Robust and reliable encapsulation of electronics for underwater applications

The market increasingly demands remote monitoring sensors and electronics for safety-related industrial equipment, transport vehicles and also building structures. In these applications the robustness of the electronics and the reliability of the packaging technology are key factors. Reliability requirements are for electronic modules are derived from environmental and operational loads. This leads to general requirements for the system concept to ensure their operation and thus system reliability. Most frequently the focus is set on thermomechanical design issues. The presented work however includes, the interpretation under a different loading scenarios - long-term use under constant media exposure in a maritime environment in seawater. The application scenario is monitoring of the foundation structure for offshore wind turbines. Specific requirements to protect the sensors and sensor electronics from the surrounding medium seawater and permanent pressure load of 3 to 6 bar in the application of water depth between 20 to 50 meters. Other environmental conditions are occurring minerals and microorganisms which can attack the package system in the long term. The permanent installation of electronics requires a system design with lifetimes in the range of the test structure itself, which is set to 10 years. The presented work includes extensive characterizations of organic potting compounds for this purpose. Emphasis has been put into the materials resistanzes to media and diffusion properties. Furthermore, aging effects and their impact will be presented on mechanical stability of the polymer systems. These include displacements of the characteristic glass transition and the variation of the elastic modulus. The results include relevant material classes and circuit board materials. As potential life-reducing mechanisms unwanted material changes through media storage and path formation within the polymer system have been identified.