An electrode assembly and method of centering an outer ring around an electrode assembly in a plasma reaction chamber used in semiconductor substrate processing. The method includes positioning the outer ring around an outer surface of a backing member of the electrode assembly, and inserting at least one centering element between the outer ring and the backing member. The centering element can be a plurality of spring-loaded centering elements received in a cavity on the outer surface of the backing member, the centering elements having a first end adapted to contact the outer ring and a second end adapted to receive a spring. The outer ring surrounds an outer surface of the backing member, such that the plurality of spring-loaded centering elements are positioned between the outer surface of the backing member and an inner surface of the outer ring.