Since it is not always possible to run all products under a single profile, most factories require product change over time in order to reset the oven to a new set of temperatures, per product class or board. Depending on the variations of PCBs, changeover time can add up to hours, days or weeks of lost production time.
So, what can you do to minimize this dead period? Determine, in advance, the best grouping of products that have shared profiles and then schedule product runs over available equipment that minimizes changeover. It is worth every minute of company effort and time to review daily production in order to run products that require small set point changes.
It is entirely possible, in an organized methodical way to consolidate groups of PCBs under the umbrella of one or more Thermal profile, I like to think of putting them into small, medium and large buckets. Testing can be done to prove to yourself and/or your customers that the profile is both producing a product within specification and, quantifiably, how deep within spec. Yes, it is possible to have your cake and eat it too!
Profiling software can do some of the heavy lifting for you. You can reload past profiles to see whether or not they can be produced at given oven set points. Every time you ask the profiling software to run a prediction analysis, it searches billions of possible combinations. If you want the deepest in spec process, it will pick the one closest to the center of all variable specs. If you want to maximize conveyor speed, it will search for that one profile that gives you the highest throughput without violating any of your parameters. As it is crunching through these possible combinations, there are millions of other profiles in spec that you don’t see because they are not the optimal profile for a given request. This is not to say that they are any worse. When you reload a recorded profile to determined fixed oven set points, there may very well be profiles that are still deep within spec that can be run under your new Reflow oven configuration. Perhaps, instead of changing your oven over 4-5 times a day, it now only needs to be changed 1-2 times.