Electrolytic Deposition Of Metals Research Articles

Fabrication of a Bioimpedance Sensor via Inkjet Printing and Selective Metallization

The significant incidence of cancer on public health in the modern industrialized world is pushing the research on novel therapeutic techniques and diagnosis tools. The latter, in particular, are of vital importance, since in many cases a prompt cancer diagnosis can significantly decrease patient’s mortality. Bioimpedance tissue analysis, in particular, is gaining attention as a promising methodology to identify tumor. Manufacturing technologies for bioimpedance probes are however still not completely adapt for cost effective mass production. In this context, the present work aims at producing a costless bioimpedance sensor by employing inkjet printing and electrolytic metal deposition. The probe manufactured in this way is successfully employed for bioimpedance testing of three animal tissues, demonstrating ability to successfully distinguish between them.

Upscaling panel size for Cu plating on FOPLP (Fan Out Panel Level Packaging) applications to reduce manufacturing cost

Abstract Electrolytic metal deposition is a key process step in the manufacturing of vertical and horizontal interconnections used in today's PCBs and IC substrates on one hand and advanced packaging applications on the other hand. Historically both application areas were clearly defined and separated by different requirements in feature sizes and substrate formats. PCBs and IC substrates were based on organic large scale substrates with rather large features while advanced packaging technology is wafer based with the capability to incorporate fine features down to a few microns. The ever increasing demand of higher performance, lower cost and thinner end user devices like smartphones require intense developments and innovation in all areas of the electronic component design including the substrate and chip packaging. Latest manufacturing technologies in both areas like fan-out wafer level packaging and advanced substrates are constantly emerging and promise to be a critical piece to meet these requirements. As a consequence both areas are currently merging while creating a new application segment. This segment combines the request of small feature sizes with the manufacturability on large scale substrates. Obviously many of the traditional process technologies like plating and available equipment cannot be easily adopted and need certain developments, adaptions and improvements. In this respect, a key challenge in the area of electrolytic metal deposition is the combination of various challenging requirements: creation of feature sizes down to 2μm L/S with heterogeneous feature density on large substrates up to 600mm at excellent metal thickness uniformity and high plating speed. The paper presents latest studies and conclusions in critical performance areas of the plating process such as electrolyte fluid dynamics, impact of anode design, pulse reverse rectification and newly designed electrolytes. Finally latest test results of optimized process conditions will be discussed in detail with different feature sizes providing data of within die and within substrate uniformity. All tests are done on panel level, both organic and glass substrates. The latest findings and achievements of the discussed panel based plating process technology will support the industry to develop panel based packaging processes that meet both technical and commercial requirements.

The geometry of nanometer-sized electrodes and its influence on electrolytic currents and metal deposition processes in scanning tunneling and scanning electrochemical microscopy

Electrodes with an effective radius of about 10 nm have been produced by a combination of electrochemical etching, electrophoretic deposition of polymer, and heat curing. Their size and stability were characterized by cyclic voltammetry. They were then used in combined electrochemical scanning tunneling microscopic (ECSTM) and scanning electrochemical microscopic (SECM) experiments. In an extension of an earlier report, electrochemical surface modification approaches are reported here. They comprise the local electrochemical removal of a self-assembled monolayer (SAM) of dodecanethiol on flame-annealed gold by an electrochemical desorption procedure. The possibility of local electrochemical deposition is demonstrated by positioning a nanoelectrode 0.5 nm above a surface and switching off the distance regulation while performing an electrodeposition of Pt at the tip. The growing deposit bridges the tip-sample gap. If the distance regulation is switched on after 1 ms, the Pt junction is disrupted leaving a Pt nanodot at the sample surface. The dot was characterized by ECSTM experiments after solution exchange. Digital simulations by the boundary element method (BEM) provide a quantitative description of Faraday currents in nanoelectrochemical assemblies. A software tool was created that can accept arbitrary geometries as input data sets. The flexibility of the simulation strategy was demonstrated by the calculation of local current densities during electrochemical copper deposition on a smooth electrode in the presence of an ECSTM tip close to the surface. The current densities deviate less than 1% from those in the absence of tip if the average current density is kept below 1 μA cm −2. SECM approach curves for nanoelectrodes were also calculated.

Al(5)Br(7) small middle dot5 THF-The First Saltlike Aluminum Subhalide.

Multiple insertion of AlBr in bonds of AlBr3 leads to Al5Br7⋅5 THF—a new type of low-valent aluminum halide. The actual, ionic structure of the subhalide [Al5Br6⋅6 THF]+[Al5Br8⋅4 THF]− (the anion is shown schematically) appears plausible on the basis of density functional theory calculations. This and similar subhalides can play the role of potential intermediates in the electrolytic deposition of metals.

Electrolytic deposition of metals on to the high-voltage contact in an electrospray emitter: implications for gas-phase ion formation

Electrolytic deposition of metals on to the high-voltage contact in an electrospray emitter: implications for gas-phase ion formation

Electrolytic deposition of metals on to the high-voltage contact in an electrospray emitter: implications for gas-phase ion formation.

The electrospray ion source is an electrolytic flow cell. Electrolytic reactions in the electrospray emitter maintain the production of charged droplets by this ion source that contain an excess of ions of one polarity. These redox reactions necessarily change the composition of the solution that initially enters the emitter. As a result, the ions ultimately observed in the gas phase by electrospray mass spectrometry (ESMS) may be substantially influenced by both the nature and extent of these electrochemical reactions. It is demonstrated in this paper that Ag(+), Cu(2+) and Hg(2+) ions in solution can be electrolytically reduced and deposited as the respective metals on to the surface of the high-voltage contact in the electrospray emitter in negative ion mode electrospray. The deposited metals are shown to be liberated from the surface by switching the electrospray high-voltage polarity to operate in the positive ion mode. The deposited metals are oxidized in positive ion mode, releasing the metal ions back into solution where they are detected in the electrospray mass spectrum. In a semi-quantitative analysis, it was found that up to 50% of the Ag(+) in a 2.5 microM solution was deposited on the high-voltage contact of the emitter as the solution flowed through the emitter. Deposition of Cu(2+) and Hg(2+) was less efficient. These data illustrate that in the analysis of metals by ESMS, one must be aware that both the concentration and form of the metals may be altered by electrochemical processes in the emitter. Hence reduction or oxidation of metals in the electrospray emitter, which may remove ions from solution, or change metal valence, would be expected to impact both quantitative metal determinations and metal speciation attempts using ESMS.

Electrolytic metal deposition onto chemically modified electrodes

Some general features concerning electrochemical metal deposition onto electrodes modified with self-assembled monolayers (SAMs) of alkanethiols are discussed. Although thiols of various chain length are briefly addressed, special emphasis is placed on copper deposition onto an ethanethiol (C2)-modified Au(111) surface. The short alkanethiol blocks the surface to a great extent but does not completely suppress charge transfer. We have used in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV) to characterize the structure and the electrochemical behavior of the C2 monolayer in sulfuric acid electrolyte before and after introducing copper ions to the system. The C2 adlayer consists of domains of two different ordered structures. It is shown that the adlayer undergoes a reversible order–disorder transition at potentials slightly negative of 0 V vs. SCE, which testifies to a surprisingly high mobility of the C2 molecules within the SAM. Copper deposition on C2-modified gold electrodes shows significant differences from the same process on the bare electrode. A sharp cathodic peak at -0.18 V vs. SCE is ascribed to the insertion of a Cu monolayer between Au and the organic adlayer. At low overpotentials the Cu deposit exhibits a ramified monatomic high morphology, if the ethanethiol adlayer is dense. Three-dimensional growth starts at large substrate defects.

The Initial Stages of Copper Deposition on Bare and Chemically Modified Gold Electrodes

This paper comprises, in the form of an overview, various aspects of the initial stages of electrolytic metal deposition, demonstrated and exemplified by the classical model system, Cu on Au(hkl). Describing underpotential as well as overpotential deposition, some of the parameters governing nucleation and growth are pointed out. The profound effect of substrate orientation is shown and various examples of the influence of organic additives on the deposition process are given. Most recently, metal deposition onto electrodes covered with self-assembled monolayers has received increased attention as a possible model system for metal deposition onto a non-conducting stirface and therefore, preliminary results for Cu deposition on alkanethiol covered Au(111) are presented.

Scanning Tunneling Microscopy for Metal Deposition Studies

Electrolytic metal deposition, particularly from aqueous solution, provides the basis for a number of indispensable industrial applications such as metal winning and refining, metal plating for corrosion protection, and surface finishing. Circuit board manufacturing in microelectronics, in particular, has renewed interest in the research of metal deposition. In addition to its industrial significance, electrodeposition is also of principal interest in regard to its fundamentals, such as, the investigation of electrocrystallization phenomena.

Electrolytic Deposition of Thin Metal Films on Semiconductor Substrates

Electrolytic deposition of metals on semiconductor electrodes was studied by a potentiostatic pulse method. Experimental data for the deposition of Pb, Ag, and Pd on , , , , and are analyzed to obtain information regarding the mechanism of deposition and the structure of the deposits. The results suggest that the actual overpotential required for the deposition of a metal depends on the relative position of the redox potential of the metal with respect to the flatband potential of the semiconductor while the nucleation behavior of the metal is influenced by the difference in work functions of the depositing metal and the substrate.

Kinetics of the initial stage of electrolytic deposition of metals III. Galvanostatic conditions

The kinetics of the initial stage of the electrolytic deposition of a thin metal film onto an inert cathode are considered for the case when the electric current flowing through the electrolytic cell is held constant with time. In studying the process the Gibbs-Thomson effect is taken into account and the cases of pure ohmic control, volume diffusion control and phase boundary transition control are examined separately. Expressions are derived for the radius of a single crystallite, the mean crystallite radius and the overvoltage as functions of time and current strength for each of the above types of growth control. Formulae are also obtained for the maximum overvoltage, the time taken to reach it and the maximum number of crystallites on the cathode as functions of the electric current. The analysis shows that the decrease in the maximum number of crystallites with decreasing current approximately obeys a power law and that there exists a critical value of the electric current, different for the different types of control, below which only one crystallite forms and grows on the cathode.

Kinetics of the initial stage of electrolytic deposition of metals I. General theory

The process of the electrolytic deposition of metals is considered as a particular case of heterogeneous phase formation. The basic set of kinetic equations describing the initial stage of formation of a thin metal film on an inert cathode is formulated in a general form. With the aid of these equations the mean crystallite radius, the overvoltage and the electric current flowing through the system can be found as functions of time if the total “ohmic” resistance of the electrolytic cell is known. Taking into account the Gibbs-Thomson effect of crystallite curvature, expressions are derived for this resistance in the particular cases when the crystallite growth is limited solely (i) by the specific electrical conductivity of the electrolyte, (ii) by volume diffusion of the metal ions from the bulk of the electrolyte towards the surface of the growing crystallites, and (iii) by impediments accompanying the transition of the metal ions through the crystallite/electrolyte interphase boundary. Finally, it is shown that electrodeposition processes characterized by other types of crystallite growth control can also be analysed by means of the basic set of kinetic equations if the total cell resistance is properly defined.

Kinetics of the initial stage of electrolytic deposition of metals: II. Potentiostatic conditions

The kinetics of the initial stage of electrolytic deposition of a thin metal film onto an inert cathode are considered with the assumptions that nucleation is completed and the overvoltage is kept constant with time. The process is studied separately in the cases of pure ohmic control, volume diffusion control and phase boundary transition control of the growth of the crystallites. Expressions are derived for the radius of a single crystallite, the mean crystallite radius and the strength of the electric current through the electrolytic cell as functions of time and overvoltage for each of the above types of growth control. The analysis shows that taking the Gibbs-Thomson effect of crystallite curvature into account leads to (i) the appearance of an intercept in the asymptotic linear dependences of the current and the crystallite radius on the square root of time for ohmic and volume diffusion control, and (ii) violation of the linear dependences on time of the square root of the current and of the crystallite radius for phase boundary transition control.

On the mechanism of electrocrystallization

The technique for the preparation of electrodes having one crystallographic plane only was applied in the investigation of the mechanism of electrolytic metal deposition. Impedance and galvanostatic transient methods as well as steady state measurements were used in the case of silver crystal planes and onp planes possessing a limited number of screw disloc silver crystal planes and on planes possessing a limited number of screw dislocations. The spreading out kinetics of mono-atomic layers on dislocation-free planes and the curent-square overvoltage law found on planes with dislocations, show that current is proportional to step length. This fact was used for the preparation of electrodes with exactly known step density.An interesting fact observed on electrodes with known step density is that the exchange current density, obtained from impedance measurement at high frequencies, is proportional to step length. This shows that deposition on a step is much easier than on a plane region. It was found that the exchange current density of ions in solution with ions in kink position is about four orders of magnitude higher than the exchange current density with adions. A simple calculation shows that up to the highest step densities (step distance of about 450 Å) used inb the present investigations the direct transfer mechanism is prevailing by at least two orders of magnitude over the surface diffusion mechanism.

Microlevelling During Electrolytic Deposition of Metals

Levelling has been studied mostly in nickel plating baths and several theories have been developed. The present paper deals with levelling in acid copper plating baths in which the following theori...

On the calculation of potential energy profile diagrams for processes in electrolytic metal deposition

The calculation of potential energy and free energy profile diagrams for successive and alternative steps in electrolytic metal deposition is described with reference to two extreme models of the entity resulting from the initial transfer of the metal particle from the solution to the surface of the metal.Neutralization of the transferred ions to form adsorbed metal atoms is distinguished from ion-transfer processes in which the transferred entity maintains ionic character, with the appropriate number of stoichiometric electrons entering the metal lattice for each ion transferred.The elementary processes considered are: transfer of ions from the solution to different types of surface sites upon the metal; surface diffusion of adsorbed ions; successive, dehydration of the adsorbed ions in lattice building.The free energies of the transition states in successive steps in consecutive ion-transfer, surface-diffusion and lattice-building reactions are compared, and the probable rate-determining process in the over-all metal deposition reaction is deduced in the cases of Cu2+, Ni2+ and Ag+ ion deposition on to the respective metals. Uncertainties in the calculation are examined.The heat of activation (ΔH0≠) for transfer of ions from the solution to the metal surface depends upon the site to which transfer occurs, that to a planar site being significantly less than that to other sites (e.g., edges, kinks, etc.) Transfer to form completely non-polar neutral adatoms has prohibitively high values of ΔH0≠Direct deposition Of Cu2+ on to surface sites would be associated with a prohibitively high heat of activation. The path Cu2+ + eM → Cu+ followed by Cu+ + eM → (Cuadion++ eM) is associated with heats of activation significantly lower than that for direct Cu2+ deposition in a single two-electron step. The free energy diagrams are consistent with the existence of a rate-determining reduction mechanism found experimentally. Near the Cu/Cu2+ reversible potential the free energy barrier for adion surface diffusion can become the highest. This is consistent with the experimental behaviour under these conditions. With Ag+ ion deposition the ion-transfer step has the highest free energy barrier at high negative overpotentials, whilst near the reversible potential the barrier for surface diffusion can become the highest. The kinetic behaviour found experimentally with silver supports the theoretical conclusions.The low exchange current density for Ni2+ ion deposition is probably associated with the instability of the simple Ni+ ion in aqueous solutions.

Mechanism of electrolytic deposition and dissolution of metals.

Mechanism of electrolytic deposition and dissolution of metals.

Mechanism of Electrolytic Deposition and Dissolution of Metals

Mechanism of Electrolytic Deposition and Dissolution of Metals

The mechanism of electrolytic metal deposition

Possible mechanisms of electrolytic metal deposition from aqueous solutions of cupric, nickelous and silver ions are examined by deriving and comparing the relevant potential energy profiles with the purpose of indicating the rate-determining step. The following steps in the overall reaction are considered: ionic transfer from the solution to surface sites; surface diffusion of adsorbed ions; successive dehydration of the adions at lattice building sites. The formation of adions and adatoms in intermediate steps is distinguished and it is shown that neutral adatom formation is unlikely. The heat of activation (∆H 0‡ ) for transfer of ions from the solution to the metal surface, depends upon the site to which transfer occurs, that to a planar site being significantly less than that to other sites (e. g. edges, kinks, etc.). Transfer to form adatoms has prohibitively high ∆H 0‡ values. Lattice building is accomplished by surface diffusion of transferred adions to edges or kinks. At each of the consecutive stages of the deposition process, a change in hydration of the ion or adion occurs and has important effects on the mechanism and kinging of deposition. Direct deposition of divalent ions on to surface sites is shown to be associated with high heats of activation and low electrochemical rate constants as found experimentally for Ni 2+ , Fe 2+ and Co 2+ deposition. When the deposition reaction can occur through an intermediate redox step involving a stable ion as, e. g. in the case of copper, it is shown that lower free energies of activation can result than if the deposition of the divalent ion occurs in one step. This is consistent with the experimental behaviour found for copper deposition. At low overpotentials, it is shown that both the steps of ionic transfer and surface diffusion would have comparable rate constants in the case of copper and silver deposition whilst at higher overpotentials, the reduction of Cu 2+ ions becomes rate determining at copper, whilst ionic transfer of Ag + ions becomes rate determining at silver. This is in agreement with the behaviour observed experimentally.

On the Effects of Ultrasound on the Electrolytic Separation of Metals

In the electrolytic deposition of metals, electrochemical quantities are affected by ultrasound. The action is similar to that caused by intensive stirring of the electrolyte in front of the cathode. This ultrasonic stirring can be explained by an increased motion caused by sound radiation pressure of the hydrogen bubbles deposited together with the metal at the electrode surface. Consequently, the deposition potential and the current yield are primarily affected. Furthermore, such properties of the metal deposit as brilliance, porosity, structure, texture, adhesiveness, hardness, and tensile strength are affected by the ultrasound. In the case of alloy baths, the composition of the deposited layer is changed. The effects of ultrasound that have been discovered up to now can have technological value only if new methods for intense and uniform sound irradiation of large baths become available.