Reflow soldering is a process in which a solder paste (a sticky mixture of powdered solder and flux) is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to controlled heat. The solder paste reflows in a molten state, creating permanent solder joints. Heating may be accomplished by passing the assembly through a reflow oven, under an infrared lamp, or (unconventionally) by soldering individual joints with a desoldering hot air pencil.
Reflow soldering is the most widely used form of soldering used for PCB assembly. It provides reliable soldering for the huge variety of component and pad sizes required, whilst being easy to monitor and control.
Infrared reflow soldering has been used for many years in PCB assembly areas, and it is now able to provide very high quality soldering that can meet the needs to todays electronics production areas.