Showing papers on "Electroplating published in 2011"

Packaging Technology for Electronic Applications in Harsh High-Temperature Environments

Abstract: Silicon-on-insulator (SOI) integrated circuits have been demonstrated for use at temperatures up to 300 °C. However, to build functional electronics, multiple devices must be interconnected to provide the desired functionality. A system-in-package approach has been developed using thick-film technology on Si3N4 ceramic substrates. Si3N4 has a near coefficient-of-thermal-expansion match to Si and a higher flexural modulus than Al2O3, which is commonly used for thick-film applications. The conductor metallization is Au. For 300 °C operation, eutectic Au-Ge die attach was used with a Ti/Ti:W/Au backside die metallization. After 3000 h at 325 °C, the mean die shear strength decreased from 3.96 to 3.33 kg/mm2, a decrease of only 16%. Formation of Au-Si-Ge ternary eutectic (melting point 326 °C) was observed and limits the use of Au-Ge die attach to 300 °C. SOI dies typically have Al wire bond pads that are not compatible with Au thermosonic wire bonding for high-temperature applications. Two plating processes have been examined: electroless Ni/immersion Au/electroless Au and electroless Ni/electroless Pd/immersion Au. The plating processes provide a barrier layer (Ni) and a wire-bondable finish (Au or Pd-Au) over the Al wire bond pads. After 10 000 h at 300 °C, the wire pull force for the Ni/Au samples decreased by ~30% due to annealing of the Au wire, while the ball shear force increased by ~35%. The daisy-chain electrical resistance remained relatively constant. For the Ni-Pd-Au samples, after 2000 h at 320 °C, the ball shear force remained constant or increased slightly, the wire pull force decreased by ~25% due to annealing of the Au wire, and the daisy-chain resistance remained relatively constant. After 3000 h, however, cratering of the Si wire bond pad was observed corresponding to some first bond pad lifts and increased daisy-chain resistance. Optimization of the wire-bonding parameters for bonding to the harder Ni/Pd/Au bond pad is required to eliminate cratering.

Electrodeposition and Growth Mechanism of Copper Sulfide Nanowires

Abstract: Thiourea (TU) is widely used as a corrosion inhibitor or as an additive in metal (e.g., copper) electroplating baths. TU facilitates the formation of uniform deposits with high brightness. In this ...

Electroless Deposition of Nickel

Abstract: Electroless (autocatalytic) plating involves the presence of a chemical reducing agent in solution to reducemetallic ions to the metal state. The name electroless is somewhat misleading, however. There are no external electrodes present, but there is electric current (charge transfer) involved. Instead of an anode, the metal is supplied by the metal salt; replenishment is achieved by adding either salt or an external loop with an anode of the corresponding metal that has higher efficiency than the cathode. There is therefore, instead of a cathode to reduce the metal, a substrate serving as the cathode, while the electrons are provided by a reducing agent. The process takes place only on catalytic surfaces rather than throughout the solution (if the process is not properly controlled, the reduction can take place throughout the solution, possibly on particles of dust or of catalytic metals, with undesirable results). Brenner and Riddell [1] invented electroless Ni plating in 1946 rather accidentally when they observed that the additive NaH2PO2 caused apparent cathode efficiencies of more than 100% in a nickel electroplating bath. This led them to the correct conclusion that some chemical reduction was involved. Further research resulted in the development of the original process that the inventors named electrodeless plating. The name soon lost the de, and later the name autocatalytic was formally adopted, although electroless is still widely used. The words are synonymous. Autocatalytic plating is defined as the deposition of a metallic coating by a controlled chemical reduction that is catalyzed by the metal or alloy being deposited. Such plating has been used to yield deposits of Ni, Co, Pd, Cu, Au, and Ag as well as some alloys containing these metals plus P or B. Electroless Cr deposition has also been claimed. Chemical reducing agents have included NaH2PO2 (the one originally used by the inventors for Ni and Cu deposition and still the most important and widely investigated), formaldehyde— especially for Cu—hydrazine, borohydrides, amine boranes, and some of their derivatives. Electroless plating possesses several characteristics not shared by other techniques, and that accounts for its ever-growing popularity. Its throwing power is essentially perfect, at least on any surface to which the solution has access, with no excessive buildup on edges and projections. Deposits may be less porous than electroplates and hence have better corrosion resistance. Power supplies, electrical contacts, and the other apparatus necessary for electroplating are not required. The process is usually an integral and necessary step in plating on nonconductors such as plastics (see Chapter 15 of this volume). The process is particularly important in the printed circuit industry. Some electroless deposits have unusual or even unique magnetic properties. Experience shows that each substrate requires its own specific techniques; depositing active metal onto the surface of a non(semi)conductor is still somewhat of an art. The surface preparation (i.e., cleaning process) requires very careful selection and application. It must be stressed that cleaning may affect the porosity of the metal deposit. Residues from cleaners and deoxidizers may create inactive spots that will not initiate electroless deposition. This may result in the necessity to have a thicker deposit before continuity is achieved. In extreme cases continuity is never reached. In general, deposition requires one or more of the following steps (see Fig. 18.1): (1) cleaning, (2) surface modification, (3) sensitization, (4) catalyzing or (30) catalyzing, and (4) activation (acceleration). Rinsing is required between the steps. We refer to the steps 3 and 4 (shown in Fig. 18.1) as sensitization and catalyzing. By these terms we mean

Electrodeposition and Characterization of Thin-Film Platinum-Iridium Alloys for Biological Interfaces

Abstract: An efficient platinum-iridium thin film alloy electrodeposition method has been evaluated to modify the surface of platinum or gold microelectrodes that are being developed for neural recording and stimulation applications. A large number of electrodeposition process variables have been investigated in terms of how they affected the properties of the electrodeposited films. Three sets of Pt-Ir films of a certain composition were electroplated on gold substrates using a potential cycling technique and characterized using microscopy, elemental analysis, nanoindentation, and electrochemical techniques to evaluate the repeatability of the electrodeposition process. Deposition rates were estimated by determining film mass and thickness as a function of deposition time. The surface morphology of the Pt-Ir films was characterized using scanning electron microscopy (SEM) and the chemical composition was determined using wavelength dispersive spectroscopy (WDS). Nanoindentation measurements showed that the hardness of the electroplated Pt-Ir thin films was nearly 100% higher than that of a Pt foil. The electrochemical properties of the films were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and compared with those of pure Pt, pure Ir and 80-20% Pt-Ir foils. The final electroplating process resulted in 60-40% Pt-Ir alloys. The film thickness increased with electrodeposition time at a rate of 16.5 nm/min and stable films with up to 500 nm thickness were obtained. Characterization by SEM and EIS revealed that the real surface area of the Pt-Ir films was much larger than that of pure Pt and increased significantly with increasing deposition time.

Metallization of Kevlar fibers with gold.

Abstract: Electrochemical gold plating processes were examined for the metallization of Kevlar yarn. Conventional Sn(2+)/Pd(2+) surface activation coupled with electroless Ni deposition rendered the fibers conductive enough to serve as cathodes for electrochemical plating. The resulting coatings were quantified gravimetrically and characterized via adhesion tests together with XRD, SEM, TEM; the coatings effect on fiber strength was also probed. XRD data showed that metallic Pd formed during surface activation whereas amorphous phases and trace amounts of pure Ni metal were plated via the electroless process. Electrodeposition in a thiosulfate bath was the most efficient Au coating process as compared with the analogous electroless procedure, and with electroplating using a commercial cyanide method. Strongly adhering coatings resulted upon metallization with three consecutive electrodepositions, which produced conductive fibers able to sustain power outputs in the range of 1 W. On the other hand, metallization affected the tensile strength of the fiber and defects present in the metal deposits make questionable the effectiveness of the coatings as protective barriers.

Electrodeposition and characterization of nanocrystalline Ni-Fe alloys

Abstract: Nanocrystalline Ni-Fe deposits with different composition and grain sizes were fabricated by electrodeposition. Deposits with iron contents in the range from 7 to 31% were obtained by changing the Ni2+/Fe2+ mass ratio in the electrolyte. The deposits were found to be nanocrystalline with average grain size in the range 20-30 nm. The surface morphology was found to be dependent on Ni2+/Fe2+ mass ratio as well as electroplating time. The grains size decreased with increasing the iron content, especially in case of short time electroplating. Increasing the electroplating time had no significant effect on grain size. The microhardness of the materials followed the regular Hall-Petch relationship with amaximum value (762 Hv) when applying Ni2+/Fe2+ mass ratio equal to 9.8.

Function and mechanism of supercritical carbon dioxide emulsified electrolyte in nickel electroplating reaction

Abstract: Physical properties of supercritical carbon dioxide emulsion (Sc–CO 2 –E) were controlled to evaluate the effects on properties of nickel film electroplated. Additive-free Watts bath was used to study sole-effect of Sc–CO 2 –E on nickel electroplating reaction. Experimental pressure, volume fraction of CO 2 and surfactant were adjusted to control physical properties of Sc–CO 2 –E. Influence of current density was also studied. Surface roughness (R a ) was found to decrease with increase in pressure, volume fraction of CO 2 , volume fraction of surfactant and current density. Reduction in R a was believed to be caused by improved homogeneity of Sc–CO 2 –E, enhanced desorption of hydrogen bubbles from surface of cathode, and increased nickel nuclei density. Grain refinement was observed when increasing pressure, volume fraction of CO 2 and surfactant, which was believed to be caused by periodic plating characteristic of electroplating with Sc–CO 2 –E. On the other hand, grain coarsening was observed with increase in current density.

Influence of Operation Parameters on Metal Deposition in Bright Nickel-plating Process

Abstract: Bright nickel deposits were electrolytically applied on steel in the nickel Watts bath. The effect of some operational parameters on metal deposition in bright nickel plating was investigated. The investigation indicated that the weight of bright nickel deposited on metal during the process of electroplating was affected by plating temperature, voltage, current density, plating bath pH and plating time. The study established that the deposition of best bright nickel was obtained at a plating temperature of 56 o C, current density of 6 A/dm 2 and plating time of 18 minutes. Brightener is used in applications requiring outstanding appearance with minimum thickness of applied nickel plating. It can also be used for heavy deposit applications because it exhibits unparalleled ductility and low stress. Brightener was used in this study to determine the best nickel plating in the process. Boric acid was added for fixing the bath pH. The compositions of the brightener and nickel solution used are included in the text.

Electrodeposition from Cationic Cuprous Organic Complexes: Ionic Liquids for High Current Density Electroplating

Abstract: The electrochemical behavior of the low-melting copper salts CuMeCNxTf2N and CuPhCNxTf2Nx = 2–4, where MeCN is acetonitrile and PhCN is benzonitrile, is presented. In these compounds, the copperI ion is a main component of the ionic liquid cation. Consequently, the copper concentration is the highest achievable for an ionic liquid and this permits to obtain a good mass transport and high current densities for electrodeposition. The cathodic limit of the ionic liquid is the reduction of copperI to copper metal instead of the breakdown of the cation as in conventional ionic liquids. It is shown that pure, crack-free copper layers can be deposited from these copper-containing ionic liquids in unstirred solutions at current densities up to 25 A dm �2

Effect of some process variables on zinc coated low carbon steel substrates

Abstract: This work investigates the effect of some essential plating variable of zinc electro-deposition on low carbon steel substrates. The variation of plating parameter, the depth of immersion, distance between the anode and the cathode on voltage, plating time and coating thickness was considered. The steel substrates were immersed into solution of zinc electroplating bath for varying voltage between 0.5 and 1.0 V. It was discovered that the sample plated at 0.8 V for 20 min gave the best plating properties and it was also observed that increase in applied voltage, plating time, depth of immersion and decrease in distance of the object (cathode) from the anode increases weight gained. Microstructural studies with SEM/OPM however, revealed fine grained deposit of the deposited zinc and the inclusion of addition agent.

Characterization and reliability assessment of solder microbumps and assembly for 3D IC integration

Abstract: In this investigation, Cu/Sn lead-free solder microbumps with 10μm pads on 20μm pitch are designed and fabricated. The chip size is 5mm × 5mm with thousands of microbumps. A daisy-chain feature is adopted for the characterization and reliability Assessment. After pattern trace formation, the microbump is fabricated on the trace by an electroplating technique. A suitable barrier/seed layer thickness is designed and applied to minimize the undercut due to wet etching but still achieve good plating uniformity. With the current process, the undercut is less than 1μm and the bump height variation is less than 10%. In addition, the shear test is adopted to characterize the bump strength, which exceeds the specification. Also, the Cu-Sn lead-free solder micro bumped chip is bonded on a Si wafer (chip-to-wafer or C2W bonding). Furthermore, the micro-gap between the bonded chips is filled with a special underfill. The shear strength of the bonded chips w/o underfill is measured and exceeds the specification. The bonding and filling integrity is further evaluated by open/short measurement, SAT analysis, and cross-section with SEM analysis. The stacked ICs are evaluated by reliability tests, including thermal cycling test (−55⇆125°C, dwell and ramp times = 15 min). Finally, ultra find-pitch (5μm pads on 10μm pitch) lead-free solder microbumping is explored.

Copper nanoparticles synthesis from electroplating industry effluent

Abstract: In present investigation, samples from wastewaters of electroplating industry were collected and analyzed for the concentration of Cu2+ heavy metal. For the synthesis of copper nanoparticles, Pseudomonas stutzeri bacterial strain was used. The bacterial strain was isolated from soil and found that it produced 50-150 nm sized cubical copper nanoparticles from electroplating waste water. The nanoparticles have been characterized by UV-visible Spectrophotometer, X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Analysis.

Electroplating apparatus and process for wafer level packaging

Abstract: An apparatus for continuous simultaneous electroplating of two metals having substantially different standard electrodeposition potentials (e.g., for deposition of Sn—Ag alloys) comprises an anode chamber for containing an anolyte comprising ions of a first, less noble metal, (e.g., tin), but not of a second, more noble, metal (e.g., silver) and an active anode; a cathode chamber for containing catholyte including ions of a first metal (e.g., tin), ions of a second, more noble, metal (e.g., silver), and the substrate; a separation structure positioned between the anode chamber and the cathode chamber, where the separation structure substantially prevents transfer of more noble metal from catholyte to the anolyte; and fluidic features and an associated controller coupled to the apparatus and configured to perform continuous electroplating, while maintaining substantially constant concentrations of plating bath components for extended periods of use.

Review of effect of ultrasound on electroless plating processes

Abstract: When an electrochemical process is performed in an ultrasonic field, a number of well known effects occur as a result of acoustic cavitation, including enhanced mass transport, thinning of the diffusion layer and localised heating. Sometimes described as sonoelectrochemistry, applying simultaneous ultrasonic irradiation with electrochemistry has proved beneficial in a range of applications that include electrodeposition, electrosynthesis and electroanalysis. Many studies of electroplating in an acoustic field have been carried out and reviews have been published. Electroless plating is also an electrochemical process with great importance to a number of industries including aerospace, electronics, photovoltaics and automotive. Among a range of benefits that have been found as a result of introducing ultrasound to these processes are improved plating rates, coverage and adhesion of the coatings. With modern demands for high speed plating, reduced manufacturing times and the plating of nanomaterials, it is ...

Electroless and Electrodeposition of Silver

Abstract: Silver metal has been known since ancient times. It is mentioned in Exodus and Genesis. There exist strong indication that man was able to separate silver from lead as early as 3000 BC. Silver may be found native and in ores. Lead, lead zinc, copper, and other ores are principal sources. Silver may also be recovered during electrolytic refining of copper. Pure silver has the highest electrical and thermal conductivity of all metals. It retains that property in the form of electroplated thin film as well. This makes electroplated silver an important component of many printed circuit systems. There is indication that silver was plated as far back as the beginning of the nineteenth century. If correct, it must have been done in connection with producingmirrors. The earliest patent for silver plating, however, was not granted until 1840 [1]. That may be viewed as signifying the start of the electroplating industry. That bath is still one of the more used ones to this day, and it is the double-silver cyanide complex [KAg(CN)2] with excess free cyanide. Over the years many other baths have beenproposed [2], such as the ones involving nitrate, iodide, thiourea, thiocyanate, sulfamate, and thiosulfate. The usages of silver plating are many. Those include mirrors and deposits for tableware due to its decorative effect as well as resistance to corrosion in its contact with foods. There are a number of industrial uses as well. Those include, but are not limited to, electronic component applications, bearings,hot-gas seals, tonamebuta few.Silvermaybeplated using either electrodeposition methods or electroless methods. We discuss here both methods, starting with the latter.