Peel strength of sputtered FCCL(Flexible Copper Clad Laminate) using Ar:O2 mixed gas preprocessing and a Ni-Cr seed layer

The PI surface was modified with ion beams in a vacuum chamber to increase the surface area. A two-way Design of Experiments (“DOE”) was performed by varying the DC power and changing the proportion of O2 gas with respect to the Ar reactive gas and measuring the peel strength between the PI layer and the plated Cu layer. The results showed that increasing the voltage level and applying mixed Ar-O2 gas makes the PI surface substantially rough, which increases the Van der Waals force as well as the chemical bonding strength. Using the oxygen gas makes the amorphous structure in the Cu layer sputtered. However, Cu plating with a high electrical current may remedy this, resulting in a good crystalline direction. It was also found that reducing the proportion of Cr in the Ni-Cr seed layer incurs a great decrease in the peel strength after the reflow process, although it requires just one etching.