Reflow in the reflow zone is the final heating zone, its role is to increase the PCB assembly temperature from the active temperature to the recommended peak temperature. The active temperature is always a little lower than the melting temperature of the alloy, and the peak temperature is always at the melting point.

A typical peak temperature range is 205-230 ° C. Setting the temperature in this zone too high will raise the temperature ramp by more than 2 to 5 ° C per second, or until the peak reflow temperature is higher than recommended. This condition may cause excessive curling, delamination or burn-in of the PCB and damage the integrity of the component.

Reflow In the reflow stage, the temperature continues to rise above the reflow line (183 ° C), the solder paste melts and undergoes a wetting reaction and begins to form an intermetallic compound layer. Reach the highest temperature (about 215 ℃), and then start cooling, falling below the return line, the solder solidified. Reflow zone should also consider the temperature rise and fall of the slope of the component can not be thermal shock.

Reflow reflow zone, its maximum temperature is determined by the PCB's temperature-sensitive components of the temperature capability. The time in the reflow zone should be as short as possible to ensure good soldering of the components, typically 30-60 seconds, long over-reflow times and high temperatures, such as reflow times greater than 90 seconds and maximum temperatures above 230 Degree, will cause thickening of the intermetallic compound layer, affecting the long-term reliability of the solder joint.