Classification and Selection of Connectors

Definition of Connector

A connector is general term for connecting two or more circuit devices. As an electromechanical component, connectors generally work in pairs and are divided into plugs (male, header) and sockets (female,receptacle).

It completes the connection and disconnection of electrical appliances through certain mechanical actions. Its main functions are:

· Transmitting signals or electrical energy

· Connecting or disconnecting circuit

Classification ofClassification of Connectorss

There are many ways to classify connectors. Connector can be classified as contact and non-contact type by different application. For example, optical fiber connectors and electrical connectors are contact types, and proximity switches are non-contact connectors. They can be classified by electrical and optical signals too. Today we are mainly talking about contact connectors for electrical signals.

Electronic connectors and their components are important supporting interface components in the equipment, scattered in various systems and parts of the equipment. They are responsible for the transmission of signals and energy. The quality of the connection is directly related to the safe and reliable operation of the entire system.

Various circuits are interconnected by various electrical connectors, such high frequency connectors and low frequency connectors, circular connectors to rectangular connectors, high-current connectors passing hundreds of amperes and high-density connectors passing weak signals,ordinary printed board connectors and special connectors for quick separation and detachment. Almost all types of electrical connectors have been widely used in various system engineering to ensure the normal performance of the equipment.

To sum up, on one hand, facing various types of application scenarios, industrial connectors classifications are extremely complicated. Therefore, with the continuous advancement of technology, more and more connectors are used on the market, and the performances of different types of connectors are also very different. Manufacturers will use materials with different characteristics to design connectors according to the application environment to ensure the stable and reliable use of the connector in different environments .

On the other hand, the reliability of the electrical connection directly determines the performance of the equipment system. The performance of electronic connectors is an overall performance evaluation, which is different from the connector terminals whose performance can be easily evaluated from the aspects of material, design, and process.

Although there are many types of connectors today, and the selection is a little troublesome for performance evaluation, the benefits of using connectors in equipment are obvious:

1. Improve the production process, the connector simplifies the assembly process of electronic products, and also simplifies the mass production process;

2. Easy to maintain and upgrade;

3. Improve the flexibility of design. The use of connectors enables engineers to have greater flexibility when designing and integrating new products and when composing systems with components. The number of wires at the connector end and the spacing of the wires make the connection more convenient and faster. It is these small details that can effectively reduce the volume of electronic products, and at the same time reduce production costs. It can be effectively used as a data line for transmission between moving main boards or between PCBs .

There are so many connectors, how to classify them?

For any molded product, connectors are essential, they are used in commonly used USB, headphone jack, Ethernet interface, as well as un-common military custom interface. Therefore, based on a wide range of markets, connector classifications are also diverse.

1. According to the interconnection of internal and external connections of electronic equipment

A: components to packages interconnection

B: package to the circuit board interconnection

C: board-to-board interconnection;

D: component-to-component interconnection;

E: components input and output interfaces interconnection;

F: System-to-system interconnection .

2. Classification according to the type of transmission signal:

A: Power connector (transmitting power);

B: Signal connector (transmission signal);

C: High frequency connector (transmitting data).

3. Classification according to electrical requirements:

A: universal connector;

B: high power connector;

C: high voltage connector;

D: pulse connector;

E: low noise connector;

F: phase modulation connector;

G: Precision coaxial connector.

4. Classification according to working frequency:

High Frequency Connectors,

High Frequency Coaxial Connectors,

Video Connectors,

Coaxial Converters,

Impedance Converters,

Mating Size Converters,

Gender Converters,

Microstrip-Coaxial Converters,

Waveguide-Coaxial Converters,

Matching Load connectors,

Low frequency connectors,

printed board connectors,

ribbon cable connectors,

integrated circuit connectors,

mixed connectors etc.

5. Classification according to environmental conditions (the picture above is waterproof connector) :

A: Sealed connector;

B: High water pressure seal connector;

C: high vacuum sealed connector;

D: Three-proof connector;

E: Radiation resistant connector;

F: high temperature connector;

G: Cryogenic connector.

6. Classification according to shape:

Circular connectors,which are mostly used in military equipment. Their connection are mainly bayonet (fast), thread, automatic locking, push-pull, straight plug

Rectangular connectors, which are widely used and developed rapidly. Many board-level connectors are rectangular connectors. (Plugs and sockets connecting ways are straight plug and screw lock.)

7. Classification according to application direction:

A: RF connector;

B: Fiber optic connector;

C: Non-contact connector (such as proximity switch)

The above classifications are all based on external or application attributes, but when it comes to each manufacturer, their classification ways are different. Although NEDA has formulated classification standard for connector component packaging, with the advancement of technology, connector classification has become more complicated. However, in terms of communication connectors, because of the cooperation of software protocols, connectors are few and can be effectively distinguished.

A. Multi-wire cable connectors, including DB connectors, DIX connectors and DIN connectors.

B. Twisted pair connectors, including RJ45 and RJ11 connectors;

C. Coaxial cable connectors include T connectors, BNC connectors and terminal resistors.

Basic Principles of Connector Selection

Ampacity

We need to pay more attention to the current carrying capacity when we are selecting connectors for power supply signals. A derating design should be adopted, and at the same time, attention should be paid to the insulation withstand voltage between the pins.

Structure size

The external dimensions of the connector are very important because the connection space is limited between products, especially the connector on the single board cannot interfere with other components. We need to choose appropriate installation method and shape according to the space and installation location. Installation include front installation and rear installation, and the fixing methods include locking by rivets, screws, collars and fast locking of the bayonet of the connector itself. Regarding connector shape, shapes are straight, curved, T type, round, square.

Impedance matching

Some signals have impedance requirements, especially radio frequency signals have stricter requirements on impedance matching. When the impedance does not match, it will cause signal reflection, which will affect signal transmission. Generally, signal transmission has no special requirements on the impedance of the connector.

Shield

With the development of communication products, EMC is getting more and more attention. The selected connector needs to have a metal shell as well as a shielding layer. The shielding layer should be connected with the metal shell of the connector to achieve the shielding effect. Using injection molding method, the plug part is wrapped with copper skin, and the shielding layer of the cable is welded with the copper skin.

Mis-insertion Prevention

There are two aspects to prevent mis-insertion. On one hand, it is related with connector itself. When the connector rotates 180 degrees or is aligned incorrectly, it will lead to wrong signal connection. Therefore, it is necessary to choose anti-mis-insertion connectors, or by adjust the connector position to make sure there is only one way for assembling. On the other hand, in order to reduce material types, different signals share the same connector. In this case, plug A may be inserted into the socket B which will cause serious consequences. Therefore, we must choose different types of sockets for A and B interfaces separately..

Reliability

Connectors are used to connect signals, so the connection parts should be reliable (for example, surface contact is better than point contact, pinhole type is better than leaf spring type.).

Versatility

Choose connectors of common materials as much as possible, especially among products of the same series. Since connectors has strong versatility, choosing connectors of common materials can reduce costs and supply risks.

Environment

Different environments such as indoor, outdoor, high temperature, heavy humidity etc have different requirements on connectors.

Insertion Frequency

The plugging and unplugging of the connector has a certain life. After the number of plugging and unplugging reaches the limit, the performance of the connector will decrease. When some signal interfaces need to be plugged and unplugged frequently, it is necessary to pay more attention to the number of plugging and unplugging of the connector when choosing a connector.

Live situation

Choose a pin type or a female type connector according to live situation

Considering

In the process of selecting a connector, factors are often interact with each other. Therefore, we must consider comprehensively in the process of connector selection to choose the most suitable connector. The selection will influence products on different degree at different stages..