Results of IPC copper foil ductility round robin study.

A round robin test program has been carried out to (1) develop typical and establish minimum ductility values for the copper foil classes in Specification IPC-CF-150E, copper foil for Printed Wiring Applications, (2) determine the precision and accuracy of Test Method IPC-TM-2.4.2.1, Flexural Fatigue and Ductility Foil, and (3) determine the bending fatigue behavior of the copper foils. This report contains a compilation of the results from seven test laboratories for copper foils from seven classes (both electrodeposited and wrought), four weights (thicknesses) and five vendors. The results show that the submitted vendor samples pass the recommended minimum ductility values, sometimes with large margins. The test method shows high precision typically resulting in sample standard deviations of less than 10 percent of the mean. The lab-to-lab accuracy shows a somewhat larger than expected test procedure dependence, in particular due to thickness measurement errors and deviations from established procedure. For severe flexing and/or continuous high-cycle fatigue applications, annealed wrought copper foil is the best choice due to its initial high isotropic ductility and its strain-hardening behavior during extended cycling.