Adhesion characteristics of Cu/Ni-Cr/polyimide flexible copper clad laminates according to Ni:Cr ratio and Cu electroplating layer thickness

The adhesion strength of Cu/Ni-Cr/polyimide flexible copper clad laminate (FCCL) was evaluated according to the composition ratio of the Ni-Cr layer and the thickness of the Cu electroplating layer, by using a 90A degrees peel test. The changes in the morphology, chemical bond and adhesion property were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The peel strength of the FCCL increased with increasing Cr content and increasing Cu electroplating layer thickness. This increasing FCCL peel strength was attributed to a lower C-N bond and higher C-O and carbonyl (C=O) bonds in the polyimide surface compared to the FCCL with a lower adhesion strength. The adhesion property of the FCCLs was significantly affected by the Ni:Cr ratio.