Precautions for temperature setting of lead-free reflow soldering

In the early stage of reflow soldering, lead containing materials are used. With the deepening of environmental protection thought, people pay more and more attention to lead-free skills, that is, lead-free reflow soldering. There are great changes in materials, especially in solder. In terms of process, the welding process has the greatest impact. This is mainly caused by the characteristics of solder alloys and the difference of corresponding fluxes.

The lead-free reflow welder system extracts the high-temperature gas flow containing a large amount of flux from the preheating area, reflow area and cooling area, and sends 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 following precautions for setting the lead-free reflow soldering curve:

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

2. Extended preheating time: properly extend the preheating time. On the one hand, too fast preheating will cause thermal shock, which is not conducive to reducing the temperature difference between components and parts that constitute the peak reflow temperature. Therefore, the preheating time of preheating shall be properly extended to make the temperature of components to be welded 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 high reflow temperature of Z, increase the width of temperature curve in the reflow zone, extend the peak time of components with small heat capacity, make components with large and small heat capacity reach the required reflux temperature, and avoid overheating of small components.