Before introducing the principle of gas phase reflow welding, let me introduce the gas phase reflow welding. Vapor phase reflow welding is also called vapor phase welding, condensation welding or cold poly welding (Vapor Phase Soldering, referred to as VPS). It is a surface mount soldering technology that uses the latent heat released when the fluorocarbon liquid is vaporized as a heat medium to provide heat for soldering SMT chip soldering equipment, mainly used for thick film integrated circuits. Because VPS has the advantages of fast heating speed and uniform temperature, it is widely used in the welding of some difficult electronic products.

The principle of gas phase reflow welding is: the liquid containing fluorocarbons can be heated to the boiling point (about 215℃) and vaporized to produce different vapors. Use it as a heat transfer technology medium to put the finished substrate into a steam oven , Research welding by analyzing the heat (latent heat) of the condensed vapor in the transfer process. When the gas-phase reflow furnace reaches the vaporization temperature, it becomes a high-density, saturated vapor in the welding zone (vapor liquid fluorocarbon layer), replacing air and moisture. In a place filled with steam, the temperature is the same as the boiling point of the liquid in the gasification technology stage. The peak welding temperature is the boiling point temperature of the carbon fluoride liquid at atmospheric pressure, which is about 215°C, and the temperature is very uniform. In addition, VPS does not need to use nitrogen, because its soldering environment is neutral, and has advantages in soldering larger ceramic BGA and plastic BGA, and lead-free soldering.

However, with the development of lead-free SMT, the industry has recently developed a new method based on the principle of spray system-spray vapor welding based on traditional vapor welding equipment. This method can not only control more accurately The quantity of welding working medium vapor can also reflow the assembly board in the closed cavity. Compared with traditional vapor phase welding, this method has more flexibility in controlling the temperature curve of reflow welding. At the same time, a vacuum is formed during welding, which can eliminate bubbles generated in the molten solder joints, improve product reliability to a certain extent, and reduce product processing costs.

In short, whether it is the traditional vapor reflow welding or the new jet vapor welding, the working principle is similar, and the welding effect is achieved through steam heat transfer.