Achieving Good Bonding Strength of the Cu Layer on PET Films by Pretreatment of a Mixed Plasma of Carbon and Copper

Abstract

Cu layers were fabricated on PET films with and without pretreatment by a mixed plasma composed of carbon and copper using a magnetron sputtering technique for potential application as the flexible copper-clad laminate (FCCL) in 5G technology. In order to evaluate the effect of carbon plasma on the composited layer, the graphite target current was adjusted from 0.5 to 2.0 A. The microstructures and properties of Cu layers on PET films with different treatments were measured by an X-ray powder diffractometer, X-ray photoelectron spectroscope, Raman spectroscope, scanning electron microscope, transmission electron microscope, scratching test, indentation test, and four-probe detector. The results showed that the organic polymer carbon structure on the surface of PET films was changed to inorganic amorphous carbon due to the effect of the carbon plasma. At the same time, the active free radicals formed in the transition process react with metal copper ions to form organometallic compounds. Under the treatment of a mixed plasma of carbon and copper, the C/Cu mixed layer was formed on the PET film at the top of the substrate. Due to the presence of C/Cu mixed interlayers, the bonding strengths between the final Cu layers and the PET film substrates were improved, and the strongest bonding strength appeared when the graphite target current was 1.0 A. In addition, the presence of the C/Cu mixed interlayer enhanced the toughness of the Cu layer on PET film. It was proposed that the good bonding strength in combination and the enhanced toughness for the Cu layer on a PET film was due to the formation of a C/Cu mixed interlayer induced by the pretreatment of a mixed plasma of carbon and copper.

Sputtered anti-reflection layer on transparent polyimide substrate improves adhesion strength to copper layer: effects of layer thickness and sputtering power

“…5(b–d) are deconvoluted into the following binding energies of 284.7 eV, 285.6 eV, 286.3 eV, and 288.6 eV, which represent the C–C, C–N, C–O, and CO bonding, respectively. 15–18 The effects of the sputtering power on the bonding ratio on the peel strength was plotted in Fig. 6.…”

“…The XPS full scan spectra of lms shown in Fig. 5 [15][16][17][18] The effects of the sputtering power on the bonding ratio on the peel strength was plotted in Fig. 6.…”

Adhesion improvement of sputtered Cu films on flexible polymer substrates through the design of metal interlayers

“…Researchers have made attempts to solve this problem through establishing chemical bonding between the polymer substrate and the Cu film based on polymer surface modification [18][19][20]. Besides, the additional metal interlayer between the Cu/polymer interface also increases the adhesion [21][22][23][24].…”

Design of metalized polyether-ether-ether-ketone based on semi-additive manufacture for 5G applications: from bottom-up assembly to selective electroplating

“…The adhesive binding mode is another option, but it still faces the challenge of thermal instability, high porosity, and uneven adhesive distribution. 15 Therefore, advanced interface design is needed to solve the contradiction between a low roughness interface and strong adhesive strength between copper and the substrate.…”