Method for adjusting the temperature setting of lead-free reflow soldering machine

The lead-free solder paste used in the lead-free reflow soldering process, most lead-free solder paste alloys, including Sn Ag Cu, have a melting point exceeding 20 ℃, which is higher than the eutectic temperature of traditional tin/lead alloys. This increases the reflow soldering temperature. This is a major feature of lead-free reflow soldering. So there is a difference between the temperature setting adjustment of lead-free reflow soldering machine and the temperature setting adjustment of lead reflow soldering process. JEENOCE will share it here.

1、 Increase the preheating temperature of the reflow welding machine

When lead-free reflow soldering, the preheating temperature of the reflow soldering furnace should be higher than the preheating temperature of the tin/lead alloy reflow. Usually around 30 ℃ high, the purpose of increasing the preheating zone temperature between 170 ℃ and 190 ℃ (traditional preheating temperatures usually range from 140 ℃ to 160 ℃) is to reduce the peak temperature and minimize the temperature difference between components.

2、 Extend the preheating time of the reflow welding machine

The temperature setting adjustment of lead-free reflow welding machine should appropriately extend the preheating time. Preheating too fast can cause thermal shock, which is not conducive to reducing the temperature difference between components in the formation of peak reflow temperature. Therefore, it is necessary to extend the preheating time appropriately to ensure that the temperature of the soldered components smoothly rises to the predetermined preheating temperature.

3、 Extending the trapezoidal temperature curve of the reflow zone of a reflow welding machine

The temperature setting adjustment of lead-free reflow welding machine should extend the trapezoidal temperature curve of the reflow zone. While controlling the optimal reflux temperature, increase the width of the reflux zone temperature curve, extend the peak time of small heat capacity components, ensure that all components of different heat capacities meet the required reflux temperature, and avoid overheating of small components.

4、 Adjust the consistency of the reflow soldering temperature curve

When testing and adjusting the temperature curve of lead-free reflow welding machines, although the temperature curves of each test point have certain discreteness and cannot be completely consistent, it is necessary to carefully adjust them to make the temperature curves of each test point tend to be as consistent as possible.

5、 Temperature setting method for lead-free reflow welding machine

1. The preheating temperature and time of the flux before dissolving tin remain basically unchanged.

2. Use two or more reflow soldering machines to heat up the welding area. The heating zone in the welding zone is used to rapidly increase the temperature, making the surface temperature of the PCB reach 10-20 ℃ above the melting temperature of lead-free tin. The second heating zone in the welding zone is used to maintain the melting temperature of the previous zone and increase the melting time. From the temperature curve, a temperature plateau is generated in the welding zone.