In the mass production pcba processing and soldering environment, the temperature profile is very important. A slow ramp-up and preheat stage can help activate the flux, prevent thermal shock, and improve solder quality when smt placement. However, when it comes to reworking, prototyping, or the first PCBA proofing project, it's easy to forget the importance of the warm-up phase, which can result in a device that is significantly compromised if not damaged. Therefore, for such an important step, why is it often forgotten in the actual operation of the smt processing plant? What are the consequences of ignoring this step?

1. What is preheating before PCBA soldering?

When technicians and practitioners hear the word "temperature profile", smt reflow soldering comes to mind. Along the extensive welding area, it is easy to see 4 main temperature control zones, resulting in the perfect weld joint. At each stage, technicians will rely on their own experience, trial and error, strict control and improvement, and each stage can improve the quality of solder joints and reduce defects. But other industrial soldering equipment may not have such precise temperature control, but they all have a preheat stage in common.

2. Flux combustion in selective wave soldering

The role of the preheating stage is to make the temperature of the entire assembly rise steadily from room temperature to a holding temperature lower than the melting point of the solder paste, about 150°C. Adjust for temperature changes to keep the slope at a few degrees per second. A period of time following the preheating stage is the soaking period, during which the temperature is maintained for a period of time to ensure uniform heating of the board. Then enter the reflow stage and start solder joint formation. During the preheating and soaking process, the volatile solvent in the solder paste is burned off and the flux is activated.

The production practice of Tongsen Electronics has proved that preheating before welding is very important.