In practice, the following ESS methods have prevailed:
- Temperature stress
- Vibration stress
- Humidity stress
in conjunction with electrical stress.
Environmental stress screening on PCBs (or other products) is achieved by thermal stress with quickly changing temperatures. ESS is the most effective method of detecting poor soldering joints and SMD processes as well as manufacturing errors before delivery.
Typical ESS profiles contain a thermal change with 5 ... 15K/min over a wide difference in temperature.
The periodic or constant switching of the boards during the thermal cycle can increase the detection of errors.
The above-mentioned results are achieved in special ESS chambers because the heating and cooling capacity as well as the amount of circulating air is considerably higher than that of a conventional test chamber. High amounts of circulating air improve the heat transition and ensure that the specimens and/or boards are homogeneously stressed.
Weiss Umwelttechnik has developed a range of systems especially for this purpose which does more than justice to the above-mentioned requirements.