Protecting printed circuit boards from condensation: why IP protection alone is not enough
Condensation is one of the most underestimated causes of failure in electronics. It occurs precisely where you least expect it: in seemingly sealed enclosures. This article explains why a high IP rating doesn't prevent condensation – and which protection strategies will truly safeguard your assembly.
To the point
An IP rating protects against water ingress from the outside, not against moisture that condenses inside. Condensation can be prevented with a conformal coating or a full potting compoundthat covers the critical areas with a hydrophobic material – in sealed enclosures, this is supplemented by pressure equalization (membrane) or a desiccant.
Why it condenses in the sealed casing
When a device is closed, air with a certain amount of moisture is always trapped inside the housing. If the temperature drops below the dew point of this air – for example, at night or when the device is switched off – the moisture condenses as a film of water on the coldest surface, often directly on the circuit board. This process repeats itself with temperature changes, and a housing that is not completely airtight even "breathes" moist air. The result is leakage currents, corrosion, and dendrite formation between closely spaced conductors. This is precisely why a high IP rating does not prevent the problem: it keeps water out from the outside, not the internal condensation.
Comparison of protection strategies
| strategy | principle | When is it useful? |
|---|---|---|
| Conformal Coating | thin, hydrophobic protective film directly on the assembly | Standard electronics, low weight, and repairability are desired |
| Full potting | Assembly completely embedded, no cavity for condensate | harsh operating conditions, high demands on sealing and mechanics |
| Pressure equalization + desiccant | Membrane allows moisture to escape, retains water | larger enclosures, in addition to coating |
Standards and testing
Conformal coatings are qualified according to standards including IPC-CC-830 and IEC 61086. Resistance to moisture and condensation is tested using cyclic wet-heat tests according to IEC 60068-2-30 or continuous climate tests according to IEC 60068-2-78 – tests that precisely simulate the temperature changes at which condensation occurs.
Material selection and products
For thin-film protection, a conformal coating such as Electrolube APL acrylic protective coating is suitable ; we can coordinate silicone and polyurethane coatings for higher temperature or chemical resistance as needed. Where maximum protection and mechanical robustness are required, full potting with an elastic silicone such as SILISIL RTV MF-Flex 20 or PRO-Cast 45 is the more robust solution. For the distinction between coating and potting, see Potting vs. Encapsulation .
Frequently Asked Questions
Does IP67 protect against condensation? No. IP67 keeps water out, but it doesn't protect against moisture that condenses inside the enclosure. For that, you need a coating, potting, or pressure equalization.
Coating or potting? Coating is lightweight, thin, and repairable, and sufficient for many applications; potting offers maximum protection in harsh environments, but is heavier and cannot be removed.
Why does the circuit board corrode despite the housing? Because trapped or incoming moisture condenses at the dew point. A hydrophobic protective film prevents the conductive water film from forming on the conductors.
Consultation and samples
Tell us about the assembly, operating conditions, and temperature profile – we'll recommend a coating or potting solution and provide a sample. Contact us or write to info@silitech.ch.
