device (SMD) resistors. Electrical tests resulted in maximum current densities higher than 100 A mm-2 and lateral breakdown voltages higher than 2kV mm-1. Thus, this paper presents essential prerequisites for a future application of the technology.