Soldering station - what is the reason for the uneven heating of lead-free reflow soldering
1. Generally, PLCC and QFP have a larger heat capacity than a discrete chip component, and it is more difficult to weld large-area components than small components.
2. In the lead-free reflow oven, the conveyor belt also becomes a heat dissipation system while repeatedly transporting products for lead-free reflow soldering. In addition, the heat dissipation conditions are different between the edge and the center of the heating part, and the edge temperature is generally low. In addition to the different temperature requirements of each temperature zone in the furnace, the temperature of the same loading surface is also different.
3. The impact of different product loads. The adjustment of the temperature curve of lead-free reflow soldering should consider good repeatability under no-load, load and different load factors. The load factor is defined as: LF=L/(L+S); where L=the length of the assembled substrate, and S=the spacing of the assembled substrate.
To obtain good repeatable results in the lead-free reflow soldering process, the larger the load factor, the more difficult it is. Usually the maximum load factor of lead-free reflow oven is in the range of 0.5-0.9. This depends on product conditions (component welding density, different substrates) and different models of reflow furnaces. To get good welding results and repeatability, practical experience is very important.
