The mechanical properties of thin metal films have been investigated for many years. How- ever, the underlying mechanisms are still not fully understood. In this paper we give an overview of our work on thermomechanical properties and microstructure evolution in pure Cu and dilute Cu-Al alloy films. Very clean films were produced by sputtering and annealing under ultra-high vacuum (UHV) conditions. We described stress-temperature curves of pure Cu films with a constrained diffusional creep model from the literature. In Cu-1at.%Al alloy films, Al surface segregation and oxidation led to a “self-passivating” effect. These films showed an increased high- temperature strength because of the suppression of constrained diffusional creep; however, under certain annealing conditions, these films deteriorated due to void growth at grain boundaries.