James R. White

Electro‐Oxidation of Formaldehyde on Thermally Prepared RuO2 and Other Noble Metal Oxides

The electro-oxidation of formaldehyde has been investigated at thermally prepared noble metal oxides, especially RuO{sub 2}, in aqueous solution. Studies were carried out on thin layers of oxide supported on Ta or Ti, and on thin, Teflon-bonded oxide layers attached to a glassy carbon rotating disk-electrode. The catalytic activity of RuO{sub 2} for HCHO oxidation was considerably greater than that of IrO{sub 2} and Rh{sub 2}O{sub 3}. At RuO{sub 2} formaldehyde was observed to undergo oxidation to formate at potentials from ca 0.75-1.25 vs. reference hydrogen electrode (RHE), and to carbonate at higher potentials. The results suggest that HCHO (and HCOOH) oxidation is mediated by higher valent states of the oxide metals ions electrogenerated at the electrode surface. Values of 10{sup {minus} 3} cm s{sup {minus} 1} (geometric electrode area based) and 10{sup {minus} 6} cm s{sup {minus} 1}(real area based) were estimated for the heterogeneous rate constant for HCHO oxidation at RuO{sub 2}. The activity for HCHO oxidation is correlated with the catalytic activity of the oxides for the oxygen gas evolution reaction.

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.

Reverse pulse plating of copper from acid electrolyte: a rotating ring disc electrode study

Coulombic or cathode efficiencies (CE) were determined for the reverse pulse plating of copper from CuSO4/H2SO4 electrolyte for a variety of pulse conditions. The CE was seen to decrease as the magnitude of the current on the anodic pulse increased. This may be explained by an increase in Cu+ intermediates near the electrode surface and was verified by polarization data obtained from a rotating ring disc electrode (RRDE). The influence of certain additives on the CE during reverse pulse plating and on the polarization curves was also examined. When polyethylene glycol and Cl− (0.86mm) were added to the electrolyte, the CE was observed to drop significantly for a particular set of pulse parameters. The polarization curves at the RRDE suggested that the copper-electrolyte interface was blocked by an adsorbed layer over a wide potential range. The results are explained in terms of a model in which Cl− ions are concentrated near the electrode surface within the adsorbed polyethylene glycol layer and this is supported by observed rotational dependencies for the RRDE.

Conduction mechanisms in contaminant layers on printed circuit boards

AC impedance methods have been utilized to explore surface conduction mechanisms on printed circuit boards (PCBs) containing various types of solder flux contaminants. Residues from water-soluble, rosin-based, and no-clean fluxes were analyzed and evaluated for their potential impact on reliability. Impedance data for intentionally contaminated PCBs having several circuit line geometries were obtained at different relative humidities. An equivalent circuit model is presented that fits the data obtained. It is used to evaluate and distinguish among ohmic, kinetic, and diffusion effects and to predict the environmental conditions that may be detrimental for various line geometries.