RESEARCH PUBLICATIONS, BOOK CHAPTERS AND U.S.PATENTS

by Dr. N. V. MANDICH, CEF

1. N. V. Mandich, "Nastajanje i otklanjanje karbonata i razlaganje cijanida iz cijanidnih rastvora za galvanizaciju", Zastita Mater., 31, (4), (1990), 151. (Yugoslavia).

Cyanide decomposition and carbonate formation, their influence on plating parameters, and methods of carbonate removal and minimization are discussed in relation to cyanide, copper and brass plating. Mechanisms are elaborated.

1. N. V. Mandich, "Pulse Plating of Acid Gold for Electronic Contacts," AESF 4 th International Pulse Plating Symposium, (Orlando), 1990.

A study was conducted to explore the influence of modulated current (PC) versus standard, Direct Current (DC) for plating of gold, in one industrial application under rack and barrel conditions. Variables explored were: plating range, distribution, porosity and attack on resist. Some improvements resulted in the case of plating range, distribution efficiencies and attack on resist, while significant improvements were obtained with the porosity, a most important factor. Theoretical explanations confirmed the experimental data and good correlations are found.

3. N. V. Mandich, "The Chemistry Of Metal Cleaners And Practical And Theoretical Aspects Of Bipolar, Cathodic And Anodic Electrocleaning And Acid Pickling", invited paper presented to ARMCO Research , Middletown, Ohio (Oct., 30th 1990).

Generally accepted as a critical step in most electroplating processes, surface preparation of metals prior to the metal electroplating step is discussed. Definitions of clean surface, influence of basic metal and choice of cleaning methods are presented. Soak, spray, electrolytic, acid, solvent and ultrasonic cleaning methods are elaborated as well as acid dip and pickling steps.

The mechanisms of cleaning action were detailed, starting with the role of inorganic builders, chelators, buffers, surfactants and solvent actions. The basics of formulating science and know-how are fashioned for different types of industrial formulations using a number of typical formulas as appropriate examples.

4. N. V. Mandich, "Metal Finishing Education and Research in the U.S.A", Trans. Inst. Met. Finish., 69, (1), (1991), 3.

Education and research in the metal finishing field in the USA were discussed in relationship to applied research done at universities, large corporations, government labs and major suppliers of metal finishing chemicals. The role of AESF was explained, particularly SURFIN as well as CEF training courses and exams.

5. N. V. Mandich, "Carbonate Formation and Removal of Cyanide Decomposition from Cyanide Plating Solution", Trans. Inst. Met. Finish. 70, (1), (1991), 41.

The conditions for cyanide decomposition and subsequent carbonate formation are detailed. The plating parameters and methods of carbonate removal are discussed with emphasis on cyanide, copper and brass plating . The chemical mechanisms involved are explained.

6. N. V. Mandich, "Electroless Catalyst Bath Optimization", Plating Surf. Finish., 78, (12), (1991), 50.

Plating parameters for an electroless plating catalyst system were optimized with the use of the Fractional Factorial Test method. A relative order of importance is established for PdCl2, SnCl2, time, temperature, chloride ion concentration and pH.

7. N. V. Mandich, "Electrodeposition Of Thin Films Of Gold By Pulsating DC Current", M. Sc. Thesis, Roosevelt University, Chicago, IL, (1991).

An investigation was made into the characteristics of gold deposits formed by pulsed current. The aspects examined were: The Bright Plating Range, Deposition Rates, Cathode Efficiencies, Porosity, Density, Plating Distribution for Rack and Barrel methods, and Attack on Resist. It was determined from Hull Cell testing that the pulse plating will increase the Bright Plating Range. From Bent Cathode testing, Deposition Rates were found to be approximately the same. Using the Nitric Acid Vapor Test , Porosity was determined and drastic improvements were found. Significant improvements were attained from a number of experiments done to determine Plating Distribution; valuable improvements in distribution resulted. Attack on Resist was found reduced. With a duty cycle of 50%, advantages of DC plating were kept (Range and Rates); but, also, advantages of Pulse Plating were retained (Density, Porosity, Distribution and Attack on Resist). A mathematical treatment is presented, treating the difference between Pulsed Plating and Direct Current plating in a semi-quantitative way.

8. S. S. Djokic and N. V. Mandich, "Effect of Tartarate on Electrodeposition of Ni - Fe Alloy", Proceedings of 78 th AESF Technical Confer., (Toronto), 1991).

It was demonstrated that the Fe content in the Ni/Fe alloy depends on the current density and on the sodium-potassium tartarate (NaKC4H4O6) concentration in the bath. With an increase in the current density, the Fe content in the alloy decreases. The NaKC4H4O6 affects the alloy composition in the concentration range less than the total Ni2+ and Fe2+ concentration in the bath. In this NaKC4H4O6 concentration range, the Fe content in the alloy increases with an increase of the NaKC4O6 concentration. When the NaKC4H4O6 concentration is greater than 0.03 mol/dm3, the Fe content in the alloy is practically constant.

9. N. V. Mandich, "Removal of Contaminants in Chromium Plating Solutions Via Porous Pot Method", Proceedings of AESF Hard Chromium Plating Workshop (Orlando), 1992.

Applications, operations and theoretical background are treated for the purification of chromium plating solutions with the porous pot technique (PPT). Complex reactions involved were explained in general form in order to help practical users understand and efficiently deploy the PPT. Operation mode and other applications of PPT are discussed

10. R. Sidhu, G.A. Krulik, N.V.Mandich, "Contribution Toward Understanding The Phenomenon Of Pink Ring," Plat. Surf. Finish., 79(6)(1992), 74.

Pink Ring is the term for a puzzling problem, which is common during manufacturing of multilayer, printed circuit boards (MLB's). It manifests itself by local delamination or dissolution of the inner-layer oxide interface around drilled holes during plating processes. The appearance of this defect is pink caused by removal of the oxide to expose underlying copper, or by reduction of copper oxide inner-layer coating to copper metal. This work describes the influence of drilling variables on panels with a prescribed oxide thickness and of glass cloth type, also using baking and chemical treatment variations, to study the appearance of pink ring. Additional experiments were performed to study the role of electroless and electrolytic process solutions on the copper oxide coating on standardized test panels. Key factors for the cause of pink ring phenomenon is identified.

11. N. V. Mandich and G. A. Krulik, "Effect Of Selected Metals On Electroless Plating Catalyst", Trans. Inst. Met. Finish., 70 (3) (1992), 117.

A hydrous melt catalyst synthesis method was used to prepare materials having large amounts of copper or tin (IV). Both additives are of commercial interest. Absorption studies showed that neither had an effect on catalyst deposition on a plastic substrate. Their effect on catalyst synthesis is discussed.

1. N. V. Mandich, and G .A. Krulik," Substitution of Hazardous for Non Hazardous Process Chemicals in the Printed Circuit Industry", Met .Finish., 90,(11)(1992) 49.

This paper discusses two sets of chemical systems used in the printed circuit industry. One set is used for desmear or etchback of the epoxy polymer. The second set concerns the metallic etch resist used during alkaline etching of the excess copper from the printed circuit board. Etchback/desmear chemistries and ammoniacal etch resist were discussed.

13. N. V. Mandich and G. A. Krulik, "A Novel Biogenic Nickel Source for Electroless Nickel Plating", Met. Finish., 90, (3), (1992), 9.

Although this paper is partially a work of futuristic contemplation, it is based loosely on fact. Many plants are known to accumulate large amounts of metal in their tissues. Frequently used in prospecting work, these plants are particularly common in nickel mining areas. Likewise, phosphorous is an essential micronutrient of plants and can be recovered from wood ash, for example. The main energy transfer compound for all living things is ATP (adenosine tripoly phosphate). It would seem reasonable to expect that some plants could produce and store hypophosphite as an energy source. This paper explores the use of "hyperaccumulator" plants from the mining area of New Caledonia as a source of nickel "sap" to be used in electroless nickel plating baths of the future.

14. N. V. Mandich, "Electroless Gold Plating With Use Of Solid (External) Nickel Catalyst", Proceeding of 79 th AESF Technical Conf., (Atlanta), 1992.

The object of this study is to find out if industrial "Hypo Gold" formulation is a true gold electroless process and if it can be used to plate gold flash over the selectively plated electronic contacts. The purpose of gold flash is to plate the entire surface of the gold plated contact with a thin layer of soft gold for the purpose of solderability. Thickness of this gold flash should be from 5-8 microinches. It is experimentally found that the addition of solid nickel in the form of e.g. wire, when barrel plating with Hypo Gold formulation, converted this system from immersion type to true autocatalytic process.

 

15. N. V. Mandich and G. A. Krulik, "Evolution of a Process: 50 Years of Electroless Nickel", Met. Finish., 90, (5), (1992), 25.

 

The evolution of Electroless Nickel (EN) processes from its accidental discovery until present state is described. Substrates for EN, different types of EN as well as applications are discussed.

16. N. V. Mandich and G. A. Krulik, "The Mechanisms of Catalytic Processes in Electroless Plating", Trans. Inst. Met. Finish., 70, (3),(1992), 111.

An attempt is made to describe some theoretical aspects concerning the Pd -Sn catalyst used for electroless plating of plastic. The work involved in actual development of a dry catalyst system is described and the application of the Fractional Factorial Method (FFM) for optimizing process parameters is detailed. An optimum set of process conditions is established for systematic testing. Further discussions focus on catalyst behavior versus substrate, etch process, neutralization and electroless nickel plating.

17. N. V. Mandich and G. A. Krulik, "On The Mechanisms Of Plating On Plastics", Plating Surf. Finish., 80, (11), (1993), 68.

This is a general, yet chemically detailed introduction to plating of plastics. The emphasis is on plating of ABS plastics, with explanations for the widespread use of this plastic. Many concepts, from the 3-dimensional structure of ABS, to the use of Pourbaix diagrams to explain electroless nickel plating, are integrated. The result is a step-by-step study of the whole process, from pre-etchants to electroless nickel. ESCA characterization and transmission electron microscopy is used to explain the surface chemistry.

18. N. V. Mandich and G. A. Krulik, "R&D In Year 2020", Electrodep.Surf. Treat. (Russian), 2, (6), (1993), 62.

This is a glimpse of one future reality, perhaps even a probable one. Advances in microfabrication, sensor design, computing power and memory increases, and increasingly evolved software show no signs of reaching a limit. What is asked, regardless of size or shape, cast off your mental shackles, and embrace microfilm/multiform robots as worthy successors to those old fashioned mechanical "men". Prospects of the advances of science in general and of ecology by 2020 in particular have been considered.

19. N. V. Mandich and G. A. Krulik, "A High Efficiency Electroless Gold Plating Bath", Electrodep.Surf. Treat. (Russian), 4, (2), (1993), 27.

A novel, electroless gold plating bath based on a new non-carbon chemical reducing agent is proposed. It is cyanide-free and contains no formaldehyde or borohydride reducing agents. This chemistry is significantly different from previous electroless gold formulations and has unique characteristics. The near neutral pH, autocatalyltic electroless gold can plate up to 0.1 micron (4 microinches of gold) per minute with a maximum thickness in excess of 10 microns. The bath is highly stable with no spontaneous plateout and can be easily controlled over multiple full replenishment cycles. It has been operated in a high production job shop, with 125-liter bath for two years.

20. N.V. Mandich and G.A. Krulik, "Chemistry Of Modern Permanganate Etch System For Printed Circuit Board Production", Plating Surf. Finish., 79, (12), (1992), 56.

The basic chemistry and modes of regeneration are explained, as well as the actions of permanganate etchants, solvent swellants and related chemical mechanisms. Permanganate etchback rates for four basic resin systems were experimentally determined. Scanning electron microscopy was used for studying the etching mechanisms involved.

 

21. N. V. Mandich and G. A. Krulik, " Fundamentals Of Electroless Copper Bath Operations In Printed Circuit Boards", Met. Finish., 91, (1), (1993), 33.

 

By exercising the proper bath control and following basic housekeeping rules an electroless copper plating line performs smoothly and reliably. Sooner or later, in less than perfectly operated lines, some problems may occur. However, most of the electroless copper plating line problems is identified, along with possible causes. Solutions for them are presented in a detailed fashion.

22. N. V. Mandich and G. A. Krulik, " Fundamentals Of Hydrogen Embrittlement ", Met. Finish., 91, (3), (1993), 54.

The complex phenomena of hydrogen embrittlement and its accompanying metallurgical background is treated in a somewhat simplistic way in order to reach the non-scientific person (the everyday plater) who deals with this subject daily. Basic principles of hydrogen movement and resulting effect on metal properties and their failures are described. Basic calculations and a simple experiment are devised as an illustration.

23. N. V. Mandich and G. A. Krulik, "Selecting and Troubleshooting Chemical Conversion Coating - I", Finishing (U.K.), 17, (11), (1993), 26.

Selection of Chromium Conversion Coatings is discussed with the emphasis on the consumer's point of view. Basic chemical and physical properties are reviewed. Selection and troubleshooting are enlightened through case studies. A comprehensive troubleshooting guide is detailed.

24. N. V. Mandich, "EMI Shielding by Electroless Plating of ABS Plastics", Plating Surf. Finish., 8, (19), (1994), 60.

Electronic equipment, especially computers, needs to be shielded from stray electromagnetic interference (EMI). Most such equipment is contained in plastic housings, which are transparent to EMI. Metal plating on plastics offers a method for economical and reliable EMI shielding. This paper explains the plating process and compares the capabilities of shielding techniques. Theoretical principles of shielding theory are also discussed.

25. N. V. Mandich and D. Tuomi, "Morphological And Chemical Comparisons Of Electroless Copper And Nickel Film Growth", Trans. Inst. Met. Finish., 72, (2), (1994), 72.

A detailed study was undertaken on one applied system used in electronic plating of ABS plastics. The macroscopic appearances were examined after short and standard etch times, after catalytic and accelerating steps, and after the electroless copper and nickel plating steps. XPS was used to examine the chemical status of the surface during different plating steps and TEM was used to analyze polymer-metal interface dependence on etching conditions. A heterogeneous multilayer structure is found to be a characteristic of these systems. The structural region of interest extends sequentially from the bulk polymer to the oxidized polymer interphase, the sorbed tin and palladium, the initial surface reaction product, structures of microscopic islands of electroless metal, and finally to the continuous metallic film. Morphological and chemical contrasts are shown between electroless nickel and electroless copper deposits.

26. N. V. Mandich and G. A. Krulik, " Selecting and Troubleshooting Chemical Conversion Coating -- II ", Prod. Finish. (U.K.), 47, (1), (1994), 20.

In the first part the basic chemical and physical properties of chromate conversion coatings and also the factors to be considered when choosing a chromate after zinc plating were reviewed. In this concluding part, the relevant chemistry is looked at in more detail. Two troubleshooting case histories and an extensive troubleshooting guide followed.

27. N.V.Mandich, "Chemistry of Solvent Conditioning prior to Permanganate Etching of PCBs", Trans. Inst. Met. Finish., 72, (1), (1994), 41.

The chemistry of the solvent conditioning step as used prior to the permanganate etching of PCB's is explained and the mechanisms involved are detailed. The use of solubility parameters as a tool for formulating proper solvent blends for solvents/conditioners ("swellants") is discussed. SEM pictures are presented to illustrate the influence of the solvent/conditioner step on surface morphology and adhesion.

28. N. V. Mandich, "Removal of Metallic Impurities in Chromium Plating Solutions by Electrocoagulation", AESF Chromium Colloquium (Orlando, 1994).

A porous pot offers a relatively low cost and effective method to remove metallic impurities from a chromium plating solution. By placing a porous pot directly into the solution, this technique removes and t maintains metallic impurities (trivalent chromium, nickel, iron, and copper, zinc ) at concentration levels below which they cause negative effects on the plating operation and deposits. Applications, operation, and theoretical background are treated for the purification of chromium plating solutions with this method.

29. N. V. Mandich, "Theoretical Considerations in Pulse-Reverse Plating", Proceedings of 81 st AESF Technical Conference (Indianapolis), 1994.

Theoretical aspects of pulse reverse plating are presented. Limiting rates of deposition, effect of anodic pulses on limiting current density, effect of periodically changing rates on deposits morphology, maximum deposition rates and amplification of surface irregularities, are discussed with respect to current.

30. N. V. Mandich, " Chemistry of Chromium ", Proceedings of 82 nd AESF Technical Conference (Baltimore), 1995.

In spite of the fact that chromium is technologically and ecologically a very important element, it is still difficult to find in one place enough details about its chemistry in relation to the electrodeposition mechanism. Chromium's stereochemistry, electrochemistry, redox reactions and structure of polynuclear chromic acids, among other important items are elaborated.

31. N. V. Mandich, " Troubleshooting in Zinc and Cadmium Plating ", Electrodep. Surf. Treat. (Russian), 4 (4) (1996),5.

Practical answers on plating difficulties during actual plating operations are rare to find in the open literature. Described is a practical approach, which will be helpful in pinpointing problems in cyanide zinc and cadmium plating. Usually plating difficulties are not confined to one particular area, therefore the discussion is broken down in to four general segments, each treated separately: Cleaning, Plating, Rinsing and Post Treatments. Further elaborated is good plating practice, which leads to profitable operations, and it is dependent upon an understanding of each plating phase, the choice of materials used, their control, and maintenance.

32. N. V. Mandich, "Practical and Theoretical Aspects of Chromium Activation and Reverse Etching", AESF Chromium Colloquium,(Cleveland),1996.

From the discussions and presented figures, practical and theoretical explanations are offered for: a) a need for cathodic activation of nickel prior to chromium plating; (b) a practice of keeping the nickel-plated parts "live" when coming out of the nickel-plating tank; (c) a need to cathodically activate the nickel in H2SO4; (d) why to go "live" in the chromium plating tank and, (e) the practice of having a greatly reduced number of anodes in the beginning of the chromium tank and "ramping-up" the current. In the case of plating chromium over chromium, the fashion of initially keeping the part cathodic at low voltage can be explained with a similar reasoning as that for preventing oxide (Cr2O3) formation and inducing its cathodic dissolution at low potentials or, expressed in shop practice terms, holding the voltage low at the beginning and "ramping-up" the current afterward.

33. N. V. Mandich, "The Mechanisms of Chromium Plating II", Proceeding of 83 rd AESF Technical Conference (Cleveland), 1996.

Even though chromium plating has been around for a long time, the electrodeposition mechanism is still incompletely understood. The present status of the theory is explained and kinetic aspects of the role of alkyl-sulphonic acids as catalysts are presented. A discussion of the chemistry of trivalent and hexavalent chromium complexes is elaborated from a fundamental and contemporary point of view.

34. N. V. Mandich, "The Mechanisms of Chromium Deposition and Dissolution under Direct and Pulse Reverse Plating Conditions", Ph.D. Thesis, Aston University, Birmingham, United Kingdom. (1995).

Different existing theories are discussed, and the original sequences of chromium electrodeposition mechanisms are presented. The present state of theories for electrodeposition with periodic current reversal (PRC) is analyzed and the existing theory of K. Popov was expanded by the introduction of a variable charge ratio. The ratio was found experimentally to be the governing factor for increased cathodic current efficiency (CCE) of chromium electrodeposition under PRC mode. Physical properties (corrosion resistance and hardness) of chromium deposits under PRC regime were investigated.

Baths containing sulfuric acid as catalyst and others with selected secondary catalysts (methane sulphonic acid - MSA, SeO2, a KBrO3/KIO3 mixture, indium, uranium and commercial high-speed catalysts (HEEF-25 and HEEF-405) were studied, with the aspects of increase of CCE.

Deposition mechanisms were studied using potentiostatic and potentiodynamic electroanalytical techniques under stationary and hydrodynamic conditions. Sulfuric acid as a primary catalyst and MSA, HEEF-25, HEEF-405 and sulphosalycilic acid as co-catalysts were explored for different rotation speeds and scans rates. Maximum current was resolved into diffusion and kinetically limited components, and a contribution towards understanding the electrochemical mechanism is proposed. Reaction kinetics was further studied for H2SO4, MSA and methane disulfonic acid (MDSA) catalyzed systems and their influence on reaction mechanisms elaborated. The charge transfer coefficient and electrochemical reaction rate orders for the first stage of the electrodeposition process were for the first time determined. A contribution was made toward understanding of H2SO4 and MSA influence on the evolution rate of hydrogen. Anodic dissolution of chromium in the chromic acid solution was studied with a number of techniques. An original electrochemical dissolution mechanism is proposed, based on the results of rotating gold ring disc experiments and scanning electron microscopy. Finally, significant increases in chromium electrodeposition rates under PRC mode were studied and a deposition mechanism is elaborated based on experimental data and theoretical considerations.

35. N. V. Mandich, "Chemistry and Theory of Chromium Deposition - Part I: Chemistry". Plating Surf. Finish., 84 (5) (1997), 108.

Although electrodeposition of chromium has been practiced for more than 75 years, the mechanism is still open to conjecture. Part of the reason is the complexity of the chemistry of chromic acid and its existence in aqueous solution in the form of coordinated octahedral complexes. These complexes vary both structurally and kinetically at different CrO3 concentrations. The chemistry of tri and hexavalent chromium is discussed, including polymerization, complex formation and related mechanisms affecting the overall deposition mechanism.

36. N. V. Mandich, "Chemistry and Theory of Chromium Deposition - Part II: Theory of Deposition , "Plating Surf. Finish., 84 (6), (1997), 97.

Various theories of chromium electrodeposition, based on wide-ranging research, are discussed, and an effort is made to show the complexity of chromium deposition reactions. Formation and properties of compact and liquid films that are the constituents of the cathode layer are elaborated including the various chromium complexes. For the first time, the complete sequences of the deposition pathways are offered in the form of the complete block diagram.

37. S. B. Lalvani, J-C. Kang and N.V. Mandich, "The Corrosion of Cu-Ni Alloy in a Chloride Solution subjected to Periodic Voltage Modulation: Part I". Corr. Science, 40 (1) (1998), 69.

The influence of full-wave sinusoidal, and positive half-wave and negative half-wave rectified sinusoidal potentials superimposed at three DC levels on a Cu-10Ni (CDA 706) alloy immersed in a 3.3% NaCl solution under nitrogen, and air purge on the material degradation behavior was investigated. The results obtained show that although the material degradation rate is strongly influenced by the choice of the applied DC potential level, the more anodic is the DC potential the greater is the corrosion rate. Evidence of intergranular corrosion and cracking is observed. No pitting is observed with alternating voltage (AV) modulation in spite the presence of chloride anions. The material dissolution rate of the alloy was found to decrease with frequency of the AV signal. The rate of alloy dissolution was found to increase with the AV peak potential, as well as with the DC potential. In general, the DC potential is observed to greatly affect the magnitude of the metal dissolution rate, more than the corresponding equivalent AV peak potential. It does not appear that imposition of AV signals alters the basic mechanism of corrosion of Cu/Ni alloys.

38. S. B. Lalvani, J-C. Kang, and N. V. Mandich, "The Corrosion of Cu - Ni Alloy in a Chloride Solution subjected to Periodic Voltage Modulation: Part II". Corr. Science ,40(2/3)(1998),201.

Corrosion of samples of CDA 706 alloy of Cu and Ni due to the superimposition of AC voltages was found to occur via intergranular corrosion and cracking mechanisms, as evidenced by scanning electron microscopy. Experiments were conducted at three different DC potentials on which sinusoidal full-wave, positive half-wave and negative half-wave voltages were superimposed under nitrogen and air purge. Evidence of significant material degradation was found even when negative half-wave rectified sinusoidal voltages were superimposed upon the test coupons. The extent of surface damage suffered by specimens was found to decrease with frequency of the applied signal. The corrosion products formed on the samples analyzed by energy dispersive x-ray analysis show a significant presence of chloride. A possible reaction pathway for corrosion mechanism is suggested.

39. N. V. Mandich, and N. V. Vyazovikina, "Kinetics and Mechanisms of the Chromium Anodic Dissolution in the Chromium Plating Solution in the Transpassive Range",47 th Meeting of International Soc. for Electrochemistry, (Veszprem, Hungary), Sept. 1996.

Electrolytic chromium has been obtained from the Sargent Bath (SB). Kinetics and mechanism of dissolution of electrolytic chromium in the Transpassive region (TP) in the SB were studied at the temperature range from 20 to 60O C. Methods used were electrochemical: potentiostatic, voltammetric, rotating ring-disc electrode (RRDE), and physical: Scanning Electron Microscopy and Auger Electron Spectroscopy. RRDE technique indicated that electrolytic chromium dissolves both chemically as Cr3+ and electrochemically as Cr3+ and Cr6+. The chemical dissolution rate was found to depend on number of variables. A plausible mechanism of chromium chemical dissolution with participation of sulphate ions and chromic acid was offered. The amount of Cr6+ formed during Cr anodic polarization in the TP region increases with its potential while the amount of Cr3+ decreases, approaching zero at high potentials. Reductions of Cr3+ content down to zero is connected with their oxidation at metal surface at E >> 1.35 V.

The suggestion about the change of the kinetics and of the mechanism of anodic dissolution in the TP region was made. It was based on the analysis of the results of chromium electrochemical dissolution in the SB and their comparison with published data. From 1.07 V-1.35 V chromium dissolves with formation of Cr3+ and Cr6+ under mixed diffusion-kinetic control. The fraction of the kinetic component is increased with the increasing potential. In the 1.35 <E <1.5 V region, dissolution proceeds through seven sequential steps, where only Cr6+ ions are formed. Six are single electron and electrochemical steps and the seventh is Cr6+ desorption step. A multistep anodic process is postulated as the charge transfer of single electron steps during the separation of the first electron. In the range of limiting anodic current the formation of Cr6+ proceeds according to one Cr oxide formation-dissolution reaction that is at dynamic equilibrium.

40. N. V. Mandich, J. R. Selman, and C. C. Lee, "Practical and Theoretical Aspects of the Removal of the Metallic Impurities by Electrocoagulation using Porous Ceramic Barrier, Plating Surf. Finish., 84 (12) (1997), 82.

Most common metallic impurities such as Ni, Zn, Fe, Cu and Cr (III) ions found in decorative (bright) or functional (hard) hexavalent chromium plating solution can be effectively removed from plating solution and concentrated as a sludge by an electrodeposition / coagulation process using a porous ceramic separator. Experiments were carried out in a laboratory scale porous pot at two current densities. The Sargent type, hard chromium plating solution containing simulated metallic impurities was used. In the same process Cr (III) is effectively reoxidized to Cr (VI ). The results show that optimum conditions for the efficient operation depend on current density, initial pH and nature of the cathode surface. From cyclic voltammograms, pH measurements, metal removal rates and theoretical principles, complex electrochemical and chemical processes involved were analyzed. They are presented as much as possible in the simplified form. An extensive set of practical guidelines is detailed.

41. N.V. Mandich and N. V. Vyazovikina, " On the Mechanism of Hydrogen Evolution during Chromium Plating ", 192 nd Meeting of Electrochemical Society, Paris, France (Aug. 1997).

Mechanisms and the kinetics of the hydrogen evolution reaction (h.e.r.) on cast and electrolytic chromium in sulfuric and chromic (250 g/l CrO3) acid and in the chromium plating (the SB bath) solutions under different conditions are studied by electrochemical methods and Auger Electron Spectroscopy. It is established that h.e.r. occurs both on passive and active chromium in all solutions under study. Thermodynamic and kinetic parameters of h.e.r. under different conditions are calculated and the mechanisms of this process on passive and active chromium were proposed. It is found that h.e.r. on passive chromium occurs by Volmer-Tafel's mechanism with a limiting step being the recombination reaction. On active chromium it occurs by Volmer-Heyrowsky's mechanism with limiting step being a reaction of electrochemical desorption. On the basis of an analysis of obtained results and published data it is also proposed that the h.e.r. on chromium in the potential range more negative than -0.90 V is controlled by planar diffusion. It is shown that Methane Sulphonic Acid addition to the chromic acid solution does not influence the kinetics and the mechanisms of hydrogen evolution on passive and active chromium.

42. R. L. Reghig and N.V. Mandich, "Throwing Power, Cathode Efficiencies during Gold Plating under Pulsating Regimes" Plat. Surf. Finish., 86 (12) 89(1999).

Cathode Efficiency and Throwing Power of pulse plated gold deposits were measured using the Haring cell. These values quantify the capability to produce uniform thickness on non-planar substrates. Throwing power was found to vary with cathode efficiency, except with 8 and 9 mili seconds ON times where throwing efficiency increased while cathode efficiency decreased. Cathode efficiency decreased with increased ON time. At long ON times (8 and 9 mili sec.), the metal ions adjacent to the cathode were depleted and hydrogen evolution occurred. The effect of the rectifier characteristics and the electrochemical system on both wave form and cathode efficiency was determined.

43. N. V. Mandich, "Important Practical Considerations in Chromium Plating - Part I", Met. Finish., 97,(6)100(1999)

Practical problems in bright (decorative) or hard (functional) chromium plating solutions are presented in somewhat detailed fashion. A phenomenological approach to troubleshooting techniques is offered together with practical methods and related tools of trade needed to understand and successfully troubleshoot this important industrial process.

In Part I, sets of plating problems, related to Low Deposition Rates, are analyzed and all important variables that can influence them are presented. Corrective actions are detailed.

44. N. V. Mandich, "Important Practical Considerations in Chromium Plating -Part II", Met. Finish. 77(7) 42 (1999).

In continuation of Part I, in Part II the next set of practical problems, related to Nodular Deposits and Imperfect Adhesion are analyzed in step-wise fashion. A number of plating problems related and interrelated to the above are presented in detail and corrective actions suggested.

45. N.V. Mandich, "Important Practical Considerations in Chromium Plating - Part III", Met. Finish. 77(8) 42 (1999).

In continuation of Parts I and II where plating problems related to Low Deposition Rates, Nodular Deposits and Imperfect Adhesion were detailed, in Part III plating problems related to gray, dull and milky deposits are discussed.

46. N. V. Mandich, "Chemistry and Theory of Chromium Deposition - Part III: Voltammetric Study", (to be published).

The deposition mechanisms with all its complexity was studied in detail using time-controlled (linear and cyclic potential polarization sweeps) and mass-controlled (rotating disc electrode) systems. The roles of the sulphates in the formation of the complexes that are present in the cathodic film are elaborated. Suggestions on the possible reactions involved are offered. The electrochemical kinetics of the reaction of incomplete Cr6+_ Cr3+ reduction is presented and it is clearly proven that it consists of diffusion and kinetically controlled components. Four different secondary catalysts were analyzed and compared with Sargent bath under different potential sweep rates and cathode rotation speeds. Increase in current efficiencies for co-catalyzed baths are obviously related to reduction of maximum current with increased sweep rates and rotation speeds. Reduction of the rate of incomplete Cr6+_ Cr3+ reduction reaction produces an increase of the rate of the main, complete reduction reaction Cr6+_ Cr0 (deposition). This then dictates the increase in cathodic current efficiency for the overall deposition process.

47. N. V. Mandich, "Chemistry and Theory of Chromium Deposition - Part IV: Electrochemical Kinetics", (to be published).

Electrochemical kinetics of Methane Sulphonic Acid (MSA) and Methane Disulfonic Acid (DMSA) co-catalyzed systems is analyzed from the theoretical standpoint. It is compared with sulphate catalyzed chromium plating bath vs. different CrO3 concentrations, CrO3/H2SO4 ratios and temperatures.

It is clearly proven that chromic as well sulfuric acid has opposite effects on the Cr6+_Cr3+ reaction. While an increase of H2SO4 content at constant CrO3 concentration increases the maximum rate, a decrease of CrO3 concentration at constant H2SO4 concentration increases the maximum current (Im). It is explained why there must be a compromise for the optimum chromic acid/sulfuric acid ratio, which is well known from electroplating practice to be 100:1. The important practical aspect, which is the ability of a plating bath co-catalyzed with alkyl sulphonic acid to operate with maximum efficiency at higher temperatures, is also demonstrated with the respect to Im. Determination of the electrochemical reaction order and charge transfer coefficient further corroborated the fact that the reaction Cr6+_Cr3+ follows the mechanism involving the mixed kinetic control; and, that is limited by the diffusion step and addition of the first electron. In connection with the established fact that MSA is also a weak catalyst for Cr6+_ Cr3+ reaction, it is concluded that the proven increase in cathode current efficiency must be due to MSA influence on the state and the physicochemical properties of liquid cathode film and on the reactions that are proceeding within the film.

48. N.V. Mandich , and J. K. Dennis, "Selenium, Indium, Uranium and Cyclohexane Carboxylic Acid (CPA) as Secondary Catalyst in Chromium Electro-plating Solutions", Proceedings of 2 nd International Chromium Colloquium, Saint-Etienne (France), April 1998.

SeO2, CPA, In2 (SO4)3 , UO2SO4 . 3H2O and K2O2VO3 . V2O5 x 3H2O (Carnotite) were used as secondary catalysts in standard (100 : 1, 240 gr /l ) chromium plating solution under DC and PRC modes. CCE's and appearances of obtained deposits were examined. It was found that SeO2 in 100-300 ppm range definitely increases CCE up to 22%, but deposits are gray. Indium produced unique results. It did not appreciably change CCE's in DC or PRC modes, and deposits were bright and exceptionally smooth. It could also be plated with sulphate ratios, used in the explored range, from 100:1 to 11:1. Adhesion was excellent. Uranium salts also presented unexpected results. PRC experiments produced the plates with exceptional brightness using the Carnotite or Uranium sulphate, without the change in CCE. However, DC plated panels with 0.5 and 1% Carnotite produced brittle panels. Addition of Dimethyl Sulphonic Acid drastically reduced the britlleness and increased the CCE. An unusual discovery was that bright panels were obtained with a 630:1 ratio, when sulphates were introduced as 0.34% addition of Uranium sulphate. CPA additions did not result in an increase of CCE when tried as a 1,2,3 and 4 ml/l additions to the standard hard chromium bath, contrary to published claims.

49. S. Lalvani, and N.V. Mandich, "Removal of Metallic Impurities in Chromium Plating Solution by Electrocoagulation", Illinois Waste Management and Research Center, Project No. 97025 (in progress).

Metallic impurities such as Ni, Fe, and Cu ions are removed from the plating solution by electrodeposition and concentrated as sludge by using a "porous pot" technique (PPT). In the same process, Cr (III) is reoxidized to Cr (VI) at the insoluble lead anode. Previous research and data from industrial operations have indicated that the PPT could be a cost-effective and environmentally friendly method to continuously separate the impurities and recycle spent chromium solutions. However, no definite data are available relating the various concentrations of impurities to the rate of their removal. This is resulting in scale-up problems for industrial porous pot operations. The objectives under study are trifold: (I) to obtain kinetic data on the removal of impurities present in various concentrations; (ii) explain and quantify the regeneration of Cr (VI) from Cr (III), that is always present in spent solutions, and (iii). to propose guidelines for purification of chromium plating baths with a PPT. Design considerations that allow scaling-up of operation (specifically the ability to determine the required volume of the porous pot for a given volume of plating solution) are established.

50. S.B. Lalvani, T. Wiltowski, A. Hubner, A. Weston, and N. V. Mandich,"Removal of Hexavalent Chromium and Metal Cations by a Novel Carbon Adsorbent", Carbon ,36(7-8)(1998),1219.

Carbon produced by the contact arc method (whereby graphite electrodes are arced in an inert atmosphere) was employed for the removal of hexavalent, Cr(VI), and trivalent, Cr (III), chromium ions as well as other metal cations from aqueous solutions. It is known that Cr (VI) is present as an anionic species in the solution. The carbon absorbent used in this study selectively removed the anions of hexavalent chromium from the solution, whereas, depending upon the solution pH, no or very small uptake of metal cations was observed. On the other hand, commercial activated carbon showed great affinity for cations of Pb, Zn and Cr (III) but none for the Cr (VI).

 

51. N.V. Mandich, S.B. Lalvani, and T. Wiltowski, "Selective Removal of Chromate Anion by New Carbon Absorbent " Met. Finish., 76(5)39 (1998 ).

 

The application of high electric current between two graphite rods in an inert atmosphere of helium resulted in the production of carbon soot. The carbon produced was employed for the removal of chromium anions and cations as well as other metal cations from aqueous solutions. The carbon selectivity removed from the solution of hexavalent chromium that is present mainly as a chromate anion. This carbon showed no to very little removal affinity for the cations of trivalent chromium, lead and zinc. At low pH values commonly used in plating industry, the carbon showed almost no removal of metal cations from aqueous solutions whereas a modest amount of metal removal was found at high pH values. The performance of this type of carbon was compared with that of a commercially available activated carbon. The use of commercial carbon resulted in the removal of cations of Cr (III) and Zn but almost negligible Cr (VI) removal.

52. N.V.Mandich, and N.V.Vyazovikina, "Kinetics and Mechanisms of Chromium Anodic Dissolution in the Chromium Plating Solution in Transpassive Range", J. Electrochem. Society (to be published).

Dissolution of chromium, previously deposited from the Sargent bath (SB), was studied by electrochemical methods with the rotating ring-disc electrode (RRDE) and Auger Spectroscopy (AES) in the Transpassive (TP) region at 20, 40, 50, 55 and 60O C. It was shown experimentally that electrolytic chromium dissolves chemically in the TP region with the formation of Cr3+ and also dissolves electrochemically with the formation of Cr3+ and Cr6+. The dissolution mechanism was found to be dependent on a number of variables. The plausible mechanism of chromium chemical dissolution with participation of sulphate ions and chromic acid was offered. With help from AES a conclusion about the change of kinetics and the mechanism of chromium anodic dissolution was proposed on the basis of our analysis and with comparison with previously published results. The anodic current efficiency was determined by RRDE and by the gravimetric methods at various anodic current densities. It was taken into account that the chromium dissolves with formation of both, Cr3+ and Cr6+ ions and that the sum of their fractions should total 100 %.

53. S.L. Guddati, T.M. Holsen, C. C. Lee, J. R. Selman and N. V. Mandich, " The use of Porous Ceramic Barrier for the Removal of the Metallic Impurities from Chromium Plating Baths", J. Appl. Electrochem., 29(12)1129(1999).

The removal of the metallic impurities from chromium plating baths was analyzed from the aspect of determining the optimum ratio of the area of ceramic barrier vs. the volume of the plating solution. The optimum current densities and the effect of the concentrations of the metallic impurities were quantified.

54. N. V. Mandich, and J. K. Dennis, "Codeposition of Nano Diamonds with Chromium", Met. Finish. (submitted for publication).

Nano diamonds were codeposited in three different types of hard chromium plating baths at two temperatures in order to improve there wear characteristics. Sargent and Fluoride type baths with nano diamonds had more weight wear loss at higher bath temperatures when compared with lower temperatures. The commercial HEEF-25 showed higher wear resistance than either of the other two baths tested. HEEF-25 wear resistance was higher at higher temperatures, which was opposite to the other two baths.

55. N. V. Mandich, and N. V. Vyazovikina, " Mechanisms of Hydrogen Evolution on Chromium in Acid Solutions", J. Electrochem. Soc. (submitted for publication).

Kinetics and the mechanisms of the hydrogen evolution reaction (h.e.r.) on a chromium cathode in sulfuric and chromic acids and in the standard chromium plating solutions under different conditions were studied by electrochemical methods. It is found that H+ reduction occurs, both on passive (Cr*) and active chromium (Cr). Thermodynamic and kinetic parameters of h.e.r. under different conditions were calculated and the mechanisms of this process on Cr* and Cr were offered. The h.e.r. on Cr occurs by Volmer-Tafel's mechanism with the limiting step being the hydrogen recombination reaction. On the Cr* cathode it occurs by Volmer-Heyrowsky's mechanism with electrochemical desorption as the limiting step. It is proposed that the h.e.r. in the electrodeposition potential range of E >- 0.90 V is controlled by planar diffusion. It is shown that Methane Sulphonic Acid addition to the CrO3 solution does not influence the kinetics and mechanisms of h.e.r. on passive or active chromium.

56. R. L. Reghig and N. V. Mandich, "Stress Determination in Pulse Plated Gold Deposits", J. Appl. Electrochem. (to be published).

Stress is determined in Pulse Plated gold deposits from a cyanide type bath. It is found that shifts in orientation from (111) texture to dual (111) - (200) corresponded to the change in nucleation density. Stresses in pulse plated films with dual (111) - (200) orientation were compared to D.C. plated films with (111) orientation. The pulse-plated gold exhibited a shift from tensile to compressive stress with increasing thickness, while the D. C. plated films were always tensile. Sorption and volume expansion was suggested to be mechanisms, which could produce stress, observed experimentally in the pulse-plated deposits.

57. N. V. Mandich, "Quartz Crystal Microbalance (QCM) Determination of Chromium Anodic Dissolution Efficiency in The Sargent Bath", Proceedings of the 85 th Annual Technical Conference, Minneapolis, ( 1998).

QCM is a modern, accurate and relatively simple and inexpensive method to study electrochemical reactions. It is usually assumed that chromium anodic efficiency is 100%, but when measured voltammetrically it is always over 100% indicating that two electrochemical dissolution reactions are simultaneously taking place.

Theoretical principles of QCM are presented and chromium ACE determined for dissolution of chromium previously electrodeposited from standard Sargent type plating solution. As suspected, chromium dissolution proceeds via two different valent states.

58. N.V.Mandich, "On the Troubleshooting Methodology", Proceedings of the AESF 86 th Annual Technical Conference, Cincinnati, Oh., (1999).

Troubleshooting will be discussed from a consultant/ troubleshooter perspective. Due to the complex nature of large number of plating systems, a generalized but systematic method based on a cause-effect approach to troubleshooting will be explained.

It has been found that together with certain critical skills, an ordered approach to the troubleshooting of plating processes is invaluable both for the troubleshooter the problem solver, and also for teaching plant personnel to solve their own problems.

We will attempt to discuss those critical skills, based on conversations with a number of troubleshooters and technical service professionals as well as out own experience. Five broad areas of competence are identified, within which there are many specific skills: (1) diagnostic ability, (2) solution and implementation skills, (3) general and specialized knowledge in electroplating technology and its related disciplines, (4) communication skills, and (5) personality attributes, i.e., an attitude, conducive in troubleshooting.

BOOK CHAPTERS :

59. G. A. Krulik, and N. V. Mandich, "METALLIC COATINGS", in: Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 8, 4th ed., pp258-291 Wiley, N.Y., (1995).

All major techniques for applying the metallic coatings are presented: Liquid-Phase Metallizing techniques (hot dip galvanizing, electroplating, fused salts plating, plating from non-aqueous solutions, electroless and brush plating); Gas Phase Metallizing (metal or chemical spray coatings, carbonizing, nitriding, and gas diffusion); Vacuum Phase Metallizing (chemical evaporation, sputtering, ion-implantation, case hardening) and Metallizing by Direct Physical or Thermal Bonding (laminating, mechanical plating, slurry coating and strip roll welding).

60. N. V. Mandich and R. Tuszynski, "METALLIZING OF PLASTICS", in: Engineered Materials Handbook, ASM International, pp. 356-364 (1995).

Metallizing of plastics is elaborated for the plating process (electroless and electroplating steps) as well as for vacuum metallizing and thermal spraying methods Selection of plastics, part design, fabrication considerations, service performances and environmental considerations are presented.

61. F. Altmayer and N. V. Mandich, "ANALYSIS AND CONTROL OF HEXAVALENT CHROMIUM PLATING SOLUTIONS" in : AESF training book: Chromium Plating for Engineering Application, AESF, Orlando, Fl. (1996).

Analytical frequency, cause of rejects, sampling of plating solutions, chemical additions and analysis of chromium plating solutions are presented. Relevant instrumental methods (ion chromatography, AA, ICP, ion sensitive electrodes), together with standard titrimetric and gravimetric methods are described. In appendices, methods for thickness testing, hydrogen stress cracking, roughness and wear are detailed, together with step-by-step analytical procedures for all constituents and contaminants present in chromium plating baths.

62. N. V. Mandich, "PULSE AND PULSE REVERSE ELECTROPLATING", in: 66th Metal Finishing GuideBook, Volume 95, No. 1A (Elsevier Publishing, N.Y.), 1998.

Electrodeposition with Pulse Current (PC) and Periodically Reversed Current (PRC), relative newcomers in the modern electrodeposition field, are discussed. They offer a number of advantages and new opportunities for practicing electroplaters. Alloys can be modulated with regard to the composition of alloying elements. Bright deposit can be obtained without separate brightening additives. Throwing power can be greatly improved and physical properties can be changed. Deposition rates can be increased due to improvement of the crystallization conditions. Mass transport limitations, for processes under diffusion control can be reduced or eliminated. Electrocrystallization conditions can be improved due to increased frequency of nucleation and dissolution of dendrites or other surface imperfections by anodic component of the current. For diffusion limited processes, practical current density can be increased due to the increase of the amplitude of the cathodic component of PRC current, which can offset any reduction in total deposition rate due to anodic dissolution.

63. G. A. Krulik, and N. V. Mandich, "Metallic Coatings-Survey", in: Concise Encyclopedia of Chemical Technology, Desk Edition 4th ed., pp1273-1276, Wiley-Interscience, N.Y., (1995).

Condensed version of Reference 63

64. N.V. Mandich and D. Snyder," Chromium Plating" in MODERN ELECTROPLATING, 4th edition, Willey, N.Y. (2000) .

US PATENTS:

65. G. A. Krulik and N. V. Mandich, " Waste Stabilization Composition for Safer Storage of Cyanide Solutions for Reclaim", U. S. Patent Appl. # 743,203 (8/91).

This invention relates to a composition useful for stabilizing free and complexed cyanide-containing waste liquids for safer storage and shipping before ultimate disposal and/or reclaim. It is especially suitable for stabilization of small amounts of used and waste solutions, rinses, paper towels, and other difficult to handle materials. The stabilized cyanide is in a solid buffered matrix, which prevents spillage or accidental cyanide gas evolution.

66. G. A. Krulik and N. V. Mandich, "Waste Treatment Composition Containing Magnesium for Treatment of Alkaline Organic Polymer Waste Solution", U.S. Patent Appl., # 753,136 (9/20/91).

The invention consists of a composition containing magnesium salts and flocculating agents, which is useful for waste treatment of organic resins contained in alkaline aqueous solutions. It transforms alkaline aqueous solutions, which contain organic polymers such as photoresists and paints to a less hazardous, easily filterable solid without the use of acids. Free alkalis are neutralized by transformation to much less hazardous solid insoluble magnesium compounds. This composition allows the neutralization and stabilization of waste liquids containing free alkalis with simultaneous agglomeration of contained organic polymers to give an easily filterable or settable solid for safer storage and ultimate disposal and /or reclaim. The composition is especially suitable for treatment of spent photoresist stripping solutions, solder mask developing solutions, and paint waste solutions.

67. G. A. Krulik and N. V. Mandich, "Low Corrosivity Catalyst for Activation Of Copper for Electroless Nickel Plating", U.S.Patent #5,212,138, (5/18/93).

The invention relates to electroless nickel plating of metals, which are normally noncatalytic for electroless nickel initiation. It is especially useful in the electronics industry, including production of electroless nickel/electroless gold tabs or surface mount pads on printed circuit boards, and for use in electroless nickel plating over copper for radio frequency interference shielding. More particularly, it is comprised of alkali halide salt solutions of palladium salt with another Group VIII precious metal salt in an inorganic acid solution, for effectively and completely catalyzing the initiation of electroless nickel plating on copper substrates.

68. G. A. Krulik and N. V. Mandich, "Low Corrosivity Catalyst for Containing Ammonium Ions for Activation of Copper for Electroless Nickel Plating ", U. S. Patent # 5,219,815, (6/15/93).

The invention relates to electroless nickel plating of metals, which are normally noncatalytic for electroless nickel initiation. It is especially useful in the electronics industry, such as for production of electroless nickel/electroless gold tabs or surface mount pads on printed circuit boards, and for use in electroless nickel plating over copper for radio frequency interference shielding. More particularly, it is comprised of ammonium halide salt solutions of a palladium salt with another Group VIII precious metal salt and acid and optionally an alkali halide salt, for effectively and completely catalyzing the initiation of electroless nickel plating on copper substrates.

69. G. A. Krulik and N. V. Mandich, "Electroless Gold Plating Composition", U. S. Patent # 5,232,492, (8/3/93).

An electroless gold plating solution is invented, comprised of a gold (I) complex, a thiosulphate, a sulfite, a pH regulator and an oxidation controller. The electroless gold plating solution uses a novel reducing agent system, the thiosulphate-sulfite-sulphate system. It shows a plating rate and a plating solution stability comparable to those of conventional gold plating solutions containing borohydride, thiourea, hydrazine, and other reducing agents.

71. N. V. Mandich, G. A. Krulik, and R. Sidhu, "Novel Electroless Silver Plating Solution", U.S. Patent # 5,322,553 (6/21/94).

This invention is an electroless silver plating solution comprised of a silver (I) complex, a thiosulphate salt and a sulfite salt. This electroless silver plating solution uses a novel reducing agent combination of thiosulphate and sulfite. It shows a plating rate and solution stability far superior to those of conventional silver plating solutions containing formaldehyde, reducing sugars, borohydride, hydrazine and other reducing agents.

72. G. A. Krulik, N. V. Mandich, and R. Sidhu, "Plating Rate Improvement for Electroless Silver and Gold Plating, U. S. Patent # 5,318,621, (6/7/94).

Electroless silver or gold plating solution comprising non-cyanide metal complex, a thiosulphate, a sulfite, and at least one amino acid is invented. These electroless plating solutions containing an amino acid exhibit and accelerated plating rate compared to identical solutions lacking amino acids.

73. N. V. Mandich, G. A. Krulik, and R. Sidhu, "Improved Process for Elimination of Pink Ring Effect in Multilayer Printed Boards Processing", U. S. Patent Appl. # 886,010,(5/20/92).

This invention is a process, which eliminates pink ring defects developed during production of multilayer printed circuit boards by use of an acidic solution of a complexing agent. It is comprised of a treatment of the traditional copper oxide layer on inner layer copper with an acidic complexing agent solution to modify the properties of the copper oxide. The treated copper oxide surface gives improved bonding characteristics and retains excellent bonding strength while showing improved resistance to pink ring defects during multilayer printed circuit board processing.

74. R. Sidhu, N. V. Mandich, and G. A. Krulik, "Solder and Tin Stripper Composition", U.S. Patent # 5,512.201 (4/30/96).

This invention relates to the removal of solder and tin films from printed circuit boards and to a new and improved method and composition for stripping the solder and tin films and the underlying tin-copper alloy from the copper substrate of a printed circuit board in a single application of the composition by spraying or dipping.

75. G. A. Krulik, N. V. Mandich, and R. Sidhu, "Regeneration and Recycle of Ammoniacal Copper Enchant", U. S. Patent Appl. # 08-141,513 (10/27/93).

This invention relates to a method to recycle an ammoniacal copper etchant, which uses metallic aluminum to remove copper without substantially adding undesirable soluble byproducts. The process is fast and efficient. The separated copper and aluminum hydroxide sludge are easily filtered from the etchant. The purified etchant is now suitable for chemical adjustment and reuse.

76. G. A. Krulik, N. V. Mandich, and R. Sidhu "Control of Regeneration of Ammoniacal Copper Enchant", U. S. Patent # 5,524,780 (07/11/96)

A method is invented for improved control of recycle of an ammoniacal copper etchant, which uses metallic aluminum to remove copper without substantially adding undesirable byproducts. Using a diluent of copper -free etchant, eliminating overheating, can control the very rapid reaction. The separated copper and aluminum hydroxide sludge are easily filtered. The purified etchant is now suitable for chemical adjustment and reuse.

77. G. G. A. Krulik, N. V. Mandich, and R. Sidhu, "Solder Stripper Recycle and Reuse", U. S. Patent # 5, 505.872 (04/09/1996).

This invention relates to the removal of Pb from spent ferric nitrate based solder, the regeneration of the spent ferric nitrate based solder strippers, and the reuse of these solutions at least one time. It is comprised of a method and process for precipitating Pb salts from used acidic solder strippers which are employed to strip solder coatings, including the underlying Sn-Pb alloy, from the Cu substrate of a printed circuit board. The method includes the use of sulphate ions which are directly added to an aqueous solution of spent solder stripper, without neutralization of the spent solder stripper, optionally in combination with nitric or methane sulfonic acid addition. After precipitation and removal of the lead salts, additional components of the solder stripper composition may be added to substantially restore the initial functioning of the solder stripper.

78. G. A. Krulik, N. V. Mandich, and R. Sidhu, "Recycle Process for Regeneration of Ammoniacal Copper Enchant", U. S. Patent # 5,556,553 (09/17/96)

This invention is a process for control of recycle of an ammoniacal Cu etchant, which uses metallic aluminum to remove Cu without substantially adding undesirable byproducts. This is accomplished by controlling the temperature and mixture rate of the removal process. Using a diluent of Cu -free etchant, heating to process temperature, then adding spent, Cu containing etchant at a controlled rate while actively cooling the system to control the temperature, can control the rapid reaction. The Cu concentration can be monitored by colorimetry while maintaining the pH above 8. The separated metallic Cu and Al hydroxide sludge are easily filtered. The purified etchant is now suitable for chemical adjustment and reuse.

PUBLICATIONS -continued

79. N.V.Mandich, " Toward Understanding of Nickel Activation and Chromium Reverse Etching," Plat. Surf.Finish.,84(12),91(1998).

Contribution is offered for better understanding of cathodic activation of nickel prior to decorative chromium plating and for reverse etching before hard chromium plating. Causes and cures for nickel passivity are contributed. Anodic etching prior hard chromium plating is analyzed in relation to the influence of the base metal and plating chromium over chromium is detailed. Practical aspects are detailed and theoretical explanations are presented for electrochemistry related to activation and reversing mechanisms.

80. J. Pattanayak, K. Mondal, N.V. Mandich, T. Wiltowski, and S.B. Lalvani, "Recovery of Metallic Impurities from Plating Solutions by Electromigration," Met. Finish.,97(3)39(2000) .

The use of various catholytes for the removal of metallic impurities by electromigration is presented. In addition, the influence of current and temperature on the removal of impurities is discussed. The results show that chromic acid is a most suitable catholyte. Its use results in little or no change in the solution pH and relatively low power consumption while maximum metal removal is obtained. The total metal removal rate from a mixture of impurities is found to be proportional to the total amount of metallic impurities contained in the solution. In general, nickel and copper are relatively easy to remove while the iron removal rate is the lowest. A list of guidelines for practical operations based upon the results obtained is presented.

81. D. W. Baudrand and N.V.Mandich," Fabrication and Plating of Multichip Modules and Hybrid Circuits", Electrodep. Surf. Treat. (Russian) (accepted for publishing).

The printed circuit board has become well known even to those who have no formal knowledge of electronics. A lesser-known but firmly entrenched and growing method of circuit manufacture uses ceramic hybrid microelectronics technology. In this process, circuit wiring is printed on a base material of ceramic (non-metallic mineral oxide) instead of a PC board, and chips and other discrete components are mounted directly onto the surface of the metallized substrate rather than pin-mounted in plated through-holes. Although surface mounting of devices is also used on PC boards, ceramic hybrids offer a number of advantages that makes their use more attractive, and in some cases mandatory. Among these are miniaturization, reliability, Thermal Coefficient of Expansion, the ability to withstand mechanical, vibrational, and thermal shock, the ability to be cut and drilled to extremely fine tolerances, ease of multi-layer manufacture, and high dielectric constant.

82. N. V. Mandich, "Electrodeposition of Binary (Au-Sb) and Ternary (Au-Cu-Cd) 18K Gold Alloys with Pulsed and D.C. Currents " ", Proceedings of the 87 th Annual Technical Conference, Chicago, ( 2000).

A number of experiments were done under laboratory conditions, evaluating 18 Karat gold as a possible substitute for pure (24K) gold, with a rack and barrel systems. Among the many available industrial 18K solutions, the two most promising were experimentally evaluated, gold alloyed with Cu and Cd (Auro Dure) and gold with Sb (E-41 gold). By comparing the 18K to the 24K deposits the following results were obtained: Porosity equal to the 24K gold, Solderability was equal or better, Hardness value was slightly higher and Electrical Resistance had no significant difference. Savings in gold metal, due to density and karat difference, including improved metal distribution variation, was approximately 46% of the total gold consumption. The 18K investigate solutions were found stable and controllable and produced consistent results over prolonged production periods. They are found to be suitable for plating many types of industrial electrical contacts as a substitute for 24K gold plating.

83. J. Pattanayak, N.V. Mandich, K. Mondal, T. Wiltowski, and S.B. Lalvani,'Removal of Iron and Nickel from Solutions by Applications of Electric Field",Environmental Technology, 20, 317(1999)

Metallic impurities such as Ni, Fe, and Cu ions in industrial chromium plating solutions can be removed by electromigration followed by electrodeposition or coagulation using a "porous pot" method. Pot is suspended in the bath and contains a lead cathode and anode. In the same process, Cr (III) is oxidized to Cr (VI) at the insoluble lead anode leading to regeneration of the plating solution. Previous research and data from industrial applications have indicated that the porous pot could be a cost -- effective and environmentally friendly method to continuously separate the impurities and recycle spent chromium plating solutions. However, no data are available that relate the various concentration of impurities to the extent and the rate of their removal. This investigation focused on the use of the of five suitable electrolytes for the removal of the impurities. Up to 60% nickel and 52% iron removal were observed in orthophosphoric acid and sodium monophosphate. In addition to these two catholytes, chromic acid appears to be the most suitable catholyte for purification where more than one metal is present in the spent solution.

84. N. V. Mandich, and N. V. Vyazovikina," On the Nature of the Cathodic Current Oscillations Observed on Chromium Cathode during Chromium Plating" 49th Ann. Meeting, International Society for Electrochemistry, Kitakyushy, Japan,( Sept.1998), Extended Abstract No P-8-15-33.

Electrochemical investigations on chromium cathode were carried out by Potential Sweep and Potential Step methods. Solution used is aerated, 2.5 M (100:1), chromium plating solution at 40, 50, 55 and 60 C0 . Voltammograms and Amperograms with sections of cathodic current oscillations were obtained. The potential range corresponding to the appearance of cathodic current oscillations on E-I and I-( curves was isolated and its dependence on potential scan rate and temperature was established.

It is found that oscillations amplitude and induction time,( , necessary for advent of cathodic current oscillations during chromium cathodic polarization are potential depended . Based on obtained results and literature data, the suggestion is offered on adsorption-desorption nature of oscillations. Adsorption-desorption processes, taking place during formation of viscous cathodic layer, in the potential range preceding chromium electrodeposition, are identified as a cause of continuous surface passivation and activation. They also cause consequent decrease and increase of cathodic current that results in appearance of oscillations on E --I and I-( curves. It is confirmed that cathodic current oscillations disappear completely when cathodic film containing mono-, di- and polynuclear aquo complexes of *, polychromates and *ions has formed and chromium deposition process has begun.

85. J. Pattanayak, N.V. Mandich, K. Mondal, T. Wiltowski, and S.B. Lalvani," Modeling a Process for Removal of Metal Ions by Electromigration and Electrodeposition" , J. Electrochem. Soc. (submitted for publication).

A mathematical model that takes into account the removal of impurities of the metal ions of Fe, Ni, and Cu from hard chromium plating solution by electromigration and subsequent electrodeposition is developed and presented. Experimental data for the metal removal at 45 0C and constant cell voltage using o-phosphoric acid as the catholyte are obtained. Up to 36% iron and 29% nickel removal is obtained in about 25 hrs. The copper removal rate is observed to be approximately four times as large as the rate of nickel removal. The experimental data were found to closely match the results predicted from the model developed. The inherent model parameters such as mobility, diffusivity, and mass transfer coefficient and metal deposition rate constants were estimated. The estimated values of these parameters are fund to be in good agreement with published data.

86. N.V. Vyazovikina and N.V.Mandich, " Study of Resistance to Localized Corrosion of High Chromium Content Alloys by Combined Use of Electrochemical and Physical Methods", Voprosi Khimii i Khimicheskoi Tekhnologii (Ukraine), 29(1) 72(1999).

Structure and phase composition of commercial chromium-iron alloys containing 16 to 60 % Cr and 2 to 5 % Al were studied by use of Electron microscopy, X-ray microprobe analysis and Auger-electron spectroscopy. Also were investigated by combined use of electrochemical and physical methods the resistance of alloys to pitting and intergranular corrosion. It was shown that in 3% NaCl and 2 M HCl solutions, Cr15Al5, Cr23Al5, Cr27Al5 and stainless steel 12Cr18Ni9Ti are receptive to pitting and Cr40Al2, Cr45Al4 and Cr60Al2 alloys are not . It was demonstrated by Voltammetric, chronoamperometric, chronopotentiometric methods and electron microscopy that Cr15Al5 and 12Cr18Ni9Ti steels are susceptible and Cr27Al5, Cr40Al2, Cr45Al4 and Cr60Al2 are not susceptible to intergranular corrosion in 2 M HClO4 + 1 M NaCl solution. High resistance to pitting and intergranular corrosion , of investigated commercial alloys containing more than 27 % of Cr is related to high content of chromium at grain boundaries and to the presence of passive films formed at their surface.

87. N.V. Mandich, "Important Practical Considerations in Chromium Plating - Part IV", Met. Finish., 97(9) 79 (1999).

In continuation of Parts I- III where plating problems related to Low Deposition Rates, Nodular Deposits , Imperfect Adhesion, and Gray, Dull and Milky deposits were detailed, in Part IV partial or poor coverage, burnt deposits as well as problems related to pitted deposits are analyzed in step-wise fashions. A number of plating problems related and interrelated to the above are presented in detail. A fundamentals of covering power, throwing p9ower, influence of base metal and current distribution are discussed

88. N.V. Mandich, "Important Practical Considerations in Chromium Plating - Part V", Met. Finish. 97(10),30 (1999).

In continuation of Parts I- IV where plating problems related to Low Deposition Rates, Nodular Deposits and Imperfect Adhesion were detailed, in Part V, plating problems related to trivalent chromium baths are analyzed as well for barrel and black chromium solution. A reversible, two buss bars plating technique is presented and it's characteristics and advantages are compared to a standard, three buss bar (two anode- one cathode ) system

89. N.V. Mandich, "Important Practical Considerations in Chromium Plating - Part VI", Met. Finish., (to be published in March 2000 issue).

In continuation of Parts I-V where plating problems related to hexavalent rack chromium plating, in this part trivalent chromium baths, barrel chromium solution and a reversible, two buss bars plating technique were detailed.

90.

91. K. Mondal, N.V. Mandich, and S.B. Lalvani "Regeneration of Cr(VI) using Bismuth doped Anode" J. Appl. Electrochem. (to be published- under peer review).

Under the application of a constant cell voltage, the hexavalent chromium from a freshly prepared chromic acid solution used as a catholyte electromigrates via a ceramic barrier to the anode while the trivalent chromium present as an impurity in the CrO3 solution is oxidized to hexavalent chromium at the anode. The rate of hexavalent chromium regeneration from trivalent chromium at the Bi-doped PbO2 anode is found to be approximately 4 times grater than the corresponding rate observed for the PbO2 coated lead (anodized lead) anode. A mathematical model that takes into account spices electromigration and associated mass transfer effects was developed and tested. The dynamic concentration data for various rate parameters.

92. N.V. Mandich, K. Mondal, J. Pattanayak, and S.B. Lalvani, "Characterization of the Chromium Deposits Obtained from Electrochemically Regenerated Electroplating Solutions" , Plating Surf. Finish., 87 (1) 75 (2000).

Two spent hard chromium plating solutions were regenerated using an industrially viable electroseparation method for the removal of metal impurities. The spent and regenerated baths were used to obtain chromium electrodeposits which are compared with electrodeposits obtained from freshly made, impurity free plating baths. The morphology of the electrodeposits was characterized by the scanning electron microscopy (SEM). Comparative evaluation of the hardness and corrosion resistance clearly shows that the physical properties of the electrodeposits obtained from the regenerated baths are superior to the properties of the electrodeposits produced from the spent solutions. These properties are close to those obtained for the electrodeposits produced from a freshly prepared hard chromium plating solution

93. N.V. Mandich and W. Saas, "Trouble Shooting decorative Nickel Plating Installations- Part 1", Plating Surf. Finish., 87(6)121(2000)

In order to help to practicing electroplaters to better cope with plating problem that occasionally will happen in their decorative nickel plating lanes, we attempted to analyze the causes of problems and offer the answers in a most possible practical fashion. For reasons of clarity, no theoretical explanations are presented at this time and technical language is used in most possible simple and plain form.

94. N.V. Mandich and W. Saas, "Trouble Shooting decorative Nickel Plating Installations- Part 2", Plating Surf. Finish., 87(7)63(2000).

Continuation of Part 1

95. N.V. Mandich and W. Saas, "Trouble Shooting Decorative Nickel Plating Installations- Part 3", Plating Surf. Finish., Accepted for publishing in Dec. 2000 issue.

The background, symptoms and causes for pores, pits, stains, blistering and "spotting-out" phenomenon are analyzed from phenomenological and practical standpoints. Origin and tests for porosity are discussed as well the detection methods. Corrective steps are presented.

96. N.V. Mandich and D. Baudrand, "Trouble Shooting Decorative Nickel Plating Installations- Part 4", Plating Surf. Finish., Accepted for publishing in May 2001 issue.

The brief historical development and basic chemical steps for metallizing of non-conductors in general and plating on ABS plastics in particular are offered. The main emphasis is directed toward presentation of a comprehensive troubleshooting guide where the focal technical problems encountered in one present day plating on plastic plant are detailed. The possible causes of plating defects and solutions of the problems are elaborated

97. D. W. Baudrand, and N.V.Mandich, " Effect of some Variables on the Properties of Nickel Deposited from Sulfamate Plating Solutions" SurfFin 2001. (to be published).

Influence of plating conditions and impurities on all major characteristics and properties of electroplated deposits from nickel solutions based on the sulfamate anion are presented. Ductility, hardness, tensile strength, intrinsic stress, deposit structure, porosity, smoothness, density, specific heat, coefficient of expansion, thermal conductivity, specific resistivity, and modulus of elasticity in tension are presented among others. Anodic reactions and breakdown of the sulfamate anion are analyzed in the view of the recent literature research data.

98. N. V. Mandich, "Electrodeposition of Binary (Au-Sb) and Ternary (Au-Cu-Cd) 18K Gold Alloys with Pulsed and D.C. Currents " 6th International Pulse Plating Symposium, Chicago, June 2000.

A number of experiments were done under laboratory conditions, evaluating 18 Karat gold as a possible substitute for pure (24K) gold, with a rack and barrel systems. Among the many available industrial 18K solutions, the two most promising were experimentally evaluated, gold alloyed with Cu and Cd (Auro Dure) and gold with Sb (E-41 gold). By comparing the 18K to the 24K deposits the following results were obtained: Porosity equal to the 24K gold, Solderability was equal or better, Hardness value was slightly higher and Electrical Resistance had no significant difference. Savings in gold metal, due to density and karat difference, including improved metal distribution variation, was approximately 46% of the total gold consumption. The 18K investigate solutions were found stable and controllable and produced consistent results over prolonged production periods. They are found to be suitable for plating many types of industrial electrical contacts as a substitute for 24K gold plating.

99. N. V. Mandich, "ELECTROPLATERS and SURFACE FINISHERS HANDBOOK"-In preparation (to be published as a book).

Comprehensive Handbook is underway. It is containing 8 chapters : Dictionary of Electroplating Terms; Operating data; Troubleshooting; Tables & Conversion Factors; Chemical, Electrochemical & Electroplating Calculations; Properties, Standards & Tests; Electrodeposition, Electropolishing & Anodizing Baths Compositions, and Mechanical Preparations of Basis Metals

100. N.V. Mandich, and J.K. Dennis, "Derivation Of Exact Equation For Current Efficiency Under Periodic Reverse Current Conditions" Met. Finish. (submitted for publication).

Exact equation that is taking into the account anodic and cathodic current amplitudes as well as variable time periods is developed. PRC chromium deposition is exemplified.

101. N.V. Mandich, "Trouble Shooting Decorative Nickel Plating Installations- Part 6", Plating Surf. Finish., Submitted for publishing.

In continuation of Parts 1-5, in Part 6, causes and some typical examples of problems that occur in electroplating as a result of thermal, mechanical surface treatments, or metallurgy of the part to be plated are discussed.

102. N.V. Mandich, "Trouble Shooting Decorative Nickel Plating Installations- Part 6", Plating Surf. Finish., Submitted for publishing.

Bronze deposition and the properties of as-plated deposits are discussed. Effect of operating conditions and baths constituents are presented. The possible causes of bronze plating defects and solutions of the problems are elaborated in the form of a troubleshooting chart.

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