Thin metal films on compliant polymer substrates are of major interest forflexible electronic technologies. The suitability of a film system for flexibleapplications is based on the electro-mechanical performance of the metalfilm/polymer substrate couple. This study demonstrates how a 10 nm Cr interlayerdeteriorates the electro-mechanical performance of 50 nm Au films on polyimidesubstrates by inducing the formation of cracks in the ductile layer. Combinedin-situ measurements of the film lattice strains with x-raydiffraction and electrical resistance with four point probe of the Au-Cr and Aulayers during uniaxial straining confirmed different electro-mechanicalbehaviours. For Au films with a Cr interlayer the film stress decreases rapidlyas cracking initiates and reaches a plateau as the saturation crack spacing isreached. Crack formation and stress drop correspond to a rapid increase in thefilm resistance. Without the interlayer the Au film stress reaches a maximumaround 2% engineering strain and remains constant throughout the experiment. Thefilm resistance is unaffected by the applied elongation up to a maximum strainof 15%, giving no sign of cracking in the metal layer. The outstandingelectro-mechanical performance of the gold film indicates that adhesion layers,like Cr, may not be necessary to improve the performance of ductile films onpolymers.