The PCB 1 wherein {HEAD ~ the metal} having a conductivity lower than the conductivity of copper is {TAIL ~ nickel} 
is
The PCB 1 wherein { HEAD ~ the metal } having a conductivity lower than the conductivity of copper is { TAIL ~ nickel }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL