Silver-graphite coating meets technical requirements

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Umicore MDS (Schwäbisch Gmünd, Germany) has developed a silver-graphite dispersion electrolyte specifically designed for coating connector contacts in high power applications. One application of this development is high power charging (HPC). The electrodes covered with silver dispersion layers deposited with the electrolyte, Arguna C-100, are extremely stable, even at high temperatures, and allow maximum charging power over the life of the charging sockets.

Contact socket and contact pin for EV charging plug coated with Umicore’s Arguna C-100 silver-graphite dispersion electrolyte.
Photo credit: Umicore MDS

Silver coatings deposited with Arguna C-100, the company says, meet increased industry demands for reliability and durability for connector contacts.

Many manufacturers and suppliers were not satisfied with the longevity of previous connector contacts to transfer high charging power from the power source to the application or battery. Fine silver coatings are beneficial in terms of electrical and thermal conductivity. The tendency to cold welding in conjunction with low hardness and high coefficient of friction leads to rapid wear of silver coatings when frequently mated. In order to achieve the required mating cycles and to minimize wear, additional contact lubricants are used on the silver surfaces. Due to the accumulation of dirt and dust particles, corrosive or abrasive foreign layers can form over time, which can lead to increased temperature and reduced charging performance.

Hard silver coatings (silver alloys) have significantly higher hardness and exhibit significantly improved vibration resistance in certain applications. However, the added metals have a detrimental effect on the electrical conductivity and the coefficient of friction is generally close to the level of fine silver.

The need for durable and high performance silver coatings for such high power applications is widespread. Especially in the field of electromobility,
a shortened service life of the charging sockets can not only result in costs in terms of material, time and service expenses, but also the image suffers. If a permanently installed vehicle entrance of an electric car needs to be replaced at an early stage or if the charging performance of the charging infrastructure continuously decreases, the reliability and quality of the supplier is often called into question.

Arguna C-100 achieves its remarkable level of abrasion resistance through
graphite particles embedded in the silver layer. As a result, the industry’s desire for high reliability and durability of the contact coating and charging socket is met, according to Umicore MDS. An optimized graphite component embedded in the silver matrix and acting as a solid lubricant makes this possible. With each friction process, a new surface is created and the abraded tips of the graphite lamellae are distributed over the friction surface. The usual abrasion of the silver surface is avoided, contact resistances are kept low and thus a continuously high load performance is ensured.

“Under laboratory conditions, an end-of-life tribometer test proves the
low and stable coefficient of friction of the Arguna C-100 coating system. Even after more than 50,000 mating cycles, a layer of silver graphite can be intact and cross compatibility with other mating contact materials like thin, hard or dispersion silver coatings completes the functionality required in the field,” explains Friedrich Talgner, Technical Applications Manager. .

The purpose of Arguna C-100 is to combine and extend the positive properties of
fine hard silver. It is designed to possess the electrical conductivity capabilities of the fine silver matrix while simultaneously increasing abrasion resistance with the addition of the solid lubrication of graphite, ultimately resulting in reduced wear.

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