Choosing the right ink is a critical success factor for fast, simple and affordable creation of printed electronics prototypes and electronically functional prints. Yet, when evaluating production systems and processes, many designers and manufacturers often neglect to take into consideration factors like ink conductivity, customization and cost.
So what should you look for when buying ink for inkjet deposition for printed electronics? Here are some tips to help you understand the issues that you need to pay attention to when selecting the best conductive ink for your particular application.
First, consider which material is best suited to your printing application. While copper is the lowest-cost option, it oxidizes quickly so it cannot be used for printed electronics applications requiring high conductivity and small prints. Instead, what’s required is a conductive ink that offers copper’s functionality, without its pitfalls. The answer is silver, which actually is more conductive than copper. Although silver inks are more expensive, silver’s extremely high conductivity enables you to use less ink and print smaller profiles. Currently, silver nanoparticles are the best-performing conductor for inkjet deposition.
Printed electronics – whether for functional boards or for prototyping and creating proofs of concept – require high conductivity. The higher the conductivity of the ink, the more advanced and precise the printing process can be. Also, the more conductive the ink, the less ink is required, so smaller, more sophisticated items – such as those that pass current in addition to signals – can be printed less expensively. Silver nanoparticles become conductive after undergoing a particle sintering process, and each ink supplier will have a recommended approach. This process is a critical part of determining how conductive the inks will be, as well as what types of materials can be printed upon.
While it would be nice to have a “one size fits all” ink, off-the-shelf solutions typically can’t provide the high quality you’re looking for. They aren’t optimized for your specific needs. Ideally, you want an ink that is custom-formulated for your particular printer, process and substrate; anything else simply will not perform as well.
Customizing inks is not an easy task; significant know-how is needed to formulate the nanoparticles to meet the specific requirements of each printing context. Our chemists at Nano Dimension, for example, optimize the particle size, viscosity, rheology, sintering temperature, ink lifetime, and so on for each of our ink customers. We also can customize for specific printing processes by enhancing adhesion, flexibility and hardness. Our nanoparticle synthesis process allows us to control the shape, size, and distribution of particles, which ensures a higher-quality and more conductive printed end-product.
Each of the factors I’ve mentioned will have an impact on the cost of the inks you choose, but it is important to take a long view of the overall project – not just the inks – when considering the true cost. For example, one material may be less costly than another, but because it has lower conductivity it uses more ink, so the cost balances out. Or an off-the-shelf ink may be less expensive than a customized formulation, however if it doesn’t work with your printer or substrate, it’s worthless. Different particle synthesis processes will also affect both cost and conductivity, the sintering step – whether chemical, heat, laser or photonic – must be suited to your overall process and materials. The best advice I can give is to do your homework, and ask a lot of questions of potential ink suppliers so you can make an educated decision about cost and performance.
As you can see, there is a lot to consider when choosing a conductive ink for printed electronics. The science behind ink formulation is extremely complex, and it’s important to work with suppliers who truly understand your application and its unique needs. After all, your end-product is only as good as the ink that’s used to print it.