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84 DESIGN007 MAGAZINE I OCTOBER 2022 to be applied with a specific printing technol- ogy, and a non-exhaustive list includes screen printing, inkjet, aerosol jet, flexographic, and gravure. Inks are formulated for attributes such as optimal conductive performance, substrate adhesion, shelf stability, and for use in a spe- cific print method. State-of-the-Art Conductive Inks While conductive screen-printed pastes— such as for solar cells, or onto polyimide such as for computer keyboards—are not new, 25 years ago the use of conductive inks outside those applications was rare. e DARPA MICE (Mesoscopic Integrated Conformal Electron- ics) program of the late 1990s and early 2000s dramatically re-evaluated the possibilities of electrically-conductive inks. Since then, the ability to widely and cost-effectively produce new materials such as nanomaterials, and the proliferation of advanced chemistries and polymer science, has led to profound progress demonstrated by modern inks. Today, the best electrical conductivities are almost on par with that of bulk silver, within a factor of two or three in some cases. Ink for- mulation chemistries are very advanced and now allow excellent adhesion to a wide range of substrates, with specific formulations avail- able for specific substrates. It is fair to say that the conductive inks community has matured substantially in the past 20 years, with new technologies coming to market, and creative and clever people joining this space each year. Why Use Conductive Inks? Simply, use of conductive inks can allow designers to think outside of the rigidity box, allowing much broader creative realization. Conductive inks are a form of additive man- ufacturing and can be applied only where needed, so they offer a very efficient use of materials. Conductive inks can be printed onto a variety of substrate materials, including sub- strates that are flexible, perhaps have already been processed with layers of added materi- als, or both. ey can be applied with minimal or no impact on any adjacent or previously applied materials, unlike other additive pro- cesses for applying conductive materials like electroplating, or subtractive processes like traditional plate and etch. A number of current electronics products and applications have been enabled by the use of conductive inks, either by design or by eco- nomic feasibility. I know many exciting and novel products in the pipeline rely on the use of conductive inks. So, What's the Catch? From a performance perspective, conductive inks just don't match the electrical conductiv- ity of etched copper for use in electronics. If the dominant design requirement is maximum electrical conductivity in a very small area or volume, then traditional etched or plated cop- per is still likely the right answer. As soon as other design requirements come into play however, such as a requirement for the utiliza- tion of flexible or low-temperature substrates, then conductive inks become more viable. e difference in performance of conductive inks means that inks are not simply a plug-and-play swap for etched or plated alternatives. Circuits must be designed from the start based on the electrical properties of the inks. Using the inks is not just about the inks themselves. Successful utilization depends on printing equipment capable of dispensing the right type and formulation. Oen the inks also require post-processing to effectively dry and sinter them. Again, as full disclosure, Nova- Centrix developed the PulseForge tools as a unique class of thermal processing equipment specifically for sintering conductive inks on temperature-sensitive substrates. An evolution of the PulseForge tools is now being used for soldering on temperature-sensitive substrates. Also, successful utilization of conductive inks requires well-trained staff who have the exper- tise to design and manufacture products utiliz- ing conductive inks, including selecting and