The invention provides an improved contact ring and an improved workpiece support, each of which is useful alone or jointly with the other in a workpiece holder for electrochemically treating microelectronic workpieces. Several embodiments of the invention provide a composite contact ring having a dielectric base carrying a conductor which delivers electric power to a microelectronic workpiece. The dielectric base may be rigid and define a plurality of rigid fingers, each of which carries a separate electrical contact of the conductor. Such a contact ring is expected to have a long service life and enhance uniformity of electrochemical treatment. Several embodiments of the invention provide a workpiece support which induces a control the flexure of a microelectronic workpiece without damaging the workpiece. This controlled flexure can ensure more uniform contact between the workpiece and a contact assembly despite variations in the workpiece and/or the contact assembly.