Analysis of contact resistance of automobile connector terminals-1
Blog | Sep 15,2022
Contact resistance is the main electrical performance of automobile connectors, which directly affects the signal transmission and electrical connection of automobile electrical equipment, and affects the stability and reliability of electrical equipment.
Improper contact resistance is the main reason for the temperature rise of automobile connectors. Reducing the contact resistance can effectively control the temperature rise, thus improving the service life and reliability of the connector. Therefore, it is of great significance to analyze the influencing factors and test methods of connector terminal contact resistance to improve the reliability and service life of the connector.
How to contact resistors work?
Contact resistance of a connector refers to the additional resistance between the contact surface of the male terminal and the female terminal after a pair of male and female connectors are inserted. Through the microscopic analysis of the terminal contact surface, the male terminal and the female terminal are inserted, the contact of the terminal is not the contact of the entire contact surface, but the contact of some points scattered on the contact surface.
The sum of the areas of each contact point is the actual contact area. The surface roughness of the contact surface determines the number of contact points, and the forward force of the terminal contact interface and the material hardness of the contact parts jointly determine the contact area of each contact point, therefore, the surface roughness of the contact interface, surface hardness and the terminal forward force determines the size of the actual contact area.
In fact, there is no truly clean metal surface in the atmosphere, and even a very clean metal surface, once exposed to the atmosphere, will quickly generate a few microns of initial oxide film. Because of the contact surface oxidation film, the actual contact area can be divided into two parts.
One is male, terminal and female terminal substrate metal contact area. It is by the male terminal and mother terminal interface between the positive forces and conduction of heat, destroy the contact surface between the oxide film formed, after the partial contact accounted for about 5% ~ 10% of the actual contact area;
The other is the contact area after the contact interface oxide film, which is formed by the isolation of the surface oxide film on the contact interface formed by the male terminal and the female terminal exposed in the atmosphere.
- The shape of the contact interface of the concentration or contraction resistance causes the current line to shrink as shown by the resistance
- Film resistance or interfacial resistance A resistance that contacts a solid oxide film and loose impurities and contaminants at the interface
The influencing factors of contact resistance
Influence of terminal material
Different terminal materials have different hardness and different electrical conductivity. According to the analysis of the action principle of contact resistance, different hardness causes the actual contact area of each contact point of the terminal contact interface is different, resulting in the actual total contact area of the terminal contact interface is different.
The effect of the actual contact area on the additional resistance of the contact interface is equivalent to the effect of the conductor cross-sectional area on the conductor resistance. Therefore, the hardness of the terminal material will affect the additional resistance of the terminal contact interface. Different electrical conductivity directly affects the resistance of the terminal contact area.
When selecting terminal materials, select materials with appropriate electrical conductivity and hardness according to the design objectives. At the same time, select materials with stable electrical conductivity and mechanical properties to ensure stable contact resistance.
Influence of terminal contact interface geometry
The influence of terminal contact interface geometry on contact resistance is mainly due to the different macroscopic contact areas formed by different geometric shapes. The difference of macroscopic contact area results in different number of contact points, so that the actual contact area is different.
Common contact interface shapes. In the contact interface, the macro contact area generated is the smallest, so the actual contact area is also the smallest; For the surface contact interface, the macro contact area generated is the largest, so the actual contact area is also the largest. Line contact interface, the generated macro contact interface is in the middle state, therefore, the actual contact area is in the middle state.
In practical application, different contact interface geometries should be selected according to different requirements. The line contact and surface contact will be affected by the terminal specifications and shape, forming different macroscopic contact areas.
For more information about contact resistance, see Automotive connector terminal Contact Resistance Resolution-2
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