A coupling (30) for the introduction of a bias voltage into a vacuum chamber. The coupling consists of a metallic ball bearing assembly (36), a bearing sleeve or cup (34), and an EMI shielding gasket (42) seated within the bearing sleeve or cup. The ball bearing assembly is fitted within the EMI shielding gasket, about a metallic shaft (32) which, in turn, is coupled to a source of the bias voltage. The bearing sleeve or cup is, in turn, coupled to a rotating component such as a platen, for receiving the bias voltage within the vacuum chamber.