Stretchable circuit with elastic bumps

Previously, the electronics devices are always integrated into a rigid substrate. Itpsilas stronger, but hardly compatible with Bio-tech or some implanted systems for human being whose packaging point should be more focusing on the flexibility or even the stretchability. Not only the packaging of the active devices but also the connections among them need to be more flexible. In other words, as to the bio-tech and textile electronics applications, we have to make the metal line among the active or passive devices more flexible or even more stretchable. For the time being, many academic institutes or industries have addressed their thoughts for improving the stretchability of the connections. They change the materials of the metal line, but itpsilas difficult to reach more than 10% stretchability, even using the SMA (Shape Memory Alloy) material. So, more efficient concept for approaching larger stretchability is disclosed. It is to directly change the shape of the metal circuit into ldquoSrdquo shape or horseshoe shape, together with using the stretchable substrates with lower Youngpsilas modulus and higher elongation ability, such like polydimethy-siloxane (PDMS) or other silicone material. In this paper, Cu and Au were used as the metal line. We also made the circuit shape as horseshoe on the temporal substrate coated with silicone robber material. After finishing all the process, the substrate would be removed. But the difference was that many elastic bumps were added on the path of each metal line. The material of the elastic bumps was silicone robber or other softer material. All the purpose was to make the metal circuit more stretchable and also to reduce the stress concentration issues when stretching. During the experiments, the stretching ability between the Cu line and Au line were compared. The effects of the different line width were also observed. The results showed that in the static stretching test, Cu line could reach 25% stretchability and Au line o- - nly had 20% stretching without having elastic bumps. However, when elastic bumps were added into the structure, the stretchability of all the metal lines could be additionally improved around 5~10%. Finally, the dynamic stretching test was finished. 500 cycles with 15% stretch was carried out as well.