PCB Fabrication

Learn the reliability design of pcb copy board contact system from scratch

by:A-TECH      2021-03-29
The correct choice of contact material can improve the reliability and life of the relay IRF520NPBF. Different relays have different types and degrees of wear on the contacts due to the different load properties and breaking capacities of the contact circuits; these factors must be considered when designing and selecting contacts and reed materials. The selected contact and reed materials should meet the following basic requirements: ①Have good electrical conductivity and thermal conductivity. ②The contact and coating materials should be able to withstand arc or electric spark wear and mechanical wear, and have certain hardness and anti-adhesion properties. ③The reed material should have good elasticity. 2) Contact contact form and shape and size design requirements ①For miniature, ultra-small and other relays with small load, the contact should be in point contact form, and the PCB copy board can increase the pressure of the contact part and destroy the pollution on the contact surface. Things. For heavy load relays, the contacts should be in surface contact form to increase the heat dissipation area and slow down the electrical wear of the contacts. ②In the contact combination form, the assembly form should be avoided as much as possible to reduce the unreliable factors caused by the assembly, and reliable welding instead of riveting. ③The contacts of different materials are used for matching to improve the arc resistance and wear resistance of the contacts. ④ The design quality of the reed should be small, and the size should not be too long. For example, using high elastic modulus materials, circuit board clones reduce the specific gravity of the material or increase the stiffness of the reed, etc., so that the resonant frequency is higher than the given environmental frequency index. So as to ensure the environmental adaptability of shock and vibration. ⑤When the rated current is passed, the current density of the reed is not allowed to exceed the specified value to ensure that the temperature rise of the reed does not exceed the allowable value, thereby ensuring the reliability of contact. 3) Design requirements for contact pressure and tracking ①Ensure reliable electrical contact between contacts and stable contact resistance. ②The tracking of the contact should be greater than the height of contact wear within the specified life. ③Appropriate selection of mechanical parameters such as contact pressure and tracking to reduce the number of contact bounces and shorten the contact bounce time as much as possible, thereby reducing the wear phase of the contact arc ablation. ④For small load and medium load relays, there should be a certain tracking between the contacts to clean the surface, reduce contact resistance and thermal effects, reduce breaking failures, and improve contact reliability; for heavy load relays, increase the contact pressure. So that the arc can be quickly broken when the contacts are disconnected.
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