We present a new low cost microfabrication technology that utilizes a sacrificial conductive paint transfer method to realize thick film copper microstructures that are embedded in polydimethylsiloxane (PDMS). This process has reduced fabrication complexity and cost compared to existing metal-on-PDMS techniques, which enables large scale rapid prototyping of designs using minimal laboratory equipment. This technology differs from others in its use of a conductive copper paint seed layer and a unique transfer process that results in copper microstuctures embedded in PDMS. By embedding microstructures flush with PDMS surface, rather than fabricating the microstructures on the substrate surface, we produce a metallization layer that adheres to PDMS without the need for surface modifications. The fabrication process begins with the deposition of the seed layer onto a flexible substrate via airbrushing. A dry film photoresist layer is laminated on top and patterned using standard techniques. Electroplated copper is grown on the seed layer through the photoresist mask and transferred to PDMS through a unique baking procedure. This baking transfer process releases the electroplated copper from the seed layer, permanently embedding it into the cured PDMS without cracking or otherwise deforming it. We have performed initial characterizations of the copper microstructures in terms of feature size, film thickness, surface roughness, resistivity, and reliability under flexing. Initial results show that we can achieve films 25-75 micrometers in thickness, with reliable feature sizes down to 100 micrometers and a film resistivity of approximately 7.15 micro-Ω-cm. Process variants and future work are discussed, as well as large scale adaptations and rapid prototyping. Finally, we outline the potential uses of this technology in flexible electronics, particularly in high power applications.

Date Published: 16 April 2014
PDF: 15 pages
Proc. SPIE 9060, Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2014, 906007 (16 April 2014); doi: 10.1117/12.2045228

Published in SPIE Proceedings Vol. 9060:
Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2014
Vijay K. Varadan, Editor(s)