SMT007 Magazine

SMT007-July2019

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92 SMT007 MAGAZINE I JULY 2019 Using a reflow oven as an example of a typi- cal lead-free solder profile, it can be noted from Figures 6 and 7 that the process involves, preheat—ramp up—reflow, and cool down with the actual reflow period in the range of 5–10 seconds maximum. In hand soldering, the same reflow profile should be evident and is a process where thermal energy is transferred from the heater through the solder tip to the joint. This takes place as follows (Figure 8): 1. When the solder tip touches the pad with solder, stored energy in the copper tip will transfer to the joint (note that the stored energy is not controllable once it touches the joint) Figure 7: Wave soldering profile to deliver the correct amount of thermal energy. Figure 6: Reflow oven temperature profile for delivering the correct amount of thermal energy.

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