I am designing a impedance controlled PCB and have ended up with 0.1mm trac ks over ground plane spaced 0.1mm away. My PCB vendor has asked me to groun d fill on inner layers of the PCB to balance the copper. I am going to use
0.2mm copper clearance (0.017 thick copper foil). Is this liable to have mu ch effect on my track impedance, my feeling is that it will reduce the impe dance by a small amount
PCB manufacture wants me to put ground fill on layers 3 and 4 to balance co pper and was worried about impedance change. My saturns PCB microstrip calc ulator give 0.1mm track z0 as 60R on outer layer, if I use saturns PCB copl anar waveguide over ground calculator it gives z0 as 74R for 0.5mm clearanc e ground fill 0.1mm over ground plane, however as ground fill clearance inc reases impedance goes up which to me is illogical, if ground fill is a long way away it should have the same z0 as microstrip. Will take your advice a nd not worry about impedances changes due to ground fill.
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