Metallization of carbon fiber reinforced polymers: Chemical kinetics, adhesion, and properties

Abstract

In the present study, we investigate different surface pretreatments and their influence on a subsequent surface metallization. A direct liquid injection metalorganic CVD (DLI-MOCVD) process is presented for the low temperature metallization of composites, ultimately aiming at the surface functionalization of 3D parts. The process involves the organometallic precursor Cu(I) hexafluoroacetylacetonate 2-methyl-1-hexene-3-yne (hfac)Cu(MHY). We determine chemical kinetics of the global deposition reaction and show the improvement of the adhesion of the Cu films by applying surface pretreatments that etch and/or activate the surface before deposition. To this purpose, gas phase and wet chemical processes are used. Gas phase pretreatments consist either in the use of a remote microwave plasma, an in situ UV oxidation, or in the deposition of acrylic acid/ethylene plasma buffer layer by using an atmospheric pressure cold plasma jet. The liquid phase pretreatment is based on a commercial series of solutions that includes swelling, oxidation, and neutralization steps. The adhesive strength of the Cu films on poly-epoxy and on carbon fiber/poly-epoxy composite surfaces is specifically investigated by scratch and cross-cut testing, and is correlated with topographical, chemical, and energetic characteristics of the surfaces prior deposition, investigated by interferometry, X-ray photoelectron spectroscopy and wettability measurements through the sessile drop method. Pretreatments result in surface functionalization and topographical changes which significantly increase the surface energy and improve the wettability. In some cases the induced modification of the microstructure of the Cu films is found to be beneficial to the electrical resistivity.

Engineering Copper Adhesion on Poly-Epoxy Surfaces Allows One-Pot Metallization of Polymer Composite Telecommunication Waveguides

“…Contact angles obtained with the five liquids are then reported in Owens-Wendt plots (not shown) [39]. The surface energies and their polar and dispersive components are presented in Table 1, along with atomic O/C ratios determined by X-ray photoelectron spectroscopy (XPS) following a procedure presented in [13]. Comparisons, including untreated CFRP surfaces are valid for wettability measurements performed on the same batch due to deviations in the manufacturing process from one batch to the other.…”

“…Despite the efficiency of these and other solutions, some of which have already been commercialized, their application to the metallization of CFRP waveguides is not straightforward due to their complex geometry. Our previous studies led to the development of a direct liquid injection metalorganic chemical vapor deposition (DLI-MOCVD) process for forming copper coatings on flat CFRP coupons [13]. Among the different pretreatments we investigated, a UV radiation-based one maintained satisfactory adhesion with low surface roughness of the CFRP plate and appropriate electrical resistivity of the Cu film of 4.3 µΩ•cm.…”

Chemical vapor deposition of Cu films from copper(I) cyclopentadienyl triethylphophine: Precursor characteristics and interplay between growth parameters and films morphology

“…As a characteristic example, specifications concerning the metallization of the internal surface of polymer waveguides include the deposition of a film composed of a several-microns-thick, highly conductive, corrosion/oxidation-resistant metal with smooth surface morphology and adherence to the composite substrate. These specifications are not necessarily compatible, since it is difficult to preserve high smoothness while promoting adhesion [8,9]. The heat sensitivity of polymers gives rise to additional constraints, namely processing at low to moderate temperatures.…”

“…The heat sensitivity of polymers gives rise to additional constraints, namely processing at low to moderate temperatures. Alternatively, chemical vapor deposition (CVD) can be used specifically in view of the possibility of achieving conformal films [9][10][11] combined with relatively elevated growth rates. Despite considerable work on the CVD of Cu, the reluctance of the process to yield smooth films remains to be overcome.…”

“…They also observed a sharp linear increase of the GR at temperatures up to 513 K, indicative of a surface-reaction-controlled regime with an activation energy of 65 kJ/mol. In another study on MOCVD of Cu, Addou et al reported two regions in the Arrhenius plot of the GR on Si substrate: a diffusion-limited regime with a minor variation of the GR (468 K-493 K) and a surface-reaction-limited region at lower temperatures, for which they report an activation energy equal to 50 kJ/mol [9]. Interestingly, the activation energy in the diffusion-limited regime, estimated from their reported Arrhenius plot(Figure 1 in [9]), is 12 kJ/mol: i.e., almost identical to the present one.…”