There are many reasons for electroplating. It can enhance a component’s strength, solderability, and corrosion-resistance. Electroplating can also improve the electrical conductivity of a base material.
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Electrical conductivity measures how well a material accommodates the movement of an electric charge. Conductivity values are generally conveyed as “percent IACS” (International Annealed Copper Standard). This standard was developed back in the early 1900s by the International Electrochemical Commission. Annealed copper, the most conductive of all metals, is defined as 100% IACS at 20ºC. All other metals are assigned an IACS percentage based on how they compare to annealed copper in conductivity.
The higher the percentage IACS, the better the base material is at facilitating the transfer of electrons from one atom to another. The lower the percentage, the better suited a metal will be to serve as an electrical insulator. (The best insulators have a 0% IACS.)
Here’s a look at IACS percentages for common base materials:
- Copper 100%
- Tellurium copper 50%
- Beryllium copper 38%
- Brass 28%
- Nickel 24%
- Nickel Silver 10%
- Stainless steel 2.7%
These base materials can be finished with different metals to improve or impede their conductivity. Copper, with its 100% IACS rating, is often the surface finish of choice for increasing conductivity. Other finishes include:
- Silver 85%
- Gold 76%
- Electrolytic nickel 24%
- Electroless nickel 2.2%
Generally speaking, if a metal is highly conductive, it will also be very conducive to soldering. Conductivity will vary depending on the thickness of the metal.
The conductivity percentage shouldn’t be the only factor when choosing a suitable plating metal. Other properties should be considered as well. For example, gold plating is corrosion-resistant, heat-resistant, durable, and highly solderable. Silver offers many of the same benefits as gold, but it costs less, is highly ductile, and offers excellent thermal conductivity.
When choosing the best materials for plating, make sure to consider the intended use of a component. For example, gold plating guns will be very different than gold plating electronics components. Take into account the different stresses a component will be subjected to as well as your budget for the project.