7.1 Temperature & Humidity Control

The manufacturing environment is a critical process variable in electronics assembly. Deviations in temperature and humidity directly correlate to defect generation in solder paste printing (viscosity changes), component reliability (moisture absorption), and electrostatic discharge (ESD) events. This chapter establishes the non-negotiable atmospheric windows required for high-reliability PCBA production.

7.1.1 PowerThe QualityHumidity &Window Backup(40% – 60% RH) 

Relative Humidity (RH) must be actively regulated between 40% and 60%.

• CleanLow Power:Humidity Risk (<30%): SpecificationsDielectric forbreakdown powerstrength conditioningof toair preventdecreases, "noise"causing exponential increases in electrostatic charge generation. Solder paste dries out on SMTthe linesstencil, (whichreducing cantackiness causeand placementcausing errors).component release failures during placement.
• TheHigh UPSHumidity Strategy:Risk (>60%): ProtocolsMoisture forSensitive Uninterruptible Power Supplies. Which machines get backup?Devices (e.g.MSDs) absorb ambient moisture beyond safe limits (per J-STD-033), Reflowleading ovensto must"popcorning" keep(delamination/cracking) theduring beltreflow. movingSolder paste absorbs water (hygroscopic), causing voiding and solder balling.

7.1.2 Temperature Stability (22°C ± 3°C) 

Solder paste is a thixotropic fluid; its viscosity is highly temperature-dependent. Fluctuations >5°C during a blackoutshift alter the printing definition, leading to bridging or insufficient coverage.

• Gradient Control: HVAC systems must prevent boardslocalized from"hot burningspots" inside).near reflow ovens or "cold spots" near loading docks.
• Grounding Architecture:Monitoring: EstablishingIndependent thedata "Singleloggers Pointmust Ground"record toTemp/RH preventat ground15-minute loopsintervals. thatAlarms interferemust withtrigger testingif equipment.limits are breached for >1 hour.

Final Checklist

Parameter	Specification	Breach Consequence
Relative Humidity	40% – 60% (Non-Condensing)	ESD (<40%) or Popcorning (>60%)
Temperature	22°C ± 3°C	Paste viscosity changes / Print defects
Data Logging	Continuous (15 min interval)	Audit failure / Root cause blindness
Recovery	< 2 hours	Production Halt