Dennis P. Anderson

Solderability assessment via sequential electrochemical reduction analysis

A recently-developed sequential electrochemical reduction analysis method permits nondestructive assessment of solderability loss associated with surface oxides on metals and can be applied to almost any part geometry, including printed wiring board through-holes and surface pads. Preliminary results indicate that metal sulphides can also be detected, at least in some cases. The type and amount of oxides detected for tin coatings are shown to correlate with solderability determined by the wetting balance method. The data indicate that formation of excessive amounts of Sn02 in the surface oxide is a primary cause of Sn solderability degradation.

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.

Reduction of metallic surface oxides via an electrochemically-generated redox species

A new method is described for removing oxides from metallic surfaces via electroless reduction by the reducing member of a redox couple that is electrochemically regenerated in a closed loop. On tin-lead coatings, which are widely used to enhance the solderability retention of electronic components and circuit boards, naturally-formed oxides are reduced to the metallic state within ten seconds by either vanadous or chromous ions in acidic sulfate solution. Wetting balance data for wire specimens show thet this reduction treatment is an effective means of restoring and ensuring solderability.