Control of Lead-Tin Fluoborate Plating Bath and Analysis of the Deposit

Each component in the lead-tin fluoborate plating bath would be quantitatively analyzed by the following procedures simply and correctly. Pb: After the excess of EDTA being added to the bath, Sn++ was oxidized with H2O2. Then, the solution was masked with triethanolamine and back titrated with Zn++ at pH=10 using BT as indicator. Sn++: After Pb was precipitated with H2SO4, titrated by iodometry. Free HBF4 and Free H3BO3: After Pb was precipitated with Na2SO4, free HBF4 was determined by alkaline titration with pH-meter to pH=3.5 as the end point. Then, pH was made to 7.0, mannite was added to it, and free H3BO3 was determined by alkaline titration to pH=8.0 as the end point. Hydroquinone: Precipitate was filtered off from the solution after the determination of HBF4 and H3BO3 and titrated with Ce+4 using ferroin as indicator after made acidic with H2SO4. Lead and tin in the deposit could be determined by the following procedures. Pb: Lead-tin plated layer was dissolved by a remover such as Enstrip TL and the excess of EDTA was added to the solution. Then, tin was masked with triethonolamine and back titrated with Zn at pH=10. Sn: The above solution wa made acidic with HCl and back titrated with Zn at pH=5 in the warm state using PV as indicator to determine Sn+Pb. Then, Sn was calculated.