_ Based on the geometry of the gaps, along with the volume occupied by the components, a product with a low viscosity offering good flow characteristics, might be useful. The specific range of the viscosity might depend on the necessity for wicking inside some of the smaller components within. In certain situations, for example impregnation, an extremely low viscosity compound would be the ideal choice. The addition of heat as well as vacuum impregnation techniques can be used to help facilitate flow properties even further.
_ To bond vertical surface, A compound which does not flow during application, essentially a non-drip compound, would be the best choice. Note that there are certain products which could remain non-drip even during the curing process at elevated temperatures.
_ In certain cases, inert fillers can be added to increase the viscosity. One commonly used thickening agent is fumed silica, which helps to increase the viscosity significantly. Additionally, some thermally conductive fillers help not only to increase the viscosity, but also to dissipate heat.