A helpful initial step to remove enclosure moisture is to characterize the enclosure environment utilizing a temperature/humidity data logger. These low-cost, battery-powered devices (~$200) record Electronic Dry Cabinets. In addition they indicate the dew-point conditions inside the enclosure (Fig. 6). Maintaining enclosure temperatures above dew-point temperatures is a requirement for condensation prevention.
Pursuing this option can be accomplished in a variety of ways, which range from desiccant to thermoelectric dehumidifiers-the challenge is always to select a choice that is inexpensive to both implement and maintain. This type of water-absorption capability of desiccant is dependent on many different factors (e.g., desiccant type, humidity, temperature). For instance, silica gel can absorb up to 40% of their weight in water. A 4’ x 6’ x 2’ electrical enclosure in a hot/humid environment would saturate 125 g of desiccant within two air exchanges. Therefore, the resulting frequency of required desiccant change-outs (which affects maintenance costs) is essentially driven by how well the enclosures are sealed. Unfortunately, with regards to desiccant regimes, each act of opening an enclosure to inspect the desiccant may serve as an air exchange.
Dehumidifiers are comparatively cheap, although finding convenient available power inside an enclosure may be problematic. The positive feature is that dehumidifiers get rid of the manual intervention connected with a desiccant regime. The negative feature of dehumidifiers is that they introduce yet another piece of equipment that can ultimately fail.
Another method is to reduce the opportunity of condensation through internal heaters (or light bulbs) to keep the inner enclosure temperature well above dew-point temperatures. The down-side is the fact higher temperatures may be detrimental to a few heat-sensitive electronic components, and the higher temperature actually allows the air to hold more moisture. Venting and fans can aid in avoiding condensation in certain situations-even though the Dry Cabinets For PCB Storage still exists. One interesting product the designers of GORE-TEX® have produced involves screw-in vents that enable enclosures to breathe, while providing a barrier to moisture and contaminants. The thought behind this type of venting is it cuts down on the stress on door seals when you can find pressure differentials in between the enclosure and the environment. By equalizing pressure, the possibility of moist air at higher pressure defeating your home seals is lessened.
Moisture-hardening of electronics includes a variety of techniques. With regards to connectors, using waterproof connectors or hardening existing connectors and splices with heat-shrink tubing can be of use to reduce water intrusion and corrosion. Avoiding horizontal orientation of components like printed circuit boards within the enclosure can minimize surfaces where condensation may collect for extended periods of time. Conformal coatings for lower-voltage printed circuit boards and using potting (see Fig. 7) of higher-voltage components greatly raise the moisture resistance of components. Potting costs vary based on the size of order, material selection jmmhra part geometry, but representative costs for very small orders (lower than 10) typically fall inside the range of $18 to $45 per part. Yet another benefit from potting is the added protection from shock and vibration.
Moisture protection of electronics is most beneficial approached by pursuing practices that maximize Desiccant Dry Cabinets during equipment installation, along with being willing to mitigate failure through anyone moisture-protection measure during operations. This strategy, along with tracking equipment-maintenance performance to know how well moisture-protection measures work, can lead to long-term minimization of electronics moisture-induced problems. MT.