Protecting PCBs 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: inside the seemingly sealed enclosure. This article explains why a high IP rating does not prevent condensation, and which protection strategies truly safeguard your assembly.
In a nutshell
An IP rating protects against water ingress from outside, not against moisture that condenses inside. Against condensation, a conformal coating or a full encapsulation that covers critical areas hydrophobically helps, supplemented by pressure equalization (membrane) or desiccants in sealed enclosures.
Why condensation occurs in a sealed enclosure
When sealing, air with a certain level of humidity 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 water film on the coldest surface, often directly on the circuit board. This repeats with temperature fluctuations, and a housing that is not completely sealed even "breathes" in humid 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, but not internal condensation.
Protection strategies compared
| Strategy | Principle | When useful |
|---|---|---|
| Conformal Coating | thin, hydrophobic protective film directly on the assembly | Series electronics, low weight, repairability desired |
| Full encapsulation | Assembly completely embedded, no cavity for condensate | Rough use, high demands on sealing and mechanics |
| Pressure equalization + desiccant | Membrane allows moisture to escape, keeps water out | larger housings, in addition to coating |
Standards and Testing
Conformal Coatings are qualified according to IPC-CC-830 and IEC 61086 . Resistance to moisture and condensation is tested via cyclic damp heat tests according to IEC 60068-2-30 or steady-state damp heat per IEC 60068-2-78, tests that exactly simulate the temperature cycles under which condensation occurs.
Material Selection and Products
For thin-film protection, a conformal coating such as Electrolube APL Acrylic Lacquer is suitable; silicone and polyurethane lacquers for higher temperature or chemical resistance can be tailored on request. Where maximum protection and mechanical robustness are required, full encapsulation with an elastic silicone such as SILISIL RTV MF-Flex 20 or PRO-Cast 45 is the more robust solution. For a distinction between coating and encapsulation, see Potting vs. Encapsulation.
Frequently asked questions
Does IP67 help against condensation? No. IP67 keeps water out from the outside, but does not protect against moisture that condenses inside the enclosure. This requires coating, potting, or pressure equalization.
Coating or full encapsulation? Coating is lightweight, thin, and repairable, and is sufficient for many cases; full encapsulation offers maximum protection in harsh environments, but is heavier and no longer removable.
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 on the conductors.
Consultation and samples
Provide us with your assembly, operating conditions, and temperature profile, and we will recommend coating or potting and provide a sample. Contact us or write to info@silitech.ch.
