Brass Substrate Research Articles

Post-fracture analyses of polyethylene—metal interfaces

We have analyzed the surfaces created by peeling deuterated polyethylene films from copper, aluminum, and brass substrates. The polymer was analyzed for metal residues by X-ray photoelectron spectroscopy (XPS), while secondary-ion mass spectroscopy (SIMS) was used to detect deuterium on the metal. Optical microscopy always indicated apparent adhesive (i.e. interfacial) failure for all polymer—metal samples, but SIMS consistently showed extensive coverage by polymer at all exposed metal surfaces. XPS of the polymer revealed traces of metal on samples peeled from copper and brass, but not from aluminum. Ellipsometry and electron microscopy confirmed the presence of a 60 ± 20 Å polymer layer on the metal surface.

Non-destructive optical inspection of evaporated fluoride glass layers

Abstract Fluoride PZG (PbF 2 , ZnF 2 , GaF 3 ) glass layers have been successfully grown on metal, glass, and semiconductor substrates by co-evaporation under vacuum conditions. When doped with a suitably chosen rare earth element, the layer becomes an active medium which can be used for making integrated optical components. In this paper, the surface quality of the layers is inspected by means of a new non-destructive optical technique: phase stepping microscopy (PSM). Interferograms from a reflection microscope are automatically interpreted using computer assisted image processing to give synthesized images of the relief of the film surface and the substrate surface buried below the film. The resolution is 1 nm in the vertical direction and 0.6 μm laterally. Results are presented of the analysis of the quality of a PZG glass layer grown on a gold-plated brass substrate. Preliminary results on ZBLAN, GaAs and InP substrates are also discussed.

Corrosion behaviour of TiN and Sn coatings deposited onto brass substrates for electrical contact interfaces

TiN films, prepared by reactive radio frequency magnetron sputtering and electroplated Sn films, are deposited onto brass substrate. They are investigated for their suitability as coatings for connectors. The contact resistances R c in static and insert mode are measured versus load F c for plane shapes in the range 0.1–10 N. Results show that TiN has a higher constriction resistance compared to uncoated brass, Sn- and Au-coated brass. Accelerated aging in a contaminated atmosphere shows that TiN surface-coated brass is partially covered by Cu 2S sulphide, while Sn-coated brass is oxidized to SnO. Also accelerated aging in a humid and “high” temperature atmosphere shows an increase in contact resistance for both coatings. In both corrosion tests, current-voltage ( I–V) plot characteristics for corroded TiN layers showed an ohmic resistance behaviour, while for uncoated brass and Sn-coated brass non-linear and breakdown effects were apparent. Finally, the tribological testing based on fretting corrosion showed that TiN coatings delayed contact resistance enhancement.

MEASUREMENT OF THE THERMAL STRESS IN SPECULARLY REFLECTING THIN FILMS USING REAL-TIME HOLOGRAPHIC INTERFEROMETRY

Abstract Thin film coatings of different materials on various substrates deposited by different techniques, have many industrial applications under widely different environmental conditions. It is well known that thin film coatings suffer from internal stresses and thermal stresses. The latter is caused by the mismatch of the coefficients of expansion of the thin film material and the substrate. Data for thermal stress of thin films is scanty and hence its measurement assumes significance. In this paper a method of measurement of thermal stress of thin films using real-time holographic interferometry is described, with particular emphasis on specularly reflecting thin films. A few thin film-substrate systems have been used for the measurements. For the copper film on brass substrate and silver on glass theoretical and experimental results are found to agree reasonably well at different temperatures. For the cases of aluminium film and magnesium fluoride film on glass there is a wide discrepancy. However it is pointed out that experimental values are closer to reality.

Fretting failure of electroplated gold contacts

Fretting tests were carried out with a sphere-on-flat geometry to investigate the failure mechanisms of electroplated gold contacts. Brass balls and plates electroplated with nickel and gold were used as contact specimens, and all fretting tests were conducted at amplitudes larger than the minimum amplitude necessary for gross slip. The friction force and the electrical contact resistance were continuously recorded during the fretting tests. Lubricated fretting tests were also conducted with mineral oil as a lubricant. Based on scanning electron microscopic and Auger electron spectroscopic observations, three stages could be distinguished. In stage I, the gold coating on both contact surfaces was pushed out along the fretting direction and nickel appeared on the ball contact surface. In stage II, cracks were initiated and propagated due to the tensile stress at the edge of the contact and the shear stress at the layer interface. Eventually wear particles were removed from the nickel-brass interface, and the brass substrate was exposed. In stage III, thin plates of oxide-covered brass were detached from the ball contact surface due to fretting wear. Accumulation of oxidized wear particles at the contact spots resulted in a sharp increase in the contact resistance. The friction coefficient was initially low but quickly reached a high steady state value in the unlubricated tests. The high friction force was responsible for the interfacial failure of the nickel-brass interface.

A study of the adhesion of thiokol-epoxy hermetics to a brass and an aluminum alloy substrate

The conditions under which hermetics can be used depend largely on the nature of the bond between the polymer and the substrate. Here we have studied the thiokol-epoxy compositions and have investigated the processes taking place at the interface between the hermetic and a brass or an aluminum alloy substrate. To establish the nature of interfacial interactions electron spin resonance (ESR) spectroscopy was utilized. The ESR spectrum of the species from the interface layer is assigned to a bivalent copper ion complex, sulfur-containing fragments being the ligands. The ESR signal intensity of the complex was maximum for the case of the brass substrate and minimum for the aluminum alloy substrate; no spectrum was detected for the glass substrate or for the bulk hermetic. The dependence of the ESR signal intensity on the free sulfur content in the hermetic was found to be opposite to the dependence of the adhesion values.

Avoiding Electrolytic and Strain‐induced Shorting Mechanisms—A Review

The paper describes two well‐known and occasionally confused mechanisms for degradation of electronic circuitry. Intended as a tutorial for individuals working in electronic packaging who have limited background in materials and little experience with these mechanisms, the paper defines and describes the two latent shorting phenomena. Major papers and conferences dealing with the phenomena are cited. Electrolytic or electrochemical shorting is an electrical field‐induced mechanism that can destroy the integrity of modern, densely packed circuits operated in the presence of moisture and ionic contaminants. Examples of copper migration to form electroplated shorts in both thick film hybrid multilayer and printed circuit multilayer boards are discussed, and common features to both systems are outlined. Related mechanisms that may occur with the simple electrochemical (metal plating) mechanisms to produce a broad array of electrical isolation breakdowns are also described. The closing of this part of the paper is a brief review of the Sarnoff‐developed RCA/GE multilayer copper materials system. By design this system solves the problems raised regarding thick film copper multilayer latent failure mechanisms. The discussion of whisker growth is limited to proper whiskers, including those that grow without the application of external stress, squeeze whiskers, and whiskers that result from classic electromigration. All of these grow from solid sources in contact with the whisker. The whisker growth direction is not electrical field related. Identification is made of Sn, Cd, Sb and Zn as the materials classically found to grow whiskers at room temperature. Avoiding the use of electroplated films of Cd, Sb and Zn in close proximity to electronic circuitry is encouraged, and the modern requirements that Sn films be used only after melting, or be alloyed with lead, and not on brass substrates are discussed. In more recent literature indium alloys have been identified as room temperature whisker growth systems. Finally, mechanical design to eliminate squeeze whisker shorting that can result from fasteners in contact with the above and other metals is briefly treated.

Zinc diffusion in tin coatings on brass

SummaryZinc diffusion from brass substrates into tin coatings adversely affects solderability. Although barrier layers are commonly used to prevent zinc diffusion occurring during long term storage, no data was previously available to predict behaviour. A detailed study of the commonly used Cu & Ni barrier layers and also an alternative Fe barrier layer beneath pure tin coatings stored in various environments is presented.

A mechanical method for applying rapidly solidified metal coatings

This paper describes a mechanical process of applying rapidly solidified (RS) metal coatings. The process comprises spraying a mixture of RS metal powder and peening particles at high velocity against the surface of substrates. By the impact of peening particles, the metal powder will be bonded to the surface and form a protective coating. Parts thus treated are expected to have not only improved corrosion resistance due to RS metal coating but increased fatigue strength by peening also. The apparatus and coating procedures are presented, and specimens of brass substrate coated with RS tin powder are shown as examples.

Friction properties of sputtered dichalcogenide layers

Only those dichalcogenides of group IV B, V B and VI B metals belonging to the P6 3/mmc and P 3 ml crystallographic groups are considered as solid lubricants. Yet sputtering, which leads to highly turbostratically disordered structures, has emerged as the ‘best’ method of preparation of self-lubricating layers. WS 2, MoS 2, MoSe 2, MoTe 2, NbS 2 and TaSe 2 have been investigated. Using similar deposition parameters, only MoS 2, MoSe 2 and NbSe 2 are consistently good lubricants. Tungsten disulphide proved incompatible with high speed steel and brass substrates. The difference in morphology, substrate compatibility and chemical stability allows for the design of self-lubricating dichalcogenide layers for individual applications

Measurement of the resistivity of thin CdS films on brass substrates

Measurement of the resistivity of thin CdS films on brass substrates

Observations on deformed electrolytically deposited Ni3P

SUMMARYElectrodeposited amorphous Ni3P was deformed in situ on a brass substrate. The films, when observed in the electron microscope, showed both light and dark bands in bright field images which were not seen in undeformed material. It is proposed that the origin of this contrast is a change of both density and structure of the material within the deformation bands.

Resistivity measurement of thin semiconductor films on metallic substrates

The resistivity of thin polycrystalline films of cadmium deposited on brass substrates has been measured by a microwave technique. The samples, of the type employed in solar-cell research, form the plane reflector of a semiconfocal Fabry-Perot millimeter-wave interferometer. The resistivity is derived by field-pertubation analysis as a simple function of the quality factors for the cavity with and without the semiconductor layer, respectively. Results are in excellent agreement with those of current-voltage measurements on samples with metallic contacts.

Barrier Layers Against Diffusion

SummaryTests have been carried out on copper and brass substrates which have been electroplated with a number of different barrier layers and then with an excess of matt tin. These samples have been heat treated to simulate accelerated storage and operation periods and observations made on the resulting intermetallic compound layers between the substrate and the tin coating. The results indicate the suitability of each barrier layer for altering the rate of growth of substrate-tin intermetallics and also the ability of the barrier to inhibit the diffusion of, specifically, zinc to the surface of the coating. On the basis of lowest barrier/coating reaction rates, iron appears by far the best choice for a barrier layer.

Mechanism of Rubber-To-Brass Adhesion : Effect of Rubber Composition on the Adhesion

Abstract A new adhesion model for the bonding of sulfur-vulcanizable rubber compounds to brass has been presented and discussed. The adhesion is explained on the basis of an autocatalytic effect of a thin film of cuprous sulfide formed on the brass surface by the combined action of sulfur and vulcanization accelerator. This film transfers sulfur atoms to rubber molecules, which results in a high rubber surface polarity. This surface bonds to brass by physical interaction. Although minute amounts of cuprous sulfide are a prerequisite, an excess of this compound is detrimental to the adhesion, as thick films are brittle and nonadherent to the brass substrate. Consequently, all parameters which affect the reactivity of a brass surface for cuprous sulfide formation, have an effect on the adhesion. These parameters are brass copper content, brass surface composition, and rubber compound formulation. The action of the various individual rubber ingredients on the reactions at the interface can be simulated by measuring the rate of sulfidation of a standard type of brass in a paraffin solution containing a simple rubber curing system. In spite of the differences between the conditions during actual rubber vulcanization and sulfidation in paraffin, the latter approach yields information which can be used to explain, on a qualitative basis and within the limits of the adhesion model, certain well-known but hitherto unexplained effects, such as the action of cobalt complexes on the adhesion. The method can also be regarded as a simple test for the effect of rubber compounding ingredients on steel cord adhesion.

Effect of Heat‐Treatments on Magnetic Properties of Electroless Nickel Alloys

Electroless deposits from various ammoniacal and acid formulations were evaluated for their ferromagnetic properties and the effects of artificial aging on these properties. Deposits from ammoniacal solutions were ferromagnetic as deposited. Deposits from acid solutions were nonferromagnetic. After heat‐treatment, all deposits exhibited ferromagnetism through a maximum, the temperature‐time relationship being different for each deposit. This phenomenon appeared to be related to the type of ligand in the solution and to the substrate rather than the phosphorus content of the deposit. Ammoniacal deposits retained magnetism at higher levels after heating for 96 hr at 400°C than any of the acid systems with the pyrophosphate deposit values being higher than citrate deposits. Deposits on aluminum substrates exhibited higher magnetization than on brass substrates or foils separated from substrates.

Further studies using rapeseed oil mixtures as cold rolling lubricants : I. Le May, K. D. Nair and M. L. J. Hoffman, Lubrication Eng., 23 (10) (1967) 415–418; 4 figs., 1 table, 10 refs.

Only those dichalcogenides of group IV B, V B and VI B metals belonging to the P63/mmc and P3 ml crystallographic groups are considered as solid lubricants. Yet sputtering, which leads to highly turbostratically disordered structures, has emerged as the ‘best’ method of preparation of self-lubricating layers. WS2, MoS2, MoSe2, MoTe2, NbS2 and TaSe2 have been investigated. Using similar deposition parameters, only MoS2, MoSe2 and NbSe2 are consistently good lubricants. Tungsten disulphide proved incompatible with high speed steel and brass substrates. The difference in morphology, substrate compatibility and chemical stability allows for the design of self-lubricating dichalcogenide layers for individual applications

Mechanism of Intergranular Stress Corrosion Cracking in 70 Cu–30 Zn Alloy

The mechanism of intergranular stress corrosion cracking in 70 Cu–30 Zn alloy was investigated by means of electron microscopy, electron diffraction and stress corrosion cracking tests using Mattsson’s solutions (0.05 M/L CuSO4+0.5M/L (NH4)2SO4) at pH values of 2.0, 7.4 and 10.0. It was found from the stress corrosion cracking tests that, at pH 7.4 a Cu2O surface film was formed on the brass and intergranular cracks occurred easily, but at pH values of 2.0 and 10.0, the brass was unsusceptible to cracking. The observation of bulk specimens by a replica technique indicated that at pH 7.4 micro-attacks initially nucleated within grains but two hours later corrosion was remarkably promoted in grain boundaries. Although the corrosion behaviours of bulk specimens depended considerably on pH values, the mode of micro-attack nucleation in thin-foil specimens did not change with pH values, but the preferential micro-dissolution in the slip steps was predominant. At pH 7.4 micro-pits formed in the slip steps consisted of Cu2O and Cu layers which were cathodic to the brass substrate, so that the brass surface was covered with these layers. As the Cu2O and Cu layers would lock the movement of dislocations on emergent slip planes within grains the absorption of dislocations and vacancies in grain boundaries would increase. In consequence, the chemical reaction in the grain boundaries would be accelerated than that in the case of no surface film layers, and the path of cracks would be formed in the grain boundaries.

光沢スズ電気メッキの耐食性

Corrosion resistance and porosity of electroplated bright tin coating on steel substrate were evaluated by salt spray test and modified ferricyanide test, and the results were compared with those of other tin coatings.Effects of diffusion of brass substrate in the electrodeposited coating were studied by sulfur dioxide test, microsection observation, and X-ray diffraction method. The results were as follows:1. Porosity of bright tin plating was lower and its corrosion resistance was higher as compared with other tin coatings.2. At places, where steel was exposed in pores of electrodeposited tin, oxygen was expelled from the corrosive solution and electrochemical behavior might be reverse. It was considered that the dissolution of tin was very little; because it was anodic to steel which was made unattached.3. Tin salts such as SnCl2 were converted to precipitated stannous oxychloride by absorbing liquor. Stannous oxychloride was insoluble in water and inhibited exposed steel from corrosion by sealing up capillary tin pores.4. Diffusion rate of zinc from brass substrate into tin coating was very higher than that of copper. The both diffusion rates were higher as compared with other tin coatings. The reason of higher diffusion rates in electrodeposited bright tin would be due to its fine crystals and richness in grain boundary.

Effect of Diffusion from Brass Substrates into Electrodeposited Tin Coatings on Corrosion Resistance and Whisker Growth

SummaryTin coatings electrodeposited direct on brass have an initial trace zinc content which makes them liable to tarnish in atmospheres containing sulphur dioxide. When more zinc reaches the surface by diffusion from the substrate, susceptibility to corrosive agents increases. Undercoats of copper or nickel are effective long-lasting barriers to zinc diffusion but permit the slower and less damaging growth of intermetallic compounds. Increased thickness of tin coating delays the arrival of diffusing metal at the surface and also reduces the effect on solderability of corrosion of a diffused coating. Diffusion is faster in tin coatings deposited bright. Tests to assess the extent of zinc diffusion and the liability of a coating to deteriorate in long storage with corrosion risk are discussed. Susceptibility of tin coatings to whisker growth has some parallel with their tendency to interdiffuse with the substrate.