Miralloy® White Bronze Plating
Metal Finishers Offering White Bronze Option for Various Applications
White Bronze is a new process offered by Arlington Plating Company. White bronze alloys have a white appearance, good electrical characteristics, without some of the skin sensitivity concerns associated with nickel plating. White bronze is an alloy consisting of a combination of copper, tin and zinc. Tri-metal alloys are white in color, similar to bright nickel, silver or rhodium and are extremely resistant to tarnish and corrosion. The alloy range is centered around 55% copper, 30% tin and 15% zinc.
White bronze is an ideal substitute for nickel and silver for high frequency RF connector and other electronic applications due to the appearance and physical properties; it is highly resistant to corrosion and wear, solderable, non-magnetic, smooth, and non-porous. The bright white finish of white bronze can also be used as an undercoat with palladium, palladium-nickel, silver or gold products or as a topcoat with those metal finishes. White bronze creates a non-toxic, non-magnetic deposit that is highly resistant to corrosion and has low porosity and a low coefficient of friction.
White bronze can be deposited to thicknesses up to 3.0 µm (120 µ-in.) for white deposits and 5.0 µm (200 µ-in.) for yellow high copper-bearing deposits. Both the white and yellow deposits can be used as intermediate layers, in combination with precious metals over tri-metal deposits. However, the mirror white copper-tin-zinc layers, with their higher contents of tin, are predominantly used as final layers. This is based on their appealing bright white color and excellent tarnish/corrosion resistance. A long-standing application is the plating of zippers, snaps and buttons with a white tin-alloy as the final finish. These deposits replace the potentially allergenic nickel deposits that were previously in use.
Tri-metal coatings are easy to plate over and, in combination with activated fluxes (RMA or RA), they show good solderability and weldability. The excellent anti-tarnishing properties and good corrosion resistance of the Cu-Sn-Zn layers more than compensate for the slightly higher contact resistance versus silver.