The development of electronic equipment towards minimizing of cost and size has lead to increased requirements on the cooling equipment for electronics. In avionics applications, constraints are put on all equipment regarding size, weight, and reliability. Additionally, harsh environmental stresses combined with relatively smallscale production reduces the possibilities for developing semiconductor components adapted for avionic use. In this thesis, an overview of current and upcoming challenges in thermal design of avionic equipment is given, followed by basic heat transfer theory, and a survey of state of the art in thermal management within avionics, thermal design tools, and reliability prediction.
The included papers focus on power distribution between the sides of a double-sided PCB as a thermal management measure. In the first paper, numerical simulation is used for evaluating the impact of power distribution on a double-sided PCB attached to the sidewall of a sealed enclosure. The enclosure is cooled by forced convection air passing along a finned heat sink tooled in the chassis wall. Paper 2 describes an experimental setup created for validating the results obtained in Paper 1. In Paper number 3, the effect of power distribution with non-uniform power configuration on the PCB sides is investigated by experimental measurements supported by simulations. In this paper, different cooling conditions, including forced convection directly on the PCB, are examined. In the article provided in Paper 4, an analytical description of the non-uniform power configuration can be found, as well as a numerical evaluation of the different power configurations discussed in Paper 3.
lt is concluded that communication between design engineers active in different spheres is a vital component for overcoming the thermal issues that are currently arising. Space must be provided in an early stage of product design phase for interdisciplinary thermal analysis and design. Furthermore, power distribution on a double-sided PCB is shown to be a thermal management measure without adding cost and weight to the electronic system. At moderate powers, maximum 36 W, and with equal power applied to all components on one side (uniform power configuration), this measure is confirmed to lower the maximum case temperature of the components by 4°C. Considering the more practical non-uniform power configuration, an even higher effect of power distribution can be achieved.
Linköping: Linköpings universitet , 2005. , 39 p.