A method is described for electrodepositing an alloy of Ni-Fe-W-P. The alloy has good corrosion and wear resistance and hence is a possible replacement for hard chromium. The electrodeposition solution contains nickel ions, iron ions, tungsten ions and phosphorous ions, and a reducing agent. The solution yields high iron content, bright level alloy deposits containing up to 40 percent iron. In another aspect of the invention, electrodeposition is carried out on a surface containing a geometric error. A sensor determines the surface topography of the surface. This is compared in a microprocessor to the desired topography. A corrective signal is sent to an electric current source to cause electrodeposition of a quantity of leveling agent sufficient to at least partially correct the geometric error.

An internal stress testing device for high speed electroplating is disclosed. The testing device comprises: a tank to be filled with a plating solution; a metal plate for anode disposed within the tank; a metal rod for cathode disposed within the tank and rotatably held by a motor at a position opposite to the metal plate for anode; a metal plate for cathode in the shape of a thin plate mounted on the metal rod; and a DC power supply connected to the metal plate for anode and the metal rod for cathode.

The dominant physical parameter that affects the internal stress of electroplated metals on substrates have been identified and their effects have been systematically studied. Thin electroplated metals have very high internal stresses, even though the substrate displacements are small. Increasing the electroplated metal's thickness greatly reduces the magnitude of the stress, which can be either tensile or compressive depending on the plating conditions, but it may not necessarily reduce the displacement of the substrate. Based on the research done in connection to this application, the relationship between the plating temperatures and the current density needed to obtain near-zero-stress state for electroplated nickel on silicon substrate can be deduced.

Optical mirror elements for high bandwidth free space optical communication are produced by an electroforming replication technique. Onto the precision surface of a mandrel that is a negative of the required optical surface a layer of metal is deposited forming an exact copy of the mandrel surface and is then separated to form the required optical element. During the production process the mandrel may be coated with a variety of materials that are then separated together with the electroformed optical element during the release step to form a monolithic structure that includes a reflective coating. The mandrel remains unchanged by the process and can then be re-used. The high cost of conventional polishing techniques is therefore limited to the production of the mandrel. The replication process results in the production of low cost optical elements suitable for high bandwidth free space optical data transmission.

An electrolytic plating process is provided for electrodepositing a nickel or nickel cobalt alloy which contains at least about 2% to 25% by atomic volume of phosphorous. The process solutions contains nickel and optionally cobalt sulfate, hypophosphorous acid or a salt thereof, boric acid or a salt thereof, a monodentate organic acid or a salt thereof, and a multidentate organic acid or a salt thereof. The pH of the plating bath is from about 3.0 to about 4.5. An electroplating process is also provided which includes electroplating from the bath a nickel or nickel cobalt phosphorous alloy. This process can achieve a deposit with high microyield of at least about 84 kg/mm.sup.2 (120 ksi) and a density lower than pure nickel of about 8.0 gm/cc. This process can be used to plate a deposit of essentially zero stress at plating temperatures from ambient to 70.degree. C.