Pb-Free Assembly - Process
Nitrogen is used for reflowing the PCB’s mostly for Pb-Free Assembly through Nitrogen tank plant which consists of Cryo Cylinder followed by a vaporizer. The purpose of vaporizer is to convert the cold liquid Nitrogen in the Cryo cylinder into gas Nitrogen. The tanks are normally filled by the supplier of Nitrogen by bringing the truck to the plant location and then pumping cold fluid Nitrogen into the cryo-tank as and when needed.
When Pb-Free Assembly is done while Nitrogen is being used, the nitrogen vaporizes at minus 196 degree Celsius inside the vaporizer and becomes a gas. Then this nitrogen gas is transported in the special copper tubing to the reflow oven.