Factors affecting uneven heating of reflow soldering equipment

The main reasons for uneven heating of components caused by reflow soldering process are: differences in thermal capacity or heat absorption of reflow soldering components, influence of conveyor belt or heater edges, and SMT reflow soldering product load. Below, JEENOCE will share the factors affecting uneven heating of reflow soldering equipment.

1、 Usually, PLCC and QFP have a larger heat capacity compared to a discrete sheet metal component, making it more difficult to weld large-area components than small ones.

2、 In the SMT reflow soldering furnace, the conveyor belt serves as a heat dissipation system while repeatedly conveying products for reflow soldering. In addition, the heat dissipation conditions at the edge and center of the heating section are different, and the temperature at the edge is generally lower. In addition to different temperature requirements for each temperature zone in the furnace, there are also differences in the temperature of the same load surface.

3、 The impact of different product loading capacities. The adjustment of the temperature curve for SMT reflow soldering should consider achieving good repeatability under no-load, load, and different load factors. The load factor is defined as: LF=L/(L+S); Where L=length of assembled substrate, S=spacing of assembled substrate.

The higher the load factor, the more difficult it is to achieve good repeatability in SMT reflow soldering process. The optimal load factor range for SMT reflow soldering furnaces is usually between 0.5 and 0.9. This depends on the product situation (component welding density, different substrates) and the different models of reflux furnaces. To achieve good welding results and repeatability, practical experience is crucial.