Effect of annealing on the interfacial adhesion energy between electroless-plated Ni and polyimide

The effect of annealing on the interfacial adhesion energy between electroless-plated Ni films and polyimide substrates was evaluated using a 180-degree peel test. The measured peel strength values decrease from 263.6 ± 7.8 J/m2 to 109.3 ± 6.4 J/m2 after annealing for 100 h at 200 °C in an ambient environment. XPS analysis on the peeled surfaces reveals that the peeling is due to cohesive failure inside the polyimide, which is related to the fact that wet treatment produces an activated bonding mechanism between electroless-plated Ni and polyimide. This implies a degradation of the polyimide structure due to oxygen diffusion through the interface between Ni and alkali wet-treated polyimide, which is also closely related to the decrease in the interfacial adhesion energy due to thermal treatment in ambient conditions.