ABSTRACTS



The following is a list of the abstracts for papers which will be presented in SECOND INTERNATIONAL SYMPOSIUM ON ADHESION ASPECTS OF POLYMERIC COATINGS. 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.)


J. Baghdachi; Coatings Research Institute, Eastern Michigan University, 430 Forest Ave, Ypsilanti, MI 48197

Dependence Of Coating Adhesion On Formulation Variables



Most polymeric coatings are composed of many interactive chemicals. Each ingredient provides specific property including adhesion. It is reasonable to believe that the interactive chemicals sooner or later if they were not polymer bound react to form new chemical species, to catalyze side reactions, diffuse or permeate through the interface and or migrate all together. This phenomenon appears to be time and temperature dependent. Therefore, initial adhesion deteriorates over time not only due to changes in the substrate/coating interface but due to the formation of new chemical species or breakdown of the functional ingredients. In this paper we describe examples of adhesion loss due to the above phenomena.


N.V.Bhat and RR.Deshmukh; Physics Division, Department of Chemical Technology, Matunga,Bombay 400019, INDIA

Characterization and Adhesion of Plasma Deposited Films on

Polyester



Adhesion of polymeric coatings on various surfaces have assumed great importance recently on account of numerous applications. For good adhesion, surface conditions are of importance. Recently treatment of surfaces with gaseous plasma have been found to yield better adhesion for metals, polymers and fibers. Treatment in gaseous plasma induces etching, cross-linking and many surface reactions leading to improvement in adhesion. The present paper describes our work regarding plasma treatment and plasma deposited films on polyester surfaces with a view of better utilization. Polyester films are used extensively for packaging, electrical insulation and printing. However it has some drawbacks such as hydrophobicity and permeation to water vapors. It was therefore thought interesting to treat the PET films with plasma and improve its properties. Commercial PET films were treated in Nitrogen and Air plasma using RF source. It was found that there is a slight weight loss and angle of contact with water increases with time of treatment. SEM studies reveal that surface morphology changes from very smooth to rough wavy structure. Adhesion was found by using peel test method. It was found that the force required to peel increases with increasing time of treatment, although initially trend is different. These PET films were then coated with very thin layer of Styrene and Acrylonitrile using the method of plasma polymerisation. This was with an aim to improve the permeability characteristics. The adhesion of the deposited films is of importance. Studies were therefore carried out on adhesion and it was found that adhesion was good and it improved when surface was pretreated with Nitrogen plasma.


Mari de Meijer; SHR Timber Research, P.O.Box 497 NL, 6700 AL Wageningen, THE NETHERLANDS

Analysis Of The Wet Adhesion Of Coatings On Wood



Maintaining a good adhesion of coatings at high water concentrations is of great importance for moisture sensitive substrates like wood. This paper describes a newly developed method to measure the adhesion of coatings on wood based on a peel test method. By means of analysing the peel force as a function of the surface structure of the wood, the influence of mechanical anchoring on the adhesion could be demonstrated. With this method several model coating formulations based on waterborne acrylic dispersions, alkyd emulsions and solventborne alkyd solutions were compared.

The measured wet adhesion is further analysed with respect to contributions of interfacial work of adhesion and the reduction of adhesion due to internal stress. Work of adhesion was calculated both according to the Lifshitz-van der Waals-acid-base theory and from polar and disperse components under dry conditions and in the presence of water. For coatings that show a strong swelling at high moisture content, the resulting hygroscopic strain causes high levels of stored internal stress which have a negative impact on the adhesion.

Because mechanical anchoring is directly related to wetting of the coating and penetration into the substrate, factors controlling these processes will be discussed. Finally some recent findings concerning the improvement of wood wettability by means of flame-ionisation will be briefly addressed.




Prof. G. Frens; Delft University of Technology, Laboratory of Physical Chemistry, Julianalaan 136, 2628 BL Delft, The Netherlands

Depletion, a Key Factor in Polymer Adhesion

The specific properties of polymers are essential for the strength of the adhesive bond. Generally, the random coil of a polymer is repelled, entropically, from an impenetrable surface by the depletion effect. To bond the polymer molecules it must be forced actively towards the interface. Suppression of depletion is brought about by adsorption of specific groups, interacting with polar sites on the substrate. Altering the balance between adsorption and depletion is the most important effect of pretreatments on the strength of the adhesive bond. Adsorption diminishes the effective distance between the surface and the adhesive polymer. This rather than the effect of polar groups on the work of adhesion, leads to order of magnitude increase of the adhesion force between polymeric coatings and a surface.


J. F. Friedrich, P. Krüger, G. Kühn, U. Schulz, J. Erdmann*, M. Möller*, A. Lippitz and W. E. S. Unger; Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin, GERMANY

*Fluor Technik System GmbH Lauterbach, Alte Bergstraße 25-27, 36341 Lauterbach, GERMANY



The Role of Fluorine in Modifying Polymer Surfaces by Gas and Plasma Pretreatment



Fluorination of the surface of poly(ethylene) or laquers used for painting automobiles and defluorination of poly(tetrafluoroethylene), PTFE, surfaces were often performed with a common goal: improvement of their adhesion properties.

Gas phase as well as plasmachemical surface fluorination of polymers like poly(ethylene) is well known to increase their wettability and adhesion properties. The gas phase fluorination of polymers is a strongly exothermal radical process resulting in a partial fluorination of their surface together with a formation of carbon radicals and olefinic double bonds. After finishing the fluorination process the resulting radicals pick up oxygen from air and form some polar groups. The number of polar groups can be increased and adjusted to a pre-selected level by using of fluorine/oxygen mixtures. Such a mixture produces F, O and OF functional groups at the polymer surface and, therefore, introduces a strong polarity. This leads to an enhancement of metal-polymer interaction in the respective composites. Exposure of a polymer surface to a CF4/O2 plasma results in similar results.

Using fluorine strongly diluted in inert gases (N2, Ar) or liquids such as freons or fomblins a more complete surface fluorination is achieved, sometimes also perfluorination is reached. Perfluorinated polymer layers show anti-adhesive properties. Moreover, highly fluorinated polymers free of oxygen groups are rather stable against ageing at outdoor conditions in different climates.

Originally perfluorinated polymer surfaces, such as PTFE, can be modified in fluorine and oxygen containing plasmas in order to give good adhesion to molded poly(phenylene) sulphide or metallization with copper. CF4/O2 plasmas usually roughen PTFE surfaces and form polar oxygen groups. The adhesion promotion effect is correlated to C(=O)F and oxygen containing decomposition products of OF groups. Other ways to enhance the adhesion properties of PTFE were examined: (i) the reduction by exposure to a H2 plasma and conversion of the CF2 groups into hydrocarbon CH2 groups, (ii) the H2 plasma reduction and the amino group functionalization using an NH3 plasma and (iii) the use of alkaline vapour and alkaline vapour plasmas. Reduction processes in solution with alkaline metals are well-known, e.g. the sodium/NH3 or the sodium/naphthalene process applied to PTFE.

A third way to promote the adhesion properties of a PTFE surface is to deposit plasma polymer layers characterized by a high density of OH, NH2 or COOH groups. Up to now, this way is not very often explored.


Luona L. N. Goh1,2, Simon Y.M. Chooi1, Yi Xu1, Mei-Sheng Zhou1, Toh S.L.2 and Tay T.E.2

1) Advanced Technology, Chartered Semiconductor Manufacturing,

60 Woodlands Industrial Park D Street 2, Singapore 738406, SINGAPORE



2) Department of Mechanical Engineering, National University of Singapore,

10 Kent Ridge Crescent, Singapore 119260, SINGAPORE



Modified Scotch Tape Test: Measurement of Adhesion of a Low Dielectric Constant Organic Polymer on Various Insulator Films



The continuing trend toward lower RC time constants in advanced integrated circuits has led to the intensive studies and development of low dielectric constant (low k) materials. However, the integration of low k dielectric materials into the circuit is challenging. One vital aspect of integration relates to the adherence of the low-k dielectric to the film that lies above and beneath it.



In the microelectronics industry, a simple scotch tape pull test (ASTM 3359-95a) is typically performed to qualitatively study the adhesion of dielectric films. In this work, a novel approach to conduct the scotch-tape test is proposed, that will be able to provide both qualitative and quantitative results. This approach employs a spring-loaded mechanism and eliminates the subjective interpretation of the results of the traditional scotch-tape test. It also provides quantitative measures of the peeling speed and force, factors which may be relevant in the characterization of the interfacial strength of thin films.



We illustrate the use of this new modified scotch-tape test (MST), together with the usual peel and stud pull tests in a study of the adhesion of multi-layered thin film structures. The structure consists of a thin film of a low k dielectric organic polymer (Flare, from AlliedSignal) with silicon nitride and silicon oxide films deposited using silane and tetraethylorthosilicate (TEOS). Since these oxide layers are often used as hard masks to pattern the low k dielectric layer, their adhesion to the low-k dielectric material is thus very important. Experimental results obtained from the proposed MST show less scatter and greater consistency than those obtained using the peel or stud pull tests.


J.J. Santana Rodríguez, F.J. Santana Hernández, J.E. González González ;

Dpto. Ingeniería de Procesos, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira, C.P. 35017, Islas Canarias, España.



Study of Different Paint Coatings as Anticorrosive Protection of Several Metals of Industrial Interest in the Canary Islands (Spain)



The atmospheric corrosion in the Canary Islands (Spain) is characterized to be very varied. This way, we have atmospheres industrial-marines and marines in the coastal areas, urban areas and rural atmosphere in the interior areas. Due to the great deterioration that the metals suffer in the most aggressive areas, different types of polymeric coatings have been studied with the purpose of determining which is the one that offers a better protection along the time in metals of great industrial interest as the carbon steel and the galvanized steel. Different paint coatings have been rehearsed composed by layers of anticorrosive epoxy (one rich in zinc, another free of lead and chromates) and modified aluminum epoxy as primer layers; thick epoxy and aliphatic polyurethane like intermediate layers and, finally, aliphatic polyurethane finishing coat and glossy finish coat. Their properties have been studied by means of classic techniques (measure of the coat thickness, pendulum persoz, scratch hardness, digital adherence, paint blistering and for established defect) and by means of electrochemical impedance measurements (EIS).


Ann M. Straccia, Larry P. Haack and Joseph W. Holubka; Ford research Laboratory, MD 3135, P.O. Box 2053, Dearborn, MI 48121-2053



Polymer Composition, Interfacial Chemistry and Adhesion in Multilayered Systems



In this work, we describe how specific details of the coating formulation can control the chemical nature of the interphase region and subsequent adhesion performance realized by the system. A statistically designed experiment, combined with interfacial characterization by X-ray photoelectron spectroscopy (XPS) on systems exhibiting weak adhesion was undertaken. Results revealed that specific blends of polymer, melamine crosslinker, catalyst and solvent can interact in ways to generate a range of chemical compositions at the interphase region resulting in varying adhesion performance. Polyester coatings employing a long-chain aliphatic acid catalyst (dodecyl sulfonic acid) exhibited a high sensitivity to the type of melamine crosslinker used. The poorest adhesion to an epoxy coating was observed when the polyester was cross-linked with a partially-alkylated, "high amino" melamine. The interfacial region of this system was dominated entirely by reaction moieties comprised of catalyst and crosslinker components of the polyester reacting with an amine terminated polyester anti-cratering agent used in the epoxy. In contrast, a similarly-prepared system using para-toluene sulfonic acid catalyst showed no adhesion performance sensitivity to changes in melamine, or to other formulation changes in general. This talk will also elaborate on further details that disclose how the overall coating composition can influence the interfacial chemistry and subsequent adhesion performance of the system.






Guido Hora; Fraunhofer-Institute for Wood Research; Wilhelm-Klauditz-Institute (WKI); Bienroder Weg 54e; D-38108 Braunschweig

U. Désor; Clariant GmbH; Division CP, LBU Emulsions, Technical Service; D-65926 Frankfurt/M



Improving Wet Adhesion of Water Borne Coatings for Wood



The adhesion of water-borne dispersions for exterior wood coatings could be failed under the influence of moisture especially during early service life. This behaviour can cause severe damages to the coated wood construction and to the image of exterior used wood. Hence, five different water borne dispersions without and with different wet adhesion promotors and one coating system based on a commercial dispersion with wet adhesion promotor were investigated. They are tested in terms of their capabilities concerning wet adhesion on different wood species and contact angle formation on a cleaned glass-plate under different conditions. Sipo Mahagony, Red Meranti, European pine sapwood and heartwood have been used as substrates directly after planing, storing for a month, extracted and enriched by extractives. Also, the influence of secondary wet adhesion promoters in the dispersions has been studied. Even though, the initial contact angles for wetting are elevated significantly and a general adhesion improvement can be derived by adding the secondary functional promoter groups. The generally higher adhesion values on tropical woods can be explained with the higher porosity and hence enhanced free surface area for mechanical bonding for these wood species.


Taiji Ikawa and Tohr Shiga; Toyota Central Research & Development Laboratories Inc., Nagakute-cho, Aichi-gun, 480-1192 JAPAN

Measurement of Internal Stresses in Polymeric Materials Using Time Resolved Fluorescence



We present a new nondestructive technique for detecting internal stresses in polymeric materials using time resolved fluorescence. The new technique is based upon an experimental result that the lifetime of fluorescence from organic molecules in a uniaxially-stretched polymer film decreases with increasing tensile stress acting on the film. The useful organic molecules as the fluorescence label were 9-methylantracence and poly(3-octylthiophene). We first measured internal stresses in thin thermosetting polymer films which were painted on a thin metal substrate using the time resolved fluorescence technique and a traditional bimetallic method. Comparing both methods, it was concluded that the time resolved fluorescence technique gave reliable values for internal stresses in the films.



The time resolved fluorescence technique was applied to analyze internal stresses in two polymeric materials. One was thin polymer films of a multilayer system coated on a metal substrate. The system was composed of electro-deposited coat, surfacer coat, base coat and clear coat. When the polymer coats were piled up, the internal stress in the upper coat was smaller than that in the lower coat. The order of internal stresses in the clear coat and base coat was 1 MPa. The effects of moisture, temperature, and light on the internal stresses were investigated. The other sample was a deformed test piece of carbonblack-filled PVC, which was injection-molded. Residual stresses at the surface of the test piece were estimated. The results obtained roughly explained the deformation aspect of the test piece. The residual stresses were monitored during annealing.


Jude O. Iroh, Ph.D; Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0012

Effect of Electrochemical Process Variables on the Adhesion of Polypyrrole Coatings onto Low Carbon Steel



(Abstract not yet available)


S. Maeda; Parker Industries, Inc., 2-11-14-12 Nakaikegami, Ohta-ku Tokyo, 146-0081 Japan

Adhesion of an Alkyd Paint on Cold Rolled Steel Sheet: Effect of Steel Surface Composition



Paint adhesion of an amino alkyd paint applied to bare cold-rolled steel sheets manufactured by different processes has been studied using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Glow discharge spectroscopy (GDS) and zeta potential measurement. The paint adhesion was strongly dependent upon the manufacturing processes: an excellent adhesion was obtained on a batch-annealed sheet, whereas the adhesion of a continuously annealed sheet catastrophically failed. Results obtained from the surface analyses showed that the outermost surface of the batch-annealed sheet was composed primarily of FeOOH except carbonaceous contamination whereas a significant amount of calcium silicate was present on the continuously annealed sheet surface. The deposition of the silicate is due to poor water rinse after the electro-degreasing by an alkaline solution prior to annealing. The metal silicates were also observed on a paint-delaminated substrate surface; therefore the adhesion failure can be attributed to the metal silicate deposition on the surface. A possible explanation for the poor adhesion would appear to involve the loss of the acid-base interaction between the amino alkyd resin and the silicate-contaminated surface because of the same basic properties.


Zhong Bin, Chirag Shah, Marufur Rahim, John Massingill; Coatings Research Institute, Eastern Michigan University, 430 West Forest Avenue, Ypsilanti, MI 48197

Coating Adhesion Improvements with Soy Phosphate Ester Polyol



Novel phosphate ester derivatives of epoxidized soybean oil have been synthesized and evaluated in solvent-borne coatings. Synthesis of these derivatives were based on earlier work with bisphenol A epoxy phosphate esters. Epoxidized soybean oil was used to prepare soybean oil phosphate ester polyols (SOPEP). It was anticipated that, like Bis A epoxy phosphate ester, the addition of phosphate moiety to the soybean oil would improve adhesion and that the resulting hydroxyl groups obtained from epoxy hydrolysis would take part in crosslinking reactions. SOPEP have typical hydroxyl numbers 130-180 and acid value 3-10 with viscosity of 900-1000 cPs.

We used SOPEP as a multi-functional reactive diluent to replace 50% of the resin in a solvent-borne alkyd bake coating cured with melamine crosslinkers. Results were excellent- pencil hardness 3H, adhesion 5B, impact resistance 160/160, and MEK Resistance >200. Other coating types also gave adhesion improvements.


Leanne Britcher, David Kehoe and Janis G. Matisons; Ian Wark Research Institute, Univ. of South Australia, The Levels SA 5095, AUSTRALIA

Assessing the Adhesion of Siloxane Polymers on E-glass Fibers Investigated by X-ray Photoelectron Spectroscopy



Siloxane polymers may be synthesized with various functional groups and molecular weight distributions which make them capable of adhering to a wide variety of surfaces. We were interested in preparing siloxane polymers which can adhere to E-glass fibers and possibly replace the silane coupling agents in composite materials. A wide range of siloxane polymers bearing hydroxyl, hydrido, methacryl, amino and trialkixy functional groups were prepared and applied to E-glass fibers. To establis the presence of the siloxane on the fibers Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) and X-ray Photoelectron Spectroscopy (XPS) were used.



This presentation will focus on the use of XPS to establish the adhesion of siloxanes on E-glass fibers. We have found that the difference between the energies of the O1s and Si2p photoelectron lines can be used to characterize the surfaces of siloxane coated E-glass fibers, as either resembling a siloxane (good coating) or the E-glass fiber (poor coating). The O1s-Si2p binding energy difference has been used to assess the adhesion of various functional siloxanes on E-glass fibers after a stringent washing procedure. The degree of siloxane coverage was found to be dependent on the functional groups pendant on the siloxane backbone.


P. Pfeiffer1, Ibrahim Nergiz2 and Mutlu Oezcan3

1) Zentrum für Zahn-, Mund- und Kieferheilkunde der Universitaet zu Koeln,

Kerpener Str. 32, 50931 Koeln GERMANY

2) Abt. f. Zahnerhaltungskunde und Parodontologie der Universitaet Hamburg,

GERMANY

3) University of Marmara, Istanbul, TURKEY



Metal Surface Conditioning Concepts for Resin Bonding in Dentistry



Although satisfactory bonding between porcelain and metal is achieved under current dental practice, during the last decade many attempts have been made to create and develop techniques for bonding composite resins to dental metals. The recommended bond strength for polymer-based crown and bridge veneering materials without macromechanical retention is at least 5 MPa (ISO 10477, amendment 1, 04-98). The purpose of this study was to evaluate the effectiveness of various surface treatments used to enhance the bond strength of composite resins to dental alloys. The procedures of Silicoater Classical, Silicoater MD, Kevloc AC and Siloc originate from the need for an intermediate layer containing SiOx or chrome endowing silica layer by heat treatment. The principle of the Rocatec system is a tribochemical application of a silica layer by means of sandblasting. After thermocycling and water storage shear bond strength was tested. The chemical bonding systems exhibited mean shear bond strengths greater than 6 MPa (control group with mechanical retention: 6 - 15 MPa). No significant differences between bond strengths of different composite resins were found. The tested chemical bonding systems can be recommended for resin-to-metal bonding as alternatives to mechanical retention.


Jan Rayss; Lab. Of Optical Fibers Technology, Marie Curie Sklodowska University, 20-031 Lublin, POLAND

Adhesion of Polymer Protective Coatings on Optical Fibres



This paper will discuss the following problem areas:




Alain A. Roche; INSA de Lyon, Laboratoire des Matériaux, Macromoléculaires (CNRS, UMR 5627), 20 Ave., Albert EINSTEIN, F-69621, Villeurbanne Cedex.: Alain-Andre.Roche@insa-lyon.fr

Interphase: Formation, Characterization and Relevance to Adherence.



Epoxy-diamine networks are extensively used as adhesives or paints in many industrial applications. When the precursors are applied on metallic substrates and cured, an interphase, having chemical, physical and mechanical properties quite different to polymer bulk ones, is created between the substrate and the polymer. Moreover, chemical reactions between diamine and metallic surfaces induce an increase in the practical adhesion (adherence). When the same epoxy-diamine mixtures are applied onto gold coated or polyethylene substrates, properties are the same as bulk ones. When epoxy-diamine mixtures are applied onto aluminum or titanium alloy surfaces, the glass transition temperature, amine and epoxy extent of reaction, the interphase thickness and amplitude, residual stresses within the interphase, Young's modulus of the interphase depend 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. Coating analyses (FTIR, FTNIR, DSC, DMTA, H+ and C13 NMR, SEC, ICP and POM) suggest that diamine monomers chemically react and dissolve the metallic hydrated oxide layer. Then, metallic ions diffuse through the organic layer to form a complex by coordination with diamine monomers (chelate or ligand). Metal-diamine complexes are insoluble, at room temperature, either in diamine or in DGEBA monomers and they induce phase separation during the curing cycle of the epoxy-diamine precursors. Furthermore, the chemical bonding of diamine monomers on the metallic surfaces and the diamine-metal crystal orientation parallel to the metallic surface within the interphase lead to chemical, physical and mechanical properties different to the epoxy-diamine network bulk ones.


Michael Rohwerder; Max-Planck-Institut für Eisenforschung, P.O. Box 140444, D-40237 Düsseldorf, GERMANY

The Scanning Kelvinprobe - a New Technique to Study the Stability of Metal/polymer Bonds



Over the last 10 years the scanning Kelvinprobe has been developed in our laboratory as a new and inspiring technique to study the stability of metal/polymer interfaces in corrosive media. The Kelvinprobe will mainly measure the electrochemically defined electrode potential at the buried interface and therefore allows conclusions concerning the nature and

rate of electrochemical reactions. In many circumstances the stability of substrate/polymer bonds is limited by electrochemical reactions, like the reduction of oxygen, which will form highly reactive intermediates able to chemically destroy bonds in the hydrocarbon chain. Recent studies have focused on galvanized steel and Al-alloys as substrates. On galvanized

steel, electron conducting oxides are present which allow rapid oxygen reduction if the surface is not treated by phosphates or chromates. In the presence of defects which penetrate the coating, either cathodic delarnination or anodic undermining is observed. Both can clearly

be distinguished by the Kelvinprobe. Surface treatments will alter the rate of electrochemical reactions and will therefore change the electrode potential as measured by the Kelvinprobe. On Al, insulating oxides are formed and electrochemical reactions are only concentrated on spots with a high local reactivity. Then cathodic delamination will no longer be observed but filiform corrosion is the dominating mechanism which leads to loss of adhesion. Also for this case, recent progress has been made using the Kelvinprobe,


Rose A. Ryntz; Visteon Automotive Systems, A Subsidiary of Ford Motor Company, 401 Southfield Road, Dearborn, MI 48121

Attaining Adhesion/Cohesion Within Painted Plastics



A growing number of automotive plastic parts, both interior and exterior, are utilizing olefin based materials to achieve cost/performance targets. Olefin based alloys, most often blends of poly(propylene) (PP) and ethylene-propylene (EP) or ethylene-butene (EB) elastomers, generally meet the increasingly stringent cost/performance targets based on "key-life" attributes, namely 10 year durability. Key attributes of performance that must be managed in PP/EP/EB alloys (often referred to as thermoplastic olefins (TPOs)), however, include adhesion, in painted applications, and cohesion, in painted or unpainted applications. This talk will focus on the key performance attributes required and discuss ways to achieve them. More specifically, paint adhesion, friction induced paint damage, and weathering characteristics of painted TPOs will be examined.


Edward O. Shaffer II; The Dow Chemical Company, 1702 Building, Midland, MI 48674

Use of the Modified Edge Liftoff Test for Measuring the Adhesion of Multilayer, Thin-Film Microelectronic Structures



Over the past several years, the relentless drive to meet the performance demands of Moore's law and the increase in BEOL delay times has led the microelectronics industry to evaluate a large number of new materials and processes. For example, in 1997 IBM announced the use of copper damascene processes to replace aluminum-tungsten subtractive process for metallization and, most recently, announced the use of SiLK* semiconductor polymer as its BEOL dielectric to replace traditional SiO2. Both of these dramatic shifts in IC manufacturing practices are the culmination of hundred's of man-years investigating the reliability of various new materials and processes. Intrinsic to the success for these materials and processes is maintaining good mechanical integrity or simply put adhesion.



Towards this, the modified edge lift off test (mELT) was developed to give IC manufacturers an easy way to evaluate the fracture toughness/adhesion of thin-film, multilayer, coatings on a rigid substrate. The test consists of applying a thick epoxy backing layer to the coatings; dicing into coupons; and cooling these until debonding is observed. From the observed debond temperature, the epoxy's stress-temperature profile, and the epoxy film height, the critical fracture intensity is calculated. In this paper, we will present results demonstrating the utility and robustness of the test; some of its limitations; and examples of its use.


Fernando Galembeck and Elizabeth F. de Souza; Institute of Chemistry, University of Campinas, P.O. Box 6154, 13083 -970 Campinas(SP), BRAZIL

Scanning Electric Potential (Sepm) and Electric Force (Efm) Imaging of Polymer Surfaces



Surface potentials on monolayers at water-air interfaces have been measured for many decades, but similar data on polymer surfaces are scarce. With the advent of the scanning probe microscopes, imaging contrast based on electrical features of the surfaces became possible, for most materials including polymers. Imaging of hexagonally packed dry macrocrystals of poly(styrene - hydroxyethylmetacrylate) reveals negatively charged particle cores, relative to the interconnecting particle shells. This result is in agreement to the available information obtained by energy-loss analytical transmission microscopy (ESI-TEM), on these particles. The examination of Stöber silica particles showed a size-dependent pattern of electrical contrast: smaller particles dry forming a well-packed film, with a significant electrical contrast from one particle to another, while larger particles do not show significant contrast, either interparticle or intraparticle. Many other polymer materials, either samples from industrial processes or laboratory specimens were examined, and electrical contrast was found in most cases. These results reveal that polymers contain microscopic domains of nonuniform electrical potentials, within a variety of patterns. This finding may help us to understand phenomena of static electricity and its role in polymer adhesion (e.g., following Derjaguin) and cohesion.


Anurag P.S. Tihaiya and James P. Bell; Institute of Material Science, University of Connecticut, 97 N. Eagleville Road, Storrs, CT 06269-3136 (USA)

Guy D. Davis; DACCOSCI Inc., 10260 Old Columbia Rd, Columbia, MD 21046 (USA)



Thomas R. Hanlon; United Technologies Research Center, 411 Silver Lane, MS 129-70, East Hartford, CT 06108 (USA)





The Residue (Smut) Formed on Aluminum Alloys During Hydrofluoric Acid Etching and its Effect on a Coating Process



Hydrofluoric acid (HF) etching was studied as a pretreatment process for aluminum alloys. A coating process involving spontaneous polymerization on aluminum surfaces was used as a basis for the study. Five different aluminum alloys (2024, 3105, 5000, 6061 and 7075) were the subjects for the study. Treated aluminum surfaces were analyzed by means of XPS, AES and ESEM. HF etching was observed to result in differing behavior among the alloys. Differences were observed in extent of etching, surface morphology obtained after etching and the quantity of residual etching product on the surface. These factors led to different coating rates on the alloys. The residual etching product ("smut") was observed to affect the polymerization rate on the surface and was critical in some cases for the coating formation. The smut consisted of hexagonal crystals and was identified as being primarily AlF--3.3H2O. Presence of smut also affected the adhesive bond strength of the coating formed on the surface.


Wim van Ooij, Danqing Zhu and Senthil K. Jayaseelan; Dept. of Materials Science and Engr., University of Cincinnati, Cincinnati, OH 45221-0012

Modification of Polymer-metal Interfaces by Functional and Non-functional Silane



Interfaces between polymers such as paints and rubber compounds were modified by silanes and the adhesion and corrosion performance determined. Electrochemical Impedance Spectroscopy (EIS) was used as the major tool to determine the properties of the system (using a non-corroding electrolyte) or the corrosion protection, using a sodium chloride solution. A universal silane systemwas found, consisting of two bis-silanes, that provide stable adhesion and corrosion protection to a wide range of metals and polymers.


Ying Wang; Motorola, Inc., 4000 Commercial Ave., Northbrook, IL 60062

Adhesion Strength of Perfluoronated Dielectric Gel to Polyphenylene (PPS) Sulfide



The adhesion strength of perfluoronated dielectric gel to polyphenylene (PPS) sulfide was investigated. The effect of different fillers in PPS as a function of plasma treatment conditions was evaluated. The change of adhesion as results of thermal baking was also addressed. The surface composition and energy were monitored and systematically quantified by X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements. The correlation between the presence of certain functional groups, change of surface energy and polarity, and variation of adhesion properties indicate that the adhesion mechanism is mainly due to van del Waals forces. A better wetting on the substrate/adhesive interface and a deeper interfacial diffusion zone are necessary conditions to achieve the optimized adhesion.