Showing papers on "Electroplating published in 1990"

Method and apparatus for adjusting plating solution flow characteristics at substrate cathode periphery to minimize edge effect

Abstract: A method and apparatus for electroplating metallized bumps of substantially uniform height on predetermined terminal areas of a substrate. Cup plating apparatus includes elements for adjusting parameters affecting the geometry of the substrate relative to the plating cup, as well as flow rate of the electroplating solution against the substrate surface. By achieving non-laminar flow of the electroplating solution near the substrate edges, the plating characteristics of the electroplating solution are altered in this region, substantialy offsetting "edge effect", so that the resulting plated bump height is substantially uniform across the substrate.

Studies on nickel coated carbon fibres and their composites

Abstract: Uniform and continuous coating of nickel was given to the carbon fibres by cementation, electroless or electroplating techniques. The coating thickness was ranged between 0.2 and 0.6 μm for all the three methods used. Coating thickness less than 0.2 μm showed discontinuous coating of nickel over the fibre surface. Beyond 0.6 μm thickness, nickel deposited in den-drite form over the continuous coating. For continuously coated fibres, the ultimate tensile properties of electroless coated fibres were near to uncoated carbon fibres suggesting adherent and defect free coating; while fibres coated by electrolytic and cementation process exhibited lower ultimate tensile strength (UTS) properties. The tensile fracture of the cementation coated fibres suggested degradation of the fibres. In composites, prepared by dispersing the coated fibres in pure aluminium matrix, no appreciable fibre-metal interaction was observed. NiAl3 intermetallics were observed around and adjacent to the carbon fibres. Sometimes carbon fibres were found embedded in massive NiAl3 intermetallics suggesting that fibre surface can also act as nucleating centre for these precipitates.

Method of fabricating high-density interconnect structures having tantalum/tantalum oxide layers

Abstract: A method of fabricating a high-density multilayer copper/polyimide interconnect structure utilizing a blanket tantalum/tantalum oxide layer that electrically connects all of the electroplating seed layers to the edge of the substrate; upon completion of the electroplating process, the excess tantalum/tantalum oxide layer is etched off to produce isolated conductor lines A multilayer copper/polyimide interconnect structure may be fabricated by repeating this fabrication sequence for each layer

Pulsed Electrodeposition of Iron‐Nickel Alloys

Abstract: This paper reports on the effects of dc, pulse, and pulse reverse current waveforms on deposition of Fe-Ni alloys studied in unagitated solutions and with a rotating cylindrical electrode. A nickel sulfamate/ferrous chloride electrolyte system at pH 2 less than 2 A/dm{sup 2}. Pulse reverse plating led to a decrease in anomalous deposition at low current densities. Rotating cylindrical electrodes indicated significant mass transfer effects at high current densities. During pulse reverse plating an increase in anodic pulse magnitude decreased anomalous deposition; pulse frequency had its greatest effect in reducing anomalous deposition between 100 and 300 Hz.

Considerations in Electrodeposition of Compositionally Modulated Alloys

Abstract: High‐quality specimens of sufficient thickness for reliable testing are needed if the enhanced properties observed for ultrastructured multilayered metals are to be understood and exploited. In the present paper, factors affecting the quality of multilayers electrodeposited from a single electrolyte, via concerted modulation of the electrode potential and electrolyte mass transport, are discussed. The importance of precise control of the potential during deposition of the more noble metal is emphasized. Results obtained by a pulse technique show that Ni passivation does not occur under the conditions used to electrodeposit Ni‐Cu multilayers. Attainable deposit quality is illustrated by tensile test data for a series of 90%Ni‐10%Cu specimens that are twice as strong as Ni and for which the standard deviations for the ultimate tensile strength and modulus are only 1.5 and 3.9%, respectively.

Cyclic Voltammetry of Electrodeposition of Metal on Electrosynthesized Polypyrrole Film

Abstract: Electrodeposition of various engineering metals on a platinum electrode with and without an electrosynthesized polypyrrole film was studied by cyclic voltammetry. Copper, nickel, lead, tin, and silver were readily deposited. The presence of a polypyrrole film generally reduces the plating rate and shifts the deposition peak potential to a more negative value. A capacitive effect is usually observed with the first scan which is subsequently dissipated due to the shunting effect of the metal deposit in the pores of the polypyrrole film. Inhibition of hydrogen evolution is found to be relatively more significant with electronegative metals such as nickel and tin, resulting in higher metal deposition current efficiency. This study shows that metal can be readily deposited on conductive polypyrrole both on its surface and within its pores, therefore providing a convenient method for producing metal‐polymer‐metal multilayer composites and metal‐modified polymer electrodes for specific applications.

Treatment of copper foil for printed circuits.

Abstract: A process for the treatment of a copper foil for printed circuits comprises forming, over the surface of the copper foil to be treated, of an electroplating alloy deposit selected from the group consisting of electroplating deposits of binary alloys composed of 20 - 40 mg/dm² copper and 100 - 3000 µg/dm² cobalt and of ternary alloys of 20 - 40 mg/dm² copper, 100 -3000 µg/dm² cobalt, and 100 - 1000 µg/dm² nickel. The copper foil treated has heat resistance, peel strength, and resistance to hydrochloric acid comparable to the Cu-Ni-treated foils. It can be etched with a CuCl₂ etchant to form 150 µm or finer-pitch printed circuits and is also etchable with alkalies. Its magnetizability is below the permissible upper limit.

Electrodeposition of zinc-nickel alloy coatings: influence of a phenolic derivative

Abstract: The electroplating of Zn−Ni alloy films from a chloride bath has been studied under different plating conditions, both in the absence and presence of a phenolic derivative. Under the conditions examined, the electrodeposition of the alloys belonged to the anomalous type. The morphology and composition of the deposits varied with current density, temperature, bath composition and additive concentration. The results show that the additive modifies the structure and surface topography of the deposits to a large extent and produces smoother deposits. The corrosion resistance of the alloys has been analyzed by means of salt-spray tests.

Limiting tin sludge formation in tin or tin/lead electroplating solutions

Abstract: Baths and methods for electroplating tin or tin-lead alloys wherein the formation of tetravalent tin and stannic oxide sludge is reduced or prevented. These baths contain a soluble divalent tin compound, a soluble alkyl or alkylol sulfonic acid at least one wetting agent, and a hydroxyl phenyl compound reducing agent. Other compounds may be added to the bath for improving its performance during electroplating.

The effect of pulsed reverse current on the polarization behaviour of acid copper plating solutions containing organic additives

Abstract: The polarization behaviour of acid copper solutions containing polyethers, sulphopropyl sulphides and chloride ions was studied using both direct and pulsed reverse current. The effect of these additives on the rest potentials of copper foils immersed in the electrolyte was also studied. Polyethers were found to have an inhibiting effect on the deposition of copper whereas the sulphopropyl sulphides produced a stimulating (i.e. depolarizing) effect. Chloride ion concentration was found to have an influence on the adsorption characteristics of the polyether. The use of pulsed reverse current in solutions containing both polyether and sulphopropyl sulphide was found to inhibit the adsorption/diffusion of the sulphopropyl sulphide at the cathode surface. Thus at higher current densities, above 2 A dm−2, the inihibiting effect of the polyether produced a shift in the cathodic polarization potential to more negative values as compared with an equivalent current density using direct current. At lower current densities, below 2 A dm−2, the depolarization effect of the sulphopropyl sulphide was still effective. This effect of pulsed current on additive containing solutions can improve dramatically the metal distribution in low current density areas on plated items. This was illustrated by plating Hull cell panels using both pulsed and direct current.

Properties of Ni-Sx electrodes for hydrogen evolution from alkaline medium

Abstract: Active layers for hydrogen evolution were prepared electrolytically from nickel-plating baths containing various amounts of thiourea. The sulphur content of the deposited layers, which is dependent on the thiourea content of the electroplating bath, ranged between 10 and 20 wt%. X-ray photoelectron spectroscopic (XPS) analysis revealed that sulphur was present in the layers not only in the form of sulphide, but also in the forms of thiourea and sulphate entrained from the nickel-plating bath. X-ray diffraction analysis showed that the coatings were poorly crystalline. Nickel sulphide, which produces an X-ray diffraction pattern, was present only in coatings deposited from baths with higher amounts of thiourea. The surface layers of such coatings contained a maximum of 10 at % nickel in the form of Ni3S2. When the Ni−Sx electrodes were under load in 1m KOH over a long period, the hydrogen overpotential was found to vary with time. On the basis of XPS measurements, the initial decrease in hydrogen overpotential was ascribed to the washing-out of adsorbed residues of thiourea. The subsequent increase in the overpotential was due to the deposition of iron on to the surface of the layers from the electrolyte used.

Electrodeposited eutectic tin-bismuth alloy on a conductive substrate

Abstract: An electroplating bath, cell and method for the electrodeposition of a wide range of tin-bismuth alloys onto a conductive substrate comprises tin and bismuth ion in aqueous solution, and an alkyl sulfonic or polysulfonic acid or salt as the electrolyte. The sulfonic component is present in amounts sufficient to maintain the bismuth in solution. In the operation of the method of the invention, electroplated tin-bismuth eutectic alloys of controlled composition are obtained. The alloys of tin and bismuth contain amounts of both metals such that the plated alloy has a melting point substantially lower than that of either metal alone, and a melting point lower than that of a tin-lead alloy.

Palladium alloy electroplating process

Abstract: An electroplating process is described for electroplating alloys of palladium and arsenic. The resulting electrodeposits are bright, ductile and remain ductile and crack-free even when the electrodeposits are quite thick. The deposits are quite hard and suitable for contact surfaces particularly in situations where wear characteristics require thick deposits. The electroplating process is also useful for making articles such as bellows by electroform procedures particularly since the electroplated material has extraordinary physical properties (good resilience, low stress and ductility) as well as good corrosion resistance.

Metallization of Printed Circuit Boards Using Conducting Polyaniline

Abstract: A novel process using polyaniline for plating through hole technology has been developed. Polyaniline was dip-coated onto printed circuit boards and in turn acted as a thin conducting electrode for the electrolytic metallization of Cu on the through holes. This eliminates the necessity for expensive precious metal seeds and toxic electroless copper baths. This process offers simplification, cost reduction, and performance enhancement over current methods used in the industry. Spontaneous deposition of noble metals, e.g. Pd, Ag, occurred on polyaniline coated epoxy substrate by simply immersing the substrate in an aqueous solution containing the corresponding metal salt, e.g., CH3-C6H4-SO3Ag, PdCl2. The thin metallic layer so plated was then used as an electrode for subsequent electroplating of Cu.

Direct electroplating of through holes

Abstract: Substantially nonconductive or semiconductive surfaces of through-holes can be electroplated directly, without an intervening non-electrolytic metallization, by a stepwise process which includes the application to the through-holes of a polyelectrolyte surfactant in solution in combination with the application of a conductive metal containing material.

Bump structure for reflow bonding of IC devices

Abstract: In a semiconductor device tape assembly bonding process the fingers (22) of a copper tape are reflow soldered to metal bumps (19) located on the semiconductor device (10). First, the semiconductor wafer is covered with a conductive film composed of thin layers of aluminum (14), nickel-vanadium alloy (15) and gold (16). The bumps are then created by electroplating gold through openings in a photoresist mask. The gold bumps (19) are overcoated with a contolled thickness tin layer and the tin is overcoated with a thin gold anticorrosion layer. The copper assembly tape is coated with a thin gold layer (23) and are lightly pressed against the bumps by means of a thermode. The thermode is quickly heated to a temperature well above the gold-tin eutectic melting temperature and then rapidly cooled. The tin layer on the bump will combine with the adjacent gold to form a liquid phase eutectic (24) which will form and contact both the copper finger and the gold bump. Upon cooling the eutectic melt will solder the finger to the bump. Since all of the tin is combined with the gold there is no metallic tin left in the system and the problems of tin whiskers and tin electromigration are avoided.

Effect of electrodeposition parameters on the microstructure and mechanical properties of Co-Ni alloys

Abstract: The effect of chloride bath plating conditions on the microstructure of Co-Ni deposits and related properties such as hardness, brittleness and tensile strength was studied. Bright smooth deposits with a high current efficiency (93%) were obtained at room temperature with current densities of 1.0–1.5 A dm-2 at pH 3.5. Hard greyish deposits of Co-Ni alloys with pits in the middle and some peeling at the edges were obtained when the current density was 3.0 A dm-2 at pH 3.5 and at room temperature. X-ray analysis confirmed that the deposited Co-Ni alloy was a solid solution with an h.c.p. lattice.

Holographic interferometry in predicting cathodic deposition of metals in aqueous solution

Abstract: A mathematical model relating surface and bulk behaviors of metals in aqueous solution has been developed. The model was established based on principles of Holographic interferometry for measuring microsurface deposition, i.e., mass gain, and with those of electrochemistry for measuring the bulk electronic current, i.e., electroplating current. The model can be utilized to predict the electroplating behavior on metals subjected to cathodic reaction in aqueous solution. In other words, the cathodic current density of metals can be predicted as a function of microsurface deposition.

Coins coated with nickel, copper and nickel and process for making such coins

Abstract: This invention overcomes problems such as pinholes and blisters in making plated coin blanks and similar articles. A ferrous metal blank is electroplated with a strike of nickel, following which a coating of copper is applied at an initial low current density followed by full current density to minimize bridging. The low current density may be about 1/6 to 1/4 of the full current density. Preferably an outer layer of nickel is applied, also at an initial low current density, followed by full current density. Annealing before or after application of the final layer of nickel is advisable. This invention also relates to the resulting coin blank and coins.

A Zinc‐Nickel Alloy Electrodeposition Kinetics Model from Thickness and Composition Measurements on the Rotating Disk Electrode

Abstract: Measurements of radial variations of composition and thickness of electrodeposited zinc-nickel alloys on a rotating disk electrode were made for deposits obtained at steady state from chloride electrolytes at different bath compositions, electrode rotation rates, and applied voltages. A two-dimensional transport model, which accounts for migration and complexation of the zinc by chloride, was used to calculate the radially dependent interfacial concentration and potential profiles for each set of experimental conditions

Suspension Electrodeposition of Phosphorus and Copper

Abstract: The codeposition of red phosphorus particles and copper from an electrolytic bath constitutes an attractive method for the production of phosphorized copper, which is the preferred anode material in bright acid copper electroplating. The effects of suspension concentration, current density, temperature, solution additives, and particle size on the amount of codeposition were determined. The behavior of this system is accurately modeled by the two-step adsorption mechanism proposed by Guglielmi

Continuous electroplating of conductive foams

Abstract: The present invention resides in the discovery that a strip of reticulated foam which is semi-conductive can be continuously electroplated, utilizing a cathode roll which is positioned, in a first electroplating zone, outside of the electroplating bath. An anode is immersed in the electroplating bath. The strip of reticulated foam is first introduced into the electroplating bath and travels in the direction from the anode to the cathode roll prior to contacting the cathode roll. In this way, the strip achieves a partial plate at the anode which provides a current path between the anode and the cathode roll effective for sustaining the plating reaction in said first electroplating zone.

Soft magnetic properties of Co-Fe-P and Co-Fe-Sn-P amorphous films formed by electroplating

Abstract: Co-Fe-P and Co-Fe-Sn-P amorphous soft magnetic alloys have been developed by electroplating. These alloys have zero magnetorestrictive compositions and show a high saturation magnetic induction B/sub s/ of 10-13.5 kG and high permeability of 3000-5000 at 5 MHz with 2- mu m thickness. It was found that the addition of Sn to Co-Fe-P improves the corrosion resistance without decreasing saturation magnetic induction. The magnetic domain structures of the thin-film head-shaped cores with Co-Fe-P amorphous films were also observed by the magnetooptical longitudinal Kerr-effect technique. It was observed that the corrosion resistivity of Co-Fe-Sn-P amorphous alloy is superior to that of Co-Fe-P amorphous alloy. >

Studies of the electrodeposition of palladium from baths based on [Pd(NH3)2X2] salts. I. [Pd(NH3)2Cl2] baths

Abstract: Spectroscopic techniques are used to confirm the chemistry of solutions of [Pd(NH3)2Cl2] in aqueous NH4Cl at various pH. In addition, potential sweep and step methods at rotating and stationary disc electrodes (both vitreous carbon and freshly plated palladium) are used to investigate palladium deposition from a standard electroplating bath, [Pd(NH3)2Cl2] in NH4Cl/NH3 (pH 8.9). The relative importance of oxygen reduction, hydrogen absorption and hydrogen evolution as competing cathode reactions under various conditions is defined and the advantage of strong convection for high rate plating is demonstrated.

Method for directly electroplating a dielectric substrate and plated substrate so produced.

Abstract: A method for the direct electroplating of a non-conducting substrate and plated substrates so produced are disclosed wherein the non-conducting substrate is first treated with a non-acidic aqueous salt solution containing a micro-fine colloidal distribution of a noble or precious metal and tin to form a strongly adsorbed, uniform, conducting layer of micro-fine colloidal metal cayatalyst upon at least a portion of the substrate surface. The conducting layer is then electroplated directly without the need for electroless plating, conversion coatings, or preferential plating solution additives.

Modeling of additive effects on the electroplating of a through-hole

Abstract: A mathematical model of copper plating of a through-hole is developed which relates uniformity of deposition to bulk electrolyte composition, applied potential difference, aspect ratio, through-hole diameter, and deposition kinetics. The electrochemical transport equations governing plating in a through-hole are solved assuming that the fluid within the through-hole is stagnant. Conditions for uniform plating are determined both for Butler-Volmer kinetics considering the effects of dissociation of bisulfate ions in the electrolytic solution and for kinetics limited by complexation of cupric ions with an adsorbed neutral additive species.

Electrodeposition of magnetic materials for thin-film heads

Abstract: Electrodeposition processes have been extensively used in thin-film head fabrication. Extremely fine features can be produced using photolithographic pattern definition followed by electroplating. Permalloy has been exclusively used for the pole material. Some critical aspects, such as film composition, magnetostriction, and stress level, were found to have a significant effect on head performance. Attempts were made to produce single-domain pole structures by lamination to eliminate output instability caused by nonrepeatable domain wall motions. Alternative improvements were brought about by increasing H/sub k/ and thus reducing the size of the closure domains. Electroplated CoFe and CoFe ternary alloy thin films were found to have very high saturation magnetization ( approximately 1.9 T). The CoFe ternary alloy has rotatable anisotropy. Higher permeability can be obtained by electroplating under an alternatingly switched field. >

Effect of pulsed reverse current on the structure and hardness of copper deposits obtained from acidic electrolytes containing organic additives

Abstract: The effect of pulsed reverse current on the grain size, surface topography and hardness of copper deposits from an acidic electrolyte has been studied using a cathodic pulse time of 10 ms, an anodic pulse time of 0.5 ms, an anodic/cathodic current density ratio of 3:1 and an average current density of 3 A dm −2 . Using these fixed conditions, the grain size and hardness of deposits obtained with various organic additive combinations were compared with those obtained by the use of direct current. It was found that in an additive-free electrolyte, the use of pulsed current increased the grain size of the deposits by an order of magnitude and reduced the deposit hardness. The addition of polyether molecules to the electrolyte was found to have a gain-refining effect with both direct and pulsed reverse current although the grain size obtained with pulsed reverse current was more uniform than that obtained with direct current. The addition of sulphopropyl sulphides to an electrolyte containing polyethers was found to produce grain growth with direct current, but grain refinement with pulsed reverse current, thus suggesting a different adsorption mechanism. A correlation was found between deposit hardness and grain size in all cases.

Area-selective metallization process

Abstract: Selective electrolytic deposition on either conductive or non-conductive bodies is provided by forming a layer of a metal which forms a plating-preventing compound on the surface of the body to be plated, and selectively interdiffusing a plating-enabling metal into the surface of that compound-forming metal in those locations where plating is desired and electroplating the body. The interdiffusion may be done before or after the plating-preventing compound has formed on the surface of the compound-forming layer. During the electroplating, the electroplating metal deposits only in those locations where the plating-enabling metal has interdiffused with the compound-forming metal. At the end of the process, the compound-forming metal may be removed in those locations where it is not covered by the electroplated metal to provide a plurality of separate plated conductors.