Shielding Material - Phosphor-Bronze


Xmultiple's Engineering Department

Shielding material is designed to satisfy the EMI requirements as well as the strength of the material.

Phosphor-bronze, an alloy patented by two Belgian metallurgists in the 1870s, and now is extensively used where toughness and resistance to wear are required. The amount of phosphorus in phosphor-bronze is less than 1 per cent and the effect it produces is probably due to its reducing action on the oxides of the other metals during the process of manufacture. Phosphor-bronze is of finer grain and color, and is believed to be much more durable, than ordinary bronze.

Phosphor Bronze is preferred to stainless steel for two reasons;

1. Phosphor Bronze has natural lubrication properties. Phosphor bronze has been used for many years in producing connectors and one reason is to reduce wear on the connector. Phosphor Bronze has a natural grease to it which helps provide easy of insertion of the male plug into the connectors. Stainless steel connector shells require to have another material introduced and mixed with it, otherwise they will wear much more quickly. The insertion cycles of all connectors are measured by the number of times the male connector is plugging and unplugging into the female connector. Studies have shown the Phosphor Bronze has a better number of cycles than stainless steel sheels.

2. Phosphor Bronze is an exact material related to all the EMI (Electromagnetic emissions) issues of connectors and designs of components and connectors used on printed circuit boards.

When designing high reliability connectors, it all comes down to shielding and, in turn, EMI/RFI protection. Manufacturers of networking and computer equipment place emphasis on shielding and low insertion losses due to greater demands for high speed transmission. Materials as well as filtering of the connector both play a key role in shielding to meet EMI/RFI requirements. Nickel-plating the connector shell and gold-plating the contacts are just a couple of ways in which insertion loss and resolution requirements are met. Connector manufacturers are also increasingly using plating on beryllium copper and stainless steel, since both materials feature excellent insertion loss characteristics.

Connectors designed with shielding typically satisfy any EMI requirement. Electromagnetic interference is also reduced through the connectorˇ¦s capacitance value. Connectors with capacitance values ranging to 50,000pF significantly reduce signal noise traveling through the device, thus directly and positively affecting the performance of the end unit.

Complex EMI/RFI electronic issues have driven connector manufacturers to develop higher-performance and more cost-effective EMI suppression filter solutions.


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