Showing papers on "Electroplating published in 1992"

Formation of microstructures by multiple level deep X-ray lithography with sacrificial metal layers

Abstract: Complex metal structures are formed in microminiature dimensions utilizing multiple mask exposures which are capable of producing substantially arbitrary three-dimensional shapes. A first layer of a primary metal is electroplated onto an exposed plating base to fill a void in a photoresist, the photoresist is removed, and a secondary metal, which can constitute a sacrificial metal, is electroplated over the first layer and the plating base. The exposed surface of the deposited secondary metal is then machined down to a height which exposes the first metal to produce a substantially flat, uniform surface extending across both the primary and secondary metals. The secondary metal facilitates machining of the primary and secondary metals because of these mechanical stability provided by the secondary metal to the primary metal. After the first layers of the primary and secondary metals have been machined, another photoresist layer can be applied over the primary and secondary metals, and a second layer of primary metal is electroplated. A further layer of secondary metal can be also electroplated if desired. The process of machining and electroplating can be repeated until the desired structure is formed. Secondary metal is removed by an etchant which does not etch the primary metal.

Nanometer‐scale electrochemical deposition of silver on graphite using a scanning tunneling microscope

Abstract: Silver pillars, 10–30 nm in diameter and 4–10 nm in height, were generated on graphite surfaces using a scanning tunneling microscope. These structures were produced following the application of tip(+), 6 V×50 μs bias pulses in dilute, aqueous silver fluoride. A pit on the graphite surface is formed during the first 5μs of the pulse, followed by nucleation and electrochemical deposition of silver at this pit. This two‐step mechanism allows silver pillars to be located with a high lateral precision on the graphite surface−independent of the proximity of the tip to preexisting nucleation sites such as step edges.

Electrodeposition of zinc-nickel alloy coatings from a chloride bath containing NH4Cl

Abstract: Zinc-nickel alloys were electrodeposited on steel from chloride baths containing NH4Cl using different plating conditions. Current density, temperature and nickel percentage in the baths were found to strongly influence the composition of the deposits and the morphology. At low current densities transition from anomalous to normal codeposition was observed. The changes in potential, current efficiency, composition and morphology which follow the transition were studied. No increase in the partial current of hydrogen reduction was observed at the potential values from which anomalous codeposition begins; this fact, plus the formation of zinc ammonium complexes, seems to exclude the precipitation of zinc hydroxide at the electrode surface. The electrodeposition of zinc-nickel alloys is discussed emphasizing the importance of kinetic parameters and cathodic potentials.

A nanometer-scale galvanic cell

Abstract: An electrochemicaI cell having a largest total dimension of 70 nm was assembled on the surface of a highly oriented pyrolytic graphite crystal by electrochemically depositing copper and silver pillars (diameter ≃150-200 A) in close proximity to one another using the scanning tunneling microscope (STM). When the surface containing both metals is immersed in a dilute copper plating solution, copper structures spontaneously decrease in size and, concurrently, silver structures increase in size. The direction and magnitude of these changes are consistent with a coupled electrochemical process in which copper anodically dissolves from the copper structures and plates onto the silver structures

Photoelectric conversion element and fabrication method thereof

Abstract: A thin film solar cell having a semiconductor layer deposited on a substrate is composed of a passivation layer made of a polymer resin coated on the upper portion of the semiconductor layer, and an upper electrode made of a conductive paste laminated on the passivation layer. Also, a collector electrode may be laminated on the upper electrode by electroplating. A method for fabricating a solar cell by depositing a semiconductor layer on the substrate includes coating a passivation layer made of a polymer resin on the upper portion of the semiconductor layer, and laminating an upper electrode made of a conductive paste containing a component capable of dissolving the polymer resin on the passivation layer. Also, the method may include laminating a collector electrode on the upper electrode by electroplating.

Method of plating a bonded magnet and a bonded magnet carrying a metal coating

Abstract: A closely adherent metal coating having a uniform thickness and substantially free from pinholes is formed on the porous surface of a bonded magnet to improve its oxidation and corrosion resistance without lowering its magnetic properties. The coating is formed by electroplating from an aqueous solution not containing chlorine, and having a pH of 5 or above. More particularly, the solution contains mainly nickel sulfate, an electrolyte in the form of an organic acid salt not containing chlorine, and a basic electrolyte not containing chlorine, and forms a nickel coating on the magnet surface.

Aqueous polysulphide flow-through electrodes: effects of electrocatalyst and electrolyte composition on performance

Abstract: Porous electrodes are required to achieve satisfactory performance of the aqueous sulphide/polysulphide redox couple in energy conversion and storage applications. A flow cell for testing flow-through porous electrodes was constructed and operated. The effects of electrode material, temperature, flow rate, and electrolyte composition were studied. Catalytic electrode surface layers of Co and MoS2 demonstrated performances which were more than adequate to meet a design goal of 10–20 mA cm−2 at less than 50mV overpotential. Flow rate variation had only a small effect on the current density-overpotential behaviour, whereas raising the temperature and/or adding dimethylformamide to the electrolyte had much larger effects. These observations are consistent with steady-state results obtained on rotating disc electrodes.

Resistive metal layers and method for making same

Abstract: Electrodeposited planar resistive layers are disclosed, which may be combined with conductive layers and insulative layers to produce laminates useful in the preparation of printed circuit boards. The resistive layers are prepared by electroplating from an electroplating bath containing a source of a normally conductive metal component and a source of a non-metallic resistance increasing additive. Planar resistors may be produced which have sheet resistances in the range of from about 15 to about 1000 Ω per square.

Influence of substrate on the electrodeposition of nickel-molybdenum alloys

Abstract: The electrodeposition of nickel-molybdenum alloy has been studied on various substrates, with the aim of determining the influence of hydrogen evolution on the formation of the deposit. Transient electrochemical methods were used. Three types of substrates were used. Glassy carbon in which hydrogen absorption cannot occur, palladium in which hydrogen diffusion is rapid, and nickel. Good and thick deposits were obtained on glassy carbon and annealed ultra pure nickel. On palladium no deposit was formed. The importance of hydrogen in the formation of the deposit was confirmed. Codeposition occurs in the same potential range as hydrogen evolution, and therefore hydrogen is trapped in the expanding lattice as seen by its oxidation during anodic polarization.

Thermal annealing of palladium alloys

Abstract: This invention is concerned with production of electrical devices comprising an electrodeposited conductive region free from cracking defects. In the production of a contact portion of the device from a metal strip electroplated with a conductive stripe of an alloy, the stripe exhibited, upon stamping and forming operation, cracked areas. Typically, the stripe coating on the metal strip, such as a copper bronze material, includes a layer of nickel, a layer of palladium alloyed with nickel, cobalt, arsenic or silver, and a flash coating of hard gold. The cracking defects were eliminated by subjecting the plated strip to an annealing treatment prior to the stamping and forming operation. After the heat-treatment, the stripe was free from cracks and separations between the successive layers.

Electroplating of Ni-Cr on steel with pulse plating

Abstract: It has been difficult to electrolytically obtain crack- free chromium plating because of the high stresses caused by several factors. Accordingly, electroplating of nickel- chromium also encounters a similar problem. Cracks in chromium- containing plating was ascribed, in a certain sense, to the formation of a hydride formed through hydrogen adsorption from the electrolyte. A periodical pulse reverse plating current would enhance the release of hydrogen and hence the elimination of cracking. The present work describes a successful process for obtaining crack- free nickel- chromium plating and the effects of experimental variables on plating compositions.

Electroplating process for enhancing the conformality of titanium and titanium nitride films in the manufacture of integrated circuits and structures produced thereby

Abstract: Highly conformal layers of either titanium, Ti, titanium nitride, TiN, or titanium oxide, TiO x , are formed on exposed surfaces of silicon substrates by first forming a very thin chemical vapor deposition (CVD) layer of either doped polysilicon or a chosen metallic silicide, such as titanium silicide, tungsten silicide, tantalum silicide, or molybdenum silicide on the exposed silicon surfaces and any masking material remaining thereon. Thereafter, the layered structure is transferred to an electroplating bath wherein a layer of titanium is plated on the surfaces of the metallic silicide film using either an aqueous electroplating solution, a non-aqueous solution or a molten salt solution. Then, the structure is transferred to either an anneal furnace or to a rapid thermal processor (RTP) and heated to a predetermined elevated temperature for a predetermined time in the presence of nitrogen, using either nitrogen gas, N 2 , or ammonia, NH 3 , to form a titanium nitride film and an underlying metal-silicon interface having a good contact resistance at the silicon substrate surface. Alternatively, titanium oxide, TiO x , films may be formed in an oxygen ambient as an excellent etch stop material, or the vias may be completely electroplated with titanium, Ti, and then annealed with no nitrogen or oxygen present in the anneal furnace or rapid thermal processor.

Apparatus and method for electroplating wafers

Abstract: An apparatus and corresponding method for electroplating wafers includes supporting a plurality of wafers on a backing board in the electroplating tank such that one surface of each wafer is masked from the electrolytic reaction. A programmable controller is used to regulate the waveform, frequency and duration of current passing between each individual wafer and a corresponding anode electrode during the electroplating process. Voltage is monitored between the wafers and the anode electrodes to ensure a proper electrical connection is maintained with each individual wafer during the electroplating process.

Method for electroplating a substrate containing an electroplateable pattern

Abstract: A method for the electroplating of conductive metal onto a substrate containing at least one hole and an electroplateable surface which is conducive to subsequent metal deposition comprises placing the substrate in close proximity to an electrode but such that there is no substantial electrical continuity between the electroplateable surface and the electrode prior to electroplating. The electroplateable surface is preferably an electroplateable pattern which comprises either a conductive metal pattern or a catalytic pattern for subsequent plating. This process can be employed with any electroplateable pattern technique which is recognized in the art such as, for example, printing, stamping, plating, photographic or electrophotographic processes. In one embodiment, this process can be employed in the production of Plated Wire, i.e., a product which can be effectively employed as a replacement for drawn wires in power distribution applications.

The effect of additives on the nucleation and growth of copper onto stainless steel cathodes

Abstract: A potentiostatic technique has been used to study the effects of chloride ion, glue, and thiourea on the initial electrodeposition of copper. A stainless steel (AISI 304) rotating disc electrode (RDE) with an electrolyte containing 40 g/1 Cu2+ and 180 g/1 H2SO4 at 40 °C was employed. The current transients from the potential step measurements for the additive-free electrolyte could be fitted to a model that assumed progressive nucleation followed by growth of three-dimensional (3-D) centers under diffusion control. The growth mechanism and the type of nuclei were also confirmed by scanning electron microscopy (SEM) of the deposit. Chloride ions (40 ppm) affect the rate of the reaction, decrease the number of nuclei, and enhance the growth process. The particular glue (TPC 69, 5 ppm) used in this work is a polarizer and increases the number of nuclei formed on the surface. For the experimental parameters used in this research, the nucleation and growth mechanism is not changed by the presence of chloride ion or glue in the electrolyte. However, thiourea (0.5 ppm) additions caused the mechanism to change to instantaneous nucleation with 3-D growth under kinetic control, and a large number of equal sized nuclei are observed on the SEM micrographs, tending to verify the proposed mechanism.

Process for zinc electroplating of aluminum strip

Abstract: A process for zinc electroplating of aluminum strip which can be performed continuously at a high speed and a high current density. The process comprises subjecting aluminum strip to anodic electrolysis in an acidic solution which may be an acidic plating bath solution or a pickling solution before the strip is subjected to cathodic electrolysis in an acidic zinc plating bath to perform zinc electroplating.

Studies of platinum electroplating baths Part I: The chemistry of a platinum tetrammine bath

Abstract: The chemistry of a new commercial electroplating bath for platinum, based on a Pt(NH3) 4 2+ salt in a phosphate buffer, is investigated using195Pt NMR and microelectrode techniques. It is shown that the maximum rate of deposition is determined by a homogeneous chemical reaction preceding the electron transfer step; the nature of this homogeneous chemical reaction is discussed.

A tartrate-based alloy bath for brass-plated steel wire production

Abstract: The plating of brass on steel from a tartrate based alloy bath has been studied using electrochemical methods and surface analysis techniques. The coating composition obtained using both direct current (d.c.) and pulsed current (p.c.) electrolysis was examined for a variety of temperatures, current densities and bath compositions. The dissolution process of a suitable composition of brass anodes was studied using small amounts of nitrate as depolarizing agent. Tests in a pilot plant showed that when electrolysis is carried outin continuo the coating composition remains constant with time (±1%). Tests were performed at cathode current densities of industrial interest (20–30 A dm−2). The Auger and XPS analyses combined with Ar+ etching indicated a homogeneous composition throughout the coating.

Investigation of solar selective and microstructural properties of molybdenum black immersion coatings on cobalt substrates

Abstract: Molybdenum black solar selective coatings have been produced on cobalt by immersion in a solution of ammonium paramolybdate and nickel sulphate. The cobalt was electroplated on nickel-plated copper prior to immersion in the paramolybdate solution. The maximum solar absorptance of the resulting molybdenum black coating was about 0.91. The minimum emittance was about 0.1 for coatings on cobalt deposited with an addition agent and about 0.23 for coatings on cobalt deposited without addition agent in the 60 °C plating solution. These differences have been related to the coating morphology determined by scanning electron microscopy. The emittance of coatings on cobalt deposited without addition agent decreases (or remains unchanged) during short-term heat treatment while that of coatings deposited on cobalt plated with addition agent increases somewhat. Reduction of the cobalt plating bath temperature to 45 °C can also lead to good initial coating properties but without the requirement for an addition agent in the cobalt plating bath. XPS studies show that the oxidation state of molybdenum in the coatings is approximately + 5 corresponding to Mo4O11. This reduces to + 4 after argon ion bombardment. Some cobalt may be present in the coatings in the form of CoO.

Controlled composite deposition method

Abstract: A composite deposit in which insoluble particles are co-deposited and dispersed in a metal matrix is formed on an article by dipping the article in a metal plating solution having insoluble particles dispersed therein and effecting an electroplating or chemical plating process. By adjusting the specific surface area of insoluble particles to be dispersed in the metal plating solution, the amount of insoluble particles co-deposited in the composite deposit can be controlled. Better results are obtained with insoluble particles having a specific surface area of 10 m 2 /g or less.

Hydrogen separation membrane and its production

Abstract: PURPOSE:To easily obtain a hydrogen separation membrane excellent in heat resistance and mechanical strength, prevented from the deposition of carbon from a gas to be treated and improved in workability by supporting a palladium alloy membrance from the both side with a metallic supporting body and metallic plate on which many narrow pores having specific pore diameter are drilled. CONSTITUTION:The hydrogen separation membrane is formed by sticking the palladium alloy membrance 12 having 1-50mum film thickness on one face 11a of the metallic supporting body 11 on which many narrow pores (h) 10-500mum in pore diameter are drilled by etching. The metallic plate 13 on which many narrow pores 1 are drilled by etching on the surface of the palladium alloy membrane 12 side is laminated on the palladium alloy membrane 12. If necessary, a metallic thin film of gold, silver, platinum, palladium, rhodium, copper or an alloy thereof is stuck by electroplating method to the metallic plate 13 with many drilled narrow pores.