Fatigue Crack Propagation Behavior in Functional Film-bonded Materials with Epoxy Bonding Layer (Noting Effects of Film Materials and Residual Stress)

摘要

Pure copper and commercial grade iron film with the thickness of 100 #mu#m were bonded to steel base plate by using epoxy resin adhesive or by diffusion, which may be used for functional film-bonded materials in electronic parts. Residual stress caused on the epoxy bonded film was compress ion fur the iron film but tension for the copper film, respectively. This compressive residual stress on the iron film protected a fatigue fracture to the inner base plate from the surface film, thus the fatigue crack propagation life increased in the iron film more than in the copper film bonded plates with the tensile residual stress on the film. Using Young's modulus E and stress intensity factor #DELTA# K _(est)/E evaluated from the measured crack opening displacement, the fatigue crack propagation rate, da/dN, was expressed by a power low of #DELTA# K _(est)/E for all film bonded plates. The da/dN values in the epoxy bonded plates was high in the low #DELTA# K _(est)/E level less than the fatigue crack propagation threshold (#DELTA# K (est)/E))_(th) for the diffusion bonded plates.