Dropwise Condensation Life Testing of Self Assembled Monolayers

The increasing thermal demand of electronics devices has pushed the limits of current two-phase thermal technologies such as heat pipes and vapor chambers. The most obvious area for thermal improvement is centered around the high heat flux generating chips including improved evaporators, thermal interfaces, etc. However, heat fluxes in the sink/condensing regions have also risen as the size of electronics packages has decreased. One way to reduce the thermal resistance associated with condensation is to promote dropwise condensation. In previous work, the condensation performance improvement using self-assembled monolayer coated surfaces (to promote hydrophobicity) has been shown. However, the question of the life of the self-assembled monolayer coatings needs to be addressed before the technology is adopted, as this has plagued other dropwise condensation coatings in the past. Presented here is a general use of self-assembled monolayer coatings to promote dropwise condensation in electronics device applications, including a summary of recent work regarding dropwise condensation on gradient surfaces. Also presented is experimental data from a life test of self-assembled monolayers on copper and gold plated surfaces. In the life test, the surfaces have been continuously exposed to saturated steam at 60°C. Both surfaces have continued to promote dropwise condensation for over 9 months under conditions representative of heat pipe electronics cooling applications.