A 3D numerical study of humidity evolution and condensation risk on a printed circuit board (PCB) exposed to harsh ambient conditions

In many applications, electronics enclosures are exposed to harsh environmental conditions. For a reliable design, it is crucially important to understand the effects of such conditions on the local climate inside the enclosures. In this study, the relative humidity (RH) and temperature inside an electronic enclosure exposed to harsh ambient conditions (relative humidity of 100% and cyclic temperature changes from 10 to 50 (°C)) are studied by developing a full 3D finite element based CFD model.

The RH evolution is studied in three stages: first, in an empty enclosure, then in an enclosure with a PCB, heatsink and a heater, and finally in the case of an internal cyclic heat load. In all three parts, the effect of the opening size of the enclosure is also studied. The numerical simulation results are compared with corresponding experimental results from the literature, and a good agreement is found.

The presence of components inside the enclosure damps the response of the internal climate to the ambient changes and this is especially the case for the aluminum heatsink. In case of exposure to RH of 100%, controlling the moisture concentration appears to be more effective than controlling temperature with the aim of reducing the condensation risk on the PCB.