Comparison of Coatings

1. Tin plated terminals

Tin plating generally has good environmental stability and low cost, so it is widely used, and there are many tin plating layers used in different aspects, such as dark tin, bright tin, and hot dip tin. Compared with other coatings, the wear resistance is poor, less than 10 mating cycles, and the contact performance will decrease with time and temperature, and it is generally used in ambient conditions below 125 °C. When designing tin-plated terminals, high contact force and small displacement should be considered to ensure the stability of the contact.

2. Silver Plated Terminals

Silver plating generally has good point contact performance, can be used continuously at 150 ° C, the cost is more expensive, it is easy to rust in the air in the presence of sulfur and chlorine, it is harder than tin plating, and its resistivity is slightly higher than or equivalent to tin , the potential electromigration phenomenon easily leads to potential risks in the connector.

3. Gold-plated terminals

Gold-plated terminals have good contact performance and environmental stability, the continuous temperature can exceed 125 ℃, and has excellent friction resistance. Hard gold is harder than tin and silver, and has excellent friction resistance, but its cost is higher, and not every terminal needs gold plating. When the contact force is low and the tin plating layer is worn, gold plating can be used instead. Terminal.

4. Coating Comparison table analysis

✸Significance of Terminal Plating Application

1. Reduced friction, lower insertion force

The main factors that affect the coefficient of friction between terminals include: material, surface roughness, and surface treatment. When the terminal material is fixed, the friction coefficient between the terminals is fixed, and the relative roughness is relatively large. When the surface of the terminal is treated with a coating, the coating material, coating thickness, and coating finish have a positive impact on the friction coefficient.

2. Prevent oxidation and rust after terminal plating is damaged

Within 10 effective times of plugging and unplugging, the terminals interact with each other through interference fit. When there is contact pressure, the relative displacement between the male and female terminals will damage the plating on the terminal surface or slightly scratch it during the movement. Traces lead to uneven thickness or even exposure of the coating, resulting in changes in mechanical structure, scratches, sticking, wear debris, material transfer, etc., as well as heat generation. The more times of plugging and unplugging, the more obvious the scratch marks on the surface of the terminal. Under the action of long-term work and the external environment, the terminal is very easy to fail. It is mainly due to the oxidative corrosion caused by the small relative movement of the contact surface, usually 10~100μm relative movement; violent movement may cause harmful wear between the contact surfaces, slight vibration may cause frictional corrosion, thermal shock and environmental influences accelerate the process.

Adding a plating layer to the terminal can not only reduce the corrosion on the surface of the terminal material, but also improve the state of insertion force. However, in order to maximize the function and economy, the plating layer mainly refers to the following conditions of use: it can withstand the actual temperature conditions of the terminal; environmental protection , non-corrosive; chemically stable; guaranteed terminal contact; reduced friction and wear insulation; low cost. As the electrical environment of the whole vehicle becomes more and more complex and the new energy era is coming, only by constantly exploring the manufacturing technology of parts and components can the rapid iteration of new functions be met.