Cleanrooms have certain temperature and humidity requirements. If humidity or temperature within a cleanroom is poorly controlled, it can harm the products being produced. This is particularly true in cleanrooms used for food production, where the harm is particularly severe. So, what are the temperature and humidity requirements for cleanrooms? What are the hazards of excessive humidity in a cleanroom? Let’s discuss these:
What are the temperature and humidity requirements for cleanrooms?
1. Cleanroom temperature and humidity must not only meet production process requirements but also meet operator comfort requirements. People are the primary source of dust in cleanrooms. Workers entering clean areas must wear work clothes and masks appropriate for the cleanroom’s air cleanliness level. Because cleanroom work clothes have poor breathability, to ensure a safe working environment for cleanroom workers and improve productivity, the temperature and humidity should primarily consider worker comfort, unless the production process has specific temperature and humidity requirements.
2. Lower humidity in cleanrooms is not always better. For electronics cleanrooms, too low a humidity level can generate static electricity, reducing product quality. Generally speaking, the relative humidity in cleanrooms for the electronics industry should not be lower than 30%. To reduce static electricity, the relative humidity in the anti-static area of a cleanroom should be no less than 50%. Furthermore, the lower the temperature in a cleanroom, the higher the construction cost and the higher the operating energy consumption.
3. Unless otherwise specified, the temperature and humidity requirements for a cleanroom are as follows: temperature between 18°C and 26°C, relative humidity between 45% and 65%. If there are specific requirements, the temperature and humidity in a cleanroom should be determined based on the specific situation and may be adjusted appropriately. For example, in an electronics factory cleanroom, unless otherwise specified, the temperature is maintained at approximately 22°C and the relative humidity between 55% and 60%. The temperature and humidity standards for SMT constant temperature and humidity workshops are: temperature 24±2°C, humidity 50±10%.
Hazards of Excessive Humidity in a Cleanroom
1. Bacterial Growth. Bacteria and other biological contaminants (mold, viruses, fungi, and mites) can thrive in environments with a relative humidity above 60%. Some bacterial colonies can thrive when the relative humidity exceeds 30%. A relative humidity range of 40% to 60% minimizes the impact of bacteria and respiratory infections. Therefore, cleanroom relative humidity must be controlled within a certain range.
2. Condensation. In a cleanroom environment with high relative humidity, capillary forces created by condensed water form bonds between particles and surfaces, increasing their adhesion to the silica surface. This effect, known as Kelvin condensation, is insignificant when the relative humidity is below 50%, but becomes the primary force for particle adhesion at around 70%.
3. Poor relative humidity control in cleanrooms can lead to static charge. When the relative humidity exceeds 50%, static charge begins to dissipate rapidly, but below 30%, it can persist for extended periods on insulators or ungrounded surfaces. A relative humidity between 35% and 40% in Shenzhen cleanrooms is a satisfactory compromise. Semiconductor workshops generally use additional control devices to limit the accumulation of static charge.
The Dangers of Poor Cleanroom Humidity Control
Poor relative humidity control can easily cause metal corrosion in cleanrooms. The rate of many chemical reactions, including corrosion processes, increases with increasing relative humidity. All surfaces exposed to the ambient air in a workshop are quickly coated with at least a monolayer of water. High humidity can accelerate these reactions when these surfaces consist of thin metal coatings that react with water. Some metals, such as aluminum, react with water to form a protective oxide layer that prevents further oxidation; other metals, such as copper oxide, offer no protective properties.
