The invention is directed to an electroplating apparatus for selectively depositing tin/lead solder bumps at a high deposition rate. The apparatus comprises a reactor bowl (35) containing an electroplating solution having free ions of tin and lead for plating onto a workpiece (25). A chemical delivery system is used to deliver the electroplating solution to the reactor bowl at a high flow rate. A workpiece support includes a contact assembly (85) for providing electroplating power to a surface at a side of the workpiece that is to be plated. The assembly contacts the workpiece at a large plurality of discrete flexure contacts (90) that are isolated from exposure to the electroplating solution. An anode (55) is spaced from the workpiece support within the reactor assembly (20) and is in contact with the electroplating solution. The electroplating solution comprises a concentration of a lead compound, a concentration of a tin compound, water and methane sulfonic acid.