Analysis of tin, lead or tin-lead alloy plating solution

A method for analyzing a lead or tin-lead alloy plating solution containing a copper ion in addition to a lead ion, comprising the steps of:

• taking a sample from the solution,
• adding an oxidizing agent to said sample thereby simultaneously decomposing thiourea or its derivative and oxidizing a monovalent copper ion in the sample to a divalent copper ion,
• adjusting the pH of said sample to between pH 4 and pH 11,
• adding a color developing agent to said sample thereby causing the divalent copper ion to develop its color, and
• quantitatively determining the concentration of divalent copper ion by colorimetry
• taking a second sample from the solution,
• adding an iodine to said second sample, causing said lead and copper ions to develop their color,
• quantitatively determining the combined concentration of said lead and copper ions by colorimetry, and
• subtracting said concentration of copper ion from said combined concentration to provide a quantitative determination of lead ion.

A method for analyzing a tin-lead alloy plating solution for quantitative determination of divalent tin ion and lead ion, comprising the steps of:

• taking a first sample from the solution,
• adding an iodide as a color developing agent to said first sample thereby causing said lead ion to develop its color,
• quantitatively determining the concentration of said lead ion by colorimetry,
• taking a second sample from the solution,
• adding thiourea or its derivative to said second sample thereby causing said divalent tin ion and lead ion to develop their color,
• quantitatively determining the combined concentration of said divalent tin and lead ions by colorimetry, and
• subtracting said concentration of lead ion from said combined concentration of divalent tin and lead ions to provide the concentration of divalent tin ion.

A method for analyzing a tin-lead alloy plating solution containing copper ion for quantitative determination of divalent tin ion and lead ion, the method comprising the steps of:

• determining the copper ion concentration of the solution,
• taking a first sample from the solution,
• adding an iodide to said first sample thereby causing said lead ion and copper ion to develop their color,
• quantitatively determining the combined concentration of lead and copper ions by colorimetry,
• subtracting said concentration of copper ion from said combined concentration of lead and copper ions to provide a quantitative determination of lead ion,
• taking a second sample from the solution,
• adding thiourea or its derivative to said second sample thereby causing said divalent tin ion and lead ion to develop their color,
• quantitatively determining the combined concentration of said divalent tin and lead ions by colorimetry, and
• subtracting said concentration of lead ion from said combined concentration of divalent tin and lead ions to provide a quantitative determination of divalent tin ion.

A method for analyzing an electroless tin-lead alloy plating solution for quantitative determination of copper ion, lead ion, and divalent tin ion, comprising the steps of:

• Step 1:
• taking a first sample from the solution, adding an oxidizing agent to said first sample, thereby converting a monovalent copper ion to a divalent copper ion, and determining the concentration of copper ion by colorimetry,
• Step 2:
• taking a second sample from the solution, adding an iodide to said second sample, measuring the absorbance of said second sample to provide a combined absorbance of copper and lead ions, subtracting an absorbance attributable to copper ion as calculated from the concentration of copper ion determined in Step 1 from the combined absorbance to provide an absorbance attributable to only lead ion, and calculating the concentration of lead ion from the absorbance of lead ion, and
• Step 3:
• taking a third sample from the solution, adding thiourea or its derivative to said third sample, measuring the absorbance of said third sample to provide a combined absorbance of divalent tin and lead ions, subtracting an absorbance attributable to lead ion s calculated from the concentration of lead ion determined in Step 2 from the combined absorbance to provide an absorbance attributable to only divalent tin ion, and calculating the concentration of divalent tin ion from the absorbance of divalent tin ion.