Mobile Phone
+86-150 6777 1050
Call Us
+86-577-6177 5611
E-mail
chenf@chenf.cn

Analysis on the Selection of Coating for Automobile Wire Harness Terminals

At this stage, in order to ensure the assembly and high integration of automotive electrical functions and meet the development of new smart electrical architectures, the generally selected connector interface has a high degree of integration (not only can transmit high-current and large power, but also can transmit low-voltage low-current analog signals), For di1fferent functions and different positions, choose different levels of connection structures to ensure that the service life of the connector is not lower than the service life of a normal vehicle. Within the allowable error range, the stable transmission of power and control signals must be guaranteed; Connectors Connected by terminals, the male terminal and the female terminal are made of metal conductive material. The quality of terminal connections directly affects the reliability of vehicle electrical functions.

1 Introduction
Harness terminals used for current transmission in vehicle harness connectors are usually stamped from high-quality copper alloys. One part of the terminal should be fixed on the plastic shell, and the other part should be electrically connected with the mating terminal. Although copper alloy has good mechanical properties, its electrical conductivity is not satisfactory; generally speaking, materials with good electrical conductivity have mediocre mechanical properties, such as tin, gold, silver, etc. Therefore, electroplating is very necessary to provide terminals with acceptable electrical conductivity and mechanical properties at the same time.

2 types of plating
Due to the different functions of the terminal and different use environments (high temperature, thermal cycle, humidity, shock, vibration, dust, etc.), the terminal coatings selected are also varied, usually through the maximum continuous temperature, coating thickness, cost, pairing and matching The appropriate coating of the terminal is to select terminals with different coatings to meet the stability of electrical functions.

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

3.2 Silver-plated terminals
Silver plating generally has good point contact performance and can be used continuously at 150°C. It is more expensive, and it is easy to rust in the air where sulfur and chlorine exist. It is harder than tin plating, and its resistivity is slightly higher than or equivalent to that of tin plating. Tin, the potential electromigration phenomenon is prone to lead to potential risks in the connector.auto connector DT 6

3.3 Gold-plated terminals
The gold-plated terminal has good contact performance and environmental stability, the continuous working temperature can exceed 125 ℃, and has excellent friction resistance. Hard gold is harder than tin silver and has excellent friction resistance, but the cost is higher, and not every terminal needs gold plating. When the contact force is low and the tin plating is worn, it can be replaced by gold plating. terminal.

Significance of 4-terminal plating application
It can not only reduce the corrosion on the surface of the terminal material, but also improve the insertion force state.

4.1 Reduce friction and lower insertion force
The main factors affecting the coefficient of friction between terminals include: material, surface roughness, and surface treatment. When the terminal material is fixed, the coefficient of friction between the terminals is fixed, and the relative roughness is relatively large. When the terminal surface is treated with a coating, the coating material, coating thickness and coating finish have a positive effect on the coefficient of friction.

4.2 After the terminal plating is damaged, prevent oxidation and rust
The terminals interact through an interference fit within 10 effective mating cycles. When there is contact pressure, the relative displacement between the male and female terminals will damage the plating on the surface of the terminals or scratch slightly during the movement. Marks lead to uneven or even exposed coating thickness, resulting in mechanical structure changes, scratches, sticking, wear debris, material transfer, etc. and heat generation. The more times of plugging and unplugging, the more obvious the scratches on the terminal surface. Under the effect of long-term work and external environment, the terminal is very prone to failure. Mainly due to the small relative movement of the contact surface, usually the relative movement of 10~100μm causes oxidation corrosion; violent movement may cause harmful wear between the contact surfaces, slight vibration may cause friction corrosion, thermal shock and environmental influence will accelerate the process.

5 Conclusion
Adding a plating layer to the terminal can not only reduce the corrosion of the surface of the terminal material, but also improve the state of the insertion force. But in order to maximize the function and economy, the coating mainly refers to the following conditions of use: can withstand the actual temperature conditions of the terminal; environmental protection, non-corrosive; chemical stability; ensure terminal contact; reduce friction and wear insulation; low cost. With the increasingly complex electrical environment of the vehicle and the advent of the new energy era, only by constantly exploring component manufacturing technology can the rapid iteration of new functions be satisfied.


Post time: Dec-06-2022