I am designing two boards that are supposed to operate at frequencies 2.45GHz and 5.8GHz.
In my design, I use simple microstrip lines (not coplanar) on FR4 substrate.
There are some quarter-wave transformers in my circuit and I was wondering how to optimize the surface finish.
I decided to remove the silkscreen from the top layer to cover it entirely in ENIG gold finish as the area of traces is quite small. However, the bottom ground plane is almost solid and covering it in ENIG is going to increase my prototype production costs.
Should I cover it with a solder mask (there will be probably some additional losses) or bear the costs? The manufacturer does not allow raw copper finish, only soldermask, ENIG or lead/tin.