Reflow soldering with nitrogen injection is simulated. Soldering is performed in a process oven that is equipped with porous panel heaters through which air or nitrogen is introduced to the reflow environment. The injected gas is introducedselectively through top or bottom infrared heaters in order to dampen temperature fluctuations which can be established by thermal buoyancy forces in the oven gas. The heat transfer processes are simulated using an existing, general numerical model thataccounts for multimode effects, and is capable of predicting large and small scale thermal and species concentration phenomena. With selective injection, it is shown that high frequency convective heating and/or cooling of the card assembly can beeliminated, and oxygen concentrations in the reflow section can be controlled to low levels.
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