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White Bronze Plating
The necessity of White Bronze plating for use on RF connectors gained popularity in the early 1990’s as cellular telephone communications and networks were taking form (History of White Bronze). White bronze is actually not bronze, but an alloy of varying amounts of copper, tin and zinc. It is commonly used in jewelry as a substitute for nickel.
White Bronze plating for RF connectors offers many advantages over Nickel or Silver plated connectors. Improved electrical and intermodulation performance, better wear characteristics in harsh conditions and low insertion loss compared to Nickel are just a few. Although Silver has been the preferred finish with outstanding electrical characteristics, it pales in comparison to white bronze mostly due to the corrosive and the tarnish effects of Silver oxide.
White Bronze is composed of Copper, Tin and Zinc. The deposited amounts of each vary in the order of about 55-60% Copper, 20-25% Tin and 15-20% Zinc. The end result is an aesthetic finish similar to stainless steel.
Advantages of White Bronze
- Low intermodulation products (more on IMD and IMP in another article)
- High corrosion resistance
- Low porosity
- Low RF losses
- Non magnetic
- Wear and scratch resistant
When exposed to harsh environments, white bronze retains its aesthetic appearance. Unlike Silver, it won’t discolor when exposed to sulphur, potassium sulphide or similar corrosive chemicals. No oxide build-up occurs in white bronze as in Nickel which can be found between its’ deposited layers. Contact resistance remains unchanged when exposed to high temperatures greater than 100°C. Also, measured results did not vary at high humidity levels.
Rapid changes in temperature can cause plating to blister or crack. White Bronze won’t succumb to either of these due to its coefficient of thermal expansion being nearly identical to brass. Brass is predominantly used in the construction of RF connectors.
Resistivity loss due to the skin depth effect is minimized by the low porosity of white bronze further reducing insertion loss at higher RF frequencies.
Substantially higher wear and scratch resistant, the hardness of white bronze is double that of silver. Again, another desired feature allowing for prolonged mateability compared to silver plated connectors.
The electrical properties of White Bronze are similar to the properties of Silver. A full discussion can be found in our article entitled “Intermodulation distortion in RF connectors”
White Bronze offers a high quality surface plating with excellent intermodulation performance when used on RF connectors in high power applications. With the many advantages over Nickel, Stainless Steel and Silver, it definitely was a good fit for our company and motivated our Engineering group to begin including it. It’s been widely used by RF and microwave communications manufacturers for 20 years now. RF will be introducing more White Bronze connectors and adapters.