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36 The PCB Magazine • January 2015 this can't technically be called printing, but is certainly bona fide additive manufacturing. 3D printing isn't just about printing plastic objects. The industrial uses for 3D printing are constantly expanding. There is a great deal of R&D dedicated to the materials that 3D print- ers can use. 3D printers are now printing or repairing fully functional mechanical and structural parts using a range of metals, alloys and ceramics. Biological structures are also printable using polymer and organic materials for body parts or pharmaceuticals. Large printers can print hous- es and developments in nano- materials that allow 3D print- ers to print incredibly small objects just microns in size. However, it's not all serious. People are having a lot of fun with their 3D printers, print- ing chocolates, cakes, pottery, pizzas and candy. In the end, it's clear that adopting 3D printing is essen- tially a question of deciding on the right additive print- ing process and developing printable materials that meet the requirements of the final product. What Does it Mean for Electronics and PCBs? There is no shortage of folks that want to 3D print electron- ics. Firstly, printers have to be able to print conductive traces, which is the domain of PE. This an advanced technological area in its own right that involves the development of conductive materials suited to a range of differ- ent substrates. Basic connections can be embed- ded in objects by 3D extrusion printers using conductive filaments. These contain conduc- tive polymers, carbon nano-tubes or other con- ductive materials. The end result, using current technologies, is a low-resolution, point-to-point conductive trace that struggles to cope with the electrical requirements of professional circuits— fun for hobbyist printers of 3D objects. For higher resolution and acceptable con- ductivity, more advanced printing solutions are required. The materials development world is abuzz with R&D for all manner of new materi- als and formulations across the whole gamut of 3D printing processes. Inkjet and aerosol PE are turn- ing to nano-inks. The nano-ink industry is currently provid- ing formulations to meet this challenge in the form of vari- ous silver nano-particle inks. These inks are suspensions of nano-meter-sized silver parti- cles that, after printing, need to be cured either chemical- ly, or by light or heat. Once cured, the particles coalesce to form a conductive solid silver trace. The technology is now developed enough that silver nano-particles are emerging as a mature technological so- lution to printing electronics. That is not to say that all sil- ver nano-particle inks are the same, nano-ink development itself is a very advanced field. Silver may be an expensive metal to use, but given that traces are so fine, not much is needed. The performance justifies the cost. Copper ink would be clearly preferable from a cost perspective but copper ink is not currently a ma- ture enough technology. Copper is much harder to print with, because oxidation issues mean that the ink isn't as easy to make or use and the end results are not robust. Carbon nano-tubes and other exotic materials may well offer alternatives in the future also. Are any companies actually printing PCBs? The ability to quickly print a two-sided PCB would certainly make life easier for many. Being able to say goodbye to etching and the myriad other stages required to quickly make a PCB at home would put a smile on anyone's face. These smiles are about to break out with the upcom- there is no shortage of folks that want to 3D print electronics. Firstly, printers have to be able to print conductive traces, which is the domain of PE. this an advanced technological area in its own right that involves the development of conductive materials suited to a range of different substrates. Basic connections can be embedded in objects by 3D extrusion printers using conductive filaments. " " 3D PRINTING PCBS continues FEaturE