In a recent survey conducted by AGM Container Controls Inc, 83% of engineers reported that addressing moisture control and condensation buildup is a significant challenge in the design and maintenance of their projects.
Here’s what you need to know about how to address moisture and condensation protection in your projects.
Moisture is held in the air and in an assembly’s hygroscopic component materials, like printed circuit boards. Frequently, the amount of moisture held in these materials far exceeds what’s held in the air, and all of this moisture is trapped in your enclosure when you close it up. You can reduce this moisture load to a safe level by baking out your assembly or purging it with dry gas in order to drive off this moisture, or by including enough desiccant in the assembly to bind up this moisture.
It’s important to know how much moisture content your assembly can handle without failing. If you know your assembly’s moisture tolerance, then you’ll be able to determine proper protection to avoid exceeding that tolerance. For instance, electronic assemblies generally require a dew point, or technically a frost point, of -3°C or below. Electronics can withstand some frost. As an alternative to maintaining such a low point, an air blanket above the electronics with a temperature of at least 40°C, used in conjunction with a membrane vent that allows water vapor to enter and exit the enclosure, can potentially work.
The individual pressures of gases, such as oxygen, nitrogen, and water vapor, all combine to create the total air pressure. Each of these gases will try to equalize pressure and diffuse or permeate through a medium such as elastomeric seals. This is important to keep in mind when considering the amount of protection provided by filling your assembly with dry gas. Since a dry-gas environment has very low vapor pressure, the water vapor in the external environment will permeate through seals in order to equalize vapor pressure. This happens even if the overall internal pressure in an enclosure is higher than the overall external pressure. Therefore, you need to choose your seals carefully, because some elastomers permeate more water than others; and you will probably need to include some desiccant to adsorb the moisture that enters your container over time.
If your product experiences elevation changes during transport (mountains or air cargo) then you need to plan for the impact that these changes can have on your enclosure's internal pressure. They will cause pressure fluctuations within the assembly enclosure. It’s common to address this type of issue with breather valves. However, breather valves allow water vapor to pass into the enclosure when they open. As a result, you need to include something inside the enclosure to handle that incoming water vapor, like desiccants. There are different ways to protect your assembly in this type of situation, for instance, a breathing desiccator could potentially be employed rather than a breather valve.
Engineers can choose from a wide variety of tools and techniques to protect their products from moisture and pressure damage. AGM Engineers can help you choose the best system for you projects. Some of the tools we provide include:
Call AGM at (520) 881-2130 or email us to speak with an AGM engineer and get detailed information about moisture protection solutions for your project
AGM Container Controls, Inc.
3526 E. Fort Lowell Rd.
Tucson, AZ 85716