26 -1 26 Electrodeposition of Polymers 26.1 Introduction 26- 1 26.2 Advantages 26- 1 26.3 History 26- 2 26.4 Process 26- 2 26.5 Equipment 26- 3 26.6 Laboratory 5 References 26- 5 Bibliography 26- 6 26.1 Introduction The electrodeposition of polymers is an extension of painting techniques into the field of plating and, like plating, is a dip coating process. The art of metal plating utilizes the fact that metal ions, usually Ni 2+ or Cu 2+ , can be discharged on the cathode to give well-adhering deposits of metallic nickel, copper, etc. The chemical process of deposition can be described as 1/2 Me 2+ + 1 F (or 96,500 coulombs) of electrons gives 1/2 Me 0 . In the case of electrodeposition of ionizable polymers, the deposition reaction is described as R 3 NH + OH – + 1 F → R 3 N + H 2 O or the conversion of water-dispersed, ammonium-type ions into ammonia-type, water-insoluble polymers known as cathodic deposition. Alternatively, a large number of installations utilize the anodic deposition process RCOO – + H + less 1 F → RCOOH. It should be mentioned that “R” symbolizes any of the widely used polymers (acrylics, epoxies, alkyds, etc.). The electrodeposition process is defined as the utilization of “synthetic, water dispersed, electrodepos- itable macro-ions.” 1 26.2 Advantages Metal ions, typically 1/2 Ni 2+ , show an electrical equivalent weight 1/2 Ni 2+ equal to approximately 29.5 g, while the polymeric ions typically used for electrodeposition exhibit a gram equivalent weight (GEW) of approximately 1600. Thus, 1 F plates out of 30 g of nickel and deposits 1600 g of macroions. If we George E. F. Brewer* George E. F. Brewer Coating Consultants * Deceased. DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Throwing Power • Maintaining a Steady State • Rupture Voltage Conveyors • Metal Preparation • Tank Enclosures • Dip Tanks • Wate r • Bake or Cure Rectifiers • Counterelectrodes • Agitation • Temperature Control • Ultrafilter • Paint Filters • Paint Makeup • Deionized 27 -1 27 Electroless Plating 27.1 Introduction 27- 1 27.2 Plating Systems 27- 2 27.3 Electroless Plating Solutions 27- 3 27.4 Practical Applications 27- 4 27.5 27.6 Stability of Plating Solutions 27- 7 27.7 Electroless Plating 27- 7 27.8 Properties of Chemically Deposited Metal Coatings 27- 10 References 27- 11 27.1 Introduction In electroless plating, metallic coatings are formed as a result of a chemical reaction between the reducing agent present in the solution and metal ions. The metallic phase that appears in such reactions may be obtained either in the bulk of the solution or as a precipitate in the form of a film on a solid surface. Localization of the chemical process on a particular surface requires that the surface must serve as a catalyst. If the catalyst is a reduction product (metal) itself, autocatalysis is ensured, and in this case, it is possible to deposit a coating, in principle, of unlimited thickness. Such autocatalytic reactions constitute the essence of practical processes of electroless plating. For this reason, these plating processes are sometimes called autocatalytic. Electroless plating may include metal plating techniques in which the metal is obtained as a result of the decomposition reaction of a particular compound; for example, aluminum coatings are deposited during decomposition of complex aluminum hydrides in organic solvents. However, such methods are rare, and their practical significance is not great. In a wider sense, electroless plating also includes other metal deposition processes from solutions in which an external electrical current is not used, such as immersion, and contact plating methods in which another more negative (active) metal is used as a reducing agent. However, such methods have a limited application; they are not suitable for metallization of dielectric materials, and the reactions taking place are not catalytic. Therefore, they usually are not classified as electroless plating. Electroless plating now is widely used in modifying the surface of various materials, such as noncon- ductors, semiconductors, and metals. Among the methods of applying metallic coatings, it is exceeded in volume only by electroplating techniques, and it is almost equal to vacuum metallization. Electroless plating methods have some advantages over similar electrochemical methods. These are as follows: A. Vakelis Lithuanian Academy of Sciences DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Deposition Rate • Solution Life • Reducing Agent Efficiency Copper Deposition • Nickel Plating • Cobalt, Iron, and Tin Factor • Solution Sensitivity to Activation Plating • Deposition of Precious Metals • Deposition of Metal Mechanisms of Autocatalytic Metal Ion Reduction 27-5 Alloys 27 -6 Coatings Technology Handbook, Third Edition A more versatile explanation of the causes of catalysis in these processes is based on electrochemical reactions. It is suggested that reducing agents are anodically oxidized on the catalyst surface and the electrons obtained are transferred to metal ions, which are cathodically reduced. The catalytic process comprises two simultaneous and mutually compensating electrochemical reactions. In this explanation of the catalytic process, electrons are the active intermediate product. However, electrons are fundamen- tally different from the conversational intermediate products of reactions. They may be easily transferred along the catalyst without transfer of the mass, and for this reason, the catalyst reaction, contrary to all other possible mechanisms (which are conventionally called “chemical mechanisms”), occurs not as a result of direct contact between the reactants, or the reactants, or the reactant and an intermediate substance, but because of the exchange of “anonymous” electrons via metal. On the metal surface, when anodic oxidation of the reducer (27.2) and cathodic reduction of metal ions (27.3) proceed simultaneously, a steady state in the catalytic system of electroless plating is obtained, in which the rates of both electrochemical reactions are equal, while the metal catalyst acquires a mixed potential E m . The magnitude of this potential is between the equilibrium potentials E c of the reducer and of the metal. The specific value E m depends on the kinetic parameters of these two electrochemical reactions. Electrochemical studies of catalytic metal deposition reactions have shown that the electrochemical mechanism is realized practically in all the systems of electroless plating. 4,6,7 At the same time, it has become clear that the process is often not so simple. It appears that anodic and cathodic reactions occurring simultaneously often do not remain kinetically independent but affect each other. For example, copper ion reduction increases along with anodic oxidation of formaldehyde. 8 The cathodic reduction of nickel ions and the anodic oxidation of hypophosphite in electroless nickel plating solutions are faster than in the case in which these electrochemical reactions occur separately. This interaction of electrochemical reactions probably is related to the changes in the state of the metal–catalyst surface. Electrochemical reactions may also hinder each other: for example, in reducing silver ions by hydrazine from cyanide solutions, their rate is lower than is separate Ag–Ag(1) and redox systems. The electrochemical nature of most of the autocatalytic processes discussed enables us to apply electrochemical methods to their investigation. But, they must be applied to the entire system of electroless plating, without separating the anodic and cathodic processes in space. One suitable method is based on the measurement of polarization resistance. It can provide information on the mechanism of the process and may be used for measuring the metal deposition rate (both in laboratory and in industry). 9 The polarization resistance R p is inversely proportional to the process rate i : (27.4) (27.5) where b a and b c are Tafel equation coefficients (b ≈ 1/ α nf ), α is the transfer coefficient, n is the number of electrons taking part in the reaction for one molecule of reactant, and f = F / RT ( F = Faraday number). Red →+Ox ne Me n+ + ne i bb Rb b = + ac pa c () R dE di i p = =0 DK4036_book.fm Page 6 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 27-12 Coatings Technology Handbook, Third Edition 13. G. Gawrilov, ChemischelStromläse/Vernickelung. Saulgau, Wurt.: Eugen Leuze Verlag, 1974. 14. K. M. Gorbunova et al., Fiziko-Khimichesklye Osnovy Processa Khimicheskogo Kobaltirovaniya. Moscow: Nauka, 1974. 15. A. Molenaar and J. J. C. Coumans, Surface Technol., 16, 265 (1982). 16. Y. Okinaka, in Gold Plating Technology, H. Reid and W. Goldie, Eds. Hatch End, Middlesex, England: Electrochemical Publications, Ltd., 1974, p. 82. DK4036_book.fm Page 12 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 28 -1 28 The Electrolizing Thin, Dense, Chromium Process 28.1 General Definition 28- 1 28.2 Applications 28- 2 28.3 28.4 Solution 28- 5 28.5 Properties 28- 5 28.1 General Definition The Electrolizing process uniformly deposits a dense, high chromium, nonmagnetic alloy on the surface of the basic metal being treated. The alloy used in Electrolizing provides an unusual combination of bearing properties: remarkable wear resistance, an extremely low coefficient of friction, smooth sliding properties, excellent antiseizure characteristics, and beneficial corrosion resistance. Electrolized parts perform better and last up to 10 times longer than untreated ones. The solution and application processes are carefully monitored at all Electrolizing facilities. The result is a fine-grained chromium coating that is very hard, thin, and dense and has absolute adhesive qualities. The Electrolizing process deposits a 99% chromium coating on the basis metallic surfaces, whereas normal conventional chromium plating processes tend to deposit 82 to 88% chromium in most applications. Electrolizing calls for the cleaning and removal of the matrix on the basis metal’s surface by multi- cleaning process, using a modified electrocoating process that causes the chromium metallic elements of the solution to bond to the surface porosity of the basis metal. It is during this process that the absolute adhesive characteristics and qualities of Electrolizing are generated. The Electrolizing coating will not flake, chip, or peel off the basis metal substrate when conventional ASTM bend tests and impact tests are performed. Three basic factors are always present after applying Electrolizing to metal surfaces: •Increased wear (Rockwell surface hardness of 70 to 72 R c ) •Added lubricity characteristics •Excellent corrosion resistance Michael O’Mary The Armoloy Corporation DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC General • Specific Thickness • Adhesion • Corrosion • Wear Resistance (Surface Hardness) • Lubricity • Conformity • Heat Resistance • Surface Preparation 28-4 Brightness • Hydrogen Embrittlement The Electrolizing Thin, Dense, Chromium Process 28 -3 •Automotive •Business machines •Cameras and projectors •Computers •Cryogenics • Data processing • Electronics •Food processing • Gauges and measuring equipment •Medical instruments •Metalworking •Molds (plastic and rubber) •Motor industry •Nuclear energy • Pharmaceutical • Photography (motion and still) •Refrigeration •Textile industry •Transportation Specifically, Electrolizing is approved and meets the following aerospace, nuclear, and commercial specifications: •Air Research Company, Garrett, CO •American Can Company • AMS 2406 • AMS 2438 •AVCO Lycoming — AMS 2406 •Bell Helicopter •Bendix Company Utica, NY, division Te terboro, NJ, division Kansas City, MO, division South Bend, IN, division •Boeing BAC 5709 Class II, Class IV QQC 320 •Cleveland Pneumatic Tool-CPC Specs (Chromium), QQC320 •Colt Industries Menasco, TX, division •DuPont •Fairchild Camera •Fairchild Republic •General Dynamics •General Electric Lynn, MA Cincinnati, OH (aircraft) Wilmington, MA Wilmington, NC (nuclear) Fitchburg, MA • Gillette Company, Boston •Grumman Aircraft DK4036_book.fm Page 3 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 29 -1 29 The Armoloy Chromium Process 29.1 General Definition 29- 1 29.2 Applications 29- 1 29.3 Surface Preparation 29- 2 29.4 Properties 29- 2 29.1 General Definition The Armoloy process is a low temperature, multistate, chromium alloy process of electrocoating based on a modified chromium plating technology. However, instead of the customary chromium plating solutions, the Armoloy process uses a proprietary chemical solution. The solution and application process are carefully monitored at all Armoloy facilities. The result is a satin finish chromium coating that is very hard, thin, and dense and has absolute adhesive qualities. Armoloy deposits a 99% chromium coating o the basis metallic surfaces, whereas conventional chromium plating processes tend to deposit 82 to 88% chromium in most applications. The Armoloy process involves cleaning and removing the matrix on the basis metal’s surface by special proprietary means and using a modified electrocoating process that causes the chromium metallic elements of the solution to permeate the surface porosity of the basis metal. It is during this process that the absolute adhesive characteristics and qualities of Armoloy are generated. The Armoloy coating actually becomes part of the basis metal itself, and the result is a lasting bond and a continuous, smooth, hard surface. The surface will not chip, flake, crack, peel, or separate from the basis metal under conditions of extreme heat or cold, or when standard ASTM bend tests are involved. Three basic factors are always present after applying Armoloy to metal surfaces: •Increased wear (70 to 72 R c surface hardness) •Added lubricity characteristics (including the ability to utilize Armoloy against Armoloy) •Excellent corrosion resistance 29.2 Applications 29.2.1 General Applications All ferrous and most nonferrous materials are suitable for Armoloy application. Service life of parts has been increased to 10 times normal life and even higher in certain applications. However, basis metals of aluminum, magnesium, and titanium are not good candidates for the Armoloy process. Michael O’Mary The Armoloy Corporation DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC General Applications • Specific Applications Thickness • Adhesion • Corrosion • Wear Resistance • Lubricity • Embrittlement Conformity • Heat Resistance • Brightness • Hydrogen The Armoloy Chromium Process 29 -5 The plating cycle times are very short, and the Armoloy chrome is deposited so rapidly that Armoloy seals the surface porosity of the basis metal before hydrogen ions can invade the surface of the basis metal. However, if required, Armoloy can be and will be postplate heat treated to specification. DK4036_book.fm Page 5 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 30 -1 30 Sputtered Thin Film Coatings 30.1 History 30- 1 30.2 General Principles of Sputtering 30- 1 30.3 Sputter Deposition Sources 30- 3 30.4 Other Process Considerations 30- 8 30.5 Properties of Sputtered Thin Film Coatings 30- 8 30.6 Thin Film Materials 30- 9 30.7 Applications for Sputtered Thin Films 30- 9 30.8 Additional Resources 30- 10 Bibliography 30- 10 30.1 History Sputtering was discovered in 1852 when Grove observed metal deposits at the cathodes of a cold cathode glow discharge. Until 1908 it was generally believed that the deposits resulted from evaporation at hot spots on the cathodes. However, between 1908 and 1960, experiments with obliquely incident ions and sputtering of single crystals by ion beams tended to support a momentum transfer mechanism rather than evaporation. Sputtering was used to coat mirrors as early as 1887, finding other applications such as coating fabrics and phonograph wax masters in the 1920s and 1930s. The subsequent important process improvements of radio frequency (rf) sputtering, allowing the direct deposition of insulators, and mag- netron sputtering, which enables much higher deposition rates with less substrate damage, have evolved more recently. These two developments have allowed sputtering to compete effectively with other physical vapor deposition processes such as electron beam and thermal evaporation for the deposition of high quality metal, alloy, and simple organic compound coatings, and to establish its position as one of the more important thin film deposition techniques. 30.2 General Principles of Sputtering Sputtering is a momentum transfer process. When a particle strikes a surface, the processes that follows impact depend on the energy of the incident particle, the angle of incidence, the binding energy of surface In sputtering, the incident particles are usually ions, because they can be accelerated by an applied electrical potential. If the kinetic energy with which they strike the surface is less than about 5 eV, they Brian E. Aufderheide W. H. Brady Company DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Direct Current Diode Sputtering • Triode Sputtering • Radio Electrical • Magnetic • Optical • Mechanical • Chemical • Decorative Frequency Sputtering • Magnetron Sputtering • Beam Sputtering • Reactive Sputtering atoms, and the mass of the colliding particles (Figure 30.1). [...]...DK4036_book.fm Page 5 Monday, April 25, 20 05 12:18 PM 30 -5 Sputtered Thin Film Coatings Plasma Ring Anode Magnetic Field Anode Cathode Cathode E×B Electron Motion E×B Electron Motion Plasma Ring Magnetic Field Cathode Anode Plasma Ultimate Electrons ? Primary Electrons Magnetic Field Line ? ? FIGURE 30 .5 Clockwise from upper left: schematic representations of planar... Chemical Vapor Deposition • Plasma-Enhanced Chemical Vapor Deposition (PECVD) 31.4 Decorative and Barrier Coatings 31-22 Decorative Coatings • Barrier Coatings Lindas Pranevicius Vytautas Magnus University 31 .5 Conclusions .31-28 References 31-28 31.1 Introduction For over 25 years, the thermal evaporation of aluminum onto thin polymeric webs, such as polyester (PET) and polypropylene... SiO2 and A12O3 coatings has created very interesting coating stack building blocks.2 Since 1980, tool coatings formed by physical vapor deposition (PVD) technologies have become a reality, and an industry has evolved around PVD tool coatings based on the work of the early pioneers in this field.3–6 31-1 © 2006 by Taylor & Francis Group, LLC DK4036_C031.fm Page 5 Thursday, May 12, 20 05 9:40 AM Vapor... (Figure 31.3) This geometry has some intrinsic advantages for the automated handling of parts Cathode E × B Drift Path N S Magnetic Pole Piece Assembly FIGURE 31.3 A rectangular or racetrack magnetron © 2006 by Taylor & Francis Group, LLC DK4036_C031.fm Page 8 Thursday, May 12, 20 05 9:40 AM 31-8 Coatings Technology Handbook, Third Edition Load Un-load Magnetrons Valve Valve Samples To High Vacuum Pump... rapidly scattered by the background gas, and the net deposition rate on a sample surface is fairly low © 2006 by Taylor & Francis Group, LLC DK4036_C031.fm Page 6 Thursday, May 12, 20 05 9:40 AM 31-6 Coatings Technology Handbook, Third Edition rf rf Rc Cc Dc Cathode Cathode Sheath Rp Plasma Anode Sheath Ra Ca Da Anode FIGURE 31.1 The rf excitation system: Ra and Rc — anode and cathode sheath resistances;... water behind the cathode face An industrial cathode of this design might have a diameter of 25 cm and be rated at a power of 25 kW The second important advantage of these magnetrons is that the utilization of the cathode is very efficient: up to 80% of the cathode material can be used for sputtering, compared to 15% for a nonrotating magnetron This results in much better efficiency and longer time periods... representations of planar magnetron, gun-type magnetron, and cylindrical post magnetron sputtering sources (Adapted from J A Thornton, in Deposition Technologies for Films and Coatings, R F Bunshah, Ed Park Ridge NJ: Noyes Publications, 1982, pp 194–1 95. ) “racetrack” effectively increases the number of ionizing collisions per electron in the plasma The magnetic confinement near the target results in higher achievable... to dc-powered plasmas, and the ability to operate at lower system pressures (0 .5 to 120 mPa) The cathode of a typical rf-diode system is usually powered through an impedance-matching device known as matchbox The function of the matchbox is to maximize the power flow from the rf generator, which has an output impedance of 50 ohms, to the plasma, which has a complex impedance usually in the 1000 ohm range... coatings based on the work of the early pioneers in this field.3–6 31-1 © 2006 by Taylor & Francis Group, LLC DK4036_C031.fm Page 5 Thursday, May 12, 20 05 9:40 AM Vapor Deposition Coating Technologies 31 -5 sibility of deposition at relatively low substrate temperatures The major roles of the plasma in various plasma-assisted processes are related to activation and enhancement of the reactions that are... involved in the overall reaction of film formation and the physical location of these reaction sites Moreover, it should be noted that the ionizing probability is maximum for electrons in the range of 50 to 60 eV and decreases with further increase in energy It is, therefore, advantageous to have low-energy electrons for ionization of the gas and vapor species 31.2.3.1 Diode Plasmas The dc-diode plasma . c () R dE di i p = =0 DK4036_book.fm Page 6 Monday, April 25, 20 05 12:18 PM © 2006 by Taylor & Francis Group, LLC 27-12 Coatings Technology Handbook, Third Edition 13. G. Gawrilov, ChemischelStromläse/Vernickelung surface is fairly low. DK4036_C031.fm Page 5 Thursday, May 12, 20 05 9:40 AM © 2006 by Taylor & Francis Group, LLC 31 -6 Coatings Technology Handbook, Third Edition Dc-diode sputtering. to specification. DK4036_book.fm Page 5 Monday, April 25, 20 05 12:18 PM © 2006 by Taylor & Francis Group, LLC 30 -1 30 Sputtered Thin Film Coatings 30.1 History 30- 1 30.2