Gas reflow welding is also called condensation welding. VPS refers to SMT SMD welding equipment that uses the latent heat released by the vaporization of fluorocarbon liquid as a heat medium to provide heat for welding. First-phase reflow thick film circuit.
1. The principle of gas-phase reflow soldering is that the liquid containing fluorocarbon can be heated to the boiling point (about 215℃) and then vaporized to produce different vapors. Using it as a heat transfer technology medium, the PCB design finished for chip processing is put into a steam furnace, and the heat (latent heat) in the process of condensed vapor transmission is analyzed for welding.
In the vapor-phase reflow furnace, when the vaporization temperature is reached, the welding zone (vapor-liquid fluorocarbon layer) becomes high density, replacing saturated vapor, air and moisture. Where the steam is filled, the temperature is the same as the boiling point of the liquid in the gasification technology stage. The welding peak temperature is that when the boiling temperature of fluorocarbon liquid is 215℃ at normal pressure, the temperature is very uniform. The welding environment of VPS is neutral, it does not need to weld large ceramic BGA, and nitrogen is used in SMT lead-free solder, which has great advantages.
Smt reflow soldering
Second, the new gas phase reflow soldering
With the development of SMT lead-free, a new method based on the principle of injection system has recently been developed for students on the basis of traditional gas-phase welding. This teaching method can more accurately manage and control the amount of steam in the welding working medium, and at the same time, reflow the assembly board in a closed cavity. Compared with the traditional method of gas-phase welding system, the degree of freedom of reflow and curve control is higher. When molten solder is welded by vacuum, the formation of bubbles can be eliminated, the reliability can be improved, and the processing cost of PCBA can be reduced.
The equipment can adopt the advanced spray gas phase welding working mode, and according to the requirements of different environmental temperature curves of enterprises, a certain amount of erotic medium fluorine oil can be sprayed into the treatment chamber. When the liquid comes into contact with the inner surface of the processing chamber, the liquid quickly evaporates to form vapor mist. By controlling the amount of fluid entering, it is possible to control the thermal energy carried by the vapor mist, and it is possible to control the temperature distribution very accurately and flexibly. Compared with traditional reflow soldering, it has some advantages, such as high reliability, no holes in solder joints, low defect rate, etc. The comparative study is suitable for the high reliability and safety requirements of China’s military PCB product technology.
