The function of the wire harness crimping terminal is to realize the connection between the terminal and the wire. The material, parameters, and specifications of the terminal and the wire itself will definitely affect the performance of the crimping terminal. In addition, the parameters of the die and the crimping of the terminal during the crimping process. Height also affects terminal performance.
The following characteristics are important to consider when selecting terminal materials:
There is a proportional relationship between electrical conductivity and thermal conductivity. The electrical conductivity is related to the electrical conductivity of the terminal and the size of its own resistance.
The terminal is divided into a crimping part and a connecting part. The elastic-plastic deformation of the crimping part causes stress between the terminal and the wire. If the stress relaxes, the contact between the terminal and the wire will become unstable. If the connection part of the terminal is To connect through plug deformation, stress relaxation and fatigue issues need to be considered
At present, enterprises pay great attention to the cost of raw materials, which is also a factor to consider.
Generally speaking, the commonly used materials for terminals are copper alloys such as brass, phosphor bronze, and beryllium bronze, and there are also some high-conductivity copper alloy materials such as K88.
Although the electrical conductivity of copper is higher than that of silver, the mechanical properties are slightly worse. Therefore, alloying elements with high electrical conductivity must be added to improve mechanical strength and heat resistance.
Therefore, we can conclude that the copper alloy is shiny and not easy to corrode. It has good formability and is the best choice for connector materials.
Different copper alloys have different material properties, and the material of the terminal should be selected according to the purpose and requirements of the terminal.
Electroplating on the surface of the terminal is a process method to solve the oxidation and corrosion of the metal on the surface of the terminal, enhance the conductivity of the terminal and reduce the contact resistance. The most commonly used terminal plating is tin plating, in addition to gold plating, silver, and nickel or chromium
Gold itself has high chemical stability, strong corrosion resistance, high-temperature resistance, easy welding, strong electrical conductivity, and certain wear resistance. However, because the metal is used for cathodic coating, the price is also relatively expensive.
Due to the thin gold coating and insufficient process technology, the coating has pores in actual production, which will cause microporous corrosion, which affects the protective performance. Therefore, it is often used in terminals. connection part to reduce the contact resistance of the connection
Silver itself also has high chemical stability, is not easy to corrode in the air, has good welding performance, and has good electrical and thermal conductivity. However, its disadvantage is that it will be halogenated or sulfided when exposed to the air containing halides and sulfides, the surface of the silver coating will be discolored, and the electrical conductivity will decrease.
In addition, microporous corrosion will also occur in case of moisture, so it is often used in the terminal connection part like gold to reduce the contact resistance of the connection.
Tin has good chemical stability, and high ductility, and is difficult to change color in the atmosphere. And because the tin plating layer is relatively soft, it can improve the running-in effect on the sliding parts of the machine. Therefore, tin plating can improve solderability and prevent nitridation. It is commonly used in electronic products and is a common terminal plating process.
In addition, there are nickel plating and chromium plating. When the thickness of nickel plating is less than 25 microns, there are more pores. In addition, the solderability of nickel plating deteriorated due to passivation. The hardness, wear resistance, and heat resistance of chromium plating are good. Chrome plating is mainly used for decorative plating and functional purposes.
It can be seen that there are many kinds of plating layers of terminals. The plating layer of the crimping part of the terminal is generally tin-plated, and the plating layer of the connecting part of the plug-in terminal is gold-plated, silver-plated, and multi-plated. required coating.
The design parameters of the terminal generally refer to the parameters of the crimping part, mainly referring to the inner and outer diameter of the terminal, the engagement length, and the depth, number, and arrangement of the dents.
The inner and outer diameter of the terminal determines the thickness of the terminal. The smaller the bending radius, the greater the relative elongation of the outer metal. When the relative elongation of the outer metal reaches the ultimate elongation of the material, that is, the bending radius reaches the minimum value, and the material will have a bending crack. The selection of terminal thickness needs to be determined according to the wire diameter of the crimped wire.
The effect of meshing length on the pull-off force of the terminal: the longer the meshing length, the larger the contact area between the terminal and the wire, and the stronger the contact between the terminal and the wire under the same crimping degree, the greater the pull-off force.
The influence of meshing length on the contact resistance of the terminal: the longer the meshing length, the larger the contact area between the terminal and the wire, and the smaller the contact resistance of the crimping terminal under the same crimping degree.
Indentations are generally present on the inner surface of the crimp portion of the terminal as a way to increase the mechanical and electrical properties of the terminal. The depth, number, and arrangement of the dents have different effects on the performance of the terminals
The wire is an important part of the terminal crimping. The main factors that need to be considered in the selection of the wire are conductor material, insulation material, and current carrying capacity.
For the same diameter, copper wire carries more flow than aluminum wire, but the weight of copper wire is also higher. Generally, the conductor is bare copper or bare aluminum, but there may be a coating on the outside of the conductor according to the need.
The common coating materials are tin and silver. In THE ENVIRONMENT CONTAINING sulfur, the coating of the wire should be tin plating, in the case of high requirements on the contact resistance of the wire, silver plating can be used to reduce the contact resistance.
The greater the resistance and resistivity of the insulation, the better. In the case of high frequency and high voltage, use insulation material with a small dielectric loss Angle tangent
Wire selection is often based on the target flow rate to select the wire. When selecting a wire, the carrying capacity of the wire is usually the first factor.
The high width of the die refers to the minimum crimp height that the terminal can achieve after crimping. If it is smaller, the upper and lower die will collide with each other and the die will be damaged. If it is found that the terminal has been crimped to the minimum crimp height, its performance is also If it is not qualified, you need to replace the die.
The thickness of the die determines the engagement length of the terminal, that is, the length of the deformed part of the crimp. The longer the engagement length, the better the mechanical and electrical performance.
However, in the current industry situation, under the premise of meeting the performance requirements, the more the terminal is. Smaller is better. On the one hand, it is miniaturization, and on the other hand, it is a cost issue.
The tensile force of the terminal mainly depends on the contact pressure between the terminal and the wire. The contact pressure between the terminal and the wire is mainly provided by the elastic deformation and plastic deformation of the terminal and the wire, which is an important factor that determines the elastic and plastic deformation of the terminal and the wire. is the crimp height
The smaller the crimping height, the deeper the pressing ground, and the greater the elastic-plastic deformation of the terminal and the wire, the greater the contact force, and the greater the tensile force. The greater the crimping height, the smaller the pressing down, the smaller the elastic-plastic deformation of the terminal and the wire, the smaller the contact force, and the smaller the tensile force.
The contact between the terminal and the wire is not a complete contact, but a contact scattered at some points on the contact surface. The gap between the actual contact area and the theoretical contact area may be several thousand times, and the resistance formed by the contact between the conductor and the conductor is called contact. Resistance, contact resistance is divided into shrinkage resistance and film resistance
Contact pressure has a great influence on contact resistance. For crimp terminals, the contact force between the terminal and the wire is formed by the elastic deformation and plastic deformation of the terminal and the wire. The crimp height directly affects the deformation of the terminal and the wire, that is, the contact force between the terminal and the wire.
In the electrical contact theory, the greater the contact pressure, the smaller the contact resistance. The sufficiently large contact pressure can cause plastic deformation of the contact surface of the terminal and the wire, increase the number of contact points, and reduce the shrinkage resistance; at the same time, it can crush the film that may exist on the surface of the terminal and the wire, reducing the film resistance.
The increase of the contact pressure can reduce the contact resistance so that the electrical performance of the terminal and the wire is very good. But it is not that the greater the contact pressure, the smaller the contact resistance, because there is material flow, so the crimp height is not as small as possible.
The increase of the contact pressure can reduce the contact resistance so that the electrical performance of the terminal and the wire is very good. But it is not that the greater the contact pressure, the smaller the contact resistance, because there is material flow, so the crimp height is not as small as possible.
To sum up the above, the crimp height plays a crucial role in the performance of the terminal. The mechanical properties of the terminal increase rapidly as the crimp height decreases. When the crimp height is less than a certain value, the mechanical properties of the terminal The electrical performance of the terminal first rises rapidly, then slowly rises and tends to stabilize with the decrease of the crimp height, and finally decreases gradually. The crimp height of a good terminal crimp is required to ensure both the mechanical and electrical properties of the terminal
The above is the analysis of the factors that affect the performance of terminal crimping. Zhejiang Lianhe Electronics Co., Ltd. is a company specializing in the production of connectors. Welcome new and old customers to come and buy