Effects of sedimentation induced filler thermal conductivity gradients on thermal reliability of potted components

In power electronic products, large components may be cooled by immersing each of the components in a cavity within the housing of the product. The small gap between the component and housing, which depends on mechanical tolerances and electrical isolation requirements, is then filled with a gap filler material (thermal potting). The gap filler forms an important conductive heat transfer path between the component and housing. This gap filler material is a colloidal suspension of small filler particles floating in a matrix, with the filler particles resulting in good bulk thermal conductivity. During assembly process, phenomenon of filler particle sedimentation occurs.Based on detailed thermal simulation models for certain components, it has been observed that the undesired thermal conductivity gradients due to sedimentation result in temperature rise of the order of 10 K. Certain limitations of assembly technologies limit the potting height achievable, further increasing the thermal aggravation due to variation in thermal conductivity.In this paper, using thermal simulation models, we study the effects of sedimentation induced filler thermal conductivity gradients on temperatures of cooled components, for a range of potting heights and gap sizes.