Analysis of the T-peel strength in a Cu/Cr/Polyimide system

The T-peel strengths were measured using a Cu/Cr/polyimide system under varying metal layer thickness and rf plasma pretreatment conditions. Measured peel strength showed reversed camel back shape against the metal layer thickness, which is quite different from the results of the 90° peel test. Elementary analysis suggests that the T-peel strength variation is a combined outcome of the plastic bending work of the metal and polymer strips, and when the latter were subtracted from the measured peel strength, interfacial fracture energies, quite independent of the metal layer thickness but increasing with the rf plasma power density were procured. Another interesting outcome is that the peel angle, the angle between the unpeeled ligament and the load axis normal, can be actually predicted and is a useful measure of the root curvature and the interfacial fracture energy.