Why is Enclosure Thermal Design Important? Before we look at the 12 key considerations in enclosure thermal design let´s first consider why thermal issues need to be considered at the system, or enclosure level. A natural focus when designing an electronics product is, well the electronics. The electronics itself however, needs to work within some kind of enclosure, be it a standardized rack system1, or a custom-built enclosure like the housing of a SmartPhone or tablet computer, or part of another product like an automotive dashboard or aircraft flight deck. In all cases, including a standardized rack system, the electronics has to be designed with the enclosure in mind, as the enclosure can act as either a barrier or a conduit for carrying the heat away to the ambient, or possibly both. Cooling is a system issue, which is why we advocate a top-down approach, starting at the enclosure level [Ref. 2]. Often the airflow inside the enclosure is complex, making CFD the only viable approach to developing a successful design. The flow is affected by the electronics and the enclosure design, hence the electronics and enclosure interact to provide the application thermal environment. In the vast majority of cases, the primary cooling medium is ambient air. Even in something as small as a notebook computer where there is very limited space, designers look to circulate the air in order to improve cooling performance, although heat spreading and conduction to the casing will be more important.