Basic Performance of Connectors

Basic Performance of Connectors
 

The basic performance of the connector can be divided into three major categories: mechanical performance, electrical performance and environmental performance.

 

1. Mechanical performance

As far as the connection function is concerned, the insertion force is an important mechanical performance. Insertion force is divided into insertion force and withdrawal force (withdrawal force is also called separating force), whose requirements are different. The maximum insertion force and the minimum separating force are stipulated in relevant standards, which indicates that the insertion force should be small from the application (thus having the structure of low insertion force LIF and no insertion force ZIF), but if the separating force is too small, the contact reliability will be affected. The insertion force and mechanical life of the connectors are related to the coating quality (sliding friction coefficient) of the contact structure (positive pressure) and the alignment accuracy (alignability).

 

2. Electrical performance

The main electrical performance of connectors include contact resistance, insulation resistance and dielectric strength.

 

> Contact resistance: High quality electrical connectors should have low and stable contact resistance. The contact resistance of connectors ranges from a few mOhms to tens of mOhms.

 

> Insulation resistance: Insulation resistance is an index of insulation performance between contacts of electrical connectors and between contacts and shells, and its order of magnitude ranges from hundreds of megohms to thousands of megohms.

 

> Dielectric strength: Also called withstand voltage or dielectric voltage, which refers to the ability to withstand rated test voltage between connector contacts or between contacts and housing.

 

> Other electrical performance

Electromagnetic interference (EMI) leakage attenuation is used to evaluate the shielding effect of electromagnetic interference (EMI) of connectors, which is generally measured in the frequency range of 100MHz~10GHz.

 

For RF coaxial connectors, there are also electrical indexes such as characteristic impedance, insertion loss, reflection coefficient, VSWR, etc. Because of the development of digital technology, in order to connect and transmit high-speed digital pulse signal, a new type of connectors, i.e. high-speed signal connectors, have emerged. Correspondingly, in addition to the characteristic impedance, some new electrical indexes have appeared, such as crosstalk, delay skew and so on.

 

3. Environmental performance

Common environmental performance includes temperature resistance, moisture resistance, salt spray resistance, vibration and shock resistance, etc.

 

> Temperature resistance

At present, the maximum operating temperature of connectors is 200℃ (except for a few special high-temperature connectors), and the lowest temperature is-65 ℃). As the current produces heat at the point of contact, resulting in temperature rise when the connector is working. Therefore, it is generally believed that the working temperature should be equal to the sum of ambient temperature and contact temperature rise. In some specifications, the maximum allowable temperature rise for connectors at rated operating currents is classified.

 

> Moisture resistance

The invasion of moisture will affect the insulation performance of connectors and corrode the metal parts. The constant hygrothermal test conditions are as follows: relative humidity 90%~95% (according to the product specification, up to 98 ℃), temperature 40 ±20 ℃, the test time is prescribed by the product, minimum 96 hours. 

 

> Salt spray resistance

When the connector works in an environment containing moisture and salt, its metal structure and contact surface treatment layer may produce electrochemical corrosion, which will affect the physical and electrical performance of the connector. In order to evaluate the ability of electrical connectors to withstand this environment, a salt spray test was prescribed. The connector is suspended in a temperature-controlled test box and ejected with compressed air with a specified concentration of sodium chloride solution to form a salt fog atmosphere. The exposure time is prescribed by the product specification for at least 48 hours.

 

> Vibration and shock resistance 

They are the important performance of electrical connectors, especially in special application environments such as aviation and aerospace, rail, and road transport. It is an important index to test the mechanical structure of the electrical connector and the reliability of electrical contact. It is clearly stipulated in the relevant test methods. The peak acceleration, duration, impulse waveform, and the time of electrical continuity interruption should be specified in the impact test.

 

> Other environmental performance

According to the operation requirements, the other environmental performance of e