Yes. Absolutely. At that frequency the signal skin effect is very pronounced, and having a nickel finish can prove to be very lossy. You may wish to investigate immersion silver finish instead.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Kelly
Sent: Thursday, March 17, 2011 8:30 AM
To: [log in to unmask]
Subject: [TN] Signal loss

Good Day To All,
We recently fabricated a surface microstrip flex circuit with 50 ohm +/- 2.5 ohms (results were good). The impedance traces were not covered with solder mask or coverlay but were plated with ENIG. The next part is where I need the help. The circuit runs at 20-26 Ghz. Customer says the return losses from the S-parameters measurements are good but the insertion losses are not (quite frankly I have no idea what this means) . Could the nickel plating be causing this issue?
Thanks.
Steve Kelly

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