Reflow Profiling

It depends on the thermal mass of your assemblies (boards and components). Generally, if boards are small with few layers, the additional mass of components may have a significant impact on reducing the peak temperature. If boards are larger with solid ground and are thermally heavy, processing this assembly with parts should not impact the peak temperature significantly (maybe decrease of up to 5 degrees C).

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This will depend on many factors: your reflow oven chamber size, your oven temperature controller, the speed of the conveyor, size and mass of your PCB, etc etc.

In practice you should adjust the profile for each case if you want to set in the optimal middle of your process window, or you can group similar boards and run them with one profile

We use Mistral 360 with glass top where you can "see" your process while board pass through the oven, you see when the paste dry, you see when the reflow starts, what is the time above liquid etc etc, and can adjust up or down with few degrees in each chamber to achieve what you want without using any profiler

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This is easy experiment. Just run no populated PCB and that a populated one using the same spot for your thermo-couples. If you have a convection oven, you might be surprised how small this difference could be if not none. In some cases, I would expect to see even the opposite - having higher temp with the parts(this air circulates and sometimes the parts can hold it in certain sections and not let it escape that quick)

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