{TAIL ~ The circuit board} 1, wherein said halogen compound is {HEAD ~ at least one compound} selected from the group consisting of YF3, YOF, LaF3 and CaF2 
{ TAIL ~ The circuit board } 1 , wherein said halogen compound is { HEAD ~ at least one compound } selected from the group consisting of YF3 , YOF , LaF3 and CaF2
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH