Silver on Nickel on Aluminum is classical for uwave parts.
But has anyone tested those Cr-containing corrosive protectant coatings, like Surtec650 ?
Bulk resistivity, permeabilty -> effective skin depth... My gut feeling is that it will be bad...
That "classic" uwave finish definitely did NOT apply for narrowband high-Q filters. Nickel was a big BIG no-no. We could even see detrimental effects (higher insertion loss) from the use of organic brighteners in the silver plate. I once evaluated many finishes applied to a standard cavity. The results are as you would expect; silver is best and things degrade rapidly with any changes. Silver is better than aluminum (bare) which is better than chromate conversion coated aluminum. Ultimately, I guess I cannot determine the meaning of your question.
Join the international conversation on a broad range of microwave and RF topics. Learn about the latest developments in our industry, post questions for your peers to answer, and weigh in with some answers if you can!