Knowledge about connectors

Author:yswl Date:2022-11-14 Reading:

As a key component of current or signal connections, connectors are also an important part of industrial systems. From airplanes and rockets to small mobile phones and TVs, connectors appear in various forms, building bridges between circuits or other components, and taking on the role of current or signal connections. Connector, that is CONNECTOR. Also known as connectors, plugs and sockets in China. Generally refers to electrical connectors. That is, a device that connects two active devices, carrying current or a signal.

Connectors are a component that our electronic engineering technicians often touch. Its function is very simple: it sets up a bridge of communication between the blocked or isolated circuits in the circuit, so that the current flows and the circuit realizes the predetermined function. Connectors are an indispensable part of electronic equipment, and you will always find one or more connectors along the path of current flow.

The form and structure of connectors are ever-changing, and there are various forms of connectors with different application objects, frequencies, power, and application environments. For example, the connector used to light a light on a court is very different from the connector used to light a hard drive, and the connector used to light a rocket. But no matter what kind of connector, it is necessary to ensure that the current flows smoothly, continuously and reliably. In general terms, what the connector connects is not limited to current. In today's rapid development of optoelectronic technology, in the optical fiber system, the carrier of the signal is light, glass and plastic replace the wires in the ordinary circuit, but the optical signal Connectors are also used in pathways, and they serve the same purpose as circuit connectors.

The birth of the connector is bred from the manufacturing technology of fighter jets. The aircraft in the battle must be refueled and repaired on the ground, and the time spent on the ground is an important factor in the outcome of a battle. Therefore, during the Second World War, the US military authorities were determined to shorten the ground maintenance time and increase the combat time of the fighter jets.

They first united various control instruments and components, and then connected them into a complete system by connectors. When repairing, disassemble the failed unit, replace it with a new unit, and the aircraft can be launched into the air immediately. After the war, AT-T Bell Labs successfully developed the Bell Telephone System, followed by the rise of computer, communications and other industries, which made connectors derived from stand-alone technology have more development opportunities, and the market expanded rapidly.

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Classification of connectors

Due to the increasing diversification of the structure of connectors, new structures and application fields are constantly emerging, and it is difficult to adapt to trying to solve the classification and naming problems with a fixed mode.

1. According to the nature of use

External connector (for external casing), internal connector (for internal casing).

2. According to the level of the connector

(1) Interconnection of components to packages (DEVICE TO PACKING):

Refers to the connection of the IC CHIP to the pin.

(2) The interconnection of the package to the substrate (COMPONENT LEAD TO CIRCCUITRY):

Refers to the connection between the COMPONENT and the PC board.

(3) Board To Board connection:

Refers to the interconnection between PC boards and PC boards.

(4) Subsystem-to-subsystem connection (SUBASSEMBLY TO SUBASSEMBLY)

(5) Connection between subsystems to I/O (SUBASSEMBLY TO I/O PORT).

(6) System to system connection (SYSTEM TO SYSTEM).

3. According to the processing method

Crimp Type, Crimp Type (I.D.CType) are also known as Piercing Type, Solder Type, Zero Insertion Type (Z.I.F Type).

4. According to the way of use

Wire-to-board connectors, board-to-board connectors, wire-to-wire connectors, sockets, input and output connectors.

5. According to the form

PCB board connector, flat cable connector, coaxial cable connector, embedded connector, pressure shaft connector, circular connector, angle connector, printed wiring board connector.

6. According to the structure

General connector, moisture-resistant and waterproof connector, environment-resistant connector, air-tight connector, fire-resistant connector, water-resistant connector.

7. According to the working frequency

Low and high frequencies (bounded by 3MHz).

8. From its versatility and related technical standards, connectors can be divided into the following categories (categories):

① low frequency circular connector;

②Rectangular connector;

③ printed circuit connector;

④ RF connector;

⑤ Optical fiber connector.

Basic properties of connectors

Connector knowledge The basic performance of connectors can be divided into three categories: namely

Mechanical, electrical and environmental properties.

1. Mechanical behavior

As far as the connection function is concerned, the insertion force is an important mechanical property. The insertion force is divided into the insertion force and the extraction force (the extraction force is also called the separation force), and the requirements of the two are different. In the relevant standards, there are provisions for the maximum insertion force and the minimum separation force, which means that from the point of view of use, the insertion force should be small (thereby a structure with low insertion force LIF and no insertion force ZIF), and if the separation force is too small, will affect the reliability of the contact. The insertion force and mechanical life of the connector are related to the contact structure (positive pressure), the coating quality (sliding friction coefficient) of the contact part, and the dimensional accuracy (alignment) of the contact arrangement.

2. Electrical properties

The main electrical properties of connectors include contact resistance, insulation resistance and electric strength.

①Contact resistance High-quality electrical connectors should have low and stable contact resistance. The contact resistance of connectors varies from a few milliohms to tens of milliohms.

②Insulation resistance is an indicator of the insulation performance between the contacts of the electrical connector and between the contacts and the shell, and its order of magnitude ranges from hundreds of megohms to several gigaohms.

③ Dielectric strength or withstand voltage, dielectric withstand voltage, is to characterize the ability of the connector to withstand the rated test voltage between the contacts or between the contacts and the shell.

④Other electrical properties.

The electromagnetic interference leakage attenuation is to evaluate the electromagnetic interference shielding effect of the connector, which is generally tested in the frequency range of 100MHz~10GHz.

For RF coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, and voltage standing wave ratio (VSWR). Due to the development of digital technology, in order to connect and transmit high-speed digital pulse signals, a new type of connector, namely high-speed signal connector, has appeared. Correspondingly, in terms of electrical performance, in addition to characteristic impedance, some new electrical indicators have also appeared. , such as crosstalk (crosstalk), transmission delay (delay), time delay (skew) and so on.

3. Environmental performance

Common environmental properties include temperature, humidity, salt spray, vibration and shock, etc.

①Temperature resistance At present, the maximum working temperature of the connector is 200°C (except for a few high-temperature special connectors), and the minimum temperature is -65°C. Since the current generates heat at the contact point when the connector is working, resulting in a temperature rise, it is generally believed that the operating temperature should be equal to the sum of the ambient temperature and the temperature rise of the contact point. In some specifications, the maximum temperature rise allowed by the connector at the rated operating current is clearly specified.

②The intrusion of moisture resistance will affect the insulation performance of the connection h and corrode metal parts. The constant damp heat test conditions are relative humidity 90%~95% (according to product specifications, up to 98%), temperature +40±20℃, and the test time is at least 96 hours according to product regulations. The alternating damp heat test is more severe.

③When the salt spray-resistant connector works in an environment containing moisture and salt, the surface treatment layer of its metal structural parts and contact parts may cause galvanic corrosion, which affects the physical and electrical properties of the connector. To evaluate the ability of electrical connectors to withstand this environment, the salt spray test is specified. It is to hang the connector in a temperature-controlled test box, and spray the sodium chloride solution with the specified concentration with compressed air to form a salt fog atmosphere. The exposure time is specified by the product specification, at least 48 hours.

④Vibration and shock Vibration and shock resistance are important properties of electrical connectors, especially important in special application environments such as aviation and aerospace, railway and road transportation. important indicator of sexuality. There are clear provisions in the relevant test methods. The shock test shall specify the peak acceleration, duration and shock pulse shape, as well as the time of interruption of electrical continuity.

⑤Other environmental properties According to the requirements of use, other environmental properties of the electrical connector include sealing (air leakage, liquid pressure), liquid immersion (the ability to resist deterioration of specific liquids), low air pressure, etc.

The basic structure of the connector

The basic structural parts of the connector are ①contacts; ②insulators; ③shells (depending on the variety); ④accessories.

1. Contacts

It is the core part of the connector to complete the electrical connection function. Generally, a contact pair is composed of a male contact piece and a female contact piece, and the electrical connection is completed by the insertion of the female contact piece and the male contact piece.

The male contact is a rigid part, and its shape is cylindrical (round pin), square column (square pin) or flat (insert). The male contacts are generally made of brass and phosphor bronze.

The female contact is the jack, which is the key part of the contact pair. It relies on the elastic structure to elastically deform when it is inserted into the pin to generate elastic force to form close contact with the male contact to complete the connection. There are many types of jack structures, including cylindrical type (splitting, shrinking), tuning fork type, cantilever beam type (longitudinal slotting), folding type (longitudinal slotting, figure 9), box type (square jack) As well as hyperboloid wire spring jacks and so on.

2. Insulator

The insulator is also often referred to as a base or an insert. Its function is to arrange the contacts at the required position and spacing, and to ensure the insulation between the contacts and between the contacts and the housing. Good insulation resistance, withstand voltage performance and ease of processing are the basic requirements for selecting insulating materials to be processed into insulators.

3. Shell

Also known as the shell (shell), it is the outer cover of the connector, which provides mechanical protection for the built-in insulating mounting plate and pins, and provides the alignment of the plug and socket when they are mated, thereby securing the connector to the device.

4. Accessories

Accessories are divided into structural accessories and installation accessories. Structural accessories such as retaining rings, positioning keys, positioning pins, guide pins, coupling rings, cable clamps, sealing rings, gaskets, etc. Mounting accessories such as screws, nuts, screws, spring rings, etc. Most of the accessories have standard parts and general parts.

Connector characteristics

1. One of the male or female contacts is flexible. The connection of the circuit can be ensured by the interconnection of the contacts.

2. The terminal part of the contact has a wiring structure that is easy to implement wires or printed wiring boards. That is, it is used for welding, encapsulation, clamping, through-hole welding and other structures.

3. The contacts are fixed in the correct position of the insulator, and the insulator can be used to maintain the voltage insulation resistance between the contacts.

4. It has a coupling structure, which is convenient for the insertion or disengagement of the contacts, and will not change position after vibration or impact.

The future development trend of electronic connector technology

Connectors, as the key components of current or signal connections, are also an important part of industrial systems. With the rapid development of personal mobile terminals, household smart appliances, information communication industry, transportation new energy industry, aerospace technology, artificial intelligence, medical electronic equipment and other fields, more and more connectors have been put forward in function, appearance, performance and use environment. high demands.

1. Development trend of miniaturization and integration

In order to meet the requirements of portable, digital and multi-functional electronic equipment, as well as production and assembly automation, electronic connectors must be adjusted in product structure. Products are mainly developed in the direction of small size, low height, narrow distance, multi-function, long life and surface installation.

Miniaturization means that the center spacing of electronic connectors (connectors) is smaller, and high density is to achieve a large number of cores. The miniaturization of consumer electronic products requires components to integrate miniaturization, thinning and high performance, which also promotes the development of connector products in the direction of miniaturization and small pitch. The miniaturization of components has higher technical requirements. All these require a strong industrial mold base to effectively support.

2. The trend of intelligent development

Today is a world with rapid development of information, no matter what kind of information or technology it is for, people's requirements are getting higher and higher. From the rapid development of information communication data, wireless interconnection has come to each of us, from the application of smart phones, smart wear, unmanned aerial vehicles, unmanned driving, VR reality, intelligent robots and other technologies, adding IC chips and The intelligent development of electronic connectors for control circuits is an inevitable trend, because this will enable electronic connectors to more intelligently grasp the use of electronic equipment, and improve the performance of the connector itself to achieve intelligent wireless bridging.

3. High-performance development trend

High-speed transmission refers to the fact that modern computers, information technology and networking technology require the time-scale rate of signal transmission to reach the megahertz frequency band and the pulse time to reach sub-milliseconds, so high-speed transmission electronic connectors (connectors) are required.

High frequency is to adapt to the development of millimeter wave technology, and RF coaxial electronic connectors (connectors) have entered the millimeter wave working frequency band.

High current is also an important development direction for many electronic connectors (connectors). Although short, light, energy saving and low consumption are the direction of consumer electronics products, the following two aspects determine the evolution of power supply to large current in quite a few applications. We take a common computer CPU as an example to illustrate the reasons: 1. The improvement of computer performance requires the CPU operation speed to increase, the number of transistors required to increase, and the power consumption to increase. Under the condition of constant voltage, the current increases in the same proportion; second, with the advancement of semiconductor technology, the working voltage of transistors Gradual reduction is conducive to reducing power consumption, but its physical characteristics determine that the reduction ratio of power consumption is less than that of voltage. Therefore, the increase of current is also an important indicator for testing the high-performance development of electronic connectors.

Anti-signal interference and shielding, when the data transmission speed increases, the influence of capacitance and impedance becomes more and more obvious. Signals on one terminal can crosstalk to adjacent terminals and affect their signal integrity. In addition, the ground capacitance reduces the impedance of high-speed signals, which attenuates the signal. In the new connector design, each signal transmission terminal is separated from each other. Differential signal pairs work well for this purpose, as each differential signal pair has ground pins on one side to reduce crosstalk. Usually the first layer is the open pin area to separate adjacent ground terminals. The next level is the ground shield mounted between the rows. The top layer application would include a metal ground structure surrounding each signal terminal. Such metal shielding achieves a good combination of data transfer speed and signal integrity.

Reliability and environmental protection in extreme environments. In the modern high-tech industry, there are many connectors involved in extreme environmental conditions, such as ultra-high temperature, low temperature, vibration, damp heat environment, corrosive environment, the electronic connector can be used effectively and normally, which makes the connector to the raw material. There are higher requirements in terms of selection, structural design and processing technology. New high temperature resistant materials, new electroplating coating process, and alloy materials with higher elasticity make future connectors more adaptable to harsh environments.

4. Beautiful appearance and fashion pay more attention to the development trend of humanization

With the continuous development and progress of multimedia and other technologies, the connector is also adapting to the continuous changes of its main body. With the increasing development of science and technology, a good connector should not only look more and more beautiful and fashionable, the material should be more and more durable, and the operation should be more and more convenient. More importantly, the connection design of its core parts should be More and more refined and sophisticated. In this way, it will not appear that the general data connector will be loose after a long time, and the data transmission part of the connector will be completely paralyzed, which will greatly damage the customer's confidence in the purchase of the main product.

Nowadays, the speed of upgrading of electronic products and equipment is very fast, which makes the future development trend of the connector industry to miniaturization, integration, intelligence, high performance and user-friendly use are the future development trends. Only in this way can we adapt to the development of the times, Otherwise, it will be eliminated from the market sooner or later.