Surface treatments for cavity filters—such as silver plating—primarily enhance electrical performance, reduce losses, and improve environmental durability. Their functions can be summarized as follows:

First, silver plating significantly reduces conductive loss on the inner walls of the cavity. Silver has one of the highest electrical conductivities among common metals. After the cavity walls are plated with silver, the surface current experiences lower resistance during electromagnetic energy transmission, thereby reducing insertion loss and increasing the filter’s Q-factor and overall frequency performance.

Second, silver plating helps improve the frequency stability of the cavity filter. With reduced surface roughness, the electromagnetic field distribution becomes more uniform, minimizing frequency drift caused by surface irregularities. This leads to more stable performance in high-frequency and microwave applications.

Finally, silver plating enhances oxidation and corrosion resistance. Bare copper or aluminum surfaces oxidize easily, degrading conductivity and long-term reliability. A silver-plated surface provides protection, ensuring that the filter remains stable and reliable under varying humidity, temperature, and long-term operating conditions.

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