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A round-robin test program has been carried out to (1) develop typical and establish minimum ductility values for the copper foil classes in the Institute for Interconnecting and Packaging Electronic Circuits (IPC) Specification on Copper Foil for Printed Wiring Applications (IPC-CF-150E), (2) determine the precision and accuracy of IPC Test Method on Flexural Fatigue and Ductility, Foil, (IPC-TM-126.96.36.199), and ASTM Method for Ductility Testing of Metallic Foil (E 796), 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 samples submitted by the vendors 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% of the mean. The lab-to-lab accuracy shows a somewhat larger than expected test procedure dependence, in particular because of thickness measurement errors and deviations from established procedure. For both severe flexing or continuous high-cycle fatigue applications, annealed wrought copper foil is the best choice because of its initial high isotropic ductility, which gives the ability to sustain severe bending and low-cycle flexing, and its strain-hardening behavior during extended cycling, which results in a cyclicly increasing tensile strength and produces extended high-cycle fatigue lives.
ductility, metallic foil/coatings, plated metal films, thin electrodeposits, rolled (wrought) foil, mechanical properties (tensile, flexural, fatigue), test precision, test accuracy
Member of technical staff, AT&T Bell Laboratories, Whippany, NJ