The basic property of connector can be divided into 3 categories: mechanical , electrical and environmental property.
1. Mechanical properties -- in terms of connection function, plug-in force(insertion force) and pull-out force (also known as separation force), is an important mechanical properties. Insertion force and pull-out force to requirements of the two are different. In the relevant standards, the maximum insertion force and minimum separation force are specified, which indicates that from the perspective of use, the insertion force is small (thus the structure with low insertion force LIF and zero insertion force ZIF), while if the separation force is too small, then it will affect the reliability of contact.
Another important mechanical property is the mechanical life of the connector which is actually an example of durability. It is referred to as mechanical operation from the national standard GB5095 based on a cycle of one insert and one pull-out to judge whether the connector can normally complete its connection function (such as contact resistance value) after the specified plug-in and pull-out cycle.
The plug and pull force and mechanical life of the connector are related to the structure of the contact parts (positive pressure), the plating quality to the contact parts (sliding friction coefficient) and the dimension precision of the contact parts (alignment degree).
2. The main electrical properties of connectors include contact resistance, insulation resistance and electrical resistance.
(1) contact resistance : high quality electrical connector should have a low and stable contact resistance. Connector contact resistances range from several milliohms to tens of milliohms.
(2) the insulation resistance measures the insulation performance between the contact parts and the shell, the magnitude is hundreds of MΩ to thousands of MΩ.
(3) electrical strength or voltage resistance, dielectric voltage resistance, is to characterize the connector contact between the contact parts or between the contact parts and the shell to withstand the rated test voltage ability.
(4) other electrical performance.
Electromagnetic interference leakage attenuation is used to evaluate the electromagnetic interference shielding effect of the connector. It is generally tested within the frequency range of 100MHz~10GHz.
For RF coaxial connectors, there are also characteristic impedance, insertion loss, reflection coefficient, voltage standing wave ratio (VSWR) and other electrical indicators. Due to the development of digital technology, in order to connect and transmit of high-speed digital pulse signals, a new type of connector appears, namely high-speed signal connector. Correspondingly, in terms of electrical performance, in addition to characteristic impedance, there are also some new electrical indicators, such as crosstalk, transmission delay, and time delay.(SKEW) etc.
3. The environmental performance includes temperature resistance, moisture resistance, salt spray resistance, vibration and impact resistance.
(1) Temperature -- So far the highest operating temperature of connector is 200℃ (except a few high temperature special connector), the lowest is -65℃. As the connector works, the current generates heat at the contact point, resulting in temperature rise, so it is generally believed that the operating temperature should be equal to the sum of the ambient temperature and the temperature rise at the contact
(2) Moisture -- the invasion of moisture will affect the connection insulation and rusting metal parts. The constant humidity and heat test conditions are 90%~95% (up to 98% according to the product specifications), and +40±20℃, and the test time is at least 96 hours according to the product regulations. Alternating the heat and humidity tests to specific requirements are more rigorous.
(3) Salt spray -- connector in the normal environment containing moisture. Salt, metal parts, contact parts surface treatment layer may face to electrochemical corrosion which affecting the physical and electrical properties of the connector. In order to evaluate the electrical connector's ability to withstand this environment, salt spray tests are prescribed. The connector is suspended in a temperature-controlled test chamber, ejected with compressed air with a specified concentration of sodium chloride solution, forming a salt fog atmosphere, and its exposure time is stipulated by the product specification with at least 48 hours.
(4) Vibration and impact -- resistance to vibration and impact is an important performance of electrical connectors, in special application environments such as aviation and aerospace, railway and road transport is particularly important, it is an important indicator to test the mechanical structure of electrical connectors and electrical contact reliability. The relevant test methods are clearly stipulated. The peak acceleration, duration, impulse waveform and the time of electrical continuity interruption shall be specified in the impact test.
(5) Other environmental performance according to the use of requirements, electrical connector to the other environmental performance and sealing (air leakage, liquid pressure), liquid immersion (tolerance to specific liquid), low pressure, etc.