Understanding connectors

Section 1: Basic knowledge of connectors
The connector is a component that our electronic engineering technicians often come into contact with; Its function is very simple: to build a communication bridge between blocked or isolated circuits within the circuit, thereby allowing current to flow and enabling the circuit to achieve its intended function. Connectors are essential components in electronic devices, and when observed along the path of current flow, you will always find one or more connectors. The form and structure of connectors are ever-changing, and there are various forms of connectors depending on the application object, frequency, power, application environment, etc; For example, the connectors used for lighting on the court, the connectors for hard drives, and the connectors for igniting rockets are very different. But regardless of the type of connector, it is necessary to ensure smooth, continuous, and reliable current flow.

Section 2:
Why do we need to use connectors
Imagine what would happen without a connector? At this point, the circuits need to be permanently connected together using continuous conductors. For example, if an electronic device is to be connected to a power source, both ends of the connecting wire must be securely connected to the electronic device and power source through some method (such as welding); In this way, it brings a lot of inconvenience to both production and use.
Taking automotive batteries as an example; Assuming that the battery cable is firmly welded onto the battery, the automobile manufacturer increases the workload, production time, and cost of installing the battery; When the battery is damaged and needs to be replaced, the car needs to be sent to a repair station, where the old one needs to be detached and the new one needs to be soldered on, resulting in higher labor costs; Having a connector can save you a lot of trouble. Just buy a new battery from the store, disconnect the connector, remove the old battery, install the new battery, and reconnect the connector; This simple example illustrates the benefits of connectors; It makes the design and production process more convenient and flexible, reducing production and maintenance costs.

Section 3: Advantages of connectors
Improve the production process of connectors and simplify the assembly process of electronic products. It also simplifies the mass production process.
1. Easy to repair: If a certain electronic component fails, it can be quickly replaced when a connector is installed.
2. Easy to upgrade: With technological progress, when connectors are installed, they can be updated with new and more complete components to replace the old ones.
3. Improve design flexibility: The use of connectors allows engineers greater flexibility in designing and integrating new products, as well as in composing systems with components.

Section 4:
Basic requirements for connectors
1. Stable contact resistance;
2. Mechanical toughness;
3. Durability;
4. Convenient installation of connectors；
5.Good meshing and separation feel;
6.Low meshing force;
7.Guided protection;
8.Adequate connectivity performance;
9.Waterproofing;
10.Anti electromagnetic radiation;
11.Easy to assemble wiring harnesses;

The connector seat has the following functions:
Support the contact parts (pins, springs, etc.) and firmly and correctly position them;
Dust, dirt, and moisture prevention, protecting the contact parts and conductors;

■ Insulate circuits from each other
The connector installed on a printed circuit board is referred to as the head, also known as the base or wafer. The main difference between the base and the seat is that the base is always installed together with the circuit pins, while the seat is just an empty shell. There are two forms of bases: covered and uncovered. Shield refers to a protective cover made of a seat or skirt around the mating part of the connector's pins and sockets. The base also has a friction lock style, which is a partially covered base with a locking device that allows the base to bond with the seat.

Contacts:
The contact part in the connector combines the two conductors (or wires) to be connected together. After combination, the circuit is connected and the current flows through the connector. There are two main types of contact parts: terminals and pins. The specific shape of the physical object varies greatly. Below are the legends for both. The terminal (or pin) has two ends: the front end and the back end. The front end always combines with the other end to form contact. The backend always serves as a terminal, either by crimping or connecting wires (conductors) (see figure below).

The metal used in the contact part of the connector
Electroplating the contact part of the connector is to improve conductivity, corrosion and wear resistance, and enhance solderability. Metals with good mechanical properties (such as formability and elasticity) often lack excellent conductivity, corrosion and wear resistance, as well as weldability. Electroplate all or selectively these metal materials to improve performance. The following table provides a summary of the main coating metals used and their characteristics.

The main electrical properties of connectors include contact resistance, insulation resistance, and electrical strength；
Contact 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.
Insulation resistance: an indicator that measures the insulation performance between the contact parts of an electrical connector and between the contact parts and the shell, ranging in magnitude from hundreds of megaohms to thousands of megaohms；
Electrical strength, also known as voltage resistance or dielectric withstand voltage, is the ability of a connector to withstand the rated test voltage between its contacts or between the contacts and the casing.

Other electrical performance
Electromagnetic interference leakage attenuation is an evaluation of the electromagnetic interference shielding effect of a connector. Electromagnetic interference leakage attenuation is an evaluation of the electromagnetic interference shielding effect of a connector, generally tested in the frequency range of 100MHz to 10GHz.
For RF coaxial connectors, there are also electrical indicators such as characteristic impedance, insertion loss, reflection coefficient, voltage standing wave ratio (VSWR), etc. Due to the development of digital technology, a new type of connector called high-speed signal connector has emerged to connect and transmit high-speed digital pulse signals. Correspondingly, in terms of electrical performance, in addition to characteristic impedance, some new electrical indicators have also emerged, such as crosstalk, transmission delay.

Common environmental performance includes low temperature, constant humidity and heat, alternating humidity and heat, salt spray test, sulfur dioxide test, and hydrogen sulfide test
Temperature resistance: Currently, the maximum working temperature of connectors is 200 ℃ (except for a few high-temperature special connectors), and the minimum temperature is -65 ℃. Due to the heat generated by the current at the contact point during the operation of the connector, it is generally believed that the working temperature should be equal to the sum of the ambient temperature and the temperature rise at the contact point. In certain specifications, the maximum allowable temperature rise for connectors at rated operating current is clearly specified.
The invasion of moisture resistance can affect the insulation performance of the connection and corrode the metal parts. The constant humidity test conditions are relative humidity of 90%~95% (up to 98% according to product specifications), temperature of+40 ± 20 ℃, and the test time is at least 96 hours according to product specifications. The alternating humidity and heat test is more stringent.
When salt spray resistant connectors work in environments containing moisture and salt, the surface treatment layer of their metal structural components and contact parts may produce electrochemical corrosion, which affects the physical and electrical performance of the connectors. In order to evaluate the ability of electrical connectors to withstand this environment, a salt spray test is specified. It suspends the connector in a temperature controlled test chamber, sprays out a specified concentration of sodium chloride solution with compressed air to form a salt spray atmosphere, and its exposure time is specified by the product specifications, at least 48 hours.
Vibration and shock resistance are important properties of electrical connectors, especially in special application environments such as aviation and aerospace, railway and road transportation. They are important indicators for testing the robustness of the mechanical structure and electrical contact reliability of electrical connectors. There are clear provisions in the relevant test methods. The peak acceleration, duration, and waveform of the impact pulse should be specified in the impact test, as well as the time for electrical continuity interruption.
According to usage requirements, other environmental properties of electrical connectors include sealing (air leakage, liquid pressure), liquid immersion (resistance to specific liquids), low air pressure, etc.