Analysis on the influencing factors of automobile connector reliability
Date：2022-11-14 18:18:08 Views：150
Connector reliability is an important factor in electronic systems and may have a significant impact on product performance. As a removable unit, its mating connector interface can be removed, allowing independent manufacturing of parts for assembly in a central location, and making it easier to maintain and upgrade components. The reliability of connector is an important factor in electronic system, and will have a significant impact on product performance.
The reliability of most connectors is mainly related to the spot shape between contacts, positive force, matching mode, contact smoothness and material properties. The working environment is mainly related to ambient temperature, environmental pollution and load frequency.
1. Spots of different shapes will lead to differences in diffusion resistance
The resistance value of the circular spot is related to the radius. The resistance value of the rectangular spot depends on the aspect ratio of the spot. The resistance value of the circular spot depends on the radius and thickness of the outer ring. The resistance value of the square circular spot is similar to the resistance value of the circular spot. The contact resistance value is related to the thickness and side length of the ring. The transmission performance of these light spots is also good or bad. For example, for the same contact area, the contact resistance of the square circular spot on the copper metal interface is the lowest, followed by the circular spot, followed by the circular spot, and the square spot has the highest resistance.
2. Matching mode The matching mode of connector can be divided into point contact mode, line contact mode and surface contact mode.
According to Holm's theorem, the more contact spots, the smaller the contact resistance. The point contact resistance is the highest, the point contact is the most, and the contact resistance is the minimum. The middle value between the line contact spot and the contact resistance. Most of the film resistances are related to the contact pressure. When the pressure is equal, the contact pressure of point contact mode is the largest, and the film is most easily damaged. As far as the film resistance is concerned, the electric contact mode is smaller than the line contact mode, and the surface contact mode is the largest.
3. Positive pressure Because the contact surface of the connector is rough and uneven, the material will be accompanied by a certain degree of plastic deformation under the action of positive pressure, which will expand the contact area, thus reducing the contact resistance. The polluted film on the contact surface of the connector will break under the action of a certain positive force, which will greatly reduce the resistance of the film. Therefore, to a certain extent, greater contact pressure is the key to ensure the reliability of connectors.
4. Contact smoothness
The influence of contact smoothness on contact resistance is essentially the influence of contact times. If the matched plane surfaces are rough, the micro depressions and bumps on the material surfaces are easy to contact each other, resulting in more contact points, thus reducing the contact resistance. At the same time, these uneven bumps also play a role in removing the oxide film and reducing the film resistance. For finish machined contact surfaces, the number of contact spots is often low, and the contact resistance is higher than that of rough surfaces, but smooth surfaces perform better in stability.
5. Material characteristics The resistivity and hardness of materials are the key factors to determine the contact resistance
Low resistivity and soft materials are the key to ensure low contact resistance. Its chemical properties and high temperature resistance determine its reliability in complex external environment. The chemically stable metal surface is not easy to produce pollution film, and the metal with high temperature resistance can resist material softening and stress relaxation caused by high temperature.
6. Ambient working temperature Current, friction and environment are the heat sources of connector temperature rise
The hardness of metal materials will decrease under the effect of such high temperature, the actual contact area and contact times will increase, and the contact resistance will also decrease. In general, the resistivity of materials will increase to a certain extent in high temperature environment, accompanied by the increase of contact resistance. The contact area and resistivity increase and decrease under high temperature environment, and their effects cancel each other, so the impact on contact resistance can be ignored. However, the influence of temperature on film resistance cannot be ignored. High temperature can catalyze the chemical reaction on the metal surface, accelerate the formation of oxides and metal diffusion, make the oxide film thicker, and increase the contact resistance. The engine will generate a lot of heat during driving, so it needs to emit steam to ensure that the connector operates within an acceptable range.
7. Environmental pollution
The impact of environmental pollution on connectors is shown as chemical corrosion and electrochemical corrosion. Chemical corrosion mainly occurs in the polluted gas environment (for example, oxygen, sulfur dioxide, chlorine, etc.), The connector generates chemicals under the chemical action of these gases, resulting in an increase in resistance. Unlike chemical corrosion, electrochemical corrosion usually requires the participation of electrolyte solution. The two metals with different electrode potentials produce potential difference in the conductive solution, and the positive and negative ions move under the action of the electric field, causing galvanic reaction to corrode the metal. Hydrogen evolution corrosion and oxygen absorption corrosion are the most common types of electrochemical corrosion.
8. The difference between load frequency and DC current transmission is that when the connector transmits AC current, it will produce skin effect (the current will gather on the conductor surface), which limits the penetration depth of electromagnetic field and makes the contraction group grow. This effect is more obvious under large load frequency.
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