Mechanical properties of electrodeposited copper foils for PCB applications

In this study, the microstructural characteristics and mechanical properties of the electro-deposited Cu foils with different preferred orientations were investigated. Three types of foils were studied, including HTE (high temperature elongation), MP (middle profile) and VLP (very low profile). Observation results indicate that the columnar grains of the HTE - MP and VLP-A samples with (220) preferred orientation were arranged with a fan-like appearance. The (200) oriented grains of samples VLP-B and VLP-C were more equi-axed. Sample VLP-D showed a strong (111) preferred orientation and possessed fine but elongated columnar grains grown along the thru-thinkness direction. There existed a close relationship between preferred orientation and nanoindentation responses. The elastic modulus in decreasing order was (111), (220) and then (200) oriented foils. Foils with different preferred orientations also behaved differently in tensile properties at room temperature, 150°C and 250°C. In general, (220)-oriented foils had better ductility, and the MP samples with (220) preferred orientation exhibited the best performance in tensile strength at different temperatures. Worthy of notice is, serrated flows in the tensile stress-strain curves appeared when tested at 150°C and 250°C, which may result from the combined effect of dynamic recrystallization (DRX) and dynamic strain aging (DSA).