Abstract
Bath analysis, comsumption of brightener, effect of temperature and impurity on bright acid stannous sulfate bath containing reaction product of aldehyde and amine, ether type nonionic surface activating agent, cresolsulfonic acid and formaldehyde were studied.
Cresolsulfonic acid and sulfuric acid in plating solution was determinated by following method:
a. Pipette a 5ml into 250ml flask.
b. Add 15ml ethyl alcohol.
c. After aging, all the precipitated tin salt was removed by filtration.
d. Add 50ml water, and boil until total volume to 50ml.
e. Titrate the tin and ethyl alchol free solution with 1.0N sodium hydroxide solution until pH4 and pH 11.5 at room temperature.
(ml N NaOH until pH 11.5)-(ml N NaOH until pH4)=37.8g/l cresolsulfonic acid
(2×ml N NaOH until pH 4)-(ml N NaOH until pH 11.5)=9.8g/l sulfuric acid
Result:
(1) Brightener was not only consumed in proportion to AH, but lost by drag-out and oxidation. It seemed better to control according to the appearance of Hull cell test.
(2) Bath temperature had to be kept at 25°C or lower; over 30°C heavy loss of Brightener and poor finish of plating took place.
(3) Impurity ions in the plating solution, Cu++, Fe++, Cl-, and NO3- of 0.001M/l and Ni++, Zn++ and NH4- of 0.5M/l had no effect on Hull cell test. Filtration with activating carbon gave good result for removing the organic impurity.
