In SMT processing, PCB substrates before the start of processing, the PCB will be checked and tested, selected to meet the SMT production requirements of the PCB, and the unqualified returned to the PCB supplier, the specific requirements of the PCB can be referred to IPc-a-610c International General Electronics Industry Assembly Standards, the following are some of the basic requirements of SMT processing of PCB.
1. The PCB must be flat and smooth
PCB general requirements flat and smooth, can not warp up, or in the solder paste printing and SMT machine placement will produce great harm, such as the consequences of cracks.
2. The thermal conductivity
In the reflow soldering machine and wave soldering machine, there will be a preheat area, usually to heat the PCB evenly, and to a certain temperature, the better the thermal conductivity of the PCB substrate, produce less bad.
3. Heat resistance
With the development of SMT process and environmental requirements, lead-free process has also been widely used, but also caused by the rise in welding temperature, the heat resistance of the PCB higher requirements, lead-free process in reflow soldering, the temperature should reach 217 ~ 245 ℃, the time lasts 30 ~ 65s, so the general PCB heat resistance to 260 degrees Celsius, and last 10s requirements.
4. The adhesion of copper foil
The bonding strength of the copper foil should reach 1.5kg/cm² to prevent the PCB from falling off due to external forces.
5. Bending standards
PCB has a certain bending standards, generally to achieve more than 25kg/mm
6. Good electrical conductivity
PCB as a carrier of electronic components, to achieve the link between components, to rely on the PCB lines to conduct, PCB should not only have good electrical conductivity, and PCB lines broken can not directly patch up, or the performance of the whole product will cause a great impact.
7. Can withstand the solvent washing
PCB in production, easy to get dirty, often need to wash the board water and other solvents for cleaning, so the PCB should be able to withstand the solvent washing, without producing bubbles and some other adverse reactions.
These are some of the basic requirements for a qualified PCB in SMT processing.
Post time: Mar-11-2022