Precautions for temperature setting of lead-free reflow soldering

In the early stage of reflow soldering, the solder is made of lead containing materials. With the deepening of environmental protection thought, people pay more and more attention to lead-free skills, that is, lead-free reflow soldering. In terms of materials, especially solder, Z changes greatly. In terms of process, the welding process has a great impact on Z. This is mainly caused by the characteristics of solder alloy and the difference of corresponding flux.

The lead-free reflow welder system is to extract the high-temperature air flow containing a large amount of flux from the preheating area, reflow area and cooling area, and send the clean gas back to the furnace after passing through the external cooling and filtration system. Another advantage of this is that when using nitrogen protection, Zhonghong intelligent reflow soldering shares the precautions for setting the lead-free reflow soldering curve:

1. Improve preheating temperature: during lead-free reflow soldering, the preheating zone temperature of reflow soldering furnace shall be higher than that of tin / lead alloy reflow. Generally, it is about 30 ℃, 170 ℃ - 190 ℃ (the traditional preheating temperature is generally 140 ℃ - 160 ℃). The purpose of increasing the preheating zone temperature is to reduce the peak temperature and reduce the temperature difference between components. Nitrogen reflow soldering

2. Extended preheating time: properly extend the preheating time of preheating. On the one hand, too fast preheating will cause thermal shock, which is not conducive to reducing the temperature difference between components and components constituting the peak reflow temperature. Therefore, the preheating time of preheating is properly extended to make the temperature of welded components rise smoothly to the predetermined preheating temperature.

3. Commonality of adjustment temperature curve: when testing and adjusting the temperature curve, although the temperature curve of each test point has certain discreteness and cannot be completely common, it should be carefully adjusted to make the temperature curve of each test point tend to be common as much as possible.

4. Trapezoidal temperature curve of extended reflow zone: Trapezoidal temperature curve of extended reflow zone. While controlling the Z high reflow temperature, increase the width of the temperature curve in the reflow area, extend the peak time of components with small heat capacity, make the components with large and small heat capacity reach the required reflux temperature, and avoid overheating of small components.