The effectiveness of water vapor sealing agents when used in application with thermoelectric cooling modules

The inherent reliability of thermoelectric modules (TEMs) can be destroyed when water vapor is allowed to condense within the device. This causes corrosion in the TEM and eventually leads to catastrophic failure. TEM manufacturers and users combat this problem by applying sealing agents to the perimeter of the devices. However, not all sealing agents are equally effective or even beneficial to long-term, reliable operation of the TEM. This paper presents an analysis on the various sealing agents used through out the industry. Sealed TEMs were cooled in a high humidity environment and monitored for the visual evidence of water and its associated weight gain. A marked difference in the effectiveness of the various sealing agents was noted. Some sealing agents, such as the ubiquitous silicone rubber, yielded unacceptable sealing capability. That is, water vapor was shown to easily penetrate the silicone based "sealant" leaving trapped liquid water inside. In sharp contrast, the epoxy sealant was found to be essentially impervious to vapor penetration.