Copper Coax and RF Connector Parts: Grades, Finish, Plating
September 26, 2026
RF connector hardware is a family of small turned parts where the material, the finish and the plating are decided by physics rather than by cost. This is how the pieces are usually specified, so your RFQ says the right things.
The parts and what each one needs
Centre contact or pin. Carries the signal. Needs conductivity and, if it is a spring contact, spring properties. Beryllium copper C17200 for sprung sockets, free-machining or pure copper for solid pins, plated for contact.
Inner conductor. The field runs on its surface. Surface finish is the specification. C11000 or C10100, silver plated on demanding parts.
Body and outer conductor. Feature heavy, threaded, knurled. Often brass or C14500 because the machining dominates and the field runs on the inner surface. The inner surface finish matters, the outer does not.
Insulators are not copper and not our subject, but their fit sets the dimensional tolerance on the copper parts around them.
Grade by part
| Part | Usual grade | Why |
|---|---|---|
| Sprung centre contact | C17200 beryllium copper | Spring and fatigue properties |
| Solid pin | C14500 or C11000 | Conductivity with cleaner threads on C14500 |
| Inner conductor, demanding | C10100 or C11000 | Finish potential and conductivity |
| Body, general | C36000 brass or C14500 | Feature heavy, field not through the wall |
| Body, lead restricted | C14500 | Same machining, no lead |
Published typical practice, not a rule. The standard your connector series is built to governs. Reference pages: C17200, C14500, C10100.
Finish is an electrical specification
Specify Ra on the field carrying surfaces and name them. Leave the outside as machined. A body with Ra 0.4 on every face costs money on faces that never see a field. See copper surface finish.
Plating stacks
- Field surfaces: silver over nickel, thickness stated on the field face
- Contact surfaces: gold over nickel is common, thickness per the connector standard
- Body exterior: nickel, or as the series specifies
State the stack per surface and whether dimensions apply before or after plating. Connector fits are tight and plating thickness is part of the fit. Plating thickness specification covers how to write it.
What to put in the RFQ
- Grade per part, with temper for beryllium copper and whether the shop ages it
- Ra on named field surfaces
- Plating stack per surface, thickness and measurement location
- Fit dimensions and whether they are before or after plating
- Quantity, because these are turned parts where free-machining grades and volume change the price sharply
- Whether the parts are also vacuum components, which changes the grade to C10100 and adds handling rules
The service page for this family is copper RF, waveguide and cavity parts, and the RFQ builder writes the material lines.
Frequently asked questions
Should an RF connector body be copper or brass?
Bodies are often brass or free-machining copper because they are feature heavy and the field does not run through the body wall thickness. Centre contacts and inner conductors, where the field does run, are the parts that benefit from higher conductivity copper or beryllium copper for spring action.
Why is the surface finish so tight on RF parts?
At high frequency the current runs in a thin surface layer. Roughness lengthens the effective path and increases loss. The finish on field carrying surfaces is an electrical specification, not a cosmetic one.
Is gold plating required?
Common on contact surfaces for low, stable contact resistance and corrosion resistance. Silver is used on field surfaces for its conductivity. Both go over a nickel barrier. Specify by surface, not by part.
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