The contact between the terminal and the wire is not completely in contact, but scattered at some points on the contact surface. The difference between the actual contact area and the theoretical contact area may reach thousands of times. The resistance formed by the contact between conductor and conductor is called contact resistance, which 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 contact height directly affects the deformation of the terminal and the wire, that is, the contact force between the terminal and the wire.
In the theory of electrical contact, the greater the contact pressure, the smaller the contact resistance. Sufficient contact pressure can plastically deform the contact surface of the terminal and the wire, increase the number of contact points, and reduce shrinkage resistance. At the same time, it can crush the film that may exist on the surface of terminals and wires, and reduce the resistance of the film.
As the contact pressure increases, the contact resistance can be reduced, and the electrical properties of the terminals and wires are very good. However, the higher the contact pressure, the lower the contact resistance. Due to the plastic flow of the material, the lower the bead height, the better.
The mechanical properties of the terminal increase rapidly as the crimping height decreases, and when the crimping height is less than a certain value, the mechanical properties of the terminal decrease rapidly. The electrical performance of the terminal rises rapidly at first, then slowly rises and becomes stable with the decrease of crimping height, and finally declines gradually. At the same time, a good terminal crimping height needs to ensure the mechanical and electrical properties of the terminal.