What are the commonly used materials and characteristics of RF coaxial connectors?

The composition materials of RF coaxial connectors can affect their mechanical, electrical, and environmental properties. Therefore, in the initial design process of the connector, the selection of base materials will determine the overall performance of the system device. As a designer of RF coaxial connectors, one must consider various requirements such as material properties, connection requirements, and cost.

Basic materials are crucial for RF transmission as they serve as the foundation for uninterrupted circuits and prevent interference to the circuit. In this chapter, we will start from the structure of RF coaxial connectors and specifically introduce the common materials and characteristics of the components that make up the connectors.

Composition of coaxial connector components

Common metal materials

Among the various components of the RF coaxial connector, the screw sleeve, main body, center pin, solder cup, and tailpipe are all metal products. Beryllium bronze, tin phosphor bronze, brass, and stainless steel are common metal materials in RF coaxial connectors, each with its own advantages.

Beryllium bronze

(1) Beryllium bronze has good electrical and heat transfer properties, fatigue resistance, and strong corrosion resistance (except for ammonia, strong acids, and alkalis);

(2) Good heat transfer performance and elasticity prevent it from melting in high temperature environments, and other properties are also not damaged by high temperatures.

Beryllium bronze is commonly used for contact holes or sockets (where electrical contacts are made), elastic pins, and external conductors at interfaces.

Tin phosphor bronze

(1) The texture of this alloy material is relatively soft and can be subjected to stress through cold processing (pressing, bending);

(2) Due to its softness, tin phosphorus bronze has become a substitute for various other copper alloys. When the production budget does not allow or the electrical performance does not necessarily require the use of beryllium bronze, tin phosphorus bronze can be used as a substitute.

Tin phosphorus bronze can be used for larger sockets, elastic contacts, or external conductors.

Brass

(1) Brass has a soft texture and is easy to machine, known as "easy to cut brass". Compared with beryllium bronze, brass has good thermal contact and thermal conductivity;

(2) It has a certain resistance to pollution and corrosion from industry, ocean, agriculture, atmosphere, and various oils. Usually, gold, silver, ternary alloys or nickel are electroplated on its surface to improve its corrosion resistance and strength.

Brass is commonly used for connector bodies, housings, outer conductors, and pins.

Stainless steel

(1) Stainless steel is suitable for areas with high material hardness requirements in the connector industry, such as external conductors;

(2) High stability, high melting point, and excellent corrosion resistance. Stainless steel is used for some parts of the connector housing, such as the outer shell.

Stainless steel is generally used as the base material, shell material, or outer conductor material.

Aluminum alloy

(1) Aluminum is generally used in alloy form, with the most typical being the "Anticoorodal" alloy.

(2)Aluminum alloy is easy to process, has good electrical properties, heat transfer properties, and self-protection characteristics (oxidation resistance), has a light texture, and has good mechanical processing performance. Sometimes it is used as a substitute for some metals (brass, stainless steel).

Aluminum alloy can be used for protective tubes and structural components of connectors.

Comparison of Common Material Characteristics

Note: The relative values range from++(very good/low price),+(good/low price), 0 (average), - (poor) to - (very poor/high price). *The contact resistance must be as small as possible (++very low, perfect)

Insulator

Also known as a base or mounting plate. It is the main component of the entire connector, determining the external dimensions and positioning of each part of the connector. Its material is generally plastic.

• Electrical insulation between terminals;
• The geometric position of the fixed end facilitates insertion and dimensional stability;
• Provide mechanical protection and support for terminals;
• Isolate the terminals from the application environment to reduce sensitivity to corrosion

Sealing Ring

Common plastic and rubber materials

Plastic and rubber materials are another important basic material in the composition of RF coaxial connectors, in addition to metal materials. Insulators and sealing rings are made of plastic and rubber materials.

Shell

 It is the outer cover of the connector

The functions include: strengthening the structure, defining the interface of male and female connectors, positioning the connector PCB, and sharing external mechanical protection.

In terms of electrical aspects, it has functions such as EMI shielding and ESD grounding.

Contact

It is the core component of a connector that completes the electrical connection function, also known as a contact terminal. Generally, a contact pair is composed of a male contact and a female contact, and electrical connection is completed through the insertion and closing of the female and male contacts.

• Male terminals are generally made of brass material, which has good conductivity but poor elasticity; The shape of the male contact piece is mostly cylindrical (round pin), square cylindrical (square pin) or flat sheet (insert);
• Female terminals are generally made of phosphor copper material, which has poor conductivity but good elasticity. The shape of the female contact piece includes cylindrical (split groove, tapered mouth), tuning fork type, box type (square socket), etc.

Attachments

Attachments are divided into structural attachments and installation attachments.

• Structural attachments: retaining rings, locating pins, guide pins, connecting rings, cable clamps, sealing rings, gaskets, etc
• Installation accessories: screws, nuts, spring coils, washers, etc