What is the basic performance of wire harness connectors?

2022-02-26
What is the basic performance of wire harness connectors?
The basic properties of connectors can be divided into three major categories: mechanical properties, electrical properties and environmental properties.  
 
1.  Mechanical properties mainly include vibration and impact resistance, locking mode, mechanical life, positioning keys, insertion force and so on.  The mechanical properties of resistance to vibration and impact is an important application in special environment such as aviation and aerospace, railway and highway transportation is particularly important, especially with the increase of aircraft or missile flight speed, vibration and impact, easy cause insulation plate joint fracture, crack, wires and contact cause fitting separation, even much more intense, especially in the resonance is disable connector.  Peak acceleration, duration and impact pulse waveform, as well as the time of electrical continuity interruption shall be specified in the impact test.  The locking mode is a safe and reliable connection mode used to prevent the separation of the connector caused by vibration, such as adding safety wire when the thread is connected.  Mechanical life is another important mechanical property.  Mechanical life is actually a durability index, in the NATIONAL standard GB5095 it is called mechanical operation.  
 
wire harness connector basic performance


It takes one insertion and one extraction as a cycle, and evaluates whether the connector can normally complete its connection function (such as contact resistance value) after the specified insertion and extraction cycle.  A positioning key is a key structure chosen to prevent the wrong insertion of the connector.  Insertion force is divided into insertion force and pull out force (pull out force is also called separation force), the requirements of the two are different.  The maximum insertion force and minimum separation force are specified in the relevant standards, which indicate that from the point of view of use, the insertion force should be small, and if the separation force is too small, it will affect the reliability of contact.  The insertion and removal force and mechanical life of the connector are related to the structure of the contact part (positive pressure), the coating quality of the contact part (sliding friction coefficient) and the size accuracy of the contact part (alignment).  
 
2.  Electrical properties mainly include contact resistance, insulation resistance, current and electrical strength.  
 
(1) Contact resistance: high quality electrical connectors should have low and stable contact resistance.  The contact resistance of the connector varies from a few milliohm to tens of milliohm.  
 
(2) Insulation resistance: measuring the insulation performance between the contacts of electrical connectors and between the contacts and the shell, its order of magnitude is hundreds of megohm to thousands of megohm.  
 
(3) The electrical strength or voltage resistance: the ability to withstand the rated test voltage between the connector contacts or contacts and the shell, depends on the gap between the circuit (that is, the contact spacing and creepage distance) and the insulation material used in the connector.  
 
④ Current: limited by the electrical connector and its terminated wire.  Other electrical properties include emi leakage attenuation, which is used to evaluate the emi shielding effect of the connector and is generally tested in the frequency range of 100MHz to 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 high-speed digital pulse signals, a new type of connector, namely high-speed signal connector, appears. Accordingly, in terms of electrical performance, in addition to characteristic impedance, there are also some new electrical indicators, such as crosstalk, transmission delay, delay, etc.  
 
3.  Environmental performance Common environmental performance includes temperature resistance, humidity resistance, and salt spray corrosion resistance.  
 
(1) Temperature resistance: the current maximum working temperature of the connector is 200℃ (except for a few high temperature special connector), the minimum temperature is -65℃.  When the connector is working, the current generates heat at the contact point, resulting in a temperature rise. Therefore, it is generally considered that the operating temperature is equal to the sum of the ambient temperature and the temperature rise of the contact point.  In some specifications, the maximum temperature rise allowed for connectors at rated operating current is specified.  
 
(2) Moisture resistance: moisture invasion will affect the insulation performance of the connector, and corrosion of metal parts.  Constant humidity and heat test conditions are relative humidity 90%~95% (according to product specifications, up to 98%), temperature +40±20℃, the test time according to product regulations, at least 96 hours.  Alternating wet - heat tests are more rigorous.  
 
(3) Salt spray corrosion resistance: when the connector works in the environment containing moisture and salt, the metal structure parts and the surface treatment layer of the contact parts may produce electrochemical corrosion, affecting the physical and electrical properties of the connector.  To evaluate the ability of electrical connectors to withstand this environment, a salt spray test is prescribed.  It is the connector hanging in the temperature controlled test box, with a specified concentration of sodium chloride solution with compressed air ejected, the formation of salt fog atmosphere, its exposure time by the product specification, at least 48 hours.  Other environmental performance: according to the requirements of use, other environmental performance of the electrical connector and sealing (air leakage, liquid pressure), liquid immersion (resistance to vice of a particular liquid), low pressure, etc.