Why all the buzz regarding Vapor Phase and Lead-free solder reflow?

Vapor Phase brings several advantages to the lead-free reflow process. One of the most significant is the ability to limit the absolute maximum temperature. Because the vapor temperature is tied to the boiling point of the vapor phase fluid, it is impossible to exceed this temperature in the reflow process. With the higher melting points of most lead-free solders, this becomes an important issue. For example, the use of a 230°C fluid will not exceed the assemblies temperature limits. This is not always the case for more traditional reflow systems where excessive heat may be required to perform proper reflow.

Another advantage to Vapor Phase is the way it transfers heat to the product. Convection and IR ovens rely on air movement or radiation to transfer heat to the product. These heat transfer methods can cause deflection, shadowing, and reflection of the heat, which in turn can cause uneven heating of the product such as hot or cold spots. These issues only become more problematic as mass differentials and package densities increase. Vapor Phase on the other hand, uses a condensation method of heat transfer. This condensation method uses a saturated vapor to transfer heat. Saturated vapor is much more uniform and able to transfer its heat to all surfaces of the product evenly regardless of mass or geometry. Saturated vapor insures that all surfaces of the product including shadowed or densely populated areas are heated in a uniform fashion.