Free-standing, parylene-sealed copper interconnect for stretchable silicon electronics

In this paper, development and characterization of a freestanding electroplated copper interconnect for applications in flexible and stretchable electronics is presented. The copper layer with typical thickness of 5 mum is plated into a photoresist mould realizing meander and mesh-like patterns. These are subsequently released resulting in a free-standing electrical interconnect that is optionally conformally coated by a ~8 mum thick Parylene N layer. Parylene sealing provides electrical insulation and increases rigidity of the structures. Tensile tests on fabricated samples have shown the elongation capability up to 300% for the mesh design and more than 1000% for the meander design. The Parylene coated samples showed increased rigidity but about 50% reduced elongation. Furthermore, parameterized FEM simulations were performed in order to estimate stress levels for different geometries under tensile stress.