Papers

AVS2001 Session AS-ThA: Adhesion and Corrosion

Thursday, November 1, 2001 2:00 PM in Room 134

Thursday Afternoon

Start	Invited?	Item
2:00 PM		AS-ThA-1 Substrate Preparation and Stud Pull Adhesion of Metal Films on Graphite-Epoxy Composites P. Kraatz (Technical Consulting Services); W. Mellberg (Lockheed Martin); G.L. Young (San Jose State University) Sputtered multilayers of chromium and copper are employed as adhesion enhancing layers on surfaces of graphite-epoxy substrates. These sputtered layers provide a basis for electroplating copper and silver. The effects of substrate preparation techniques upon adhesion strength of deposited metal films are investigated. The stud pull adhesion test is employed as a tool for quantitative measurement of adhesion strengths of metal films on graphite-epoxy substrates. Preparation techniques studied include wet or dry abrasion, using "Scotch Brite" or 400 grit sandpaper, and non-abrasive cleaning, using surfactants, water, and solvents. For as-sputtered material, highest stud pull strengths are associated with wet abrasion and pre-sputter cleaning with aqueous surfactants, DI water, and solvents. Lowest adhesion strengths are associated with non-abrasive cleaning, using the same agents. Effects of thermal cycling in air upon adhesion vary with surface preparation before sputtering. Dry abrasion and solvent cleaning lead to the highest adhesion strengths after thermal cycling, while non-abrasive cleaning is again associated with the lowest strengths. Adhesion of electroplated silver and copper to sputter coated graphite-epoxy also varies with surface preparation before sputtering. In contrast to as-sputtered results, abraded surfaces are associated with reduced plating adhesion, and unabraded surfaces with enhanced plating adhesion. Surface analysis (AES and ESCA) results suggest that formation of a thin carbide phase at the interface between the graphite-epoxy and sputtered chromium correlates with higher adhesion strength, while unusually high oxygen content at the interface correlates with lower adhesion strength.
2:20 PM		AS-ThA-2 Polymer-metal Interfaces: The Influence of a Metallic Surface on the Interphase Formation Mechanisms A.A. Roche (INSA de Lyon, France); M.-G. Barthés-Labrousse (CNRS, France); J. Bouchet (INSA de Lyon, France); F. Debontridder (CNRS, France) Epoxy-diamine networks are extensively used as adhesives or paints in many industrial applications. It will be shown in this paper that studies carried out starting from the adsorption of simple diamine molecules to the application of an epoxy-diamine mixture onto oxidized metallic surfaces can lead to a better understanding of the chemistry inducing the interphase formation and to the adhesion mechanisms of epoxy systems on metallic substrates. Results obtained following deposition of either pure diamines or mixtures of epoxy and diamines onto gold and aluminum surfaces will be presented. When mixtures of epoxy-diamine are applied onto gold coated substrates, the properties obtained for the coating are the same as the bulk network ones. When the precursors are applied on oxidized or hydroxylated metallic substrates and subsequently cured, an interphase is created between the substrate and the polymer, which has chemical, physical and mechanical properties quite different from the bulk polymer ones. For example, when mixtures of epoxy-diamine are applied onto aluminum surfaces, the glass transition temperature, the reaction rate between amine and epoxy, the interphase thickness, the residual stresses within the interphase and the Young’s modulus of the interphase all depend on the amine nature (aromatic, aliphatic or cycloaliphatic), the stoichiometric ratio, the processing conditions (time and temperature), the organic layer thicknesses and the metallic surface treatment nature. Characterization of the metallic surfaces (XPS, IRRAS, GXRD) shows that, whatever may be the surface treatment of the metallic substrates, adsorption of the diamine monomer onto the metallic hydroxylated surface leads to both Lewis (bonding between the metallic surface cationic sites and the diamine nitrogen atom) and Brønsted (bonding between the hydroxyl groups and protonated amine function) acid-base interactions. The change in the ratio between Brønsted and Lewis type interactions can be ascribed to the differences in hydroxylation of the superficial oxide layer. Besides, coating spectroscopy data (FTIR, FTNIR, DSC, DMTA, H+ and C13 NMR, SEC, ICP and POM) suggest that diamine monomers dissolve the metallic hydroxylated oxide layer. Then, the metallic ions diffuse through the liquid organic layer to form a complex by coordination with diamine monomers (chelate or ligand). When metal-amine complexes are mixed within the DGEBA monomer a phase separation is induced during the curing cycle, leading to the formation of a new network. Furthermore, when the organo-metallic complex concentration is higher than the solubility product, these complexes crystallize as sharp needles. They align themselves parallel to the metallic oxidized surface and act as oriented short fibers in an organic matrix thus leading to an increase of its mechanical properties.
2:40 PM		AS-ThA-3 Acid-base Characterisation of Metallic Surfaces M.-G. Barthés-Labrousse (CNRS, France)
3:20 PM		AS-ThA-5 Effects of Plasma Treatment on Solder Resist Investigated by Contact Angle, XPS and AFM F.L. Hall, C.A. Bradbury (Micron Technology Inc.) During the initial development of the chip on board (COB) fine ball grid array (FBGA) process, repeated reliability failures resulting from delamination between the epoxy molding compound and the solder resist interface created a need to investigate treatments to improve adhesion between these surfaces. One such means for improvement was exposing the solder resist to plasma prior to molding. A study of the effects of plasma treatment on solder resist as it applies to the assembly of COB FBGA packages was performed. In this study, solder resist samples were subjected to direct and downstream plasma treatments at various settings. The treated samples were then examined for chemical and physical changes via X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and contact angle. Changes in the surface during storage were also evaluated.
3:40 PM		AS-ThA-6 Correlation between Surface Topography and Corrosion Rate: An Investigation by Scanning Force Microscopy J.E. Castle, P.A. Zhdan, P. Singjai, T. Simpson (University of Surrey, U.K.) In the course of our work with many metals, alloys and inorganic materials in media of differing levels of aggression we have found an interesting broad correlation between surface topography and the extent of aqueous corrosion. The correlation is particularly apparent when use is made of scanning force microscopy (SFM) to monitor surface roughness under conditions in which the extent of corrosion can be measured by an independent method - such as solution analysis. This enables corrosion rates to be inferred from in-situ or ex-situ measurements of surface topography, made by SFM, in media or with surfaces that are not amenable to normal means of corrosion rate measurement. We draw attention to this correlation using several examples, such as etching of copper, corrosion of duplex steel and ferritic steel in hydrochloric acid, or the corrosion of brass in aerated water, and corrosion of pottery glaze in alkaline wash, which have been chosen to illustrate the phenomenon in both etching and in oxidising conditions. Underlying reasons for the correlation are discussed and it is shown that a useful outcome of the work is that it permits measurements by in situ SFM to be used for interpolation or extrapolation of data obtained by electrochemical methods or by analysis of the corrodent solutions. The SFM as an instrument is becoming widely available and this method of measurement thus has a wide application. It is suggested that as more robust forms of the SFM instrument become available, there is the possibility of using this technique as a corrosion monitor under circumstances in which measurement of corrosion rate is difficult by more conventional methods.
4:00 PM		AS-ThA-7 Corrosion Studies Using X-Ray Techniques H.S. Isaacs (Brookhaven National Laboratory) A major advantage of x-ray techniques is that they allow in situ studies of the processes taking place. A range of applications of synchrotron x-rays for the study corrosion will be briefly reviewed. These include novel atmospheric measurements using ionize air to determine Volta potentials usually made using Kelvin probes, and scanning x-ray fluorescence techniques for the analysis of corrosion products at the corroding interface and within solution. Emphasis will be given to the measurement of passive oxide films. These are a few nanometers thick and responsible for corrosion resistance. Examples using x-ray absorption will be given of the chemistry of passive oxide films on iron and stainless steels, their electrochemical formation, dissolution, and the behavior of chromium, the critical additive to stainless steels.
4:40 PM		AS-ThA-9 The Physical and Chemical Surface Structure of Iron Exposed to Carbon Tetrachloride-Saturated Water D.J. Gaspar, A.S. Lea, M.H. Engelhard, D.R. Baer (Pacific Northwest National Laboratory); R. Miehr, P.G. Tratnyek (Oregon Graduate Institute) The corrosion of metallic iron by carbon tetrachloride (CCl₄) has been studied by surface analysis techniques, including time-of-flight secondary ion mass spectrometry (TOF-SIMS), Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy (XPS). Permeable barriers made of "zero-valent" iron powders are among the methods being considered to assist environmental remediation by catalytic destruction of halogenated solvents. Understanding the chemical and physical properties of the corrosion layer formed on the iron particles is critical in the design of advanced catalysts for environmental remediation because the oxidized layer on the surface of the metallic iron particles is modified during reduction of the halogen-containing species. Among the specific questions is the nature of "active" sites that may facilitate the reduction of the halogenated hydrocarbons. To this end, selected polycrystalline zero-valent iron particles were treated with CCl₄-saturated water for a period of 1-7 days, and the physical and chemical structure of the surface was studied. The chemical and physical structure of the oxidized iron surface was then examined, revealing localization of chloride within etch pits.
5:00 PM		AS-ThA-10 Adsorption of Organic Acids onto the Surface of 2024-T3 Aluminium Alloy: The Role of Intermetallic Particles A.J. Roberts (Kratos Analytical Ltd., UK); D. Engleberg, Y. Liu, G.E. Thompson, M.R. Alexander (UMIST, UK) Self-assembled monolayers of alkyl-phosphonic and carboxylic acids have been proposed as alternatives to conventional chrome-based pre-treatments for corrosion protection of aluminium. These organic pre-treatments aim to form coupling layers between the air-formed aluminium surface and the resin component of paints and adhesives.¹ Commercial aluminium alloys contain intermetallic particles which mechanical and chemical finishing processes may expose at the surface.² Analysis is complicated by the size of the particles that can range from 0.1-10µm. Auger analysis has suggested preferential adsorption of long chain phosphonic acids at iron-containing inclusions in an AlMg1 alloy, although no chemical state or quantitative information was presented.³ Small area and imaging XPS, with a Kratos Axis Ultra spectrometer, has been used to obtain quantitative elemental and chemical state information from such particles (Al₂Cu and Al₂CuMg) at the mechanically polished surface of Al 2024-T3, an alloy of importance in the aerospace industry. Alkyl-phosphonic and -carboxylic acids were adsorbed from dilute solutions allowing comparison of coverage and chemical state between the second phase intermetallics and the hydrated alumina surface of the matrix. Comparison is also made with the adsorption characteristics on super pure Al.⁴ Polarisation modulation IRRAS provides complimentary information on the interfacial bonding and degree of order within the monolayers. ¹I Maege et al. Macromol. Symp. 126 (1997) 7. ²I Pires et al. Transactions of the Institute of Metal Finishing 78 (2000) 179. ³Ch. Bram et al. Fresenius J Anal Chem 358 (1997) 108. ⁴ TA Lewington et al. Comparison of alkyl-carboxylic and phosphonic acid monolayer formation on Al, in preparation for submission to Surf. Interface Anal.