Korea Institute of Materials Science develops high-hardness, low-friction Ag-PTFE composite plating

Kim Se-il (left), a senior researcher at the Korea Institute of Materials Science, and Lee Su-jin, a student researcher, who conducted the study. [Korea Institute of Materials Science]
Kim Se-il (left), a senior researcher at the Korea Institute of Materials Science, and Lee Su-jin, a student researcher, who conducted the study. [Korea Institute of Materials Science]

South Korean researchers have developed a technology that makes silver plating on electrical components harder and more resistant to friction and wear.

The Korea Institute of Materials Science (KIMS) announced that a research team led by Kim Se-il of its Energy and Environmental Materials Research Division developed an Ag-PTFE composite plating technology that is harder and more wear-resistant than conventional silver plating. The team achieved this by stably dispersing PTFE nanoparticles in a cyanide-free acidic silver plating solution, simultaneously securing hardness and low-friction, wear-resistant performance that had previously been difficult to achieve together.

Electric vehicle connectors, automotive relays and electronic switches all contain metal contact points that carry electrical current, and silver plating is widely used because of silver's high conductivity. Silver is a relatively soft metal, however, meaning that repeated connector insertions and removals, or the continuous operation of relays and switches, can easily scratch and wear down the surface. Damage to the silver plating layer destabilizes electrical contact, creating demand for technology that improves durability.

Researchers had previously explored embedding low-friction PTFE (polytetrafluoroethylene) particles — commonly known as Teflon — into silver plating layers to help components move smoothly. The approach came with drawbacks: PTFE particles tend to clump in plating solutions, adding more weakens the plating layer while adding too little provides insufficient friction reduction. Achieving high hardness and low-friction properties at the same time had therefore been considered a major technical challenge.

The research team precisely controlled the dispersion of PTFE nanoparticles — which tend to clump in plating solutions — to simultaneously improve the hardness and low-friction, wear-resistant performance of the silver plating layer. In the cyanide-free acidic silver plating solution, the team applied fluorosurfactant FC-4 and adjusted the solution's acidity, surfactant concentration and PTFE content so that the particles would not stick together and would instead distribute uniformly throughout the plating layer.

A conceptual diagram showing PTFE dispersion control using a surfactant and the formation of an Ag-PTFE composite plating layer. [Korea Institute of Materials Science]
A conceptual diagram showing PTFE dispersion control using a surfactant and the formation of an Ag-PTFE composite plating layer. [Korea Institute of Materials Science]

Uniformly dispersed PTFE acts as a solid lubricant within the silver plating layer, reducing friction, while silver crystals form smaller and more densely packed, making the layer harder. The resulting Ag-PTFE composite plating layer showed approximately 23 percent greater hardness than pure silver plating, a low friction coefficient of 0.2 or below, and superior wear resistance.

The technology can be applied to components whose metal surfaces repeatedly come into contact and move against each other — including electric vehicle connectors, relay contacts, switches, lead frames and electronic component terminals. It is expected to extend component service life, reduce replacement and maintenance costs, and improve the long-term reliability of electric vehicles and electronic products.

"We will be able to realize a high-performance silver plating layer that reduces the burden of using cyanide while withstanding repeated contact environments for longer," Kim said. "Going forward, we plan to verify performance on actual components such as electric vehicle connectors and electronic component contacts, then expand to large-area and mass production processes to increase the technology's potential for industrial application."

The findings were published in Surface and Coatings Technology, an international journal in the field of materials engineering.


nbgkoo@heraldcorp.com