D. R. Vigliotti

Jet and Laser‐Jet Electrochemical Micromachining of Nickel and Steel

Experimental results on jet and laser-jet electrochemical micromachining of nickel and steel in neutral solutions of sodium chloride and sodium nitrate are reported

Laser‐enhanced jet plating: A method of high‐speed maskless patterning

We describe a metal deposition technique that combines free‐standing jet plating with an intense laser beam, directed collinearly along the jet. Experiments were made to deposit gold areas on nick‐plated beryllium‐copper substrates. The deposits are found to be crack‐free and dense, possessing excellent adhesion to the substrate. Deposition rates for 0.05‐cm‐diam gold spots are on the order of 10 μm/s, faster than any previously reported rate for gold plating.

High‐speed electroplating of copper using the laser‐jet technique

The laser‐jet electroplating technique has been applied to the high‐speed deposition of copper at rates up to 50 μm/s. The high plating efficiency of the Cu/Cu++ system makes the deposition rate independent of laser power (unlike that of gold). On the other hand, the morphology of the copper is greatly improved with increasing laser power. Four‐point probe measurements for laser‐jet copper depositions indicate a resistivity close to that of the published bulk value.

Structural changes in Se‐Te bilayers by laser writing

Transmission electron microscopy is used to characterize the hole‐formation process due to laser writing in evaporated and sputtered Te thin films and in a Se‐Te bilayer. Bilayers, with Se as the top layer, combine the effect of an antireflective coating with protection against oxidation and provide the advantage of alloy formation during spot writing. Solidification of the melt in the Se‐Te spot takes place as an amorphous alloy resulting in smooth‐rimmed, clean holes. In contrast, Te crystallizes from the melt, giving rise to uneven rims and debris inside the spot.

Laser chemical etching of metals in sodium nitrate solution

A focused cw argon‐ion laser has been used to etch several metals, including copper, molybdenum, nickel, niobium, and stainless steel in a 0.5M sodium nitrate neutral salt solution. Exceedingly smooth etch surfaces have been obtained for several of these metals with etch rates as high as 4 μm/s. Experiments were carried out as a function of laser intensity and laser dwell time to etch arrays of small holes, 100 μm or less in diameter on the different samples. From experiments performed in water under similar laser conditions we conclude that melt or near‐melt temperatures are required to obtain etching in the salt solution. A comparison of the power required to produce incipient etching is made with calculated temperatures obtained for similar powers using a theory which approximates the experimental conditions. These calculated temperatures are reasonably close to the melt temperatures for most cases and offer supporting evidence for our etching model.

Thermoelastic hologram for focused ultrasound

An acoustic holographic lens structure is described for generating thermoelastic waves from the energy of absorbed laser excitation. The structure uses a large area optically absorbing surface to permit the megahertz ultrasound to be focused for nondestructive evaluation applications. Experimental results for the spatial distribution of 10‐MHz ultrasonic waves obtained from the hologram are presented.

Copper microcircuit repair of opens using thermally driven exchange plating

A two‐step method for the repair of circuit board defects consisting of complete opens is described. First, a small copper bridge is grown in unacidified copper sulfate solution by passing a few milliamperes of ac current at a frequency of 2–2000 kHz through the break. Local Joule heating results in copper deposition and bridging of the open via thermally driven exchange plating. For the second step, the cross section of the repair is increased by exchange plating in acid copper, using up to ∼1 A of ac current at a frequency on the order of 60 Hz or greater.

Laser etching of metals in neutral salt solutions

We report new findings that relate to rapid maskless laser etching of steel and stainless steel in neutral solutions of sodium chloride, sodium nitrate, and potassium sulfate. Etch rates have been determined as a function of laser power, laser on‐time, and solution concentration. The morphology of laser‐etched holes obtained in these solutions was compared with holes obtained in pure water. Results indicate that some controlled melting occurs under certain laser conditions in addition to the metal dissolution process induced by the locally intense heat of the laser beam.

MASKLESS LASER PATTERNING OF INSULATING FILMS FROM SALT SOLUTIONS

Insulating thin‐film patterns have been deposited on a variety of metal surfaces using focused laser light incident on samples submerged in both electrolytic and electroless nickel solutions. Deposits occur only where the laser radiation is absorbed by the substrate. For a single scan, the patterned film can have dimensions as small as 25 nm in height, 4 μm in width. Scanning electron microscope and electrical probing measurements confirm the insulating nature of the films.

Copper exchange plating on palladium and its relation to circuit repair

We describe a series of experiments using local heating to deposit copper from solution onto a palladium pattern. We show that palladium, the more noble metal, does not dissolve during thermally induced exchange plating when sacrificial copper is appropriately placed with respect to the palladium. Rather, the palladium becomes cathodic locally without dissolution, consistent with its position in the electronegativity series. However, without sacrificial copper, no deposition occurs. These results help to explain the mechanisms for a recently described electrochemical ‘‘open’’ microcircuit repair method.