Characteristic of the Deposits from Alkaline Platinum-Tin Alloy Plating Bath

Platinum-tin alloy plating in a platinum plating solution in the presence of potassium hexahydroxoplatinate and potassium stannate added was studied. Up to 100g/L tin was added to the bath, which contained 10g/L of platinum and its effect on deposit efficiency and alloy composition was analyzed. Based on this, the current efficiency was determined and found to decrease from 90% to 30% with the addition of tin from 5g/L to 10g/L to 15g/L. When more tin was added, current efficiency became about 40%. The codeposition of tin was about 30wt%. Deposits containing 15 to 25wt% of tin were observed to have in excess of 600Hv Vickers hardness. X-ray diffraction imaging determined that, with tin codeposition, platinum deposits were no longer oriented to (200) and the diffraction peak range were broadened.