Thin steel foils have been successfully demonstrated as outstanding substrate materials for flexible electronics because of their high mechanical strength, flexibility, light weight and thermal stability. This work investigates mechanical limitations of thin film materials on steel foil substrates. We characterize a three layer structure consisting of 100μgm thick stainless steel foil as the substrate, followed by 1μgm thick spin-on-glass passivation layer and 0.3μgm thick patterned aluminum interconnect layer on top with varying widths between 10- 35μgm by means of a bending experiment. A collapsing radius test method was adopted for the bending experiment and an elliptical curve fit was used to facilitate the strain measurement. The failure strain of aluminum interconnect layer was detected by monitoring the continuity of the test circuit during the experiment. The corresponding results reveal that the passivation layer cracked at a tensile strain of 0.46% and delaminated at a compressive strain of 0.68%. The metal interconnect layer ruptured at a tension strain of 1.26% and delaminated from substrate at a compressive strain of 1.22% due to the delamination of the passivation layer underneath. We determined that the failure of the aluminum interconnect under tension was due to localized elongation caused by cracking of the passivation layer underneath and concluded that a wider interconnect could withstand a larger strain. The stainless steel foil plastically deformed at a relatively small strain of 0.13%; thus, the use of stainless steel with reversible bending capability for flexible electronics is mostly limited by the minimum elastic bending radius of the steel substrate. The flexibility of steel foil based devices can be effectively improved by decreasing the substrate thickness.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
T. Afentakis, M. Hatalis, A. Voutsas, and J. Hartzell, IEEE Trans. Electr. Dev., 53, 815 (2006)10.1109/TED.2006.871174
C.C. Wu, S.D. Theiss, G. Gu, M.H. Lu, J.C. Sturm, S. Wagner, and S.R. Forrest, IEEE Elect. Dev. Lett., 18, 609 (1997)10.1109/55.644086
Z. Suo, "Fracture in Thin Films." Encyclopedia of Materials: Science and Technology, second edition, pp. 3290–3296, Elsevier Science (2001)10.1016/B0-08-043152-6/00587-8
J. Lewis, S. Grego, B. Chalamala, E. Vick, B. Chalamala and D. Temple, Mat. Res. Soc. Symp. Proc. 814, 1851–1859 (2004)10.1557/PROC-814-I8.5
T. Kater, Philips Research Report 2002/812 (2002)
T. Li, Z.Y. Huang, Z. Suo, S.P. Lacour, S. Wagner, Appl. Phys.Let. 85, 3435–3437 (2004)10.1063/1.1806275
G. Crawford, Flexible flat panel displays, (John Wiley & Sons, Ltd, 2005), p.112
H. Kuwamura, ”Research on light-weight stainless steel structure in JAPAN” (2003)
S. Greek, F. Ericson, S. Johansson, M. Füresch and A. Rump, J. Micromech. Microeng. 9, 245–251 (1999)10.1088/0960-1317/9/3/305
D. Gianola and W. Sharpe Jr , Experimental techniques, 28, 23–27 (2004)10.1111/j.1747-1567.2004.tb00182.x
Z. Chen, B. Cotterell and W. Wang, Engineering Fracture Mechanics 69, 597–603 (2002)10.1016/S0013-7944(01)00104-7
About this article
Cite this article
Kuo, PC., Chouvardas, V.G., Spirko, J.A. et al. Mechanical Limitations of Materials for Steel Foil Based Flexible Electronics. MRS Online Proceedings Library 1030, 314 (2007). https://doi.org/10.1557/PROC-1030-G03-14