Tri-metal plating

What tri-metal is

Tri-metal is an alloy of copper, tin and zinc plated in one layer. A common composition is roughly 55% copper, 30% tin and 15% zinc. It has a bright, white, silver-like colour.

Why it is used on RF connectors

• Non-magnetic. Magnetic layers such as nickel can cause passive intermodulation (PIM), unwanted signals that interfere with mobile network equipment. Tri-metal avoids this, so it is used on connectors and parts in the RF path.
• Nickel-free. It suits parts that are handled, where nickel allergy is a concern.
• Tarnish-resistant. It keeps its appearance in storage and service better than silver.
• Hard and solderable. It stands up to handling and coupling, and can be soldered.

Centre contacts are usually silver or gold plated, with tri-metal on the outer body.

Copper underlayer

We plate tri-metal over a copper underlayer in most cases. The copper helps adhesion and levels the surface, and keeps the whole coating system non-magnetic.

What to put on your drawing or enquiry

• Base material and grade
• Tri-metal thickness in µm, and any underlayer
• Any PIM or salt spray requirement
• Areas to plate or mask
• Quantity per lot and expected yearly volume

Specifications

There is no single international standard for tri-metal. It is usually specified on the connector maker's own drawing or plating specification. Send yours with your drawing and we will confirm whether we can meet it.

Thickness measurement

Tri-metal thickness is measured on our Fischerscope XRF instrument, which does not damage the part.