SMT Environment

Temp. and humidity levels are dependant upon your chemical (paste and adhesive) specifications. Ballpark I'd say 70�F and 40%-45% RH are good targets, as our paste spec. says optimal ranges are 70-77� and 30-70 RH.

As far as air quality, if you build a room with doors (not a warehouse), keep some positive pressure (compensate for your reflow exhaust requirements), and keep the room clean, normal commercial office type HVAC filtration should be enough.

That said, I think that I'd want a cleaner room to do 0201 and 16 mil pitch assembly in than I would for 1206 and 50 mil pitch, just to be on the safe side.

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I have never seen any industry standards for setting up an SMT assembly facility, but I�ll offer some basic advise. An ideal SMT assembly facility is one that is clean and well lit and has environmental controls to maintain temp and RH. Temp of 24C (75F) and RH of 45% I have found to be ideal. You need to balance; more RH reduces ESD issues, but is not good for components and some solderpastes. Your ideal facility maintains the 24C temp and 45% RH all day and all year round. This can be accomplished with systems that maintain these levels, such as HVAC systems and misting devices. Also, it is important to set up the ventilation to the facility to be positive pressure. Ventalation must be filtered. This will cut down on dust getting into the plant. Sticky floor mats placed at the entrances will remove dirt and dust from the footgear of people entering the plant. ESD safe floor surfaces to choose from are epoxy floors, tile and even paint. Some surfaces will require ESD waxing, others just regulator cleaning. On electrical issues, clean isolated electrical power supply and good grounding is very important for equipment. Also, the higher power the better. If in the USA, be sure the plant will have 480VAC power. This will reduce kW cost of running the soldering machines and any other high-power equipment you may utilize. Finding a good electrician and HVAC vendors will be very valuable for consulting on these matters. People tend to work longer and more effectively when they are comfortable. Lighting can affect a person's level of comfort; so lighting designs are increasingly tailored to ensure personal comfort while providing effective illumination. About 100 foot-candles is bright enough. UV-filtered fluorescent lamps are most popular. New lighting systems are recommended for highest efficiency. It is not recommended to have windows or skylights as sunlight effects temp too much. Hope this helps.

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Steve / Pete,

Thanks very much for the info. That should be enough to give our facilities guys something to work on for the next couple of weeks.

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