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JUNE 2023 I DESIGN007 MAGAZINE 53 Figure 1 shows the skin depth of copper (Cu) and the plating material of fabricated transmission lines 4 . e results demonstrate that Pd had the deepest skin depth, followed by gold (Au), silver (Ag), copper (Cu), and nickel (Ni). Ni, which is ferromagnetic, with the highest magnetic perme- ability, has a shallow skin depth, whereas a low elec- trical conductivity, Pd, has improved skin depth. At 1 GHz, the skin depth of Ni is less than 0.5 µm. M a c D e r m i n d A l p h a worked in collaboration with Rogers on the sig- nal loss testing. Figure 2 is a Rogers signal loss test vehicle drawing. It con- tains identical top and bottom halves. To test the surface finish contribution in signal loss testing, the test vehicle is cut in half. One half is coated with the finish of interest while the other half remains uncoated. Both halves are subject to signal loss testing. e difference between the two signal loss results equals the loss from the surface fin- ish. e data on the uncoated board is called Figure 1: Skin depth in Cu and other plated finishes. Figure 2: Rogers signal loss test of a vehicle consisting of identical top and bottom halves.