What Is a Combined Temperature + Humidity Test?
What Is a Combined Temperature + Humidity Test?The combined temperature-humidity test is a climatic test in which a product is exposed simultaneously to high temperature and high relative humidity (%RH) conditions to evaluate its environmental durability. This test represents a much more aggressive and demanding environmental condition than temperature-only or humidity-only tests, because high temperature accelerates chemical reactions while humidity creates a conductive medium for those reactions.
The combination of temperature and humidity can cause serious damage to products, including electrochemical corrosion, electrical leakage currents, drops in insulation resistance, blistering of coatings and paints, oxidation of fasteners, and ionic migration and dendrite formation on PCBs. For this reason, combined temperature-humidity testing is critical for electronic boards (PCBs), automotive and defense electronics, sealed-enclosure systems, and industrial devices that operate outdoors.
A combined temperature + humidity test is generally applied as follows:
- Defined temperature level (°C)
- High relative humidity level (%RH)
- Long-term exposure (hours or days)
| High Temperature | High Humidity |
|---|---|
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When these two effects are applied together, the degradation mechanisms on the product increase exponentially.
In temperature + humidity tests, the risk of condensation during temperature transitions is a critical parameter.
- Condensation forms when the surface temperature drops below the dew point
- This creates a serious short-circuit risk for electronic systems
For this reason, temperature ramps and transitions are applied in a controlled manner during testing.
Throughout the test the product:
- Can be monitored while operating (operational test)
- Can be assessed for structural effects in the unpowered state (storage test)
Test conditions are defined according to the products use environment and the applicable standards.