Reflow welder, also known as reflow welder or reflow furnace, is a machine that uses a heating condition to heat and melt the solder paste to make the surface mount components firmly integrated with the PCB solder paste alloy.
Affecting the technological factors:
There are three main factors, such as the difference of heat capacity and heat absorption of reflow element, the edge effect of the transmission belt or the heating machine, and the load of reflow soldering parts.
1. generally, PLCC and QFP have larger heat capacity compared with a discrete chip element, and larger components of welded joints are more difficult than small components.
2. in the reflow soldering furnace, the transmission zone is reflow welding at the same time, and a heat dissipation system is formed. In addition, the edge of the heating part and the central heat dissipation environment are different, the edge temperature is usually low, and the temperature of the same surface is different except the temperature demand in each temperature zone.
The effect of the difference on the load of 3. weldments. The setting of temperature curve for reflow soldering should be considered in good repeatability under conditions of no load, load and different load factors. The load factor is defined as LF=L/ (L+S), where the length of L= assembled substrate and the interval of S= assembled substrate.
Reflow technology to obtain reproducible results, the load factor is more difficult. The maximum load factor of reflow furnace is 0.5~0.9. It depends on the type of weldment (element welding density, different substrate) and the difference type of reflow furnace. To achieve better welding results and repeatability, practical experience is very important.
The technology of reflow soldering is growing with the emergence of miniaturized electronic products. It is mainly used for welding components at various levels. The solder paste for this kind of welding technology is solder paste. Apply a suitable and suitable form of solder paste on the pads ahead of time, then attach the SMT components to the corresponding position; the solder paste has a certain viscosity, fixed the components, and then put the plaster on the components into the reflow machine. The transmission system drives the PCB through the temperature regions set by the machine, and the solder paste is welded to the printed board through drying, preheating, melting, wetting, and cooling. The core step of reflow soldering is to use external heat source to make the solder melt and reflow and infiltrate, and then process the welding process of PCB.
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