Try to keep the exposure time above Tg to less than two minutes.Ĭomponents may be damaged by excessive heat. The glass-transition (Tg) temperature of common laminated substrate material is between 120° and 130☌. Substrates can be damaged by excessive exposure to heat. Four major factors influence the design of a reflow soldering profile (check with suppliers to obtain exact figures): The cool-down phase helps to control dwell time and cool the substrate back down to room temperature. During the reflow phase, substrate, components and solder particles reach soldering temperature and, as a result, solder joints are formed. During this phase, solvent evaporation commences, flux activation occurs, and the substrate and components are gradually heated. All actions that lead up to proper soldering happen during preheat. Substrate and component cool down.The preheat phase is the preparatory phase. Solder particles melt, solder joints form5. Five specific phases actually take place during reflow soldering:ġ. The reflow process can be described in three basic phases: preheat, reflow and cool down. I have successfully used this approach for more than six years with different equipment and solder pastes. A gradual linear ramp up to the peak temperature and back down again is recommended. The situation changed when convection-dominant equipment was introduced because the user was able to create and achieve the desired reflow soldering profile. The historical reflow soldering profile, "ramp-soak-spike," evolved when infrared reflow equipment dominated the industry (i.e., equipment capability drove the profile). Numerous factors influence this profile each needs to be carefully studied and understood. Before a reflow soldering method is defined or equipment is selected, a time/temperature reflow soldering profile must be created.
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