Reflow Oven Exhaust

We're installing our first SMT line and my boss asked me a question I couldn't answer right off the top of my head. I have been an SMT process engineer for about 12 years and I guess this just never came up before. I was surprised but it made good sense for him to ask the question. Can anyone offer any input?? Is there a way to supply outside unconditioned air to a forced convection reflow oven? If we are exhausting 500-600 cfm and the oven is drawing it's air from inside the building, and we are conditioning (heating/cooling/humidifying/dehumidifying) that air, then it stands to reason that we are wasting an awful lot of our factory conditioned air, i.e. WASTING ALOT OF MONEY!! My boss is pretty tight with his $$$. I know one option is to buy a filtration system and exhaust the air back into the facility, but the last time I did that, the filtration system was pretty expensive. Any inputs appreciated. DB

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DB Sure, it is always possible to "duck in outside air" to use with production equipment, but be careful, you have to determine the air quality required for your process. Cosnsider moisture, contaminates and the actual forcing of air into a confined area. Air pressure introduced from an oustide source of none filtered air will introduce turbulants in the reflow zone creating reflow results that you will not be able to control or explain. Forced air will certainly disturb the actual reflow temperature which will result in major problems controlling the oven profiles. Your boss mignt think he is "WASTING ALOT OF MONEY!!", but when he has to pay for the poor finish product results the money spent on air conditioning will mean very little. Being tough on the amount of money spent is your boss's responsibility, but I am sure if the throughput goes down, the SMT process engineers cannot explain the lower yields, he will reevaluate the cost savings. Filteration systems can be purchased and used to condition and reintroduce air into the physical plant (building) this works fine in the Northeast where we have one or two days a bit colder than some, but to introduce heated filtered air into a room during the hot weather might cost more than it is worth. In short be careful not to upset your present air conditioning system. Just my two cents worth, sorry I got carried away... Wayne

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