As the main electrical property of car connectors, the contact resistance directly affects not only the signal transmission and electrical connection of the automobile electrical equipment, but also its working stability and reliability. Improper contact resistance is the main cause of temperature rise in car connectors. The temperature rise can be controlled effectively by reducing contact resistance so as to improve the service life and reliability of car connectors.
Therefore, it is of a great significance to analyze the influencing factors and test methods of contact resistance of the automotive connector terminal to improve the reliability and service life of car connectors.
Contact resistance works as follows:
The contact resistance of car connectors refers to the additional resistance generated between the male terminal and the female terminal contact surface after a pair of male and female connectors are plugged into each other. Through the micro analysis of the terminal contact surface, it is known that after the male and female terminals are plugged into each other, the contact between them is not on the whole surface, but at some points scattered on the contact surface. For that reason, when we calculate the actual contact area, what should be included is the sum of the areas of the contact points only. The roughness of the contact surface determines the number of contact points, while the positive force of the terminal contact interface and the material hardness of the contact pieces jointly determines the contact area of each contact point. Therefore, the surface roughness, surface hardness and terminal positive force of the contact interface together determine the actual contact area.
In fact, the truly clean metal surface is non-existent in the atmosphere, and even very clear metal surface, once exposed to the atmosphere, quickly produces a few microns of incipient oxide film.
Due to the presence of oxide film on the contact surface, the actual contact area can be divided into two parts. The first is the contact area between the male terminal and the base metal of the female terminal, which is formed by the positive force between the contact surface of the male terminal and the female terminal and the thermal action during conduction destroying the oxide film between the contact surface. That part of contact accounts for about 5%~10% of the actual contact area. The second is the contact area after the contact interface oxidation film, which is formed by the isolation of the contact interface by the surface oxidation film caused by the exposure of the male terminal and the female terminal to the atmosphere.
The additional resistance of the contact interface of the automotive connector terminal consists of the following two parts:
1. The resistance shown by the contraction of the current line due to the shape of the concentrated resistance or contraction resistance contact interface.
2. Film resistance or interfacial resistance encounters the resistance of the solid oxide film and the looser impurity contaminant at the interface.
