No manufacturer can wait years to find out whether a product will survive years of real-world service. Accelerated life testing solves this by deliberately applying environmental stress beyond normal conditions — elevated temperature, humidity, or both, in controlled, repeatable profiles — to compress years of gradual degradation into days or weeks of chamber time. The IEC 60068 series is the standard framework most of this testing is built around.
Why "Just Run It Hot" Isn't a Test Plan
Different failure mechanisms respond to different stress types, and a poorly chosen test profile can either fail to reveal a real field failure mode, or induce a failure mode that would never actually occur in real service.
The Core Test Types
Constant temperature (dry heat / cold), IEC 60068-2-1 and 2-2. The simplest profile: hold the sample at a fixed elevated or reduced temperature for an extended period, targeting material degradation and electronic component drift following predictable temperature-dependent kinetics.
Damp heat (steady state), IEC 60068-2-78. Combines elevated temperature with high, controlled relative humidity — commonly 85°C/85%RH — to accelerate moisture-driven failure mechanisms: corrosion, electrochemical migration, delamination, and moisture absorption.
Thermal cycling / change of temperature, IEC 60068-2-14. Cycles the sample between temperature extremes, targeting solder joint fatigue and cracking from thermal expansion mismatch. This covers both gradual, ramped cycling and rapid thermal shock — covered as its own topic in our thermal shock testing guide.
Damp heat cyclic, IEC 60068-2-30. Combines cycling temperature while maintaining high humidity through the cycle, replicating real diurnal climate variation more closely than either test alone.
Matching the Test to the Failure Mechanism
| Real-world concern | Most relevant test type |
|---|---|
| Component drift, material aging under sustained heat | Constant temperature (2-1, 2-2) |
| Corrosion, electrochemical migration, moisture absorption | Damp heat steady state (2-78) |
| Solder joint fatigue, gradual thermal expansion cracking | Thermal cycling, ramped (2-14, slow rate) |
| Cracking from sudden, severe thermal transfer | Thermal shock (2-14, rapid transfer) |
| Realistic diurnal/seasonal climate simulation | Damp heat cyclic (2-30) |
| Outdoor/coastal corrosion specifically | Salt spray |
Why Temperature and Humidity Stability Matter as Much as the Setpoint
A chamber's headline temperature range is only part of what makes accelerated testing meaningful. Stability and uniformity directly affect whether test results are reproducible and comparable between runs. For damp heat testing specifically, humidity control adds a further layer of complexity — chambers built primarily for dry thermal cycling don't necessarily have the humidity control hardware needed for genuine 85°C/85%RH testing.
From Accelerated Test Data to a Real Lifetime Estimate
Running an accelerated test and getting a pass/fail result is useful, but extrapolating that into an actual predicted field lifetime requires a defined mathematical model relating the accelerated stress condition to real-world operating conditions, as covered in our TM-21 extrapolation discussion for LED-specific degradation.
Practical Test Program Guidance
For general electronics without unusual environmental exposure, constant-temperature and damp-heat-steady-state testing covers the most common reliability questions efficiently. For products genuinely exposed to repeated thermal cycling, thermal cycling testing targets fatigue-driven failure modes. For products combining significant thermal cycling and humidity exposure, damp heat cyclic testing gives the most realistic combined-stress picture.