1.
The welding quality drops: the solder joints of electronic components will heat up every time they pass through the furnace. If the temperature is too high or the heating time is too long, the welding quality may decrease. Excessive welding temperature may lead to melting, diffusion and even welding peeling of solder joints.
2.
Thermal stress: repeated heating in the furnace will cause thermal stress of PCB and electronic components. The continuous heating and cooling process may lead to the expansion and contraction of PCB, which may lead to the change of PCB shape, and may even lead to poor contact between PCB layers or intermittent lines.
3.
Aging of components: continuous furnace feeding may lead to thermal aging or performance degradation of some sensitive electronic components. Some electronic components may not be able to withstand the strain of high-temperature heating for many times, resulting in component parameter deviation, shortened life or failure.
4. Uneven heating: Multi-pass heating may lead to uneven heating, which may lead to poor welding. Temperature differences between different electronic components and areas may lead to unstable or invalid welding.
5. Assembly deviation: Repeated furnace passing may lead to position deviation or dislocation of electronic components on PCB, thus affecting circuit connection and function.
In order to minimize the impact of repeated furnace passing, manufacturers often optimize the assembly process, such as controlling temperature, time and heating mode, and taking measures such as preheating before furnace to reduce the adverse impact on circuit boards and electronic components. In addition, the use of good quality electronic components and reasonable PCB layout can also reduce the potential problems of repeated furnace ventilation.