ABSTRACTS

The following is a list of the abstracts for papers which will be presented in THE EIGHTH INTERNATIONAL SYMPOSIUM ON METALLIZED PLASTICS: FUNDAMENTAL AND APPLIED ASPECTS. The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)

Integration of Plasma Modified Parylene-n and Silver Metallization for Integrated Circuits.

To meet integration requirements, parylene-n (Pa-n) and silver were studied for ULSI circuits because of their favorable properties, low dielectric constant (2.65) and low resistivity (1.59 mW-cm) high, respectively. Surface modification of Pa-n by means of a low power oxygen plasma helped to increase adhesion between the two surfaces. The enhancement was due to the increased roughness and mechanical interlocking. Thermal stability and texturing of Ag films on Pa-n were confirmed using X-ray diffraction analysis. Rutherford back scattering spectrometry (RBS), secondary ion mass spectroscopy (SIMS), and electrical analysis showed no significant diffusion of Ag into Pa-n.

Adhesion Enhancement of Noble Metals on Polymers by Interface Tailoring

(Abstract not yet available)

Bundesanstalt für Materialforschung und -prüfung (BAM), (Federal Institute for Materials Research and Testing), 12000 Berlin, (GERMANY)

Plasma Polymer Interlayers in Metal-Polymer Composites Used as Adhesion Promoters

Plasma polymer interlayers with a high concentration of monosort functional groups (COOH, OH, NH₂) are well-suited to investigate different types of chemical or acid-base type interactions between metals and such functionalized polymer surfaces. It seems to be very important to understand the process of pulsed plasma polymerization used to form such monosort polymer surfaces. Therefore, it was started with general investigations of the styrene polymerization. Styrene is a classically polymerizing vinyl monomer. It was expected that styrene preferably polymerizes in the plasma-off period of the pulsed plasma giving rise to a radical gas phase graft process. Later on, these scientific findings should help to deposit well-structured adhesion promoting layers from acrylic acid, allylamine and allylalcohol.

The formation of plasma polymer layers using styrene as monomer were re-examined using low wattage and pulsed r.f. discharges. The resulting elemental composition and structure of these pulsed plasma polymerized styrene layers (pp-PS) were compared with classic PS and with those of continuously working r.f. plasma produced PS (cw-PS). The applied effective energy per monomer molecule passing through the plasma zone was calculated for both the pulsed and the continuous plasma. Efforts were made to measure the characteristics of micro or milli second plasma pulses as well as the response of a styrene vapour plasma measured in terms of collision rates and ion densities. The same layers were examined by means of XPS without exposure to air prior to analysis. Core level and valence band spectra of the pp-PS suggest the existence of a chemically rather defined PS. Moreover, TOF-SIMS results show indications of the existence of regular styrene polymer repetition units (104 Da). Nearly complete solubility in tetrahydrofurane seems to confirm the regular pp-PS structure. Field Flow Fractionation experiments confirm the existence of a oligomer fraction with around 5000 Da (polymerization degree ca. 50) but a fraction with 107 Da dominates the spectrum. A small residue is insoluble. cw-PS is only partially soluble and FFF spectra could be measured only from the soluble fraction. These results suggest a structure of pp-PS closely to that of classic PP. Thermogravimetric measurements did not show significant differences in the thermal degradation between pp-PS and cw-PS but strong differences to classic PS.

The results of PS polymerization were adapted to the polymerization of allyl and acryl monomers. The functional groups were retained in these polymer layers to at least 60%. They were used as anchoring points for the interaction with polymers and metals in composite materials.

Combination of Inorganic and Organic Layers as Key Issue for High Barrier Films

Compared to rigid materials, the advantage of flexible films consist in low material consumption and low costs, especially for packaging applications. High cost efficiency can be reached already by using films from polyethylene terephthalate or polyolefines. However, the barrier properties of mono- or multi-layer polymer films against the permeation of oxygen, water vapor and aroma substances do often not fulfil the requirements of the packaging industry. Vacuum web coating of the polymer films is the most cost efficient technique for increasing barrier properties. For this purpose Aluminum (Al) or oxides (AlO_x and SiO_x) are used. In spite of the great amount of about 20,000,000 mē of vacuum web coated films world wide per year, the permeation mechanism are well understood just for oxygen. In terms of a quantitative prediction, there is still a deficit for water vapor and especially for aroma permeability.

The paper gives a background of the permeation process through inorganic barrier layers. There, the permeability is controlled by the structure of the inorganic layer and the polymer layers next to it. Numerical simulations are used for quantifying the transmission rates through different material combinations. Examples of the positive impact of thin organic barrier layers next to the inorganic layer are shown. These layers can either be on the substrate film, as co-extruded PEN or lacquered acrylate layers, or as top-coat on the barrier layers, such as ORMOCER^® and protein lacquers. Additionally, the impact of the structure of the vacuum web coated layer on the final barrier properties is demonstrated.

Characterization of the Metal/PTFE Interphase by XPS and AFM

The chemical and physical characteristics of the metal/polymer interface determine several important properties including wear and adhesion. We report results from a systematic investigation of the metal/poly(tetrafluoroethylene) (PTFE) interphase resulting from titanium, iron and copper physical vapor deposition characterized using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). On PTFE, titanium formed titanium (III) fluoride (TiF₃) and titanium carbide (TiC), iron formed iron (III) fluoride (FeF₂), while copper was unreactive. Titanium in contrast to iron produced no cross-linked species and CF₃ groups, postulated to arise from -F- intermediates. Simultaneous C-F and C-C bond breaking kinetics, however, can rationalize the absence of these species during titanium metallization. The inertness of copper is a consequence of the larger magnitude in the C-F bond strength compared to that of Cu-F. Pretreatment of native PTFE by Ar⁺ ion or X-ray irradiation did not modify the chemical reactivity of the polymer surface during subsequent Cu deposition, although significant morphological changes were observed on PTFE by AFM. In contrast, post-treatment of the Cu/PTFE interface by Ar⁺ ion or X-ray irradiation was required to produce copper (II) fluoride (CuF₂). In the case of iron and titanium/PTFE systems, X-ray post treatment resulted in increased metal fluoride at the interphase.

New Developments in the Adhesion Promotion of Electroless Ni or Cu Films on Polymer Surfaces

(Abstract not yet available)

Metal/Polymer Nanocomposite Films for Functional Applications

(Abstract not yet available)

Mechanism Study of Direct Plating on Plastics with Palladium as Activator

Further study on the mechanism of direct plating via palladium-based activator was carried out based on the dual-reaction model firstly proposed from this laboratory.

We tested the performance of direct plating after every step including activation, acceleration and sulfide promotion. We found a two-step voltage decay when electroplate with constant current after activation which indicates a two-stage reaction mechanism.

The effect of tin compound on the activity of the Pd/Sn catalyst was also explored. We compared the plating rate after promotion of two kinds of palladium catalyst, Pd/Sn colloid (with Sn) and organic palladium colloid (without Sn), to explored the effect of tin ion. We found organic palladium colloid (without Sn) has no promotion effect on plating rate after promotion, which implies the stannous ion probably possesses addition function other than the stabilizing effect commonly recognized.

We also tested the effect of oxidation on plating rate after activation. We found the stability of Pd/Sn layer will increase by oxidation process and won't cause adverse effect on the plating rate, which provide us a new method of metallization of non-conductive substrate for PTH process.

Polyaniline-Palladium Composite Coatings for Metallization of Polyethylene Substrate

The coating of low density polyethylene (LDPE) films with a polyaniline-palladium composite layer was investigated. The LDPE surface was first graft copolymerized with acrylic acid (AAc) to enhance the adhesion of the polyaniline-palladium layer. Two methods of forming the polyaniline-palladium layer on the LDPE were investigated. In the first method, polyaniline was first deposited on the AAc-graft copolymerized LDPE, followed by reaction with Pd(NO₃)₂. This results in a layer of palladium being deposited on the polyaniline surface. In the second method, polyaniline powder was first reacted with Pd(NO₃)₂ and the powder was then treated with N-methylpyrrolidinone and coated on the AAc-graft copolymerized LDPE. In both methods, the amount of palladium deposited can be varied by controlling the reaction time and the proportion of palladium to polyaniline used. In the second method, nanosized palladium metal particles are distributed in the polyaniline coating rather then confined to the surface of the polyaniline layer. In both cases, the palladium metal particles confer surface conductivity to the LDPE substrate even with the polyaniline in the undoped state. The adhesion of the polyaniline-palladium coating to the AAc-graft copolymerized LDPE substrate is excellent at low palladium content but is significantly weakened when a high palladium content interferes with the interactions between the polyaniline and the AAc-graft copolymerized chains. A high grafting density of AAc will promote better adhesion.

Electroless Plating of Copper on Poly(tetrafluoroethylene) Films Modified by Surface Graft Copolymerization and Quaternization

Argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) films were subjected to UV-induced surface graft copolymerization with a tertiary amine monomer, N,N'-(dimethylamino)ethyl methacrylate (DMAEMA) and its quaternary ammonium salt, 2-(trimethylammonium)ethyl methacrylate chloride (TMMAC). The DMAEMA graft-copolymerized PTFE (DMAEMA-g-PTFE) surface was further reacted with 3-bromopropylamine hydrobromide (3-BPAH) to introduce the NH2 and the quaternary amine groups on the DMAEMA-g-PTFE film (the Q-DMAEMA-g-PTFE film). The surface composition and the degree of quaternization (DQ) of the surface-modified PTFE films were determined by X-ray photoelectron spectroscopy (XPS). The DMAEMA-g-PTFE, TMMAC graft-copolymerized PTFE (TMMAC-g-PTFE) and the Q-DMAEMA-g-PTFE surfaces can be activated directly by PdCl₂, in the absence of prior senstization by SnCl₂ (the "Sn-free" activation process). Electroless plating of copper could be carried out effectively on the so-activated DMAEMA-g-PTFE, TMMAC-g-PTFE and Q-DMAEMA-g-PTFE film surfaces. A shorter induction time for the electroless plating of copper was found for the TMMAC-g-PTFE and the Q-DMAEMA-g-PTFE surfaces than for the DMAEMA-g-PTFE surface. The T-peel adhesion strength of the electrolessly deposited copper on the Q-DMAEMA-g-PTFE surface was improved to about 8 N/cm, in comparison to only about 4 N/cm for the DMAEMA-g-PTFE surface, about 3 N/cm for the TMMAC-g-PTFE surface, or about 0.6 N/cm for the PTFE surface with Ar plasma treatment alone.