In the mid-1990s, there was a trend to transfer to infrared + hot air heating in reflow soldering in Japan. It is heated by 30% infrared rays and 70% hot air as a heat carrier. The infrared hot air reflow oven effectively combines the advantages of infrared reflow and forced convection hot air reflow, and is an ideal heating method in the 21st century. It makes full use of the characteristics of strong infrared radiation penetration, high thermal efficiency and power saving, and at the same time effectively overcomes the temperature difference and shielding effect of infrared reflow soldering, and makes up for the hot air reflow soldering.

This type of reflow soldering furnace is based on the IR furnace and adds hot air to make the temperature in the furnace more uniform. The heat absorbed by different materials and colors is different, that is, the Q value is different, and the resulting temperature rise AT is also different. For example, the package of SMD such as lC is black phenolic or epoxy, and the lead is white metal. When simply heated, the temperature of the lead is lower than its black SMD body. Adding hot air can make the temperature more uniform, and overcome the difference in heat absorption and poor shadowing. Infrared + hot air reflow ovens have been widely used in the world.

Since infrared rays will have adverse effects of shading and chromatic aberration in parts with different heights, hot air can also be blown to reconcile chromatic aberration and assist the deficiency of its dead corners. Hot nitrogen is the most ideal for the hot air to be blown. The speed of convective heat transfer depends on the wind speed, but excessive wind speed will cause the displacement of components and promote the oxidation of solder joints, and the wind speed should be controlled at 1. Om/s~1.8III/S is suitable. There are two forms of hot air generation: axial fan generation (it is easy to form laminar flow, and its movement makes the boundary of each temperature zone unclear) and tangential fan generation (the fan is installed on the outside of the heater, which generates eddy currents on the panel so that each temperature zone can be heated. precise control).