The safe regime of humidity/temperature combination inside the device is defined by the critical humidity level at which the functionality of the PCBAs (or other parts) get affected. Although it varies based on the functionality of the device, some generalization can be done based on allowable leakage current and water layer formation due to various PCBA related factors. Therefore it is necessary to understand the relation between water layer formation, influencing factors, and failure mechanisms to define safe climatic domain levels.
Testing on TestPCBs as well as on industrial devices/ enclosures carried out in relevant standardized accelerated test environments such as those defined in: IEC 60068-2-30, MIL-STD-810G, ISO 8092-2 and IPC-TM-650. Harsh, salt-containing corrosive environments are considered as well.