Soft X-ray microspectroscopic imaging studies of exfoliated surface between fluoropolymer and Cu plate directly bonded by plasma irradiation with ammonia gas

The F, C, O, and N elemental distribution maps at the exfoliated surfaces of Cu plate after peeling the fluoropolymers from Fluorinated ethylene propylene (FEP)/Cu and Perfluoroalkoxyalkane (PFA)/Cu pieces which were bonded by plasma treatment including amino acid were performed by microscopic synchrotron radiation (SR) spectroscopic imaging measurements. The spatial elemental distribution pattern of exfoliated Cu after peeling PFA/Cu piece was not detectable by scanning electron microscopy with energy dispersive X-ray spectroscopy imaging alone, was revealed by SR-based soft X-ray microspectroscopy. We also obtained the microprobe X-ray fluorescence spectra and microprobe near-edge X-ray absorption fine structure spectra. Based on these measurement results, it is considered that the delamination of FEP/Cu piece mainly caused by resin failure, while the delamination of PFA/Cu is caused by interfacial delamination in addition to resin failure. The Hard X-ray photoelectron spectroscopy was also performed to confirm that the bonding via nitrogen is formed. Our SR-based analyses provided confirmation that fluoropolymers and Cu plates are bonded by N-mediated chemical bonding. The present study insists that the technique and plasma bonding process reported are expected to contribute to the development of new devices and systems consisting of fluoropolymers and metals. •Soft X-ray microspectroscopic imaging was performed on the peeled surfaces of the Cu substrates bonded with fluoropolymer FEP and PFA which were surface-modified with plasma treatment.•SEM observations showed that the FEP had a scaly pattern, while the PFA was flat.•μXRF imaging revealed that the residuals at the scaly edges of the FEP were resin, and that resin residuals were present in the very thin film of the PFA as well.•The N component was detected from μXRF imaging and HAXPES measurements.•Our study indicates that high adhesion was achieved by N-mediated bonding at the interface of Cu/FEP and Cu/PFA.