Cameron Ogden

Tensile properties of acid copper electrodeposits

For proprietary acid copper sulphate electroplating baths representing two major categories identified previously, deposit tensile properties are presented as functions of the bath additive and chloride concentrations. The effects of species that accumulate in the bath during circuit board plating and of variations in current density and the concentrations of copper sulphate and sulphuric acid are also discussed.

Degradation in nickel-cadmium cells studied by impedance measurements

Abstract The impedance of 12 A h NiCd sealed cells was evaluated as a nondestructive, in situ means of determining cell lifetime, particularly with respect to the probability of premature failure. The NiCd cell impedance was measured (10 000 to 0.0004 Hz) as cells were subjected to charge/ discharge cycle testing under a variety of temperature and depth-of-discharge conditions. The results indicate that cell degradation is reflected in the low frequency impedance characteristics associated with diffusional processes. The slope ( W ) of the low frequency portion of complex plane impedance plots obtained from totally discharged NiCd cells was found to increase with charge/discharge cycling. In addition, based on data for two cells, a high or rapidly increasing W value signals imminent cell failure by one mechanism. Degradation by another mechanism is apparently reflected in a fall-off of the imaginary impedance component at low frequencies. The frequency dependence of the absolute cell impedance at low frequencies (0.5 - 0.005 Hz) was found to vary monotonically with cell state-of-charge.

Electrochemical Photocapacitance Spectroscopy: A New Method for Characterization of Deep Levels in Semiconductors

Electrochemical photocapacitance spectroscopy (EPS) offers advantages over similar solid-state photocapacitance spectroscopic techniques. In the EPS method, the capacitance of a reverse-biased semiconductor electrode is measured as a function of the wavelength of incident sub-bandgap light. In the present work, EPS is shown to be an extremely sensitive means for characterizing deep levels in semiconductor materials. For horizontal Bridgeman-grown n-GaAs, a hole trap, the chromium phototransition, and two electron traps were detected. The energies and densities of states for these levels correspond well with values reported in the literature for solid-state studies of similar materials. 21 refs.

Tensile properties and morphology of pyrophosphate copper deposits

New data which precisely define the effects of various operating parameters on the tensile properties of electrodeposits from the dimercaptothiadiazole/copper pyrophosphate system are presented. Two additive concentration ranges yielding high ductility and high tensile strength are delineated. Characteristic deposit microstructures are identified and correlated with the tensile properties. The results are interpreted in terms of the mechanism by which the additive functions, and implications for circuit board plating are discussed.

Evaluation of agitation within circuit board through — holes

A method is presented for determining the rate and uniformity of solution mass transport to the outer surfaces and within the through-holes of multilayer printed circuit boards. The method is based on the measurement of the diffusion-limited currents for a fast redox reaction at strategically located inert electrode probes. A specially fabricated test board and an electrolyte which hydrodynamically simulates the copper pyrophosphate system are described. Results are presented for a typical agitation scheme based on gas sparging and slow board motion. The method provides the basis for evaluating and improving bath agitation schemes and should be applicable to a variety of systems.