Reading time ( words)
What is the suggested humidity level for an electronics assembly facility? Do the same limits apply within a 100,000-class cleanroom?
Humidity limits are a combination of ESD control (at the low end) and suitability for use with assembly materials (at both ends).
Low relative humidity (RH) can allow for higher static charges to build on objects. J-STD-001G requires an assessment of the suitability of ESD controls when the RH drops below 30%. This is the primary concern in a cleanroom environment due to the typically higher level of sensitivity of the parts that require cleanroom assembly environments.
Low RH can also affect solder pastes, especially OR-class pastes. Some of the volatile ingredients in the paste formula can be more susceptible to effects from a low RH environment, and this can reduce print performance and stencil life. High RH environments can lead to poor slump resistance of pastes. The range at which pastes are affected by RH will vary based on formulation, so you will need to consult the manufacturer and technical documentation for any paste product.
Jason Fullerton is the customer technical support engineer at the Assembly Division of MacDermid Alpha Electronics Solutions.