Copper micro-electrode fabrication using laser printing and laser sintering processes for on-chip antennas on flexible integrated circuits
Flexible, stretchable, wearable, portable…this is what many applications today ask electronics to be. This means that novel manufacturing processes and materials are required to build electronics on unconventional substrates. Direct printing followed by selective sintering of metal nanoparticle inks is a promising approach to accomplish those goals. This technique offers high fabrication speed and high resolution, but metals with a high conductivity and environmental stability are required. Since most nanoparticle inks tend to oxidize quickly during the sintering process, gold and silver are typically used, which are definitely not in line with the concept of low-cost electronics.
In their work, O. Koritsoglou and coworkers reveal to us their recipe to solve this issue. They developed an oxidation-free fabrication process for high-conductivity copper patterns by laser printing combined with laser sintering. By optimizing the metal content and the composition of the copper nano-ink, they achieved a record low resistivity of 3.3 μW∙cm, which is only twice that of bulk copper, together with high fabrication speed (about 1 m/s) and high reproducibility (5 μm line width variation) of the printed patterns. The effectiveness of the technique is nicely demonstrated by realizing a low-resistance spiral structure meeting the requirements of a loop antenna for a near-field RFID system.
The reported results prove that laser additive manufacturing is a fast, powerful, and cost-effective technique for realizing metallic structures on arbitrary substrates, such as small-form on-chip antennas on flexible integrated circuits.