When SAMTEC selects a connector for your application, it is important to select a companion connector with a similar plating material in the contact area. Different metals in the contact area can cause galvanic corrosion. Galvanic corrosion is an electrochemical process in which when two metals come into electrical contact in the presence of an electrolyte, one metal preferentially corrodes the other.
The figure below shows how different electroplating materials react with each other in terms of their potential. The greater the absolute value at the intersection of two electroplating materials, the greater the possibility of galvanic corrosion. If the number is highlighted in green, the material combination has a low current potential and is preferred. If the numbers are highlighted in yellow, the combination is not optimal, but is still acceptable. If it is not highlighted, the potential is high and you may not want to use this combination.
Plating options on connectors:
Most PCB-grade connectors are either gold-plated, tin-plated, or have selective gold/tin. Designers often ask us which plating finish we recommend. There are many considerations to consider (as evidenced by the variety of plating options on most basic connectors), but the best plating surface finish meets your system requirements at the lowest cost. In other words, make sure it works and meets your quality design specifications, but don’t over-engineer the plating.
Gold is usually specified for high reliability, low voltage or low current applications. Gold is used in high cycle applications because it is rugged and has excellent wear resistance (this is an example of a high cycle connector).
Tin is a lower cost alternative to gold and has excellent weldability. Unlike gold, tin is not a precious metal. The tin plating begins to oxidize the moment it is exposed to air. Therefore, the tinning contact system requires a larger normal force and a longer contact wiping area to break through this oxide film. Hopefully this video shows you what I’m trying to explain. The connectors shown are SSW series.
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