Localized, maskless electrodeposition of lead-tin solder from a sulfonate electrolyte has been achieved by means of laser enhancement. Well defined spots and lines with good surface morphology have been deposited on copper and nickel substrates. This is possible because the laser is found to reduce the deposition overpotential on these substrates.Electrodeposited lead-tin solder alloys are used in a number of electronics applications (1, 2). Through-mask plating is typically employed to deposit the solder onto geometrically defined areas. We report here the results of a study to examine the feasibility of utilizing laser enhancement as a means of achieving maskless electrodeposition of solder alloys. The use of laser-enhancement to produce maskless, localized electrodeposition of gold (3) and copper (4) has previously been investigated. It has been shown that sufficient thermal enhancement of transport and kinetics can be achieved for these metals that localized deposition, often at very significant rates, can be obtained with no significant background plating outside of the illuminated area. Laser enhancement has also previously been applied to alloy electrodeposition, primarily for hard gold alloys. The deposit compositions are found to differ significantly from those obtained under normal, nonlaser plating conditions. The laser enhancement favors only one of the alloy components (5). In fact there are no reports of laserplated alloys containing more than a few percent of the alloying element.A methane sulfonate lead-tin plating electrolyte was employed in the present work. Preliminary studies indicated that the application of laser enhancement to electrolyte compositions typical of those used for conventional 60 Sn/40 Pb plating gave deposits that were primarily tin. For this reason we employed an electrolyte with 20 g/liter each of lead and tin (added as methane sulfonates) for the alloy deposition. This tin concentration represents half of that used in a typical 60/40 plating bath. The electrolyte also contained 81 ml/liter of methane sulfonic acid (70%). The as-supplied tin methane sulfonate concentrate contained < 1% of a proprietary anti-oxidant, identified as a dihydroxy aromatic. Two additives, 5 ml/liter of the surfactant octylphenoxypolyethoxyethanol (Triton-X-100) and 0.25 g/liter of 2-4, dimethoxybenzaldehyde (brightener) were used. These additives had been found to be effective in other studies by us on lead-tin electrodeposition from methane sulfonate electrolytes (6). In particular the Triton X-100 was necessary to prevent dendritic growth.A cw argon ion laser (wavelength 488 nm) was focused to a spot on a glass slide substrate coated with approximately 500 A Cr and 2000 A Cu or Ni. The specimen was immersed vertically in the unstirred electrolyte adjacent to the end quartz window of a glass cuvette. Initial experiments involved electrochemical polarization measurements, both with and without laser illumination. Polarization measurements were conducted on electrodes that were covered with photore...

A study was conducted to provide data on which to base a corrosiveness test for the thermal insulating materials used in residential structures. Several possible test methods were compared. The materials tested included celluloses containing several different fire-retardant additives, glass fiber, rock wool, and a urea formaldehyde foam. Because of their widely differing physical properties, testing was conducted in water leachants made from the insulations. In addition, a test was performed that simulated the condensation conditions that might occur in a residence. It was found that two leachant-based methods could be suitable for accelerated corrosiveness testing of thermal insulation. One method involved determining the corrosion rate of metal coupons immersed in leachant for 14 days at 45°C. The other test was cyclic potentiodynamic voltammetry, which can be completed in only a few hours.

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The corrosiveness of various residential thermal insulation materials was tested under simulated field conditions in a test wall structure. The test was conducted under controlled conditions typical of winter in the absence of a vapor barrier to create relatively severe moisture transport and possible condensation. The house-wall simulation was achieved by constructing a test panel containing 50 compartments into which various insulation materials were installed. The panel was located in an environmental chamber. The test samples included various cellulosic, glass fiber and rockwool insulations as well as sterile cotton as a control. Steel and copper coupons together with water-cooled copper pipes were embedded in the insulation and exposed for six months. It was found that moisture absorption by the insulation was the primary factor in causing corrosion but required that chemical activity from insulation components also be present. No corrosion occurred in the absence of insulation or in rockwool and glassfiber insulation. All cellulose insulations caused some corrosion; mostly this was minimal, but in a few cases severe pitting resulted. Such behavior of the cellulose did not correspond to previous laboratory test results in saturated insulation or leachants made from the insulation. However, laboratory testing of leachants made from some of the cellulose after the simulated wall test showed a change in pitting tendency, suggesting that time and/or exposure to moisture can change the corrosiveness. This should be further explored.