Films have been often resin-bonded to base plates for electronic parts requiring various high quality-functions. If these parts should be fatigue-fractured, the expected function would no longer be performed. It is necessary, therefore, to clear an important factor controlling the fatigue fracture of these parts. In this work, as the model specimens, the commercial grade iron films with the thickness of 100μm were bonded to the steel base plate by diffusion, or by using cyanoacrylate and epoxy resins. In the fatigue testing results obtained using these specimens, including the film thickness of 50 μm bonded with epoxy resin, there was a tendency for the adhesive resin layer to fracture readily at the initial fatigue stage but to protect a damage caused in the base plate during fatigue, thus resulting in the increase of the fatigue lives of the film-bonded plates. This tendency was extremely strong for the fllm-bonded plate with compressive residual stresses on the film subjected to the shrinkage deformation of epoxy adhesive resin, in the solidification during a cooling process.
