The function of pcb reflow furnace and nitrogen (N2)

- Sep 18, 2018-

In the process of PCBA processing, the SMT reflow furnace and nitrogen (N2) are mainly used to reduce the oxidation of welding surface and improve the wettability of welding, because nitrogen is a kind of inert gas, which is not easy to produce chemical compounds with metals, and can avoid the oxidation reaction of oxygen in air when it comes into contact with metals.

The principle (mechanism) that using nitrogen can improve SMT solderability is based on the fact that the surface tension of solder under the nitrogen environment is smaller than that exposed to the atmosphere, which improves the fluidity and wettability of solder.Secondly, nitrogen reduces the solubility of oxygen (O2) in the original air and the material that can contaminate the welding surface, which greatly reduces the oxidation of solder at high temperature, especially the improvement of the quality of the second reflow welding

So actually printed circuit board (PCB) in the first side (1 st side) reflow soldering, reflow, circuit board the second plane (2 nd side) of the surface treatment is actually experiencing the same high temperature at the same time, the surface of the circuit board processing will have been destroyed by high temperature, especially using the OSP surface treatment of the board, and oxidation at high temperatures is sharp, and the nitrogen can at first after reflow soldering is greatly reduced when the second plane degree of oxidation surface treatment, make its can hang on to the second surface of furnace to get the best welding effect.

In addition, if the circuit board is left idle for too long after the first reflow soldering before the second reflow soldering takes place, it is also easy to cause oxidation problems and cause the problem of soldering or empty soldering when the second reflow soldering occurs.

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