2020 Volume 59 Issue 1 Pages 238-242
Fatigue endurance of copper foils on Flexible Print Circuits （FPCs） is critical factor for the life of electrical devices. In recent years, FPCs are adopted for not only smartphones and tablets but also on–vehicle apparatuses and wearable devices. In this report, fatigue endurance of copper foils is evaluated by torsion test, vibration test and thermal cycle test for more practical evaluation methods as well as by IPC sliding bending test for a general evaluation method. It is found that highly flexible rolled annealed copper foil （RA）, which has extremely cubic recrystallization texture, shows higher fatigue endurance than electro deposited copper foil （ED） in the all fatigue tests. The longer life of RA can be explained by a relationship between a progress direction of intrusions in copper foil and grain boundaries vertical to the stress axis.
