Question: Is it necessary to replicate the thermal profiling process during long term mass production of products?
While we are discussing this, is it also necessary to recheck the accuracy of the reflow oven profiles periodically, and if so how often?
Answer: Checking profiles on an ongoing basis is a must due to the deterioration of the equipment and the variations in the settings. If the product volume is high and the mix is low, then I would recommend checking the thermal profile before every shift. Whereas if the product volume is low and the mix is high, which indicates the thermal requirements of the oven has to be changed, then I would recommend checking the thermal profile prior to running the boards which would determine whether or not the oven has stabilized at the correct temperature to run product.
This may sound like overkill, but the variation in component sizes and the heat absorption rate of each component and the board as well is different. The reflow process is a general heat application system, meaning it heats everything in the oven based upon the oven temperature and conveyor speed. To verify the board is getting the correct amount of heat to prepare and dry out the solder paste and reflow the solder paste for a long enough dwell time to solder all the components, the thermal profile is your due diligence in verifying the process compatibility.