What is electroplating lead-tin alloy

Lead-tin alloy plating is widely used in industry. By changing the concentration ratio of two metal ions in the plating solution, various lead-tin alloys with different lead and tin contents can be obtained. Alloys containing 6% to 10% tin in the coating are plated on steel strips to improve corrosion resistance, solderability and adhesion to paint, and have good lubricating properties; coatings containing 15% to 25% tin are commonly used in Surface lubrication, adhesion and soldering; alloy coating containing 45% to 55% tin can be used to prevent corrosion of seawater and other media; coating containing 55% to 65% tin can improve the solderability of the surface of electronic components. Adding 1% to 3% of lead to pure tin can prevent the formation of "tin whiskers". The content of tin in the lead-tin alloy coating increases with the increase of tin content and current density in the bath.

The standard electrode potential difference between lead and tin is very small (Pb/Pb2+ is -0.126V, Sn/Sn2+ is -0.136V), and the hydrogen overpotential is high, so it can be controlled by controlling the lead and tin content ratio and current density in the bath. To achieve co-deposition in a simple strong acid plating solution, lead-tin alloy coatings of various required proportions are obtained.

1) The alloy coating with tin mass fraction of 5% to 15% has good anti-corrosion performance and lubricating performance, and is often used for anti-corrosion of steel products.

2) The alloy coating with a mass fraction of 6% to 20% of tin has excellent wear-reducing performance and is often used for electroplating on the surface of sliding bearings.

3) The alloy coating with a mass fraction of 60% to 65% of tin has excellent corrosion resistance and solderability, and is often used for electroplating of printed circuit boards.

4) The alloy coating with tin mass fraction of 75% to 90% has good solderability and is often used in the electroplating of electronic component leads.

5) If 1% to 3% lead is added to pure tin plating, it can effectively prevent the formation of tin whiskers.