Printed conductive structures on flexible substrates
Techniques like laser patterning and photolithography are great for standard ICs. But flexible substrates need low processing temperatures and are more difficult to align, making production processes a lot more complicated. To avoid these issues, this program aims to develop simple printing-based processes that will keep production costs low and be scalable for smaller, more complex features as flexible electronics systems develop.
The program is driven by the requirements of OLEDs and organic photovoltaics, but its results will also apply to many other applications. In particular, it looks at manufacturing both conductive features for active circuit components and non-conductive 3D structures such as separators, light guides and micro-fluidic channels. In both cases, the goal is to enable smaller feature sizes and fast low-temperature processing.
There’s a strong focus on improving existing printing techniques. For example, current inkjet printing can produce small features, but isn’t fast enough for cost-effective manufacturing. In contrast, screen printing is fast but doesn’t have the necessary resolution. Holst Centre and its partners are working on both ends of this spectrum to create a range of fast, high-resolution techniques to suit different applications.
For conductive structures, there is also emphasis on developing new highly conductive inks that will work with plastic substrates. This is a three-pronged attack.
- New ‘conductive building blocks’ such as silver nano-particles and complexes
- Target: reduce final resistivity to less than 5 times that of bulk silver
- Improved ink formulations for specific applications
- Low-temperature, high-speed sintering to create highly conductive tracks
- Target: below 120 °C and in less than 1 min
This is a true end-to-end program. It includes partners from every link of the value chain: precursor and ink suppliers, printing, sintering and manufacturing equipment vendors, end-user device manufacturers. The final goal is to enable modular systems that can be incorporated into reel-to-reel production lines operating at 10 meters per minute.