Environmental Stress Test
An environmental stress test is a verification test in which the board is exposed to operating environment conditions such as temperature, humidity, vibration and dust, and its behaviour is monitored. The aim is not to break the product but to see which symptom appears under which condition and at which point the design leaves margin.
In practice the three stresses that give the most information are:
- Temperature cycling: the board is moved repeatedly between cold and hot extremes. Because of different expansion coefficients, the fatigue that will occur over time in the solder joints becomes visible early this way.
- Humidity: at high relative humidity, condensation opens leakage current paths between two conductors. The drop in insulation resistance on uncoated boards shows up here.
- Vibration: heavy components, connectors and cable connection points are the weakest links. A vibration test usually changes the mechanical fixing solution.
During the test the product is kept running and its outputs are monitored; only checking "is it still working" at the end of the test hides a behaviour that appears at the temperature extreme and then reverts. The choice of test ranges is made according to the product's real usage environment: a tractor cabin, the inside of a panel and a boat console have different profiles from one another.
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